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Geology of the country around Hastings and Dungeness. Memoir for 1:50 000 geological sheets 320 and 321 (England and Wales)

R. D. Lake and E. R. Shephard-Thorn

Bibliographical reference Lake, R. D. and Shephard-Thorn, E. R. 1987 Geology of the country around Hastings and Dungeness. Mem. Br. Geol. Surv., Sheets 320 and 321, England and Wales.

British Geological Survey, Natural Environment Research Council

London: Her Majesty's Stationery Office 1987. © Crown copyright 1987. First published 1987. ISBN 0 11 884411 3. Printed in the United Kingdom for HMSO Dd 240414 C20 11/87 398 12521

Other publications of the Survey dealing with this district and adjoining districts

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Preface

This memoir describes the geology of the district covered by the Hastings and Dungeness (320/321) New Series Sheet of the 1:50 000 Geological Map of England and Wales. The primary six-inch geological mapping was carried out between 1958 and 1970, by E. R. Shephard-Thorn, R. D. Lake, R. A. B. Bazley, E. A. Edmonds and J. G. O. Smart, with S. C. A. Holmes as District Geologist. This work replaces the former 'one-inch' New Series geological sheets published in 1928 which were based on the Old Series 'One-inch' sheets 4 and 5 published in 1863 and 1864. A memoir describing the geology of the New Series sheets 320 and 321, by H. J. Osborne White, appeared in 1928. The geology of the Hastings–Rye district was also illustrated by a 1:25 000 sheet in the 'Classical areas of British Geology' series, issued in 1977.

This account describes the geology of the Hastings Beds in their type area, and that of the inliers of Purbeck Beds near Brightling and Netherfield. The Flandrian deposits making up the southern part of the Romney Marsh–Dungeness Foreland complex are also described.

Specialised contributions include those of the late Dr F. W. Anderson on Wealden and Purbeck ostracod faunas, Dr B. M. Cox on the concealed formations (Chapter 2), Mr A. A. Morter on the Wealden and Purbeck macrofossils and Mr M. A. Perkins on water supply. Dr C. P. Sladen of British Petroleum has summarised the clay mineralogy of the Hastings Beds and Purbeck Beds based on his PhD research on specimens from the Hastings–Cliff End coast section and the BGS Fairlight Borehole.

Our thanks are due to the farmers and other landowners of the district for permitting access to their property during the surveys. We are also grateful to the following bodies for assistance or information received: British Gypsum Ltd, the Central Electricity Generating Board, the Department of the Environment, Eastbourne Waterworks Company, East Sussex County Council, Kent County Council and the Southern Water Authority. The British Petroleum Company kindly allowed the use of material from an unpublished report on the Pevensey–Bexhill area by the late A. H. Taitt. Professor P. Allen, FRS, of the University of Reading, has been of great assistance in providing information related to his own extensive work on Wealden sediments. Dr W. A. Wimbledon made valuable comments on the naming of Portland Beds ammonites from the Fairlight Borehole and Dr M. Feist has provided information on Cretaceous charophytes.

This memoir was written by Mr Lake and Dr Shephard-Thorn and includes compilations from the geological notes of the other surveyors. It has been edited by Mr J. E. Wright.

G. Innes Lumsden, Director, British Geological Survey Keyworth, Nottingham NG12 5GG. 14th July 1987

Notes

National Grid references are given in square brackets throughout the memoir; those without initial letters lie within the 100 km square TQ (or 51).


Geology of the country around Hastings and Dungeness—summary

This memoir describes the geology of parts of East Sussex and Kent; the district includes the resorts of Bexhill, Hastings and St Leonards and the historical towns of Battle, Rye and Winchelsea. The non-marine Hastings Beds of Lower Cretaceous age underlie much of the ground and give rise to pleasantly varied relief in the western part of the district. East of Hastings these beds form rugged sea cliffs up to 150 m high, which are interrupted by steep wooded glens. Older strata, the Purbeck Beds, crop out in small inliers in the north-west, near Battle, and these contain economic deposits of gypsum in their lowest part. The eastern district comprises the low-lying reclaimed coastal deposits of Romney Marsh and part of the shingle foreland of Dungeness.

A number of exploratory boreholes have been sunk near Hastings in recent years. The results of these, which provide an insight into the Mesozoic and Quaternary history of the district, are summarised herein. The geology of the coast sections is described in a separate appendix.

(Geological succession)

Geological sequence

The drift deposits and solid formations exposed at the surface or proved in boreholes and underground workings within the district are tabulated below:

DRIFT

Quaternary

Blown Sand

Peat

Alluvium

River Gravels, first terrace

Marine Beach Deposits and Tidal Flats

Marine Alluvium, Sand

Marine Alluvium, Clay

Storm Gravel Beach Deposits

Head

SOLID

Thickness m

Cretaceous

Wealden

Weald Clay

up to 14 proved

Hastings Beds

Tunbridge Wells Sand

up to 110

Wadhurst Clay

15–60

Ashdown Beds

115–215

Jurassic

Purbeck Beds

55–155

Portland Beds*

13–43

Kimmeridge Clay*

420

Corallian*

up to 77 proved

* Proved only in boreholes and underground workings

Chapter 1 Introduction

Topography

The countryside within the area of the combined Hastings and Dungeness 1:50 000-scale geological map forms part of the counties of East Sussex and Kent and displays a pleasant variety of scenery. The broad topographical features are illustrated in (Figure 1) and the outline geology in (Figure 2). The generalised geological sequence is tabulated on the inside front cover. The ground reaches a little over 150 m above OD. In the north and west the higher ground is moderately well dissected and includes the eastern extremity of the High Weald which is made up of much-faulted strata of the Hastings Beds. In marked contrast, the southern and eastern portions are characterised by wide expanses of reclaimed coastal marshland with shingle ridges and sand dunes rising a few metres above them. Offshore, the submarine relief appears to be very gentle, with the sea bed sloping gently to 10 fathoms (18.3 m) across a broad shelf up to 10 km wide. Beyond the 10-fathom line the depth increases more rapidly. The cuspate shingle foreland of Dungeness extends to the edge of the shelf (Figure 1), and it appears that its eastward growth has been limited by this feature.

The major watershed of the Weald enters the district in the north-west, just south of Brightling, and continues to the ESE through Battle to meet the sea at Fairlight. There is a clear relationship between geological structure and relief in this area. The rivers Tillingham and Brede, follow the broadly E–W pattern of strike-faulting (Chapter 5), and structural highs, defined by the strike-faulting, coincide with topographic highs; for example, the high ground of the watershed ridge is composed mainly of the relatively older Ashdown and Purbeck beds, whereas the lower areas on its flanks are underlain by Wadhurst Clay and Tunbridge Wells Sand. The major valleys, such as those of the Brede and Tillingham, have broad alluvial floodplains up to 1 km wide but in contrast, the headwaters and lateral streams of these rivers tend to have short steep courses, deeply incised into the interfluves. Outcrops of hard sandstones, limestones and ironstones in these streams give rise to miniature gorges and waterfalls. It would appear that the youthful aspect of these tributary streams reflects rejuvenation caused by the drop in sea level during the last glacial period. In the east, the rolling ground of the Hastings Beds outcrop is limited abruptly by the old cliff-line around the inner edge of the marshland.

The maritime associations of the district are well known and during the 13th and 14th centuries Hastings, Lydd, Rye and Winchelsea were part of the confederation of the Cinque Ports, important in the defence and trade of England. Subsequent economic and geographical changes have been such that now only Rye, with its long narrow tidal harbour, has any claim to be a port. Hastings, St Leonards and Bexhill have developed as holiday resorts since the early 19th century.

Agriculture is important inland and is favoured by the mild climate and generally good soils. Dairy and sheep farming, market gardening and fruit-growing are the most important activities. The rich pasture lands of Romney Marsh continue to be famous for sheep rearing, although parts of the marshland are now given over to arable crops. The sand dunes at Camber have been developed as golf links. Aggregate is, or has been, worked from the shingle areas west of Rye Harbour, Northpoint Beach and around Lydd.

History of previous research

The Hastings district is important in geological studies of the Weald as the type area for the Hastings Beds.. From the beginning of the 19th century, geological knowledge of the area expanded with the development of the seaside resorts as increasing numbers of visitors and new residents took an active interest in the exposed rocks and their fossils.

A broad stratigraphy for the Cretaceous rocks of southern England was given by Coneybeare and Phillips (1822), who recognised Weald Clay and 'Iron Sands' as subdivisions of the Wealden. This latter term was formally introduced by Martin (1828) in his memoir on West Sussex. An accurate sketch of the Hastings coast sections accompanied a short paper by Webster (1829). This included notes on the calcareous 'Tilgate Stone' lithologies that are now known to occur in sandstone near the base of the Wadhurst Clay.

A wide-ranging stratigraphical survey of the Jurassic and Cretaceous rocks of southern England was made by Fitton (1824, 1836). In the latter paper he described sections west of Hastings, and illustrated the silicified fossils of the tree fern 'Endogenites' (now Tempskya) that had been discovered near the town. His short account of the geology of the Hastings district (1833), includes useful local details. Fitton was the first to recognise clearly that the Wealden sediments had been laid down in non-marine environments, although J. Sowerby (1812) had previously alluded to this possibility in describing Viviparus from the Large-'Paludina' limestone of the Weald Clay, near Bethersden in Kent.

Dr Gideon Mantell, the discoverer of the dinosaur Iguanodon, described the fossils of the South Downs (1822) and the geology of south-east England (1833). In the latter account he divided the Wealden lithostratigraphically into the Weald Clay, above, and the Hastings Beds (sands) below. He also proposed the term 'Ashburnham Beds' to include the argillaceous lower Ashdown Beds seen around Hastings and the upper Purbeck rocks exposed in the Sussex inliers.

Mantell's type locality at Ashburnham subsequently proved to be sited on the Wadhurst Clay, the confusion having arisen through the similarity in lithology of the Wadhurst Clay and the higher Purbeck shales. Mantell's stratigraphy was thus soon superseded.

The present stratigraphical subdivisions of the Hastings Beds, as listed below, were introduced by Drew (1861, 1864), who had played a major part in the original geological survey of the Weald:

Hastings Beds

Tunbridge Wells Sand

Upper Tunbridge Wells Sand

Grinstead Clay

Lower Tunbridge Wells Sand

Wadhurst Clay

Ashdown Sands

The Ashdown Sands were named from the Ashdown Forest area, where some 200 m of dominantly sandy strata are present. In the eastern Weald, and especially around Hastings, there are mottled silty clays in the lower exposed part of the formation. These are prominent in the cliffs around Fairlight Head, and were named the Fairlight Clays by Gould (in Topley, 1875). Recent work has shown that such clays can occur at almost any horizon and do not warrant formational status. Present usage combines Ashdown Sands and Fairlight Clays in the Ashdown Beds formation, the clays being mapped separately where possible. Morter (1984), in a regional study of Purbeck–Wealden bivalve faunas, used the older terminology in an informal sense for broad correlation, and employed the informal term 'division', for the Ashdown Sand division (the upper arenaceous strata) and the Fairlight division (Fairlight Clays facies). The latter extends down to the top of the Greys Limestones Member of the Purbeck Beds, which he suggests should be taken as the base of the Wealden. The Wadhurst Clay is named from its development around Wadhurst in Sussex, where it approaches 60 m in thickness, in dominantly clay facies. Around Hastings, however, the formation includes a number of sandstone beds. Some of these sandstones are strongly cemented by calcite and were given the name 'Tilgate Stone' by Mantell, from Tilgate Forest in North Sussex. This has no stratigraphical significance and is used nowadays to describe any calcareous sandstone development within the Hastings Beds. The Tunbridge Wells Sand crops out widely around Tunbridge Wells, where it can be subdivided because of the presence of the Grinstead Clay, but in the Hastings district the formation cannot be thus diyided.

The present district forms part of that covered by the 'Old Series' one-inch geological sheets 4 and 5, published in 1863 and 1864. In 1875 the work of all surveyors was brought together in a single memoir for the whole Weald by Topley. This account reviewed the stratigraphy and structure of the Jurassic and Lower Cretaceous rocks in regional terms and Topley's achievement was honoured, on its centenary, by the publication of a commemorative part of the Proceedings of the Geologists' Association in which Kirkaldy (1976) gave an account of the work of the early surveyors of the Weald. The publication of Topley's memoir marked the end of an era. The broad stratigraphical and structural geology of the Weald had been described, and further progress had to await refinements in mapping techniques, palaeontology and petrology and the sinking of exploratory boreholes.

In the late 19th century little was known of the subsurface geology of southern England, but considerable interest was shown in exploration for coal resources near London, and a number of deep boreholes were sunk. In the present district, the first were the two Sub-Wealden Exploration boreholes sunk near Netherfield (Willett, 1878), which failed to find coal, but discovered gypsiferous strata in the basal Purbeck Beds and thick developments of the Portland Beds, Kimmeridge Clay and Corallian. Subsequently a borehole near Battle (Lamplugh, 1917a) proved a similar sequence starting in the Ashdown Beds and ending at 630 m in Corallian strata. This information, together with that from borings in Kent, led Lamplugh (1919) to recognise the 'inverted' structure of the Weald i.e. that an anticline of Cretaceous rocks overlay a deep basin of Jurassic rocks. Several more recent deep boreholes and geophysical work have amplified the structural picture drawn by Lamplugh (Lees and Cox, 1937; Lees and Taitt, 1946; Taitt and Kent, 1958; Falcon and Kent, 1960; Terris and Bullerwell, 1965). A Bouguer gravity anomaly map for the 1:250 000 Dungeness–Boulogne sheet which includes the present district, was issued by BGS in 1986. It is now known that the Hampshire Basin and the Weald are underlain by a basin of Jurassic rocks, more than 1500 m thick and which are floored by strongly deformed Devonian and Carboniferous rocks. The structures in this basement have largely determined those in the overlying Mesozoic strata (Shephard-Thorn, Lake and Atitullah, 1972; Lake, 1976).

New Series one-inch geological sheets for Hastings (320) and Dungeness (321) were compiled with some revision from the Old Series maps and issued in 1928 with a joint sheet memoir appearing in the same year (White, 1928). At about this time the Weald Research Committee of the Geologists' Association was set up to study various aspects of Wealden geology. Contributions on the present district included those of Milner and Bull (1925) on the Eastbourne–Hastings coast sections and Sweeting (1930) on the structure of the Ashburnham–Battle–Crowhurst area.

The researches of P. Allen over about 40 years from the 1940's constituted a major contribution to the understanding of Wealden sedimentary environments (e.g. Allen, 1949a, 1959, 1976, 1981). His studies used the derivations of pebbles and heavy minerals and he first attempted to interpret the Wealden sediments in terms of broadly deltaic environments (1949a), as did Taylor (1963). In this model fluvial sandy sediments from source areas in Cornubia, the London Platform and northern France accumulated in a muddy Wealden lake or lagoon, forming a coalescing set of deltaic fans at several horizons. The formation of these was controlled by eustatic movements and the sequences were regarded as a number of megacyclothems. Allen's deltaic eustatic model was superseded by a fluvial model in which the tectonic framework controlled sedimentary patterns (Allen, 1976, 1981). Stewart (1981a and b, 1983) subsequently modified Allen's fluvial model by recognising the importance of relatively high sinuosity, suspended-load channel deposits in the Wealden.

Following the discovery of gypsum in the Sub-Wealden borings, commercial mining commenced at Mountfield about a century ago, and still continues. A new mine was opened at Brightling in the early 1960's after an extensive programme of exploratory boreholes. An account of the stratigraphy and structure of the Purbeck inliers, taking account of mining and borehole information, was given by Howitt (1964). Shortly afterwards, during the present survey, a new account of the stratigraphy and structure, together with a description and analysis of the ostracod faunas, was prepared by Anderson and Bazley (1971).

Sedimentological and stratigraphical data on the Wealden and Purbeck rocks have been provided by several cored BGS boreholes in south-eastern England. Those within the present district include Cooden (Lake, 1975), Fairlight (Holliday and Shephard-Thorn, 1974), Westfield, Little Maxfield and Icklesham.

Palaeontological research on the Wealden and Purbeck rocks dates from the early discoveries of Mantell and his contemporaries. Most of the plant and vertebrate fossils now in museums were collected during the 19th century. The famous Black Horse Quarry, near Telham, yielded many vertebrate teeth and bones from a bone-bed horizon low in the Wadhurst Clay and many plant and vertebrate fossils were collected from the Hastings cliff sections. The Wealden reptiles were monographed by Owen (1857) and the plant fossils of the 'Fairlight Clays' were described by Seward (1894, 1895, 1913). A review of the Wealden flora was undertaken by Watson (1969) and the macrofossils and spores were studied by Hughes (1955, 1958, 1976) and Batten (1969, 1975).

The occurrence of fossil horsetails forming soil-beds in the Wadhurst Clay was described by Allen (1941, 1947, etc) and Anderson and others (1967). These and other plant macrofossils and spores have provided evidence on the nature of the flora which occupied emergent ground in the depositional swampy basins and the adjacent territory. Reptilean footprints, at first mistaken for those of giant birds because of their bipedal habit, were early noted in the Hastings cliff sections (Tagart, 1846; Beckles, 1852, 1854; Tylor, 1862); their occurrence was reviewed by Sarjeant (1974). Most of the footprints seem to be of a characteristic three-toed form representing Iguanodon; they provide evidence of extremely shallow, if not emergent, conditions (see Allen, 1976). Teeth of primitive mammals from the Cliff End Bone Bed were first described by A. S. Woodward (1911). Their occurrence was subsequently reviewed and new species described by Clemens (1963) and Clemens and Lees (1971). The Cliff End Bone Bed is believed to be contemporaneous with that at Telham, also in the lower part of the Wadhurst Clay. The fossil sharks of the English Wealden were described by Patterson (1966). Anderson's research between 1940 and 1982 on Wealden and Purbeck ostracod faunas (e.g Anderson, 1940, 1967; Anderson and others, 1967; Anderson and Bazley, 1971) provided a broad zonal scheme of correlation and also an index of relative salinity. Morter (1984) reviewed Purbeck–Wealden bivalve faunas, in which he recognised a number of faunal assemblages, which could be matched with variations in palaeosalinity.

Comparatively little detailed work has been carried out on the petrography and mineralogy of Wealden and Purbeck sediments of the Hastings district, with the exception of the basal Purbeck evaporites. The occurrence of spherulitic siderite (sphaerosiderite) in the Fairlight Clays near Hastings was noted and described by Spencer (1925). Work on the heavy mineral suites of Wealden rocks was initiated by Milner (1922), and subsequently employed by Allen in his reconstructions of Wealden palaeogeography. Some Wealden sediments were described and figured by Taylor (1963). The clay mineralogy of selected Wealden clays was described by Tank (1962) and Perrin (1971) catalogued the clay minerals present in typical examples of Wealden sediments. Detailed studies of the clay mineralogy of the Purbeck–Wealden rocks of north-west Europe were carried out by Sladen (1980), who contributed the results of his work on material from the Fairlight Borehole and Hastings cliff exposures to this memoir (Appendix 2).

Much interest has been attracted by the cuspate shingle foreland of Dungeness, which falls within the present district and the adjacent parts of the Romney Marsh. The development of the foreland was interpreted from the pattern of old shingle ridges and historical evidence by Lewis (1932). A similar treatment of the ridges west of Rye Harbour was given by Lovegrove (1953). Deep sections revealing the lithology and structure of the beach deposits, in the excavations for Dungeness 'B' nuclear power station, were recorded by Hey (1967).

The history of the reclamation of the marshlands in adjacent areas, extending back possibly to Roman times, was described by Smart (in Shephard-Thorn and others, 1966; in Smart and others, 1966). Similar conclusions were reached by Green (1968), following the soil survey of Romney Marsh. A brief outline of the Holocene development of the

Romney Marsh area, based on a limited number of radiocarbon-dated samples, was been given by ShephardThorn (19 6). Eddison (1983) published a revised view of the development of the barrier beaches at Dungeness.

The water supply of the district was developed following the growth of the seaside resorts and in about 1830 the Hastings and St Leonards waterworks were established and set about the construction of various reservoirs, deep wells and associated works. The story of the undertaking up to 1970 was recorded by Coleman (1971), who noted that Topley gave a consultant's report on the town's water supply in 1875. A number of wells for public and private supply were sunk during the 19th and early 20th centuries and details of these were collected by the Geological Survey and published as county water supply memoirs (Whitaker and Reid, 1899; Whitaker, 1908, 1911). A memoir on the wells and springs of Sussex was later prepared by Edmunds (1928). A joint well catalogue for the Lewes, Hastings and Dungeness sheets was compiled by Cole and others (1965).

The area has associations with iron working going back at least to Roman times and continuing up to the closing of the last Wealden furnace at Ashburnham in 1828. The industry exploited clay ironstone ore from the Wadhurst Clay and local charcoal. Topley (1875) reviewed the evidence of this activity (bell-pit scars, slag and cinder heaps, dams etc) while details of individual sites were collected by Straker (1931). Sweeting (1930, 1944) wrote on the industry around Ashburnham and on its history in the Weald in general. The Wealden Iron Research Group has since done much work on the industrial archaeology of various sites (Cleere and Crossley, 1985).

Boreholes drilled in the search for oil or coal in the eastern Weald, have in general been unsuccessful, although an accidental discovery of natural gas was for many years used to light the railway station at Heathfield. They have however, provided useful stratigraphical information and formed the basis of the commercial exploitation of gypsum at Mount-field and Brightling. This and other aspects of the economic geology of the Weald, were reviewed by Highley (1976). ERST

Chapter 2 Concealed formations

Jurassic

The Portland Beds, Kimmeridge Clay and Corallian Beds have been proved by boreholes in the Hastings district. These concealed strata were investigated by the 'SubWealden Exploration' borings which were sponsored by the British Association for the Advancement of Science. Drilling was begun in 1873 at a site [TQ 7195 1931] north-east of Nether-field to establish the stratigraphical sequence down to the Palaeozoic basement and to prove whether productive Coal Measures occurred there. Two holes were drilled on the site and have subsequently become known as Mountfield No. 1 and No. 2 boreholes. No. 1 reached a total depth of 1017 ft (310.0 m) and No. 2 1906 ft (580.9 m) (Glen, 1876). However, the Jurassic sequence proved to be much thicker than anticipated and only Upper Jurassic strata were penetrated. The stratigraphical interpretation of the cores was carried out by TOpley and summary logs and other stratigraphical information were published for both boreholes (Topley, 1875, pp.41–44; Glen, 1876, pp.265–270; Topley in Willett and Topley, 1874, pp.492–496, 1875, pp.22–27; Topley in Willett, 1876, pp.347–349). Topley believed that both boreholes bottomed in Oxford Clay, but recent examination of the logs and collected specimens suggests that the first and shallower hole terminated in Kimmeridge Clay, as noted by Edmunds (1928, pp.154–155), and the second hole in Corallian Beds. Prior to this recent review, the lowest 36.5 m of beds in the second borehole were classified in BGS records as Oxford Clay. Regrettably this erroneous data was used to construct the generalised vertical section on the 1:50 000 geological map, published in 1980.

In 1907–9, another borehole was drilled by the South Eastern Development Syndicate near Battle [TQ 7573 1706], about 4.5 km south-east of the Mountfield site, to a depth of 631.2m (Lamplugh, 1917a; Edmunds, 1928, pp.54–55). Lamplugh believed that it ended in the basal beds of the Kimmeridge Clay or the uppermost part of the Corallian; the latter interpretation is now thought correct. The Guest-ling No. 1 Borehole [TQ 8344 1390] drilled by the Gypsum Mines Company (now British Gypsum) (Howitt, 1964) and the BGS borehole at Fairlight [TQ 8592 1173] (Institute of Geological Sciences, 1971, p.22) both reached the upper part of the Kimmeridge Clay.

A summary of the strata below the Purbeck Beds proved in the more important boreholes is given in (Table 1).

In the BGS collection, a representative set of specimens is available from the Fairlight sequence, but there are no long runs of core for the Battle, Mountfield and Guestling boreholes so that only limited information is available for the greater part of the Kimmeridge Clay and for the Corallian Beds. However, the various sequences can be pieced together and may be correlated with the published descriptions for Dorset (Cox and Gallois, 1981), the Warlingham Borehole, Surrey (Worssam and Ivimey-Cook, 1971) and a revised interpretation of the Brightling No. 1 Borehole (Falcon and Kent, 1960), which lies close by on the eastern margin of the adjacent Lewes (319) sheet (Figure 3; Lake and others, 1987).

The following notes combine information from all the available boreholes in this district.

Corallian Beds

The Corallian Beds, of Oxfordian age, cored in the Battle and Mountfield No. 2 boreholes are the oldest strata proved in the district. The lowest available specimens from the Mountfield No. 2 Borehole show 4.5 m of oolitic-pelletal limestones to a depth of 544.4 m. Below this, for a thickness of about 36.5 m, to the base of the hole, Topley described a predominance of silty mudstones within which occurred a 5 m limestone band (Glen, 1876). These latter beds are assigned to the Corallian by analogy with the sequence in the Brightling No. 1 Borehole. In the Battle and Mountfield No. 2 boreholes, the oolitic limestones are overlain by about 21 m of dark grey and fissile mudstones with pyritised trails and a more-or-less pyritised shelly fauna including Corbulomima, Pinna, Protocardia, and perisphinctid ammonite nuclei; Lingula also occurs. These strata are in turn overlain by about 9 m of calcareous mudstones with cementstones which, in the Battle Borehole, yielded common Pinna, with other bivalves including Corbulomima?, Grammatodon, Pleuromya cf. alduini (Brongniart) and oysters. The uppermost part of the sequence consists of some 6 m of pelletal and shelly cementstones and mudstones with rhynchonellids and terebratulids, a cidarid spine and oyster fragment. A shelly pelletal cementstone with rhynchonellids at about 612.7 m in the Battle Borehole matches a similar bed or beds at 504.8 and 506.6 m in the Mountfield No. 2 Borehole.

Kimmeridge Clay

The Kimmeridge Clay is separated into lower and upper divisions, each with distinct ammonite faunas: the Lower Kimmeridge Clay is characterised by species of Pictonia, Rasenia and Aulacostephanus, and the Upper Kimmeridge Clay by species of Pectinatites, Pavlovia and related forms. Both Lower and Upper Kimmeridge Clay fossils have been recognised amongst the collected specimens and, although the specimens are far from representative, it seems likely that a full Kimmeridgian zonal sequence is present (Figure 3).

The base of the Kimmeridge Clay and of the Kimmeridgian Stage is taken at about 609.6 m in the Battle Borehole and at 503.5 m in the Mountfield No. 2 Borehole, at an upward change from an apparently calcareous and dark grey mudstone sequence with cementstones, which may be shelly and/or pelletal, to a sequence of siltstones and sandstones interbedded with silty calcareous mudstones and cementstones.

In the Lower Kimmeridge Clay, the few ammonites, although poorly preserved, are sufficient to give some reasonable stratigraphical control. In the Battle Borehole, Rasenia? occurs at 579.1 m (?cymodoce Zone), Aulacostephanus at 548.6 m (including the finely ribbed A. eulepidus (Schneid) which is characteristic of the mutabilis Zone), 487.7 and 432.8 m; and Laevaptychus at 426.7 m. In the Mountfield No. 2 Borehole, the ammonites include ?A. eulepidus at 469.7 m and A. sp.between 321.3 and 295.4 m. The first named ammonite at Mountfield occurs in a sequence of pale grey, calcareous mudstones between about 469.7 and 454.2 m. From this interval, old manuscript lists of additional specimens record the crinoid Pentacrinites' between 472.1 and 462.1 m, which suggests a correlation with the Pentacrinus Band that has been recorded elsewhere in England in Bed 18 (mutabilis Zone) of the standard numbered bed sequence of the Kimmeridge Clay (Gallois and Cox, 1976). The oyster Nanogyra occurs in the lower part of the sequence, together with pectinids such as Entolium. The calcite-cemented sandstones in the upper part of the Lower Kimmeridge Clay, some of which are glauconitic, are rich in Nanogyra virgula (Defrance). Crustacean fragments also occur with rhynchonellid and terebratulid brachiopods. Brachiopods are particularly common in cementstones at the base of the sequence.

In the Hastings district, the base of the Upper Kimmeridge Clay marks an upward lithological change from the more sandy sequence of the Lower Kimmeridge Clay to a sequence of sparsely shelly, pale grey, calcareous 'dicey' mudstones and shelly, locally fissile, mudstones, including oil shales. The boundary can be fixed at about 426.7 m in the Battle Borehole and at about 294.1 m in the Mountfield No. 2 Borehole. These mudstones contain an abundant bivalve fauna dominated by Astarte spp., 'Lucina' minuscula Blake, Modiolus autissiodorensis (Cotteau), Protocardia morinica (de Loriol), together with Discinisca latissima (J. Sowerby), Lingula and small gastropods including Dicroloma. Fragments of the ammonite Pectinatites, which is used for zonation at this level, occur at various horizons, but there are only two specifically determinable specimens. However, together with some widespread marker bands which can be recognised in the cores either from the specimens or the descriptive logs, they facilitate reasonable stratigraphical control.

Throughout much of England, there is a well developed sequence of oil shales at the top of the wheatleyensis Zone (wheatleyensis Band of Gallois, 1978). In Dorset, this sequence includes the Blackstone, which is a massive oil shale with calcareous and pyrite concretions. Specimens from 225.3 m in the Mountfield No. 2 Borehole are of a similar lithology and include the ammonite Pectinatites (Virgatosphinctoides) cf. wheatleyensis Neaverson. Glen's (1876) published log does not differentiate these beds, but some old manuscript lists of additional specimens indicate 'oil shales' at 224.3 m so that a correlation with the wheatleyensis Band seems justified. The White Stone Band which marks the base of the pectinatus Zone is the thickest of the coccolith-rich marker bands which occur in the English Kimmeridge Clay (Gallois and Medd, 1979). In the Mountfield No. 1 Borehole, the 'Hard light-coloured bed, very rich in Petroleum' recorded by Topley (1875, p.43) at 182.9 to 183.5 m is presumed to be the White Stone Band. Comparison of the published logs of the two Mountfield borings suggests that the 'Brown Limestone' at 185.0 to 185.5 m in Mountfield No. 2 may be the same bed (Glen, 1876, p.268). The White Stone Band can also be recognised in the nearby borehole at Brightling at about 243.8 m. At 365.8 m in the Battle Borehole, there are specimens of very pale brown oil shale which are lithologically similar to some of the coccolith-rich horizons of the pectinatus Zone, between the White Stone Band and the Freshwater Steps Stone Band, in Dorset (Gallois and Medd, 1979).

The highest beds of the Kimmeridge Clay consist predominantly of dark grey, calcareous, silty and bioturbated mudstones, with paler more calcareous mudstones containing interbedded thin argillaceous limestones. The macrofauna of these beds is dominated by bivalves which include Camptonectes morini (de Loriol), Grammatodon rhomboidalis (Contejean), Hartwellia hartwellensis (J. de C. Sowerby), Isocyprina (Venericyprina) argillacea Casey, Modiolus autissiodorensis (Cotteau), Pleuromya autissiodorensis (Cotteau), Protocardia morinica (de Loriol) with Astarte, Corbulomima, Entolium, Myophorella, Nuculana, Oxytoma and oysters. The brachiopods Discinisca and Lingula also occur, with the gastropod Procerithium and fish fragments. At this level, the ammonite fauna is poorly preserved and fragmentary, and can generally only be determined as 'pavloviids'. There is no reason to suspect that the sequence is incomplete and the three highest ammonite zones of the Kimmeridgian are probably all represented (Figure 3). The top 23 m of the Kimmeridge Clay was cut by the BGS Fairlight Borehole, which terminated in that formation. The bivalve assemblage includes Grammatodon rhomboidalis, Hartwellia hartwellensis and Isocyprina (Venericyprina) argillacea and, together with specimens of Pavlovia, is particularly abundant in the lowest beds of the Fairlight Borehole sequence (below about 393 m). Partial phosphatisation also occurs at this level and at 391.82 m a shelly band with a brown ?phosphatic nodule is possibly equivalent to the Rotunda Nodules (rotunda Zone).

Portland Beds

The Portland Beds consist of silty and/or calcareous mudstones, siltstones, fine-grained calcareous sandstones and cementstones. The macrofauna is dominated by bivalves which include Camptonectes lamellosus (J. Sowerby), Entolium sp., Isognomon bouchardi (Oppel), Lima cf. boloniensis (de Loriol), Modiolus autissiodorensis (Cotteau), M. boloniensi (de Loriol), oysters including Liostrea and Nanogyra, Protocardia dissimilis (J. de C. Sowerby), Thracia cf. incerta (Thurmann) and trigoniids including Laevitrigonia gibbosa (J. Sowerby) and Myophorella cf. incurva (Benett). Brachiopods (Discinisca, Lingula and Rhynchonella) are also present, with crustaceans and serpulids. In the Battle and Fairlight borehole cores, ammonites generally occur as rather poorly preserved fragments or specimens of which so little can be seen in the core, because its diameter is only 8 cm or less, that they are not determinable; nevertheless, they do provide some zonal information. Only the lowest three of the six Portlandian ammonite zones (Figure 3) can be recognised. These are based on the following determinable ammonites: in the Fairlight Borehole, Epivirgatites? at 368.48 and 367.59 m (albani Zone), Glaucolithites. sp.at 365.61, 362.59 and 362.56 m (glaucolithus Zone) with Glaucolithites? at 358.01, 355.17 and 353.77 m; in the Battle Borehole Glaucolithites? at about 289.6 m (glaucolithus Zone) and Galbanites? at about 278.9 m (okusensis Zone).

In the Dorset type area, the base of the Portland Beds has been taken at different levels by different authors because the boundary lies within an upward lithological transition from clay to silt and sand (Townson, 1975). In the Hastings district and elsewhere in the Weald where the Portland Beds are more argillaceous in character, the lithostratigraphical boundary is even more difficult to pick. It has, therefore, most commonly been taken arbitrarily at the most conveniently correlated horizon. This is usually the beds in which the earliest Portlandian ammonite fauna (albani Zone) is found because in the Dorset type area, the base of the

Portland Beds and the Portlandian Stage have traditionally coincided. However, Townson (1975) redefined the base of the Portland Beds in Dorset at the base of the Rhynchonella Marls, so that the basal Portland Beds became Kimmeridgian in age. In the Fairlight Borehole the transition from Kimmeridge Clay to Portland Beds spans some 15 m (from about 370.7 to 387.3 m). The boundary was taken at 373.53 m, at the base of a thin (0.15 m) argillaceous limestone below a relatively thick (2.70 m) bed of bioturbated calcareous sandstone with mudstone partings and nodular limestones, and with a fauna including Camptonectes lamellosus, Myophorella and Discinisca. The occurrence of albani Zone ammonite fragments at 368.48 m suggests that the lithostratigraphical boundary at Fairlight may coincide with the base of the Portlandian Stage. However, at Battle, the base of the Portland Beds is only 0.6 m below proven glaucolithus Zone, which suggests that the underlying uppermost Kimmeridge Clay may be of Portlandian age. No relevant material is available from the Mountfield and Brightling boreholes. BMC

Lower Cretaceous and Upper Jurassic rocks proved in trial boreholes at Dungeness

During 1983, a number of site investigation boreholes were sunk at Dungeness, on behalf of the Central Electricity Generating Board. These were cored down to depths between 120 and 250 m below the surface and proved an interesting Lower Cretaceous–Upper Jurassic sequence. The formations show a reduction in thickness, of 50 per cent or more, compared with their equivalents in the western part of the district, around Hastings, 20 km to the west.

The CEGB have kindly given permission for the following abstract of the sequence to be included in this account. The formational thicknesses are provisional, awaiting further study of the cores. The 'solid' rocks are everywhere overlain by about 40 m of Flandrian marine sediments and storm beach deposits.

In the Dungeness boreholes the Kimmeridge Clay comprised dark grey mudstones with thin calcareous beds and bands of phosphatic nodules. The Portland Beds included calcareous mudstones and siltstones with cementstones in their lower part and bioturbated shelly fine-grained sandstones above. The base of the Purbeck Beds was marked by a thin group of evaporites, equivalent to the Gypsiferous Beds Member. The rest of the Purbeck sequence included calcareous mudstones with sands and thin limestones, similar to the strata in the western part of the district. A possible representative of the Cinder Bed Member was noted about 40 m above the base of the formation. The junction with the Ashdown Beds was taken at the highest of a series of thin shelly limestones, thought to be equivalent to the Greys Limestones Member farther west. The Ashdown Beds comprised siltstones and red mottled mudstones with subordinate fine-grained sandstones. ERST

Chapter 3 Jurassic–Cretaceous: Purbeck Beds

The Purbeck Beds in the Sussex inliers are the oldest rocks to crop out in the Weald. The inliers are partly fault-bounded, horst-like structures, which mark the highest structural level within the core of the Wealden anticlinorium (Chapter 5). There are three inliers, north of Brightling [TQ 685 215], between Hollingrove and Netherfield [TQ 710 197] and near Archer Wood [TQ 750 180].

The divisions of the Purbeck Beds used in this memoir are shown with their approximate thicknesses in (Table 3), which compares them with the sequences of Howitt (1964) and Anderson and Bazley (1971).

The divisions employed here are not the same as those of the geological map (1980) but are considered to be more clearly defined than those used formerly. The new sequence is based largely on the results of two BGS cored boreholes, at Broadoak [TQ 6195 2214] about 7 km WNW of Brightling (Lake and Holliday, 1978), and at Fairlight [TQ 8592 1173] (Holliday and Shephard-Thorn, 1974). The Lulworth and Durlston beds are of formational status and were originally proposed by Casey (1963) as major divisions of the Purbeck Beds (Group). He claimed that the Cinder Bed represented a widespread marine transgression and should be a suitable horizon to take as the base of the Cretaceous in the Weald. The Cinder Bed is now given formal status as a member (Lake and Holliday, 1978). However, recent studies of the charophytes obtained from boreholes in the Weald, by Dr M. Feist of Montpelier University, indicate the presence of Globator maillardi, a Berriasian form, below this level, within the Broadoak Calcareous Member (personal communication). It follows that the location of the system boundary in the Weald is subject to review and may lie at the base of the Gypsiferous Beds Member (cf. Wimbledon and Hunt, 1983). The Ashdown Beds–Purbeck Beds boundary is now more clearly defined as the top of the lithologically distinct Greys Limestones Member. In the eastern part of the district however, at Fairlight and Dungeness, this member is not typically developed.

The Purbeck Beds consist largely of bluish grey calcareous mudstones, with minor developments of limestone, sandstone, siltstone and ironstone. Economically important evaporite deposits form the lowest (Gypsiferous Beds) member. The limestones include calcilutites and shelly calcarenites; in the past they were extensively worked for lime-burning and building-stone, as 'Blues' and 'Greys' respectively; old quarries and bell-pit scars mark the former sites of this activity and are useful in mapping the limestones in wooded country. The lowest exposed beds lie just below the horizon of the 'Blues Limestones' (in the Broadoak Calcareous Member). The sandstones occur mainly but not exclusively, below the level of the Greys Limestones Member.

Surface exposures are generally rather poor, and those in the steeply incised stream valleys have often been disturbed by valley-bulging. In addition, landslips and cambers on valley slopes also disturb the strata. For these reasons thickness measurements have come mainly from boreholes or underground sections, such as the Main Adit [TQ 7208 1943] and Goldspur Drift [TQ 7280 1895] at Mountfield mine (Howitt, 1964, pp.81–84). (Figure 4) relates the Fairlight and Broadoak borehole results to other borehole and adit sections in the district.

Gypsiferous Beds Member

The Gypsiferous Beds Member is between 16 and 20 m thick in the area of the inliers, and includes four seams of gypsum-anhydrite separated by limestone and mudstone. In detail this sequence is largely made up of sabkha cycles (Shearman, 1966) which have been described by Holliday and ShephardThorn (1974) and Holliday and Lake (1978). The basal or No. 4 seam is irregular in thickness and mineral content (Howitt, 1964, p.81) and is separated from the Portland Beds by a thin laminated silty limestone, 0.15 m thick. The thicknesses of the higher No. 3 and No. 2 seams were noted by Howitt to be about 2.4 and 1.5 m respectively. The highest, or No. 1 seam is roofed by cross-bedded siltstone with bone fragments (Howitt, 1964, pp.81–83) suggesting an erosional interval, but there is no evidence to suggest that major channelling took place. The gypsum seams are absent in places, owing to recent dissolution by meteoric waters, particularly on the north flank of the Hollingrove–Nether-field inlier, adjacent to the Mill Wood Fault. Solution voids have been seen in the No. 1 seam in Brightling Mine.

In the Broadoak Borehole, gypsum is more abundant than anhydrite and decreases in proportion downwards, apart from the No. 4 seam in which the amount of gypsum increases downwards (Holliday and Lake, 1978). In the Fairlight Borehole five seams of evaporite were intersected; the most complete gypsification was noted in the lowest beds, immediately above the water-bearing Portland Beds (Holliday and Shephard-Thorn, 1974, p.12). Howitt (1964, p.89) noted that in the mine area the No. 1 seam 'contains generally a higher proportion of gypsum to anhydrite' and that 'the gypsum-anhydrite ratio varies also with the amount of cover' thus inferring a meteoric origin for the hydrating water. Replacement of anhydrite by gypsum is, however, more complete in the mine area where it extends to depths of about 300 m, greater than at Broadoak, where it extends to 133 m or less. Celestite, calcite, chert and quartz occur in association with the gypsum-anhydrite rocks.

The other lithologies in the Gypsiferous Beds Member comprise laminated silty micritic limestones, partly of algal origin, with calcareous shaly mudstones and thin intraclast breccias. Dolomites have been recorded locally both in the limestones and in the gypsum-anhydrite rocks, in which the nodules were formed by displacement of algal-laminated sediments (Holliday and Lake, 1978). Fossil material is generally rare, although fossilised wood and bone material have been recorded in the roof shale of the No. 3 seam (Howitt 1964) and above the No. 1 seam.

Broadoak Calcareous Member

This member consists mainly of grey pyritic calcareous mudstones with subordinate limestones and is broadly equivalent to the 'Rounden Greys' and 'Blues' of earlier authors, although calcilutites of 'Blues' type also occur in the succeeding beds. In the Broadoak Borehole calcilutites are common throughout the sequence; pellet limestones and algal limestones occur in the lower beds. Shelly limestones occur in the upper 13 m, and ostracods are locally sufficiently abundant to form limestones up to 5 cm thick. Some of the lowest limestones have been previously named (Figure 4; Howitt, 1964, fig. 2). The most distinctive of these is the Mountfield Adit Limestone, an oolitic sandy limestone with a pelletal base, which lies 4.5 m above the Gypsiferous Beds Member at Broadoak. The Broakoak Calcareous Member is 56 m thick at Broadoak.

Locally cycles of the following type may be recognised:

Rootlets and drifted plant debris occur locally, particularly in the upper beds, and bioturbation is widespread throughout. The macrofauna is abundant only in the highest beds of this member. Gastropods (Hydrobia), fish remains and fragmental shell debris were noted locally in the cores of the Broadoak Borehole. Small bivalves (cf. Corbula) were recorded by Howitt (1964, p.83) in the Icehouse Limestone 4.5 m above the Mountfield Adit Limestone.

The Main Blue Limestone (of earlier authors) was noted to contain oysters (cf. Praeexogyra distorta (J. de C. Sowerby)) (Figure 4; White 1928, p.13; Howitt, 1964, fig. 3). No distinctive fauna was identified at this level in the Broadoak Borehole, and oyster debris was noted at other horizons in the Broadoak Calcareous Member from three mineral boreholes in the Hollingrove–Netherfield area (see also Morter, 1984, p.22). It thus appears that the correlation of the Main Blue Limestone is doubtful.

Plant and Bone Beds Member

This sequence comprises dominantly cyclic beds of shelly mudstones and limestones with rootlet horizons and greenish grey mudstones whose stratification has been largely destroyed by roots so that they resemble a seatearth. The last-mentioned lithology characterises this member, the base of which was taken below the lowest 'seatearth' in the Broadoak Borehole. Where complete the upward-fining cycles recognised in the Broadoak Borehole comprise the following units:

This subdivision is 14 m thick at Broadoak and the highest calcilutite which is of Blues Limestone type, occurs 10 m above the base. Howitt (1964, p.85) described comparable beds, some 19 m thick, in the Goldspur Drift, and noted abundant associated vertebrate and plant debris.

Cinder Bed Member

This member comprises a sequence of shelly mudstones and limestones, which totals 6 m in thickness in the Broadoak Borehole. The Cinder Bed 'horizon' of earlier authors has been generally recognised by the occurrence of a shell bed of Praeexogyra distorta. Morter (1984) showed that other bivalve faunal associations were present in the associated beds, which by analogy with modern faunas may reflect polyhaline to nearly euhaline depositional environments. The Cinder Bed Member thus includes the full group of shelly lithologies at this level, which represent the increased salinities associated with a marine incursion. In the Broadoak Borehole P. distorta occurs in great abundance 2.5 m below the top of the member, forming a shell bed. This oyster bed in Sussex has been correlated with the Cinder Bed of Dorset and used to support the hypothesis of a widespread, nearly fully marine incursion (Casey, 1963; Casey and Bristow, 1964).

Arenaceous Beds Member

This member is distinguished in the area of the inliers by the presence of prominent sandstones within a sequence of mudstones. Three sandstones, 1.4, 1.7 and 3.4 m thick, are present in the Broadoak Borehole (Lake and Holliday, 1978, fig. 2) and the base of the member is taken at the erosion surface below the lowest sandstone. The sandstones contain abundant plant debris, generally coarsen upwards and have eroded tops; the upper sandstones have gradational bases. Between the sandstones there are intervening mudstones and limestones that typically tend to be cyclically deposited in the following pattern:

Howitt (1964, p.90–91) described somewhat similar cycles in the Heathfield No. 7 Borehole [TQ 5860 2150] to the west of the inliers.

The member is 19.2 m thick in the Broadoak Borehole. This thickness is comparable with the estimate of Howitt (1964, p.84) making allowance for the modification of the base of the division (which gave a thickness of 16.4 m).

Greys Limestones Member

This member comprises grey shaly mudstones with shelly partings, and limestones composed of disarticulated valves of Neomiodon. The latter fossil is characteristic of this member, the base of which is taken at an erosion surface above the highest sandstone of the Arenaceous Beds Member in the Broadoak Borehole. Calcareous siltstones occur within the sequence, as do pelletal limestones which are taken to indicate internal erosional activity. Howitt (1964, p.79) recognised shales with 'beef' calcite and clay-ironstone as an individual unit at the base of the 'Greys', which Bazley (in Anderson and Bazley, 1971, p.11) included within his Upper Purbeck (Table 3). In the Broadoak Borehole, which commenced just below the mapped base of the Ashdown Beds, about 22 m of the Greys Limestones Member are present, this figure being comparable with previous authors' estimates. Bazley distinguished an upper division of his 'Upper Purbeck', consisting mainly of medium grey mudstones with subordinate silts, sandstones and nodular clay ironstones lying above his Greys Limestones. The former division, the 'upper clay', was shown to be of Upper Purbeck age whereas the Greys Limestones Member is of Middle Purbeck age (Anderson, 1985).

Thickness of Purbeck Beds

Because of the lack of a precise definition of the boundary between the Ashdown Beds and the Purbeck Beds and difficulties of correlation, varying estimates have been made of the thickness of the Purbeck Beds. In the area of the inliers Ho.witt (1964, p.85) quoted 121 m, whereas Bazley stated that a thickness of 146 m was general. A thickening of the sequence westwards to 134 m at Heathfield was noted by Howitt (1964, pp.90–91). Howitt's figures do not, however, include the upper clay unit of Bazley, which is 12 to 18 m thick. At Broadoak, the borehole proved 134 m of Purbeck Beds and the full thickness has been estimated at 137 m, without compensation for dip (Lake and Holliday, 1978).

The logs of exploratory boreholes for the gypsum mines in the Hollingrove–Netherfield area show thicknesses varying from 95 to 173 m. Clays of Fairlight Clays facies are present in the area (Howitt, 1964, p.81) and have been proved in boreholes up to 27 m thick. The misidentification of these clays, and of the Arenaceous Beds Member for basal Ashdown Beds, by the borehole-loggers, may account for the wide disparity of thicknesses recorded. If allowance is made for these errors, the thickness variation ranges from 109 to 149 m and most estimates range between 126 and 136 m which are probably typical figures. At Dungeness, trial boreholes indicated a reduced thickness of about 55 m for the Purbeck Beds (see Chapter 2).

It has been noted, however, in the Fairlight Borehole and in some mineral boreholes in the vicinity of the outcrop area, that mudstones with calcareous sandstones overlie shelly mudstones of definite Greys Limestones (Purbeck) lithology. The lithostratigraphical classification of these mudstones is in doubt. They may represent the upper clay division of Bazley, which is now regarded as a lateral variation of the Fairlight Clays facies. The present authors define the top of the Purbeck Beds at the top of the Greys Limestones Member (see (Table 3)) as proposed by Lake and Holliday (1978). RDL, ERST

Ostracod zones of the Purbeck Beds

The zonal scheme in this account is based on the distribution of species of the ostracod genus Cypridea which provide a much greater variety of forms than those of other contemporary genera. Anderson (1985; in Anderson and Bazley, 1971) reviewed the zonal schemes of earlier authors and proposed the scheme illustrated in (Table 4).

Faunal cycles

The sequence of ostracod faunas in the Purbeck and Wealden strata is characterised by repeated alternation between assemblages composed mainly of Cypridea (C phase) and others in which the dominant forms are genera other than Cypridea (S phase). In the latter assemblages a large number of genera are present, though few are represented by more than two or three species.

It is widely assumed that all the species of Cypridea lived in similar, but not necessarily identical conditions, and that the salinity of the water was one of the major factors determining their distribution. Because the Cypridea and non-Cypridea assemblages appear to be antipathetic it is also thought that the non-Cypridea species preferred conditions different to those favoured by Cypridea, this difference being one of salinity with the Cypridea favouring the less saline water. These faunal variations were probably controlled by climatic factors which resulted in alternating periods of lighter and heavier rainfall causing changes in the salinity of the water. These faunal alternations, each referred to as a faunicycle (equivalent to C + S phase), form a useful basis for correlation throughout southern England, although they may not accord precisely with the evidence of molluscs or lithostratigraphy (Morter, 1984, p.225). (Figure 5) illustrates the faunicycles found in the Broadoak and Fairlight boreholes and the Goldspur drift.

Stratigraphical correlation of the higher Purbeck Beds

The evidence from the Broadoak Borehole shows that the Greys Limestones Member is of Middle Purbeck age (cf. Anderson and Bazley, 1971, p1.1). These beds are poorly exposed and it was not previously possible to obtain micro-palaeontological samples to correlate with confidence between the faunicycles established in boreholes and the mapped subdivisions of this part of the Purbeck Beds. The new borehole data indicate that the top of the Greys Limestones Member, taken by Lake and Holliday (1978) as the lithostratigraphical top of the Purbeck Beds, approximates to the top of the Middle Purbeck as defined by ostracods (Figure 5). In the Fairlight Borehole the top of the Purbeck Beds has been taken at the top of the highest shelly mudstone (at 219.15 m), which is also close to the top of the Middle Purbeck.

The upper clay unit of the outcrop area (Table 3) which contains subordinate silts, sandstones and nodular clay-ironstones was assigned to the Upper Purbeck on ostracod evidence by Anderson and Bazley (1971, p.11). The relationship of this clay to the remainder of the sequence is not known in detail. It may have a gradational base and be genetically related to the Greys Limestones Member. Alternatively and more probably, the clay may be comparable with that proved in the Fairlight Borehole above 219.15 m and represent part of the Fairlight Clays facies, of the lower Ashdown Beds.

Lithological sequence in the Fairlight Borehole

(Figure 4) shows a skeleton log of the Fairlight Borehole, the detailed record being available on open file at BGS. Shephard-Thorn (in IGS, 1971, p.22) gave a provisional summary of the Purbeck Beds in the borehole and Holliday and Shephard-Thorn (1974) described the evaporite beds. A comparison was made between the Broadoak and Fairlight sequences by Lake and Holliday (1978). The sequence in the Fairlight Borehole differs significantly from that at outcrop. The beds down to 238.18 m depth are dominantly shelly and may be regarded as broadly equivalent to the Greys Limestones Member, although the cyclicity of bedding noted at Fairlight is absent in the Broadoak Borehole sequence. The presence of 'seatearths' and channels at Fairlight indicates a depositional environment near the margin of the main basin.

There are no cyclic beds with sandstones strictly comparable with those of the Arenaceous Beds Member although a thin sandy siltstone at 250.88 m might be the nearest equivalent. The cyclic beds below the Greys Limestones Member are however similar to those which occur within the Arenaceous Beds at Broadoak although the limestone unit is replaced by a calcareous siltstone at Fairlight. It is probable therefore that the sequence at Fairlight is a facies variant of both the Greys Limestones and Arenaceous Beds members of the outcrop area, with significantly less sandstone.

At Fairlight the Cinder Bed, Plant and Bone Beds and Broadoak Calcareous members are similar to their equivalents in the outcrop areas. Thin limestones at 278.64 and 315.85 m in the Fairlight Borehole may correlate with the Eight-foot Grey and Mountfield Adit limestones respectively.

The Gypsiferous Beds Member at Fairlight comprises five seams of evaporite, named A to E, in contrast to the four present at outcrop. The sequence at Fairlight is thicker with a greater proportion of carbonate rocks, with more and generally thinner, sabkha cycles and with a greater thickness of 'non-sabkha' measures (Holliday and Shephard-Thorn, 1974; Holliday and Lake, 1978). The latter authors discussed the correlation of the seams and suggested that greater differential subsidence and more marked lateral facies changes are indicated in the Fairlight area at the end of Gypsiferous Beds times, accounting for the presence of the additional seam (A). RDL, ERST, AAM

Details of surface exposures

Only the more important surface exposures are briefly described below.

Brightling

Shelly limestones up to 0.3 m thick are exposed [TQ 6805 2146] north of Icehouse Wood. These beds occur in the lower part of the Broadoak Calcareous Member. Howitt (1964, p.83) described a crystalline limestone with small thin-shelled bivalves and ostracods which 'crops out in a stream having its source in Icehouse Wood [TQ 6812 2157]'. He termed this bed the Icehouse Limestone. The 'Blues Limestones' are well exposed along a path cut for the cableway linking the Mountfield and Brightling gypsum mines. One limestone in the middle of this sequence [TQ 6843 2152] contains fine layers at the top that are full of Chara stems and gyrogonites.

Hollingrove–Netherfield

Strata above the worked Greys Limestones, including some now grouped with the Ashdown Beds are exposed in the Darwell Stream [TQ 6958 2004] as follows:

Thickness m

Ashdown Beds: mudstones, nodular clay-ironstones and sandstones

1.77

Purbeck Beds (Greys Limestones Member): mudstones, clay-ironstones and thin limestone

2.31

In Darwell Wood the 'Blues Limestones' are exposed [TQ 7073 2011] and there are many small outcrops of beds from higher in the Purbeck in forestry drives and streams. North of Netherfield in the River Line, there are exposures of various parts of the Purbeck Beds. The Cinder Bed Member was proved at one locality [TQ 7159 1908] where the downward sequence is: mudstone 1.2 m; shelly limestone 0.28 m; shelly mudstone 0.9 m.

Sections described by Howitt (1964) from the River Line, where it passes through Limekiln Wood north-east of the Sub-Wealden borehole site are no longer visible. To the south-west of the mine Howitt (1964, fig. 4) described the discontinuous section in the stream bed from the upper 'Blues Limestones' to the 'Greys Limestones', which showed typical lithologies including the 'Main Blue Limestone'. RDL, RABB, AAM

Chapter 4 Lower Cretaceous: Wealden

Introduction

The Wealden Series includes a sequence of mudstones, siltstones and sandstones which lie between the Purbeck Beds and the Lower Greensand of the Weald, and these strata have been stratigraphically divided into the Hastings Beds and the Weald Clay. Within the Hastings and Dungeness district, outside of the Purbeck inliers, almost all of the ground west of Rye and Winchelsea is covered by the outcrops of the Hastings Beds and there is only a very restricted outcrop of the Weald Clay near Cooden.

The series is classified into mainly muddy or sandy divisions as follows:

Weald Clay

up to 14 m (in district)

Tunbridge Wells Sand

up to 110 m

Wadhurst Clay

15 to 60 m

Hastings Beds

Ashdown Beds (mainly sandy with local clay facies: 'Fairlight Clays')

115 to 215 m

The total thickness of the Hastings Beds is about 380 m at outcrop in the western part of the district. In the east, at Dungeness, a reduced thickness of only about 165 m was indicated by trial boreholes (Table 2).

The common lithologies of the Hastings Beds are fine-grained sandstones, siltstones, silty mudstones and mud-stones, with subordinate thin shelly limestones and bands of nodular clay-ironstone; silts predominate overall. Elsewhere in the Weald the Tunbridge Wells Sand has been separated into upper and lower divisions by the presence of the Grinstead Clay, but this does not occur within the present district where the Tunbridge Wells Sand is not divided. It does however locally contain red-mottled silty clays some of which may equate approximately to the Grinstead Clay.

It is thought that the Wealden sediments were deposited in predominantly freshwater environments in a large 'lake' or 'lagoon' that occupied much of the present Hampshire Basin and Wealden areas and extended eastwards into the Paris Basin. The sediments were mainly derived from source areas in the London–Brabant massif to the north and Cornubia to the west, but there is also evidence for a southerly derivation of certain strata. The thicker sandy units are attributed to influxes of clastic sediment, possibly consequent on rejuvenation of the source areas by block-faulting. Most of the clay rocks were laid down in distal environments including bays and lagoons, but some were deposited in more proximal fluvial overbank environments.

Allen (1949a, 1959) recognised large-scale cyclical sedimentation within the Hastings Beds and originally suggested that the siltstone–sandstone bodies within them were deposited in a series of prograding deltas, in which the following typical cyclothem is repeated several times:

The red-mottled clays are taken to indicate periodic emergent conditions, which led to the partial oxidation of the clays and the development of soil profiles and sphaerosiderite. The red-mottled clays which occur within the Ashdown Beds and Tunbridge Wells Sand differ, both in their scale of development and in the presence of sphaerosiderite, from those present at the top of argillaceous formations, which are thin and generally lack sphaerosiderite. The sphaerosiderite occurs as radially crystalline spheres, about 1 mm in diameter, commonly intimately associated with fossil root traces, in rocks which closely resemble Coal Measures seatearths. These rocks probably represent the development of plant communities and soil profiles on over-bank alluvial deposits (Unit 1), but very rarely show any trace of a coal or similar organic deposit above the root horizon.

The massive sandstones (Unit 3) are typified by the Top Ashdown Sandstone and the overlying pebble beds (Unit 4) are taken to represent significant transgressive episodes. Allen (1959) recognised three major cyclothems in the Wealden Series, essentially pairs of sandy and muddy formations. These comprised the Ashdown Beds and Wadhurst Clay; the Lower Tunbridge Wells Sand and Grinstead Clay and the Upper Tunbridge Wells Sand and Weald Clay. He later (1976) discarded his deltaic model in favour of a fluvial one in which alluvial and lagoonal mudplains were periodically invaded by sandy sheets laid down by braided rivers. In the new model each 'megacycle' is taken to represent a pulse of increasing stream energy caused by periodic uplift and subsequently, 'the mud-swamp regime re-asserted itself, once more with tenuous marine connections and/or sensitivity to evaporation'. Brackish-water faunas within the sequence, such as those which characterise the Wadhurst Clay, reflect periods of reduced run-off and the consequent flow of saline water into the basin.

Allen (1981) subsequently modified his fluvial model by envisaging a proximal fan-apex zone, a medial braid-plain zone, a distal meander-plain zone, with similar inter-fan areas, and a basinal pro-fan zone of lagoons and bays.

Stewart (1981, 1983) suggested that some of the major siltstone-sandstone bodies were formed by lateral accretion as major channels migrated. Smaller-scale sand bodies represent minor point-bar sequences and alternate with overbank clays that were partially oxidised during periods of low water-table. Stewart's fluvial model involves much lower stream energies than Allen's and envisages meandering, rather than braided, streams with high suspended loads.

The environments of the source areas of Purbeck–Wealden rocks were studied by Sladen and Batten (1984), using clay mineralogy and palynology. They suggested that the more arenaceous episodes, typified by the upper Ashdown Beds and Lower Tunbridge Wells Sand, represent periods of relatively high rainfall, with acidic leaching of soils and weathering profiles, linked to uplift of the source areas. The thick clay formations, including much of the Purbeck Beds, 'Fairlight Clays' facies, Wadhurst Clay and Grinstead Clay represent periods of low rainfall when more alkaline soil profiles were developed.

In the course of the recent survey some exposures formerly described by White (1928) were placed in revised stratigraphical context, where necessary. Similarly the list of fossils given by White (1928, pp. 72–75), is now regarded as being stratigraphically in error. ERST, RDL

Faunas

Ostracod zones

Ostracods are the most abundant fossils in the Wealden and are present in sufficient diversity of form for them to be used as a basis for the biostratigraphical division of the Wealden. The ostracod genus Cypridea, which probably lived by preference under mixohaline conditions, includes a large number of species and subspecies and is ideally suited for use in the division of the succession. The ostracod faunas show a salinity-controlled cyclicity comparable with that in the Purbeck Beds (p.14) with alternating low salinity faunas, dominated by Cypridea species (C phases) and higher salinity forms (S phases). One C phase with its succeeding S phase constitutes a faunicycle (Anderson and Bazley, 1971).

The ostracod zones listed below are all characterised by assemblages of species of the genus Cypridea (Table 5).

In the C. paulsgrovensis Zone few species are represented, although individuals may be numerous. Apart from the name fossil only C. laevigata and C. tuberculata are common.

The C. aculeata Zone contains an ostracod fauna richer and more varied than any other part of the Wealden. The name fossil itself is a variable species and together with C. bispinosa dominates the fauna. Two other distinctive species C. recta and C. melvillei, are characteristic of the zone. In the Wadhurst Clay, the S-phase forms include species of Darwinula, Mantelliana, Orthonotacythere, Rhinocypris, Theriosynoecum and Timiriasevia. FWA

Detailed information on the Wealden faunas has been provided by Anderson (1962, 1967, 1985) and Anderson, Bazley and Shephard-Thorn (1967). The late Dr Anderson's results on material from the BGS Cooden Borehole are described in more detail by Lake (1975). RDL

Molluscan faunas

Bivalves and gastropods occur commonly in the Wealden clay formations, locally in sufficient numbers to form thin monospecific shell limestones, such as the 'Paludina'- limestones of the Weald Clay. They are generally rare in the sandy formations.

The shells collected by Mantell and Fitton in the early nineteenth century were first described by J. Sowerby (1812), J. de C. Sowerby (in Fitton, 1836) and Forbes (1851). Subsequently the bivalve families Corbiculidae and Neomiodontidae were reviewed by Casey (1955a, 1955b). The mollusca of the Weald Clay were studied by Morter (in Worssam, 1978) who also (1984) re-examined the PurbeckWealden molluscan faunas and related them to various salinity ranges.

Wealden vertebrates

Bones and teeth of reptileans, mammals and fish, have been collected from the Wealden rocks of the Hastings district. They are most common in the clay formations, concentrated in one of the several thin 'bone-beds' and associated with developments of calcareous 'Tilgate Stone' (p.27). The Cliff End Bone-Bed, of the lower Wadhurst Clay (p.67), has its type exposure in the present district, and is noteworthy as the source of some of the earliest Cretaceous mammalian remains (A.S. Woodward, 1911; Clemens, 1963; Clemens and Lees, 1971).

Saurian footprints

Fossil footprints, believed to be those of Iguanodon and related forms, were first recorded over a century ago, when their true affinity was not recognised. A review of these occurrences and their descriptions in the literature was given by Sarjeant (1974). The footprints are usually preserved as casts of sandstone or siltstone, overlying the mudstone in which the prints were initially made, and are thus commonly seen on the undersides of fallen or overhanging blocks in coast sections. Although these fossils have little stratigraphical value, they indicate shallow water conditions succeeded by rapid deposition of the overlying sand or silt which assured their preservation as casts.

Most of the footprints are large three-toed casts from 0.4 to 0.6 m from toe to heel (Plate 2), but a number of smaller casts of 0.2 to 0.3 m length were noted in the present survey. Some of these may represent juvenile Iguanodon, but others may relate to smaller genera whose affinities have not yet been resolved.

The first published record of a footprint found in the district was in 1846 when Taggart presented a specimen to the Geological Society of London. Footprints discovered in the Bexhill area were described by Beckles (1854, pp.456–462) and Tylor (1862) summarised these finds in a description of the footprints found in fallen rock-masses west of Ecclesbourne Glen. In 1978 saurian footprints were rediscovered in the sandstone reefs on the foreshore at Bexhill [TQ 7446 0705], below Channel View. It is probable that one of Beckles' sites lies between the recent foreshore example, noted above, and the former cliff at the site of the present day De La Warr Pavilion [TQ 741 071]. Beckles' second locality, 'half a mile to the west of Bexhill opposite to the [Martello] Tower No. 47' about [TQ 738 070], showed widely distributed impressions. These two occurrences lie within the middle part of the Tunbridge Wells Sand, above the red mottled clays. The other series of footprints, recorded by Beckles to the west of Tower No. 49 about [TQ 7095 0640] were in the Weald Clay and those to the 'west of Galley Hill' (probably at Little Galley Hill [TQ 767 079], see White (1928, p.49), were in the Ashdown Beds (pp.61–62).

In the cliffs east of Hastings several other occurrences of fossil footprints have been noted in Ashdown Beds strata. Near Lee Ness Ledge [TQ 867 108], casts of three-toed footprints of Iguanodon, up to 0.5 m in length, are commonly observed on the lower surface of the Lee Ness Sandstone (p.65) in cliff overhangs and on fallen blocks. The prints az e preserved as sandstone casts. Series of up to 5 or 6 'steps' have been noted on fallen blocks. The Lee Ness Sandstone footprints are presumably the same as those referred to by Dixon (1850, p.145). Smaller three-toed prints have also been noted on fallen blocks of sandstone and siltstone near Goldbury Point [TQ 877 114]. RDL, ERST

Stratigraphy

Ashdown Beds

The Ashdown Beds comprise sandstones, siltstones and mudstones with subordinate lenticular beds of lignite, sideritic mudstone and sphaerosiderite nodules. Although siltstones dominate the sequence in the east of the district, an upper sandy division about 30 to 50 m thick can be distinguished from the more argillaceous beds which make up the rest of formation and are locally red-mottled. These two divisions, the Ashdown Sands and Fairlight Clays of early authors, have a total thickness of between 180 and 215 m, although there is a marked attenuation immediately south-west of the district (Lake and others, 1987) and at Dungeness, where a thickness of about 115 m was proved in trial boreholes. The base of the Ashdown Beds has been taken at the top of the Greys Limestones Member of the Purbeck Beds. At the junction with the overlying Wadhurst Clay a massive sandstone is generally, but not invariably, present. This is the Top Ashdown Sandstone (Allen, 1949a) which is up to 10 m thick. The overlying Top Ashdown Pebble Bed is taken as the basal bed of the Wadhurst Clay although locally the boundary may be more complex.

Although the formation has an extensive outcrop in the Hastings district it is not possible to determine the full succession at any one locality. In the coast-section, east of Hastings the top 130 m are exposed, down to just below the Lee Ness Sandstone. Inland, the basal beds surround the Purbeck inliers, but elsewhere less than 100 m of the upper beds are typically present at outcrop. The BGS Fairlight Borehole [TQ 8592 1173] (Figure 6) provided a fully cored sequence of the Ashdown Beds, but the logs of previous deep boreholes tend to be unreliable because the silty lithologies were not distinguished by the drillers and were often erroneously classified as clays because of their plasticity in the wet state. BGS boreholes at Cooden, Icklesham, Little Maxfield and Westfield (Figure 6) provided additional cored sequences of the upper part of the Ashdown Beds.

With the exception of plant and fish detritus and root traces, fossils are generally extremely rare. An ostracod horizon has been recognised in boreholes about 60 m below the top of the formation and estheriids occur at certain levels. Saurian footprints have been observed on the lower surface of the Lee Ness Sandstone and at other levels in the lower exposed part of the Ashdown Beds (Sarjeant, 1974). Well preserved plant fossils have been collected from the 'Fairlight Clays' in the past and are found in several museum collections (Watson, 1969; Hughes, 1976). Batten (1969, 1976) and Hughes (1955, 1958) have also published studies of Wealden plant spores.

Sedimentary facies

Sedimentary facies were best studied in cored boreholes (Figure 6) or on the excellent coast sections. In the inland areas where exposures are generally poor, it was difficult to relate the evidence from restricted exposures to sedimentary facies with confidence. For example, coarsening-upward sequences were believed to be present in the Westfield area, but locally it proved difficult to distinguish this style of sedimentation from that present at the Ashdown Beds–Wadhurst Clay boundary. Further difficulties were experienced with some of the clays in the upper Ashdown Beds which superficially resemble the Wadhurst Clay in the weathered state; typically the mudstones of the Ashdown Beds weather to ochreous and pale grey mottled silty clays and are readily distinguished from the khaki or greenish grey clays of the Wadhurst Clay.

Channel-fill deposits

Broad flat-bottomed channels occur at several horizons in the Ashdown Beds of the Hastings–Cliff End coast section (Appendix 1). The channels are typically floored with a mud-flake conglomerate, consisting of shards of ferruginous mudstone and siltstone with plant detritus and rare bones, and with a matrix of variable grain-size. Where sand predominates, large-scale cross-beds are present whereas rhythmic alternations in grain-size characterise the finer-grained in-fills which commonly contain abundant comminuted plant detritus. The largest example [TQ 882 122] near Haddock's Cottages (Plate 3) was described by Allen (1962, p.221; 1976, p.394) and Stewart (1983, fig. 4, p.375). Local examples of dewatering structures suggest intervals of rapid sedimentation.

Coarsening-upward sequences

These sequences are 3 to 6 m thick and have been identified in borehole cores and exceptionally in coast sections. Characteristically the following lithologies are present in descending order:

The siltstone unit may alternatively comprise rhythmic alternations of dark silty mudstones and siltstones, giving a striped appearance. Although the evidence is limited it is possible that these cycles may persist laterally over some distance (Lake and Young, 1978 p.15).

Coarsening-upward sandstones

This facies is comparable to but coarser-grained than that above and units (i) and (ii) are condensed or absent. The sandstones contain increased amounts of argillaceous material downward and are capped with a pebble bed or are coarse grained towards their tops. These beds are laterally persistent and sheet-like and are characterised by the Top Ashdown Sandstone.

Red-mottled argillaceous beds

The clays of the lower part of the Ashdown Beds, the Fairlight Clays of early authors, typically show colour mottling in shades of grey, green, red, brown, yellow and purple. In borehole cores the mottling is locally vertically aligned, suggesting association with root formation. Sphaerosiderite, which is abundant in this lithology is scattered unevenly and is commonly associated with roots or forms ovoid aggregates up to 0.3 m in diameter.

Comparison with similar lithologies in the Tunbridge Wells Sand, suggests that the colour mottling of argillaceous beds is probably laterally impersistent and they may pass into grey beds

Correlation of the upper Ashdown Beds

(Figure 6) illustrates the sequence in the upper Ashdown Beds as seen in cored boreholes at Glynleigh [TQ 6085 0637] (on Sheet 319), Penhurst [TQ 7050 1634], Westfield [TQ 8204 1614], Little Maxfield [TQ 8414 1532], Icklesham [TQ 8763 1586] and Fairlight [TQ 8592 1173].

Although many of the variations in grain-size of these rocks are oscillatory, distinct coarsening-upwards and fining-upwards sequences were recognised in places. The fining-upward sequences were generally associated with channel fills. Rootlet beds, green mudstones and red-mottled beds are grouped together in this diagram because they appear to pass into each other in some cases.

A tentative correlation is made between six of the borehole sequences in (Figure 6) which show an overall tendency to coarsen upwards to a level, approximately 25 m below the top of the Ashdown Beds, above which finer-grained sediments recur. The higher strata show a progressive tendency to coarsen upwards and within these beds coarsening-upwards cycles culminate in the Top Ashdown Sandstone; bivalves occur near the base of the upper beds in the Icklesham Borehole.

The Ashdown Beds–Wadhurst Clay transition

Elsewhere in the Weald this boundary is typically sharply defined and broadly shows the sequence described by Allen (1959) (see p.18), but in the Hastings district several differing sequences have been observed as follows:

  1. The succession follows the sequence shown on p.18 although the Top Ashdown Pebble Bed is locally absent, e.g. in the north-west of the district.
  2. The sequence is gradational and comprises a passage series of medium-grained sands with interbedded clays, e.g. in the south-west of the area where the Ashdown Beds are concealed by younger strata (Lake and Young, 1978, pp.14–15).
  3. The sequence is modified by secondary channel-structures which cut down into the Top Ashdown Sandstone, e.g. in the Baldslow (Hastings) area.
  4. The sequence is repeated in the Cliff End Sandstone 'microcyclothem' as follows (downward sequence): laminated silty mudstone; Cliff End Sandstone, fine-grained massive rooty sandstone, locally with a top pebble bed, gradational or sharp base, up to 10 m; laminated silty mudstone with a siderite nodule horizon, formerly termed 'Endogenites' Beds, up to 3 m; Top Ashdown Sandstone, massive fine-grained sandstone locally with a top pebble bed, up to 10 m. This succession is present in the coast-section between Hastings and Cliff End, and in the immediate hinterland.
  5. The sequence is modified by the presence of more than one coarsening-upward sequence in the Top Ashdown Sandstone.

These variations may reflect the pulsatory nature of the Wadhurst Clay transgression which was modified by the development of channels and perhaps sand-bars. Near the margins of the basin, changes of base-level would have caused significant alterations in the palaeogeography and in the balance between the sediment influx and the rate of deposition.

The base of the Wadhurst Clay is generally taken at the base of the Top Ashdown Pebble Bed. In sections where this pebble bed is absent, a rippled surface, without pebbles, caps a massive sandstone which may contain one or more pebbly layers. In these instances the base of the Wadhurst Clay has been drawn at the rippled surface.

The coast section

The Ashdown Beds are well exposed in the cliffs east of Bexhill and between Hastings and Cliff End which are detailed in Appendix 1. A generalised stratigraphical sequence for the coast sections is given in (Figure 7), while the broad relationships of the rocks in the cliffs east of Hastings are illustrated by sketch sections in (Figure 8). Comparative sections in the Ashdown Beds exposed in the cliffs between East Cliff, Hastings and Ecclesbourne Glen are shown in (Figure 9). Other detailed sections are illustrated by (Figure 22), (Figure 23), (Figure 24), (Figure 25), in Appendix 1.

Ashdown Beds in the Fairlight Borehole

A brief description of the BGS Fairlight Borehole [TQ 8592 1173] was given by Shephard-Thorn (in IGS, 1971, pp.21–22). The complete record of the hole is available on open file at BGS.

The Ashdown Beds between 212.52 and 219.15 m (the top of the Purbeck Beds) comprise alternating sandstones and mudstones. In the mudstones above, to a depth of 202.79 m, two sandstones occur which form parts of coarsening-upward cycles similar to those in the Arenaceous Beds of the Purbeck, but rooty mudstones cap each sandstone and a shelly fauna is absent. Fine-grained sediments dominate the sequence above up to 130 m where sandy, muddy siltstones occur (below 118.78 m). Siltstones and mudstones predominate again in the beds above but sandstones are more common in the uppermost 35 m of the Ashdown Beds, above 42.27 m.

Most of the mudstones below 42 m tend to be olive or greenish grey, massive and uniform in appearance and are of the seatearth' type but commonly lacking rootlet traces. Laminated mudstones only occur in association with coarser sediments except below 163 m where they are more common and some of these show bioturbation structures. Sphaerosiderite is common throughout the formation, especially in the argillaceous beds. Sideritic nodules and replacive beds occur locally below 114 m depth and are particularly common in the argillaceous beds below 180 m.

Few useful marker horizons can be recognised in the sequence proved by this borehole, although the Lee Ness Sandstone may be represented by the beds above 130 m. RDL, ER ST

Wadhurst Clay

The Wadhurst Clay comprises mainly grey mudstone which weathers at the surface to heavy, ochreous-mottled, greenish grey and khaki clays. Kaolinite, illite and smectitevermiculite are the chief constituents of the clay rocks. Subordinate lithologies include sandstone, siltstone (commonly interlaminated with the mudstone), conglomerate, clay-ironstone (siderite mudstone) and shelly limestone. Locally, arenaceous beds may be calcite-cemented forming hard, bluish grey calcareous 'doggers' and beds termed 'Tilgate Stone' (White, 1928, pp. 24–25). These are often variably decalcified to ochreous rottenstone sometimes leaving a core of calcareous material.

The Wadhurst Clay has an extensive outcrop, particularly in the central part of the district. The thickness varies from 30 m in the Lewes district to the west (Glynleigh Borehole), to around 40 m near Bexhill and Battle and up to 53 m at Westfield. Around Peasmarsh (Tenterden district), north of Rye, the Wadhurst Clay is up to 46 m thick (ShephardThorn and others, 1966, p.58) but at Dungeness the thickness proved in trial boreholes is approximately 15 m.

The basal beds are commonly exposed in sand pits which worked the Top Ashdown Sandstone beneath. Above the Top Ashdown Pebble Bed, (a pebbly sandstone which is taken here as the base of the Wadhurst Clay) interbedded siltstones and clays pass upwards into a soil bed with roots and rhizomes of the horsetail, Equisetites lyelli (Mantell), in the position of growth. Shell beds with Neomiodon medius (J. de C. Sowerby) ('Cyrena'), succeed the thin dark clays above the soil bed. The soil bed which has been termed the Brede E. lyelli Soil Bed (Allen, 1941; 1947), is generally the best preserved although other soil beds and their associated rootlet horizons occur widely throughout the formation. The above sequence, which is typical of most of the Weald, is present in the northern part of the district. In the south-east, especially in the coastal area east of Hastings, the prominent Cliff End Sandstone, up to 10 m thick, occurs in the lower beds and is often only separated from the Ashdown Beds by a metre or so of shales with ironstone. Locally the Cliff End Sandstone is capped by a thin rippled bed of pebbly sand, the Top Cliff End Pebble Bed, which is analagous to the Top Ashdown Pebble Bed, though of limited lateral extent.

In the western part of the district, between Penhurst and Bexhill, where the full succession is preserved, the Wadhurst Clay contains only one fairly persistent sandstone marker, the Northiam Sandstone, about 10 m below the top of the formation. In the eastern parts of the district the succession is rarely complete because of erosion, and is also much disturbed by faulting.

Cored boreholes in the Lewes and Hastings districts have shown, however, that the mudstone lithologies may be split into broad lithological divisions (Lake and Young, 1978) as follows (Figure 10) and (Figure 11): 5 Green or red and green mottled mudstones

Divisions 1 and 2 approximately follow the basal sequence outlined by Allen (1959; see p.18). Division 3 typically demonstrates the following lithologies:

The greenish grey mudstones are often thinner than the lower units and may be locally absent. This division is, however, notable for the number of erosion surfaces present (below the lowest unit) and reflects more variable conditions within the basin of deposition.

In the Hastings and Dungeness district the basal conglomeratic horizon of division 4 is a calcareous sandstone with bone debris, ironstone pebbles and mudstone pellets and has been correlated with the top of the Northiam Sandstone (see below). The red and green mottled mudstones of division 5 weather to a uniform dark red colour and form a useful horizon for mapping purposes. The red beds occur close to, but not necessarily immediately below, the base of the Tunbridge Wells Sand, which is taken at the bottom of the overlying silty beds.

Minor lithologies within the Wadhurst Clay

Sandstone beds

The presence of extensive sandstones within the Wadhurst Clay is confined mainly to the Hastings district and its immediate environs. These beds comprise fine-grained sandstones, with subordinate siltstones, often poorly cemented and commonly with winnowed bivalve shells. Locally, however, a secondary calcite cement may be present, particularly in the thinner beds. The carbonate material was apparently derived from the adjacent mud-stones (and perhaps also from the solution of bivalve shells within the sandstones) and may be only patchily developed, for example, between joint surfaces. Relatively recent weathering processes have caused the decalcification of the cemented lithologies near the surface: this phenomenon has imparted a 'gingerbread' texture to the weathered zones.

Locally these beds are massive and well jointed, particularly where a calcite cement is present; in many cases however, the sandstones show thin planar bedding or festoon cross-bedding structures. Some examples show a tendency to coarsen upwards, others show a lack of grading features and may have erosional bases. In places pellet beds or pebble beds may be present, particularly at the top of the Coarsening-upward examples.

When traced laterally some sandstones show a remarkable persistency and sheet-like form; others are less persistent and apparently show considerable variations in thickness although the structural complexities of the outcrop area do not always permit definite correlations to be made.

Conglomerates and 'bone-beds'

The presence of pebble beds, pellet beds (mud-flake conglomerates) and erosional surfaces associated with sandstone bodies has been noted above. Other coarse-grained beds occur within the Wadhurst Clay and have been termed 'bone-beds' by Allen (19496) because they contain vertebrate fragments. These beds are typically poorly sorted, with abundant fish and reptile fragments and broken mollusc material. The larger organic fragments may lie at high angles to the bedding (Allen, 19496, p.278).

Allen distinguished two main lithologies, one of lenticular muddy sand, the other of cross-bedded conglomerate or sandstone with quartz and chert pebbles, and slightly abraded fragments of siderite mudstone. The latter type commonly rests with an irregular base on sandstone, and calcite cement is present locally throughout. A third variety noted by Allen (1949b, p.282) comprises a mud-flake conglomerate set in a clay or siltstone matrix.

The first type is represented only by the Brede Bone-Bed and occurs in the basal beds of the Wadhurst Clay, whereas the second (the Cliff End or Telham Bone-Bed) lies within shales above the Cliff End Sandstone or on top of the main 'Tilgate Stone' horizon. These latter are not necessarily equivalent beds (see (Figure 10)).

It is necessary in this context to distinguish intraconglomeratic horizons from other 'bone-beds' since vertebrate material is relatively common in the Wadhurst Clay generally, and its presence is not of necessity sedimentologically significant. It is probable that only the pebbly variety is of strati-graphical importance since this reflects a high energy environment of deposition. The bone-beds have a limited distribution, being confined to the extreme eastern part of Sussex and adjacent parts of Kent (Allen 1949b, fig. 45).

Sideritic mudstones (clay-ironstones)

Siderite is present as relatively thin nodular or tabular bands throughout the formation, and formerly provided an important source of iron ore for the Wealden iron industry. The thickest and historically most important ores occur in the basal beds of the Wadhurst Clay. Bell-pit scars in woodland commonly indicate the site of former mining for ore. The siderite occurs as an early diagenetic replacement in mudstones and shelly limestones. Conglomerates within the Wadhurst Clay contain significant amounts of sideritic material. In borehole cores siderite nodules and associated mudstones show penecontemporaneous deformation structures and a tendency to be nucleated around rootlet traces. This suggests a strong genetic link with biochemical precipitation processes. The ironstone seems to have formed penecontemporaneously at or just below the sediment-water interface. Bivalve and ostracod shells preserved in ironstone have usually escaped the flattening generally found in mudstones, which supports the idea of syndepositional formation of the ironstone.

Shelly limestones

Shelly detritus is common throughout the formation and consists mainly of disarticulated or fragmented valves of the bivalve Neomiodon. sp.The mode of preservation suggests that much of the shell material was subject to current-winnowing prior to deposition. Less commonly the gastropod Viviparus. sp.is present at discrete levels. Locally the shell-beds are thick enough to form limestones which may be laterally persistent for some tens of metres.

The shell beds are in places interbedded with calcareous siltstones. This lithology is more resistant to weathering processes and is therefore commonly found in the surface brash.

Stratigraphical correlation

The presence of thick sandstones in the Wadhurst Clay and the structural complexity of the central area make the correlation of individual lithological markers difficult. Allen (1976, fig. 2) summarised the lithological variations of the Wadhurst Clay and formalised certain stratigraphical members, drawing much of his information from the south-east Weald. The persistence of some of the subdivisions, particularly the soil beds, is uncertain and the interrelationship of the sandstones and associated bone-beds is also somewhat conjectural. In the eastern part of the Hastings district where the Tunbridge Wells Sand has been removed by erosion, it is not possible to evaluate the full succession.

There does appear to be a correlation between the broad lithological divisions (1–5) (Figure 10) and (Figure 11) and the micropalaeontological zonation based on ostracods (see p.19). In particular the base of division 3 lies generally at about the level of the Kingsclere faunicycle and the base of division 4 lies in or immediately above the Lindfield faunicycle (Anderson, 1985).

The following members were recognised by Allen (1976, fig. 2) in ascending order above the Top Ashdown Pebble Bed:

  1. Brede Bone-Bed. This was noted to comprise (Allen, 1949b, p.277) thin lenticles of buff sand which were also markedly transgressive. But for this last fact, the significance of this horizon would be in some doubt since the bed lies within the lowest metre of the formation, within the passage series, and may therefore reflect localised concentrations of bone material in a varying environment.
  2. Brede Soil Bed. Allen (1976, appendix I) described this horizon as 'Weald-wide' and occurring in silts or lenticular siltstones and clays ('passage beds'). The distribution of localities in the south-east Weald was figured by Allen (1947, fig. 55) where the soil bed represents an in-situ community. In the coastal area between Hastings and Rye however, the typical 'stem and rhizome-bearing layer has not been recognised and only occasional rootlets bear local testimony to its former presence' (see Allen 1947, appendix 2). This bed typically occurs 0.4 to 1.0 m above the Top Ashdown Pebble Bed.
  3. Cliff End Sand Member (Cliff End Sandstone of this account). This comprises massive sandstone, up to 10 m thick and of apparently sheet-like form, which is exposed in the cliffs between Hastings and Rye and crops out extensively in their immediate hinterland. Prior to the present survey, this sandstone was erroneously taken to be the top of the Ashdown Beds. The discovery of basal Wadhurst Clay ostracod faunas in the underlying shales with ironstone ('Endogenites' Beds of old authors) has clearly demonstrated that the sandstone forms part of the Wadhurst Clay formation (p.70). The top of the sandstone is commonly purplish in colour due to the presence of finely divided organic material; long slender hollow stems with lateral rootlets have been seen to extend downwards for 4 m or more. This association represents the Fairlight Soil Bed (Allen, 1976, appendix 1). Locally, as for example at High Wickham [TQ 8296 0999] and in former quarries near Fairlight Church, a pebble bed caps this member (here called the Top Cliff End Pebble Bed). To the north and west of Hastings a calcareous sandstone is present at about the same stratigraphical level, but it is characterised by festoon cross-bedding structures and an apparently erosional base and thus may not be strictly equivalent to the Cliff End Sandstone. On the other hand it may represent a different facies of the same age.
  4. Cliff End Pebble (Bone) Bed. (Cliff End Bone-Bed of this account). This bed is present in the cliffs at Cliff End [TQ 887 128] 2.5 m above the Cliff End Sandstone and has also been noted near Guestling and at Rye. It is noteworthy for containing mammalian remains (Clemens, 1963; Clemens and Lees, 1971) in addition to abundant reptilian bone fragments and fish remains.
  5. Telham Pebble (Bone) Bed. Allen (1976, fig. 2) was uncertain as to the stratigraphical level of this bed and its relationship to the Cliff End horizon. He listed a number of localities for this horizon (1949b, p.279) which overlies the main 'Tilgate Stone' horizon. A bone-bed at Maplehurst Wood [TQ 8100 1307] probably lies at a similar level but within shaly clays. It is probable that the Telham Pebble (Bone) Bed which lies 6 to 10 m above the Top Ashdown Pebble Bed is the same as the Cliff End horizon although the sandstones below are not strictly equivalent.
  6. Hog Hill Sand Member. This sandstone was formerly confused with the Cliff End Sandstone (Allen, 1959, pp.296–297; Shephard-Thorn and others 1966, fig. 6). At Hog Hill [TQ 889 157] the base of this sandstone, which is up to 8 m thick, lies some 25 m above the Top Ashdown Sandstone and 15 m above the Cliff End Sandstone. The base of this unit is however irregular in nature, suggesting the presence of channel-structures and it is not possible to correlate this sandstone confidently with those present at about this level farther west.
  7. Northiam Sand Member (Northiam Sandstone of this account). This sandstone was originally described, though not named, by Shephard-Thorn and others (1966, pp.46–47) in the Northiam and Tenterden areas to the north of the present district. A pebble bed and a soil bed overlie this unit at Northiam. In the Hastings district an extensive sandstone body is present at a comparable level about 10 m below the base of the Tunbridge Wells Sand and up to 7 m thick. It has a sheet-like form, coarsens upwards and is capped, locally at least, by a pebbly pellet bed. The pebbly horizon has been correlated with a conglomeratic horizon in the area to the west of the district and this separates divisions 3 and 4.

Because of the uncertainty of the various lithological correlations it is proposed that the above terms should only be used in a localised and informal sense, with the exception of the Cliff End Sandstone and the Northiam Sandstone. (Figure 10) summarises the local succession outlined by Allen (1976, fig. 2) and (Figure 11) the regional correlations of the present authors. The latter diagram is based on the cored boreholes at Glynleigh [TQ 6085 0637], Cooden [TQ 7043 0641], Penhurst [TQ 7050 1634], Bexhill [TQ 7206 Q974], Westfield [TQ 8204 1614] and Little Maxfield [TQ 8414 1532]. The erosion surfaces indicated are probably minor features related to local washouts or to the cyclic bedding of division 3. The latter may be more extensive, possibly related to regional, oscillations of base-level. Rootlet horizons are more abundant in the eastern part of the district (i.e. at Westfield and Little Maxfield), particularly in divisions 1 and 2. These beds include a number of sandstones which suggest more shallow-water conditions which would have favoured vegetative colonisation.

Environment of deposition

It is thought that the Wadhurst Clay accumulated under lagoonal conditions. Allen (1976) modified his original (1959) deltaic model of Wealden sedimentation to one of a variable-salinity mudplain and emphasised the extensive presence of rootlet horizons as an indicator of persistent shallow-water conditions. In the Hastings district the variable lithological sequence contrasts markedly with that of the Central Weald and suggests a marginal facies from which further environmental parameters may be deduced. In particular the presence of a varied transitional sequence at the base of the formation, cyclic bedding, sandstone bodies and bone-beds indicate marginal conditions. Although rootlets, soil beds and seatearths are common throughout the formation the evidence for emergence is limited. The red-mottled clays at the top of the Wadhurst Clay are taken to indicate emergent conditions which permitted partial oxidation to take place (Lake and Thurrell, 1974) but this lithology does not generally occur elsewhere in the sequence, except in the Glynleigh Borehole (see (Figure 11)). The rootlets, which are very common, penetrate the sediments to considerable depths and originate from discrete horizons where the parent soil bed may or may not be preserved. Other evidence of shallow water conditions such as mudcracks or reptilian footprints is uncommon. In contrast, however, current activity was apparently persistent and many lithologies such as the shelly horizons demonstrate winnowing effects. It would appear therefore that the environment was variable, probably in an oscillatory fashion.

Following the main transgressive phase, which was itself pulsatory, open water conditions persisted throughout much of the district; the shelly mudstones of division 2 contain few soil horizons although rootlets are fairly common. The Hog Hill Sand Member and comparable sandstones at this level are probably channel-fill deposits. Laterally thin sandstones are present which represent overbank flood deposits. The precise position of the erosional level represented by these sand bodies in the sequence is uncertain but probably the main phase of channelling heralded the conditions of division 3, when oscillations of base-level caused both channelling of the mudstones and extensive soil bed developments. These sandstones have been described previously as 'flat-bottomed channel-fills, some connected by thin 'wings' representing their overspills' (Allen, 1976, p.404). The Cliff End Sandstone falls within the lower part of division 2 and could be considered to represent a barrier bar within the Wadhurst Clay 'lagoon' or alternatively a sheet sand or major channel fill. On balance the sedimentological characters accord best with those of a barrier bar (p.70).

The Northiam Sandstone, at the top of division 3, is probably a (barrier bar) deposit comparable with the Cliff End Sandstone and marks the termination of the regressive trend to be succeeded by a return to open-water shelly mudstone facies and the ensuing emergence reflected by the colour-mottled mudstone facies at the top of the formation.

The bone-beds within the sequence were regarded as the product of floods by Kirkaldy (1939, p.387) but subsequently as winnowed concentrations comparable with the other Wealden pebble beds (Allen, 1976, p.406).

Two lines of evidence support the idea of variations of salinity in the Wadhurst Clay 'lagoon'. Anderson's studies of the ostracod faunas showed that the dominant Cypridea fauna of freshwater affinities was periodically invaded by a small group of species of 'marine' affinities, in a cyclic fashion. He introduced the terms 'C' and 'S' phases to represent these fluctuations. Additionally research on palaeosalinity, based on measurements of the proportions of the carbon isotopes, C12 and C13, in fossil shell material (Allen and Keith, 1965; Allen, Keith, Tan and Deines, 1973), confirms that the variations did occur and suggests that certain bivalves, such as Neomiodon, appear to represent a 'marine' or relatively saline environment. RDL, ERST

Tunbridge Wells Sand

The Tunbridge Wells Sand of the Hastings district is composed of siltstones with subordinate sandstones and mudstones; thin lignites and sphaerosideritic beds are present locally. In the present district there is no Grinstead Clay to separate the sand into upper and lower divisions as has been done elsewhere in the Weald (Bristow and Bazley, 1972).

At outcrop the base is typically sharply defined and is commonly marked by a line of springs thrown out at its junction with the underlying, impermeable Wadhurst Clay. Study of the cores of the BGS Cooden Borehole [TQ 7043 0641] (Lake, 1975) permitted the division of the Tunbridge Wells Sand into the following four broad lithological divisions:

Divisions 1 to 4 are 30, 6, 42 and 28 m thick respectively in the Cooden Borehole, with a total thickness of 106.7 m. Division 1 contains a prominent group of sandstones, about 15 to 20 m above the base of the subgroup. Division 2 is believed to occupy a fairly consistent range of lithostratigraphical horizons in the Pevensey–Bexhill area, although the red mottling is known to be an impersistent feature. Division 3 contains the thickest sandstones, which have been termed the 'main sandstone group' (Lake and Young, 1978). Abundant channels are present in the Tunbridge Wells Sand, and their basal lag deposits include sandstones, pellet beds and sphaerosideritic beds. The clasts in the pellet beds are commonly monogenetic and of sandstone, siltstone or mudstone; carbonaceous debris and ironstone fragments also occur.

The top of the Tunbridge Wells Sand is sharp and well defined both at outcrop and in boreholes in this district, although elsewhere in the Weald this boundary is gradational and difficult to define (e.g. Lake and Young, 1978).

Fossils are generally rare with the exception of poorly preserved unionid bivalves, plant detritus and root traces. Gastropods have however, been noted at Galley Hill [TQ 759 076] and ostracods were found at two horizons at 67 and 64 m below the top of the Tunbridge Wells Sand in the Cooden Borehole.

The largest outcrops occur around Catsfield and in the area from N infield to Bexhill. Smaller outcrops lie to the north of the Purbeck inliers and at Westfield, The Ridge and St Leonards. South of the Whydown Fault the base of the subgroup dips from about 15 m below OD at Hooe, to 111 m below OD at Cooden (Figure 15). Borehole evidence is lacking from the Bexhill area but at Galley Hill the base probably lies at 40 m below OD.

Regional correlation and depositional environment

The dominantly fine-grained deposits of division 1 were probably deposited on a mature alluvial floodplain. The red-mottled siltstones and mudstones of division 2 extend to the Central Weald, where they overlie the Grinstead Clay (Lake and Thurrell, 1974). The mottling reflects a diachronous emergence which permitted partial oxidation of the mud-stones and which may have caused the influx of coarse sediment and reinvigorated channelling activity seen in division 3. The depositional environment of division 4 is not fully understood (Allen, 1976, p.409) but may be one of high-sinuosity streams, slow rates of deposition and perhaps a distal nearshore position. This top division generally marks the gradual transition to the lagoonal conditions of Weald Clay times with a progressive reduction in the input of coarse sediment. RDL

Weald Clay

In the Hastings district only the lowermost beds of the Weald Clay are present and they crop out in a narrow coastal strip at Cooden. The beds comprise bioturbated grey silty mudstones and muddy siltstones which are virtually barren of fauna and weather at the surface to pale grey and greenish grey clays. Locally the basal mudstones are weakly sideritised. These beds were formerly regarded as belonging to the Wadhurst Clay (e.g. White, 1928, p.54) but the recent survey and the evidence of the BGS Cooden Borehole [TQ 7043 0641] have led to a complete reassessment of the stratigraphy.

To the west of the district the full thickness of the formation was proved to be 158.9 m in the BGS Ripe Borehole [TQ 5059 1052]. A borehole [TQ 6768 0563] immediately west of the geological sheet boundary at Rockhouse Bank proved an estimated 30 m of Weald Clay to overlie Tunbridge Wells Sand. The Cooden Borehole proved only 13.5 m of these beds (Lake, 1975).

The depositional environment of these clays was discussed by Allen (1981).

Details

The following detailed descriptions (given in descending order) are generally confined to critical sections which provide the basic evidence for the general conclusions listed above. The coastal section is described in Appendix 1.

Ashdown Beds

Many of the inland exposures lie in the Top Ashdown Sandstone. For convenience the basal beds of the Wadhurst clay, which overlie this horizon and include the Top Ashdown Pebble Bed, will also be described in this section.

Northern area, between Mountfield and Rye

In the northern part of the district between Mountfield and Rye, including the Tillingham valley, the exposed Ashdown Beds are dominantly sands and silts. The uppermost Ashdown Beds, much deformed by valley-bulging, were proved in trial boreholes and the cut-off trench at the Darwell Reservoir site [TQ 720 214] (p.47). A road-bank section [TQ 7694 2134] near Swaile's Green shows the topmost Ashdown Beds as 1.8 m of sandy silt with sandstone bands. Massive sandstones at the same stratigraphical level are exposed in the road cutting [TQ 7764 2122] at Cripp's Corner and in a quarry [TQ 7852 2149] to the west of Miles's Farm, where they are 4.5 m thick. RDL

The old quarry [TQ 7825 2095] to the west of Cattsgreen Farm, which is now used as a Council depot, shows beds somewhat lower in the sequence. These total about 6 m of ochreous and grey silts with sandstones.

East of Conster Farms the Top Ashdown Sandstone is exposed in a series of stream sections, roadbanks and small quarries, including the exposures listed below. A stream section in Osier Gill [TQ 8442 2145] 700 m north of Conster Farms shows the following succession: Wadhurst Clay with ironstone nodules, poorly exposed; Top Ashdown Pebble Bed, pebbly sand with rippled top, 0.15 m; Ashdown Beds, sandstones, brown and grey with silty bands, 3.75 m. The old quarry [TQ 853 209] in King Wood exposes the following beds: Wadhurst Clay, grey clay with ironstone nodules, 0.3 m; Top Ashdown Pebble Bed, pebbly sand with rippled top, 0.1 m; Ashdown Beds, silt and sandstone, 1.3 m.

A stream section in The Gill [TQ 8823 2169], east of The Hermitage, exposes about 4.5 m of mainly fine-grained sandstone with a thin calcareous band ('Tilgate Stone') of 0.05 m at the top. These beds apparently mark the transition between the Ashdown Beds and a sandstone within the Wadhurst Clay. RDL, ERST, JGOS

Western area, between Mountfield and Ashburnham

In the area between Ashburnham and Mountfield the Ashdown Beds at outcrop consist mainly of fine-grained sands alternating with silts. The total thickness of Ashdown Beds proved by boreholes in this area is between 200 and 215 m. The massive Top Ashdown Sandstone forms an excellent feature below the Wadhurst Clay throughout the area. Boreholes have proved the presence of 'Fairlight Clays' lithologies in the vicinity of the Hollingrove–Netherfield Purbeck inlier. A clay seam, 3 m thick, was mapped in Burnthouse Wood [TQ 7360 1815] about 75 m above the base of the formation, but there is a lack of persistent, mappable clay horizons anywhere within the sequence, even in the lowest Ashdown Beds north of Netherfield; sand and silt are the dominant lithologies. Red clay was noted by White (1928, p.58), however, together with pale grey, lilac and brick-red sandy silt with seams of iron-cemented sandstone, on the slopes around the Purbeck inlier of Limekiln Wood. Most of the valleys in this area are deeply dissected and small exposures of the sands and silts of this formation are common, including those described below.

The following section in Darwell Stream [TQ 6861 1950] exposes one of the more silty horizons within the Ashdown Beds: fine-grained sandstone, 0.3 m; pale grey silts, 2.4 m; fine-grained sandstone, 0.15 m; pale grey silts, 0.9 m. These silty horizons are seldom visible in exposures as they degenerate rapidly on weathering and this particular horizon lies about 45 m below the top of the Ashdown Beds.

Even the lowest parts of the Ashdown Beds are generally sandy in the Darwell Wood area, proving the essentially local and impersistent nature of the informal 'Fairlight division' of Morter (1984). This is demonstrated by the sandy soil within the area of Darwell Wood immediately north-east of Darwell Hole and a former exposure of at least 10 m of sandstone in an old quarry [TQ 6984 1965], about 75 m above the base of the Ashdown Beds, together with an exposure of about 1.2 m of yellowish brown massive fine-grained sandstone which lies only about 6 m above the base of the Ashdown Beds, in an old sandpit [TQ 7074 1940], 220 m west of Darwell Beech.

The Top Ashdown Pebble Bed is not present everywhere but was found at several localities. About 290 m south-west of Gifford's Farm crags of massive sandstone, 1.8 m high, at the top of the Ashdown Beds are capped by a pebble bed, 0.03 m thick [TQ 6849 1883]. In an old quarry [TQ 6959 1873] 370 m south of Darwell Hole the following sequence was exposed: Wadhurst Clay, grey clay with thin siltstones, 0.3 m; Ashdown Beds, sandstone, 0.15 m; pebble bed, pebbly sand, 0.03 to 0.1 m; pale grey sandstone, 2.4 m.

In Ibrook Wood [TQ 7098 1826], about 450 m south of Netherfield, a ride through the plantations has followed the dip-slope of the bedding plane at the top of the Top Ashdown Sandstone. The Ashdown Beds–Wadhurst Clay junction is very well exposed and a pebble bed forms the path's surface for about 20 m. The total sequence seen is: Wadhurst Clay, siltstone and shale, 0.6 m; Ashdown Beds, sandstone with rippled top, 0.15 m; pebble bed, 0.03 to 0.15 m; sandstone, 2.1 m. The pebble bed can, in places, be seen to lie on an uneven erosion surface cut in the sandstone below and it is thickest in the resulting hollows. In several places where the pebble bed is 0.15 m thick, lenses of sand up to 0.03 m thick appear within the pebble bed itself. The pebbles are up to 12 mm in diameter but the average size is considerably less than this. It would appear that more than 90 per cent of the pebbles are siliceous and well rounded with a quartzose sand matrix. A few clasts are of soft, buff grit and of siltstone, and were probably formed by penecontemporaneous erosion of Ashdown Beds sediments. The siliceous pebbles are mainly white and pink quartz, with some quartzites and cherts. The cherts are sometimes visibly banded and at this locality usually patinated and decomposed to a soft 'white chalky looking stuff' (Topley, 1875, p.84). Silicified limestone pebbles are also present; one was noted to include a brachiopod fragment. Dark phosphorite pebbles are common.

Crags of Top Ashdown Sandstone up to 3 m high are present near Rocks Farm, about 725 m ENE of Ashburnham Furnace [TQ 6918 1732]. A section in a nearby quarry [TQ 6875 1647] revealed the Ashdown Beds–Wadhurst Clay junction: Wadhurst Clay, clay with thin siltstones and sandstones, thin sideritised limestone with Neomiodon sp., 1.2 m; Ashdown Beds, sandstone, brown, rippled top, 0.4 m; sandstone, carbonaceous, 0.01 m; pebble bed, 0.08 m; sandstone with carbonaceous partings, 0.05 m; pebble bed, 0.03 to 0.05 m; sandstone with pebbles, 4.6 m. The presence of more than one pebble bed and of thin carbonaceous layers is noteworthy.

The sequence proved in a trial borehole at Penhurst [TQ 7050 1634] is illustrated in (Figure 6). In Cowland Wood [TQ 7033 1588], 520 m SSW of Tower House, a massive cross-bedded, well jointed, pale grey sandstone at the top of the Ashdown Beds forms crags up to 6 m high. Similar crags 3 m high, which are seen in a road cutting [TQ 7070 1622], 180 m south-west of Tower House, are formed by a massive sandstone horizon immediately below the Top Ashdown Sandstone.

Other outcrops in the Top Ashdown Sandstone are seen in an old quarry [TQ 7248 1710] in Ashes Wood, 700 m east of Foxhole Farm, where about 3.7 m are exposed, and in the A21 road cutting [TQ 7452 1639], near Battle, where faces of massive sandstone about 6 m high are present in places. RABB, RDL

Upper Brede valley

In the upper part of the Brede valley between Mountfield, Battle and Sedlescombe, the Ashdown Beds comprise fine-grained sands with silts and subordinate clays. Auger evidence suggests that part of the sequence may be rhythmic, with discontinuities at sand/clay interfaces. Unlike the area farther west, thick clays are present in the lowest exposed part of the sequence. Although these clays are not red-mottled, they are of basically similar facies to those of the 'Fairlight Clays' of the coast. The total thickness of Ashdown Beds in the upper Brede valley is not known but the Battle Borehole [TQ 7573 1706], which started close to the top of the formation, proved only 105 m of Ashdown Beds above the Purbeck Beds. This suggests the presence of faulting and a major fault has been mapped nearby.

The Top Ashdown Sandstone does not generally form a good feature hereabouts and may be masked by wash. Locally it thins to less than 3 m and is underlain by a greenish grey clay bed. This sequence is distinguished with difficulty from the basal beds of the Wadhurst Clay which locally include a sandstone bed of comparable thickness.

Informative exposures are rare in this area, but sandstones and siltstones commonly crop out in the beds of the minor tributary streams.

A small section [TQ 7861 1918] in Churchland Wood, north-east of Sedlescombe, showed the following sequence: Wadhurst Clay, mudstones with thin siltstone and sandstone lenses, 0.9 m; Top Ashdown Pebble Bed, pebbly sand with rippled top, 0.01 to 0.06 m; Ashdown Beds, sandstone with silty partings, 1.2 m. RDL

Lower Brede valley

In the area around Brede and Udimore the exposed Ashdown Beds comprise an upper division about 20 to 30 m thick of sands and silts with subordinate clays overlying a lower dominantly argillaceous division up to 30 m thick. The Top Ashdown Sandstone is up to 3 m thick but includes silty interbeds and forms only weak features.

An old quarry [TQ 8034 1903] in Plains Wood exposes the following section in the top Ashdown Beds: Wadhurst Clay, silty clay, 1 m; Top Ashdown Pebble Bed, pebbly sand with rippled top, 0.08 to 0.1 m; Ashdown Beds, sandstone, locally ferruginous, 0.5 m.

The highest Ashdown Beds are exposed in a stream section [TQ 8291 1929] in Well Wood, south of Broad Oak, where the composite section in the gully and waterfall is as follows: talus, slipped clay with shell bed fragments; Ashdown Beds, massive sandstone (forms lip of upper fall), 1.1 m; grey silt, 1.1 m; massive sandstone, 1.7 m; grey silt, 1.8 m; sandstone, 0.6 m; silt, 0.6 m. No pebble bed was found in this section. In the stream-bank [TQ 8294 1923] below, 3.4 m of interbedded silts and silty sandstones are exposed. The sections once visible in Hare Farm Lane, Brede [TQ 8315 1845], but now much overgrown, provided the type locality for Allen's (1949a, pp.267–270, fig. 1) 'typical' Wealden deltaic cyclothem. ERST, RDL

South-western outcrops, around Ninfield

In the Kitchenham area [TQ 680 130] the upper Ashdown Beds comprise silts with subordinate sands.

An exposure at Tilton [TQ 7175 1298], in a private driveway, shows 4.5 m of fine- to medium-grained sandstone with clayey and carbonaceous partings, load casts, pebbly bands and a rippled erosion surface. Similar lithologies were noted at a nearby pit [TQ 7155 1300] at Hophouse Farm where 1.5 m of thinly bedded silty sandstone overlies 1.5 m of massive sandstone with a rippled separating surface. In both localities it is probable that the upper beds belong to the Wadhurst Clay and the lower unit is the Top Ashdown Sandstone.

Crowhurst, Battle and Westfield area

In the area [TQ 748 130] south-west of Fore Wood the Ashdown Beds below the top sandstone comprise sands and silts. A clay bed is present 15 m below the top of the formation. A pit [TQ 7455 1335] in Stumblet's Wood, south of Peppering Eye Farm exposed the following sequence: talus of siltstone and mudstone; Ashdown Beds, pebbly sandstone, 0.05 to 0.13 m; pebble bed, 0.05 m; mudstone with plant fragments, 0.01 m; sandstone with rippled top, 0.05 m; mudstone, 0.01 m; sandstone, 1.2 m. Across the valley a tributary stream section [TQ 7487 1352] exposed the following beds: clayey wash; shelly limestone, 0.03 m; sandstone, shelly at top, 0.09 m; sandy clay, 0.08 m; pale grey sandstone, 1.8 m. Although no pebble bed was seen, it is probable that the lowest bed is the Top Ashdown Sandstone.

Up to 6m of Top Ashdown Sandstone is exposed in the ravine-like tributary valley [TQ 7550 1300] in Fore Wood. At the head of this feature, 3 m of fine-grained, thinly bedded sandstone is exposed which is more massive and coarser in the topmost 0.6 m. Thin silty interbeds, about 0.03 m thick, are present towards the base of the section.

Between Battle and Crowhurst the Top Ashdown Sandstone is generally massive or thickly bedded and 3 to 4 m thick. Below this the Ashdown Beds comprise sands and silts with subordinate clays. The medium-grained 'silver sand', typical of the Top Ashdown Sandstone, has been quarried extensively in the past, notably near Brakes Coppice Farm [TQ 7654 1332], at Blackhorse Hill [TQ 7715 1447]; [TQ 7757 1440]; [TQ 7776 1445] and in Crowhurst Park [TQ 7722 1348].

An old quarry [TQ 7675 1354] at Brakes Coppice Farm exposes the following sequence: clayey wash with pebble bed debris, 0.3 m; sandstone with partings of silt, clay and lignite, 0.9 m; sandstone with silty partings, 0.23 m; massive sandstone, 0.6 m. This section is unusual for this area because it shows beds other than the typical massive sandstone below the Top Ashdown Pebble Bed.

In the Baldslow area the Top Ashdown Sandstone is exposed in a number of quarry sections. The roadside pit [TQ 7893 1308] north of Beauport Farm exposes the sequence: fine-grained sandstone, 0.15 m; silty mudstone with channelled base, 0.45 m; fine-grained sandstone, 0 to 0.08 m; sandstone, pebbly near top, 0.3 m. The lowest sandstone is the Top Ashdown Sandstone.

The former Baldslow Quarry [TQ 7976 1290], exposes up to 6 m of cross-bedded medium-grained Top Ashdown Sandstone. Much of the bedding is related to large-scale cross-sets, but cosets with small-scale cross-bedding are also present locally. Lenticular beds of pebbly material which contain flakes of mudstone up to 0.15 m long are found towards the base of the section. One lens, or more correctly a set of 'stringers', contains coarsening-upwards sequences within the pebbly material.

A disused quarry 300 m to the south [TQ 7973 1265] at Harrow Lane showed in 1967 the sequence of beds illustrated in (Figure 12). The lower part of the old quarry [TQ 7990 1255] at Harrow Lane had been back-filled by 1967 but three sections in the upper face were visible and these are shown in the figure. These sections illustrate the complexity of the Ashdown Beds–Wadhurst Clay transition, as discussed previously, and indicate considerable reworking and channelling of the sediments at this level.

Southern area, between Crowhurst and Bulverhythe

In the area between Crowhurst and Bulverhythe the upper Ashdown Beds crop out extensively in the Combe Haven valley and its tributaries. At least 30 m of the topmost part of the formation is exposed. The sequence consists dominantly of fine-grained sands but with subordinate silts and clays towards the south. The Top Ashdown Sandstone is up to 5.5 m thick in the Crowhurst area, but in the south around Bulverhythe finer-grained channel-fill deposits are present at this level and the top sandstone may be only 1 m thick.

Up to 5 m of well bedded, fine-grained, ochreous sandstone which was medium-grained and more massive in the upper beds was exposed in an old, presently overgrown quarry [TQ 763 113], adjacent to the former railway line, near Croucher's Farm. The basal Wadhurst Clay and Top Ashdown Sandstone are exposed in a small adjacent pit [TQ 7634 1123] as follows: Wadhurst Clay, grey mudstone, 0.2 m; Top Ashdown Pebble Bed, pebbly sand with mud flakes, 0.15 m; Ashdown Beds, sandstone with silt laminae, 1.5 m. Up to 5.5 m of massive, fine-grained, white Top Ashdown Sandstone is exposed in the old quarry [TQ 7633 1084] at Adam's Farm. A small section [TQ 7630 1083] in the north-western corner of the pit exposes the basal beds of the Wadhurst Clay and the topmost part of this sandstone: Wadhurst Clay, sandstone with mudstone bands, 0.16 m; Top Ashdown Pebble Bed, 0.06 m; Ashdown Beds, sandstone, 0.45 m.

Old workings around the margin of the Combe Haven marshes expose the Ashdown Beds–Wadhurst Clay sequence. A small exposure [TQ 7738 0943] 900 m west of Filsham Farm shows the Top Ashdown Pebble Bed 0.02 m thick overlying 0.4 m of medium-grained sands. The quarry [TQ 7687 0905] to the east of Pebsham Farm exposed about 8 m of massive, pale grey, medium-grained sandstone below the Wadhurst Clay in 1968. This sandstone contains pebbly stringers, brown silt partings and silt pellet beds and overlies 0.6 m of interbedded purplish grey mudstone and medium-grained sandstone.

A somewhat different sequence is exposed in the quarry [TQ 7800 0888] at Harley Shute: sandstone with silty partings, 6 m; sandstone with mudflake partings, 0.3 m; mudstone pellet bed, 0.03 to 0.05 m; massive sandstone, 2.4 m; silty clay forms the quarry floor. The topmost sandstone seems to be a channel-fill deposit. The overlying beds are exposed in a quarry face [TQ 7779 0900] in the nearby caravan park: clayey wash, 0.3 m; Top Ashdown Pebble Bed, 0.03 m; sandstone, 0.6 m. RDL

Eastern outcrops, between Westfield, Hastings and Fairlight

This is the type area for the 'Fairlight Clays' of earlier authors. It has long been recognised that these variegated silty clays occur at a number of horizons alternating with sandstone and silt beds, and that they form a local facies of the Ashdown Beds, which is more or less restricted to this part of Sussex. They do not thus warrant formational status and have been mapped simply as 'clays within the Ashdown Beds' in the present survey. Although it has been possible to delimit the outcrops of the alternating sandstones and clays by augering and feature mapping, their overall lithological uniformity has made it almost impossible to correlate between fault-blocks in this structurally complex area. The area also contains numerous exposures of the Ashdown Beds–Wadhurst Clay junction but only a few examples have been selected for detailed description.

In the fault-bounded block of country east of Three Oaks and north of the Guestling Green Fault, five fairly continuous bands of grey silty clay with occasional red-mottling have been mapped. Fine-grained sandstones and silts make up the intervening strata; the second of these arenaceous horizons in ascending order, contains many small quartz pebbles that appear in the soil. This horizon is exposed in Halfhouse Wood, immediately east of the Three Oaks Fault, where ferruginous sandstones up to 1.5 m thick form a small waterfall in the stream [TQ 8410 1458], but no pebbles were noted here.

South of Westfield, between the Tanyard and High Lankhurst faults, red-mottled grey silty clays, alternating with thin beds of silty sandstone and silts crop out widely, but exposures are poor. The plane of the Marsham Fault is exposed in the stream bank [TQ 8369 1333]; massive ferruginous sandstones dip northwards at 60 to 70° on the north side of the fault whereas to the south thinly-bedded, buff and ochreous sandstones dip vertically. A further 100 m upstream, beds around the Ashdown Beds–Wadhurst Clay junction which dip NE at 50°, are exposed south-west of the fault as follows: Wadhurst Clay, silts and sandstone, 2 m; weathered shales, 3 m; Ashdown Beds, massive sandstone, 2 m; no pebble bed seen. The high dips hereabouts are associated with the Marsham Fault but the lower dips in the sandstones north of the fault may reflect cross-bedding or valley-bulging.

South of the High Lankhurst Fault steeply dipping beds, at the Ashdown Beds–Wadhurst Clay junction, are exposed in an old quarry [TQ 8111 1380] near Hole Farm, where grey-green shales with thin siltstones, sandstones and ironstone nodules up to 0.4 m thick overlie the Top Ashdown Pebble Bed. The latter is 0.15 m thick and is a coarse-grained ferruginous sand with a rippled top and contains quartz and chert pebbles up to 7 mm in diameter. Beneath, the Top Ashdown Sandstone, which is seen for 0.9 m, is fine grained and friable with bands of brownish ferruginous staining and dips northeast at 45–60°.

The junction is again seen in old quarries in Coghurst Wood [TQ 8330 1347] where 2.5 m of basal Wadhurst Clay shales containing thin siltstones and sandstones, overlie the rippled Top Ashdown Pebble Bed, which is 0.10 m thick and itself overlies 2.4 m of massive, mainly medium-grained, well jointed, white sandstone at the top of the Ashdown Beds. Quartz pebbles are abundant in the top 0.3 m of this sandstone and occur more sparingly to 0.9 m below the top.

The road-cutting between Guestling Hill [TQ 848 131] and Friar's Hill [TQ 858 134] formerly showed about 45 m of alternating sandstones and silty clays, with occasional seams of carbonaceous shale, all more or less highly inclined to the NNE, the true dip ranging up to about 40°. Faulting, contortion, and mashing of the beds was apparent in places, but the most remarkable feature of the section was the overturning and attenuation of the sandstones and clays (from 0.6 to 3 m below the surface of the ground), attributable to soil-creep (White, 1928, p.60 and fig. 13, p.76). The continuations of the Haddock's Reversed Fault and Marsham Fault are crossed by the road in question and it is probable that one or other of these faults is responsible for the disturbance figured by White (but not accurately located). The strata range downward from about 30 m below the top of the Ashdown Beds.

Immediately east of the Silverhill Fault, an old quarry near the school [TQ 801 113] exposes the top of the Ashdown Beds beneath a cover of Wadhurst Clay as follows: Wadhurst Clay, shale and silt, 2.7 m; Top Ashdown Pebble Bed, pebbly sandstone with rippled top, 0 to 0.12 m; Ashdown Beds, massive sandstone, 5 m. In Old Roar Gill, which runs southward from Silverhill Park to Buckshole Reservoir, the stream has cut through the cover of Wadhurst Clay to produce a steep sided ravine in the top Ashdown Beds sandstones. Only one of the many sections is described here, but they are generally similar in lithology. At the head of the gill just below the iron footbridge [TQ 8046 1203] the following sequence in the upper part of the Ashdown Beds is exposed in a waterfall and the adjacent valley sides: sandstone, massive, 2.4 m; sandstone, hard (forms lip of waterfall), 0.6 m; sandstone, blocky, laminated, 0.6 m; sandstone, massive, 0.6 m; siltstone, 0.9 m; sandstone, laminated (forms overhang), 1.5 m; mudstone, soft, 0.6 m; flaggy sandstone and siltstone, 3 m. The contact with the Wadhurst Clay is not clearly exposed here or elsewhere in the gill. Many other sections in sandstones and siltstones are visible as the gill is followed downstream.

In the St Helen's and Ore suburbs of Hastings, eastward to the Mallydams Fault, the Ashdown Beds below the top sandstones consist chiefly of grey silty clays, locally red-mottled, with thin interbedded silty sandstones. There are few natural exposures in this largely built-over area. Bricks were formerly made at two sites near Ore [TQ 837 123] and [TQ 836 119], using the local clay.

Trial boreholes on the site of the power station at Broomgrove [TQ 826 109] proved sequences of compact silty mudstones, with only minor sandstone developments, to depths of 24 m below the surface.

In Hastings, south-east of the White Rock Fault and south of the Ore Fault, strata high in the Ashdown Beds underlie the valleys east and west of West Hill. The thick top sandstones form steep valley sides. There are few exposures in the urban area apart from those around the castle. An old quarry behind the houses forming Milward Crescent [TQ 822 098] displays up to 15 m of sandstones similar to those of the crags at the castle. On the east side of West Hill, the popular tourist attraction, St Clement's Caves [TQ 824 097], has been excavated in massive sandstones at the same horizon, high in the Ashdown Beds.

Ashdown Beds crop out widely in the faulted country between Fairlight and Pett, but extensive Head deposits obscure some of the eastward facing slopes and valleys. Here again grey silty clays with thin interbedded sandstones make up most of the exposed sequence and there are few visible sections.

An old quarry [TQ 8519 1183] in the grounds of Fairlight Lodge exposes the basal beds of the Wadhurst Clay above the Top Ashdown Sandstone as follows: Wadhurst Clay, clay-ironstone, 0.2 m; shale and sandstone, 0.87 m; shell bed with Neomiodon, 0.1 m; shale and siltstone, 0.58 m; Top Ashdown Pebble Bed, pebbly sand, rippled, 0.05 m; Ashdown Beds, sandstone, 2 m. These beds dip gently to the SW.

Pett Level, Winchelsea, Rye and Romney Marsh

Ashdown Beds are sporadically exposed in the abandoned sea-cliffs bordering Pett Level and the 'island' of Winchelsea. A few of the best exposures are listed below.

In the old cliffs north of the Pickham Fault, near the sheepfold [TQ 8923 1480], massive, well jointed, medium-grained sandstones rise above the marsh surface for 3 m. Their top is channelled for a depth of up to 1 m hereabout, and if the channel is traced north-eastwards for 70 m [TQ 8926 1484], it is seen to cut down more deeply and the channel-fill sequence totals about 5.7 m of sandstone, silty shale and mud-flake conglomerate. Another channel which is seen 80 m to the north-east along the old cliff [TQ 8935 1500] is filled with massive, silty grey and ochreous sandstone up to 1.7 m thick. The channel is cut into a sequence of sandstones and silts, the erosion surface having a hardened ferruginous crust. About 40 m to the north-east along the old cliff [TQ 8938 1502] there is a section in about 5 m of sandstone with bands of silt and clay, some with sphaerosiderite. A concealed gap of about 1.5 m separates the bottom of this section from the top of the massive channel-fill sandstone in the previous section.

North of the Pannel Sewer, up to 30 m of strata near the top of the Ashdown Beds are exposed in the foot of Wickham Cliff and around the Winchelsea 'island'. Sandstones up to about 15 m thick occupy the top of the formation, and rest on grey silty clays which extend down beneath the marshland surface. Wickham Cliff is much overgrown, but some sections across the Ashdown Beds–Wadhurst Clay junction are exposed in the old cliffs and sunken lanes of Winchelsea. A selection of these, illustrating the main lithological characters of the beds are shown in (Figure 13). The Top Ashdown Pebble Bed is well developed at all these sites and

ranges from 2.5 to 12.5 cm in thickness. The underlying massive sandstone, which is about 2 m thick, is characterised by trough cross-bedding and by dark planty and clay partings which pick out the sedimentary structures; in one locality it was seen to fine upwards. At each site a band of coarse sand lay at, or near, the base of this sandstone, which rests on interbedded grey silty clay and fine-grained ochreous sand. The Wadhurst Clay strata in these sections are discussed below.

Across the Brede Level, the top Ashdown Beds crop along the foot of Cadborough Cliff, but are much obscured by landslip. A bore at Cadborough Pumping Station [TQ 9121 2010], which was sunk in 1898, entered Ashdown Beds beneath alluvium at 5.5 m below surface and penetrated sandstone, silt and clay to a final depth of 18.9m. Other later boreholes were sunk to depths up to 31.7 m, and encountered mottled silty clays below about 20 m.

The gentle north-easterly dip takes the top of the Ashdown Beds down beneath the surface of the alluvium encircling the 'island' of Rye where the old cliffs are formed by the Cliff End Sandstone. Several boreholes have penetrated Hastings Beds beneath drift in the marshland area to the east. These are believed to be Ashdown Beds on lithological grounds, but some uncertainty must remain since the structure of these concealed outcrops is unknown.

At Lydd Camp a trial bore for water [TR 041 201] was sunk in 1895, from a surface level of about 5 m above OD to a final depth of 122.7 m. The solid rocks encountered beneath marine drift, some 12 m below OD, show considerable small-scale variation as recorded in the driller's log (Whitaker, 1908, pp.163–165), but consist chiefly of grey silty clays, mottled in part, interbedded with thin very fine-grained sandstone beds. They appear to resemble the Ashdown Beds of 'Fairlight Clays' facies exposed on the coast near Fairlight. ERST

Wadhurst Clay

North-western area, around Brightling, Mountfield and Penhurst

Details of the Darwell Reservoir sections are illustrated in (Figure 18). About 4m of grey, greenish and reddish mudstone, with siltstone bands, was exposed in 1969 in a cutting in Vinehall Road [TQ 750 209]. Sandstone and siltstone beds, which may be as much as 3 m thick locally and which form local features, are found within the Wadhurst Clay of this area. These include the Northiam Sandstone which lies about 6 m below the top of the formation (Figure 10) and crops out in Creep Wood [TQ 7049 1646]. ERST, RABB

North-eastern area, around Brede, Udimore and Rye

In the area around Brede and Udimore, sandstones equivalent to the Cliff End Sandstone lie just above the base of the Wadhurst Clay. They are generally from 1.2 to 5 m thick, but may be absent locally. This bed was formerly extensively worked as 'Tilgate Stone' which was used for roadstone and building purposes.

Around Brede, 'Tilgate Stone' was formerly quarried from the sandstone horizon just above the base of the Wadhurst Clay in numerous small workings, now much overgrown or backfilled. Old workings were noted at Reyson's Farm [TQ 832 192], where Allen (1949b, p.280) recorded a section in dark shales with Neomiodon and ostracods and with siltstone and sandstone bands, together with a 0.15 m bone-bed. Allen referred to the bone-bed as a representative of the Telham Bone-Bed horizon; it is hence probably equivalent to the Cliff End Bone-Bed. It is interesting to note that here the bone-bed rests on top of a calcareous sandstone bed, whereas at Cliff End it lies 2.9 m above the top of the Cliff End Sandstone which is capped by the Cliff End Pebble Bed.

To the east of Brede village, sections in the sides of sunken lanes and adjacent pits have been recorded by a number of workers over the last century. Topley (1875, p.63) described a roadside section [TQ 8314 1848] about half-a-mile (0.8 km) east of Brede Church in clay and shale with ironstone, interbedded with sandstones. The lower sandstone of this section occurs just above the base of the Wadhurst Clay and is probably an equivalent of the Cliff End Sandstone. This locality is probably close to Allen's (1947, p.314) No. 44 Stubb Lane site [TQ 8217 1853] from which he recorded the Brede E. lyelli Soil Bed, the Brede Bone-Bed and the Top Ashdown Pebble Bed (Figure 10). The nearby locality in Hare Farm Lane [TQ 8314 1844] is the type locality for the basal Wadhurst Clay cyclothemic sequence proposed by Allen (1949a, p.270, fig.l).

Near Udimore, lower Wadhurst Clay beds cap the interfluve between the Tillingham and Brede valleys. Here again a prominent sandstone of 'Tilgate Stone' type occurs just above the base of the formation. It was formerly much worked for roadstone. A valuable section through the lower beds of the Wadhurst Clay and the top of the Ashdown Beds may be seen in the sides of the sunken lane, known as Dumb Woman's Lane, which descends from the main road at Three Chimneys [TQ 8970 1936] to the Brede floodplain. This section is as follows: Wadhurst Clay, weathered, 0.9 m; Top Cliff End Pebble Bed, 0.03 m; Cliff End Sandstone, 2.5 m; gap, 0.45 m; clay-ironstone, 0.15 m; 'Tilgate Stone', 0.45 m; silts, 0.76 m; shell bed with Neomiodon, 0.18 m; sandstone, silt and clay with ironstone nodules, 2.6 m; Top Ashdown Pebble Bed, 0.03 m; Ashdown Beds, sandstone, 1.98 m; gap, 1.42 m; clay, 0.6 m. ERST

A stream west of Great Fagg [TQ 8973 1987] showed the following section in Wadhurst Clay: clay, 1 m; sandstone, 4.6 m; 'Tilgate Stone', 0.2 m; shales, silt and clay-ironstone, 0.45 m. JGOS

The old sea-cliff [TQ 9078 1953] at Cadborough showed a section in about 2.5 m of sandstone with shell moulds and plant debris, bands of 'Tilgate Stone' and with clay-ironstone at the base. These beds are equivalent to the Cliff End Sandstone. ERST

North of Rye, in the old sea cliffs facing eastward over the marshland, at Point Hill, some small sections were recorded in 1957. Near Saltcote Place [TQ 9245 2138] the following section across the Wadhurst Clay–Ashdown Beds junction was seen: Wadhurst Clay, sandstone, 1.8 m; mudstone with E. lyelli on thin rippled coarse sand (Top Ashdown Pebble Bed), 1.2 m; Ashdown Beds, sandstone, 3.2 m.

The cliffs surrounding the 'island' of Rye are cut in the Cliff End Sandstone and the base of the Wadhurst Clay is concealed beneath alluvium. The higher, built-up part of the old town is underlain by clays. The most accessible sections are those near the steps from the Undercliff to Watchbell Street [TQ 9195 2018]: Wadhurst Clay, weathered shale; Cliff End Bone-Bed, coarse sandstone with pebbles, 0.25 m; silt, clay, sandstone and shale, 1.23 m; Top Cliff End Pebble Bed, rippled sandstone, 0.1 m; Cliff End Sandstone, sandstone with plant debris and a band of 'Tilgate Stone' doggers, c.9 m. JGOS, ERST, RDL

Western area, around Ninfield and Crowhurst

In the Ashburnham Place area the topmost beds of the Wadhurst Clay include red clays typical of division 5 (Figure 10).

In the area to the north and east of Ninfield the Northiam Sandstone is probably present as a continuous bed but it is too thin to be mapped as such. North of Crowhurst it is said to be at least 5.5 m thick in a well section [TQ 7606 1348] and, locally at least, its top is marked by a pebble bed.

In the Telham Hill area [TQ 760 140] at least three major sandstones are present between the Ashdown Beds and the Northiam Sandstone, but the presence of very silty beds in the sequence tends to blur the succession and flexuring near faults complicates lateral correlation.

The Northiam Sandstone (Figure 10) is exposed in the road cuttings near Telham Hill [TQ 759 141]; [TQ 762 140] and near Pyes Farm, Crowhurst [TQ 7607 1353]: typical thinly bedded, fine-grained sandstones are exposed.

The section in the lower Wadhurst Clay at Blackhorse Hill [TQ 769 142] is now obscured, but was described by Dawkins. It includes about 5 m of shales with ironstone, plant debris, 'Cyrena' and Cypridea on 0.6 m of grey clay with the Telham Bone-Bed (0.1 m) in the lower part. These strata overlie about 1.4 m of 'Tilgate Stone'. The conglomeratic bone-bed was described as 'a mass of coprolites, bones, teeth, scutes and ganoid scales of irregular thickness' with 'pebbles of white quartz which vary in size from a pigeon's egg to a pea'. The faunal list includes Megalosaurus, Iguanodon, Goniopholis crassidens, Teleosaurus, Leiodon, Plesiosaurus?, Chelone, Pterodactylus, Ganoidea and Hybodus (Dawkins, in Topley, 1875, pp.63–64).

More recent excavations at the Gravel Pits, Blackhorse Hill [TQ 778 140] in the 1960's, for low quality hoggin material, worked a sandstone bed at a similar horizon which mainly comprised decalcified flaggy 'Tilgate Stone'. A trial-section [TQ 7777 1405] made in 1967 near the entrance to this pit showed a 1.5 m section in sandstone and sand with shell moulds.

The succession at Rackwell Wood, Crowhurst [TQ 764 124] was described by Sweeting. (1925, pp.410–418). This can be summarised as follows: clay and loam, 1.1 m; shales with ironstones and selenite, 4.1 m; Telham Bone-Bed, 0.025 to 0.076 m; sandstone, 1.68 m; 'Tilgate Stone', 0.9 m; dark blue clay with ironstone. The 'Tilgate Stone' was noted to contain casts of 'Cyrena'; Unio and Viviparus and bone fragments. Concretionary masses of calcite-cemented material were recorded in the overlying sandstone which contained molluscan moulds and, at the top, bone fragments, there being a passage into the bed above. The bone-bed contained quartz granules (0.1 to 1.4 mm in diameter) and scattered worn bone and teeth fragments. The ground-mass was noted to be a calcite and limonite-cemented, fine-grained sand with glauconite present as a notable accessory. The fauna collected by Sweeting from the bone bed and determined by Swinton (in Sweeting, 1925, p.11), included teeth and scales of the fish Lepidotus, probably Lepidotus mantelli Agassiz and teeth of the crocodile Goniopholis crassidens Owen. This quarry is now degraded but the Top Ashdown Sandstone is, however, exposed in the valley some 7 to 10 m below the old quarry floor: this is one of the few localities where the Telham Bone Bed can be related to this member in structurally simple ground.

The sandstone which forms an outlier at Green Street [TQ 767 118] lies 15 m above the base of the formation and is at least 10 m thick. It probably results from the coalescence of thin separate sand beds which occurs in the Nash's Farm area, and may be correlated with the outcrop at Upper Wilting Farm [TQ 773 109].

Hollington area, north of Hastings

In the area between Hollington and Castleham Farm, the composite succession proved in trial boreholes is as follows:Tunbridge Wells Sand, 7.6 m; Wadhurst Clay (upper part), 6.7 m; Northiam Sandstone, c.13 m; Wadhurst Clay (middle part), c.24 m; 'Tilgate Stone' with bone fragments, 1.2 to 2.4 m; Wadhurst Clay, to 4.6 m. Boreholes for the Adelaide Road development, Hollington [TQ 796 112] proved the following composite sequence north of the Wilting Fault: Tunbridge Wells Sand, at least 12.6 m; Wadhurst Clay (upper part), 8.7 m; Northiam Sandstone, at least 8.8 m; Wadhurst Clay (middle part), to 18 m.

Eastern area, between Westfield and Winchelsea

In the area between Westfield and Winchelsea, north of the Guest-ling Green Fault, the Wadhurst Clay contains at least four major sandstone bodies. Although the sandstones are locally impersistent and in places have markedly irregular bases, which suggest channel-structures, in a general way they may be regarded as occurring in two groups which fall within divisions 1 and 3 of (Figure 10).

The Cliff End Sandstone is a single unit, up to 8 m thick, close to the base of the formation in the area between Winchelsea and Hog Hill. Westwards a greater thickness of clay underlies this sandstone and it also splits into two in the area [TQ 860 155] near Guestling Thorn. Two sandstones were noted at this level in the Little Maxfield Borehole whereas at the Westfield Borehole three thin sandstones were noted (see (Figure 11)).

The higher group comprises the Northiam Sandstone and a lower sandstone which is roughly equivalent to the Hog Hill Sand Member (see p.30). Both are present with a thin clay separation near Little and Great Knight's Farms [TQ 830 169], at Three Oaks [TQ 840 146] and in the area [TQ 875 147] south of the Pannel Sewer. North and east of these localities only the lower sand body is generally preserved as outliers, as for example at Icklesham and Hog Hill.

West of Westfield in the area between Spraysbridge Farm [TQ 799 161] and Pattletons Farm [TQ 827 161], the sandstones in the Wadhurst Clay consist largely of fine-grained sands although pebbly sand was augered at two localities near Pattletons Farm [TQ 8270 1642, 8272 1592] and at two sites [TQ 8215 1583], [TQ 8202 1541] to the east of Downoak Farm, in each case near the top of sandstone bodies.Many quartz pebbles up to 12 mm in diameter were noted in the soil [TQ 830 151] in a comparable situation to the south-east of Oak Wood.

The main road descending Crowham Hill to Brede Bridge was improved in 1937 and the section was recorded by Allen. This is summarised as follows: Tunbridge Wells Sand, c.9.3 m; Wadhurst Clay, clay and shale, grey and mottled purple and red, c.6.7 m; sandstone, 0.76 m; clay, 0.73 m. It is interesting to note that here, as in the nearby Westfield Borehole [TQ 8204 1614], grey clays as well as mottled red clays occur below the top of the formation (Figure 11).

The sandstone beds of the lower group are exposed in waterfalls in North Wood. The higher section [TQ 8416 1582] shows: 'Tilgate Stone', 0.15 m; shale and mudstone, 0.35 m; 'Tilgate Stone', 0.15 m; mudstone, 0.08 to 0.13 m; sandstone and shale, 0.18 m; sandstone, irregular top, 0.08 to 0.23 m; mudstone and shale, 1.33 m. The lower exposure [TQ 8417 1586] probably continues the succession downwards: shale, up to 1.8 m; sandstone, up to 1.95 m.

The basal beds of the Wadhurst Clay are exposed in a stream gully [TQ 8714 1667] about 300 m north of Toke Farm, Icklesham, where the succession is as follows: sandstone, 4 m; sideritic shelly limestone, 0.45 m; shale, 0.3 m; 'Tilgate Stone', 0.08 m; shales with shells and lignite, 0.68 m; siltstone and sandstone, c.1.6 m; shale, 0.25 m; Top Ashdown Sandstone, sandstone, 2.1 m. A stream section [TQ 8755 1613] in the Cutthorn Gill on the south side of the ridge at Icklesham shows a sequence in the lower beds of the Wadhurst Clay, including the Cliff End Sandstone: clay, 1 m; sandstone and silt, 0.3 m; Top Cliff End Pebble Bed, pebbly sandstone, rippled top, 0.1 m; Cliff End Sandstone, sandstone, 0.38 m; pebble bed, 0.05 m; sandstone, 0.3 m. A waterfall section [TQ 8751 1611] lower down the stream probably continues the sequence downwards as follows: sandstone and silt, c.4 m; clay, 0.45 m; 'Tilgate Stone' channelled in shales with siderite and lignite, 1.1 m; shell bed, 0.1 m; mudstone, up to 1.2 m. The Top Ashdown Pebble Bed was located in the stream bed below, which proves that the sandstone within the sequence is the Cliff End Sandstone. The Icklesham Borehole [TQ 8763 1586] lies 275 m, south-east of this locality.

A brown sandstone with seams of small quartz pebbles, near the base of the sandy beds, was noted in the lane-banks [TQ 8845 1565] just south-west of Elms Farm (White, 1928, p.69). This sandstone is the Hog Hill Sand Member (Figure 10).

Small exposures [TQ 8890 1584]; [TQ 8905 1585] to the south of Hog Hill show the topmost beds of the Cliff End Sandstone. Up to 2.4 m of massive sandstone is present at the former locality whereas decalcified 'Tilgate Stone' overlies 1.2 m of sandstone at the latter. Comparable lithologies are present in the road-cutting [TQ 8975 1631] south of Wickham Manor, where the Cliff End Sandstone is about 7 m thick. A pebbly sand was augered at the top of this sandstone at only one locality [TQ 8947 1585] in the Hog Hill area. The basal shales of the Wadhurst Clay are thin and much obscured by sandy wash hereabouts and so have not been shown separately on the geological map.

In the Winchelsea area, the Cliff End Sandstone is exposed, together with the topmost Ashdown Beds, in the former sea-cliffs and in lane sections (Figure 13). The Top Ashdown Pebble Bed is present in all these sections. Above it, shales with interlaminated siltstones and sand lenticles up to 0.3 m thick, are in turn overlain by a prominent band of clay-ironstone nodules with pronounced 'boxstone' weathering. The ironstone band 0.15 m thick is directly overlain by the Cliff End Sandstone, seen up to 4.5 m, which here shows a spectacular development of 'Tilgate Stone' and related decalcification phenomena. The sandstone is fine grained, less friable than at Cliff End, and shows trough cross-bedding with shell moulds on the bedding planes.

The lower of the two groups of sandstones is exposed [TQ 8630 1460] in Guestling Wood, where up to 2.4 m of massive, fine-grained sandstone with silty partings is present. Old quarries [TQ 8642 1421]; [TQ 8651 1423] to the south near Fairlight Wood show comparable sections, apparently at the top of this sandstone, in faulted ground. The former quarry shows the following sequence: clay and shale with sandstone bands, c.1.5 m; pebble bed with rippled top, 0.04 m; sandstone with lignite near top, 3 m.

South of the Pannel Sewer, small roadside quarries expose the following section near Watermill Cottages [TQ 8640 1515]: clay and clay-ironstone, 0.3 m; pebble bed, up to 0.08 m; sandstone, c.3.9 m. This area of Wadhurst Clay is entirely fault-bounded so that it is hard to be certain of its precise correlation. It would seem that the Cliff End Sandstone is not developed hereabouts and that the sandstone exposed is approximately equivalent to the Hog Hill Sand Member. RDL, ERST

Southern coastal area, between Bexhill and Hastings

In the Bexhill area, no evidence was found to justify the extensive Wadhurst Clay outcrop shown on the Old-series geological map. The BGS Cooden Borehole [TQ 7043 0641] (Lake, 1975) proved Weald Clay at the surface but the Wadhurst Clay succession in the borehole may be summarised as follows (see also (Figure 11)): Wadhurst Clay (upper beds), 7.68 m; Northiam Sandstone, 5.24 m; Wadhurst Clay (cyclic sequence) faulted at base, 11.67 m.

In the coastal tract, proceeding eastwards, Wadhurst Clay is first encountered at the surface in the area round Pebsham Farm [TQ 765 090] to the east of the Sidley Fault. A well defined 'Tilgate Stone' horizon which is generally decalcified is present in the upper beds to the west of Pebsham Farm. To the north of the farm, gas-pipeline excavations proved the existence of a small outlier of Tunbridge Wells Sand [TQ 7668 0954] overlying red clay and a thin shelly sandstone about 5 m below the base of the former. It is probable that the 'Tilgate Stone' horizon is equivalent to the Northiam Sandstone.

To the east of Pebsham Farm the following succession was exposed in a quarry [TQ 7687 0905] in 1968: mudstone with plant debris and bands of ironstone, sandstone and shelly limestone, c.2.6 m; siltstone, 0.48 m; Top Ashdown Pebble Bed, 0.05 m; Ashdown Beds, —. In the Harley Shute area [TQ 783 093] a prominent sandstone up to 15 m thick is present at least 25 m above the Ashdown Beds. This sandstone is regarded as equivalent to the Northiam Sandstone.

A temporary exposure made in 1973 at West Ascent (St Leonards) [TQ 7982 0885] showed the following section: talus, 0.6 m; mudstone and siltstone, 1.4 m; pebble bed, 0.08 m; sandstone, 1.15 m; sandy mudstone, 0.7 m. The pebble bed is possibly the 'thin conglomerate, containing remains of Iguanodon and other reptiles, and of Lepidotus fittoni, noted for 'presumably no great distance' on the foreshore below St Leonards Church (White, 1928, p.47 after Parish, 1833, p.3), It may be equivalent to the Cliff End Bone-Bed.

The geology of the St Leonards area to the north of the former sea cliff is complicated by faulting. The paucity of exposures makes interpretation difficult under these circumstances. A section has been recorded, based on boreholes along the line of the Bopeep railway tunnel [TQ 7909 0905]–[TQ 8025 0936]. It is not clear whether the Northiam Sandstone is present in this area, as a bed of significant thickness, and this factor is critical to the interpretation of the stratigraphy. It is probable that the thin sandstone which is present at outcrop [TQ 792 093] south of Filsham Road is this member but a temporary exposure [TQ 7922 0973] at Gresham Way, 500 m to the north, showed beds higher in the sequence, which are allocated on the 1:50 000 geological map to be Tunbridge Wells Sand and the topmost Wadhurst Clay, as follows: Tunbridge Wells Sand, sandstone and silts, 2.7 m; Wadhurst Clay, clay with ironstone nodules, 1.25 m; 'Tilgate Stone' decalcified, 0.1 to 0.3 m; clay, 1.5 m. A large block of pebbly sandstone was seen in the spoil material but its source could not be determined. The absence of distinctive red-mottled clays in this sequence is anomalous and it is possible that the upper arenaceous beds belong to the Northiam Sandstone. RDL

South-eastern area, between Baldslow, Hastings and Cliff End

In the area between Baldslow [TQ 797 131], Hastings and Cliff End, at least four major sandstones are present in the Wadhurst Clay. The lowest of these is the Cliff End Sandstone which is present as a continuous unit in the coastal tract eastwards from West Hill, Hastings [TQ 825 102] to Cliff End and also occurs near St Helens [TQ 820 120]. The irregular disposition of sandstone bodies in the Silverhill Park area [TQ 807 102] and the paucity of reliable sections between St Leonards and Baldslow makes correlation further west speculative.

The Northiam Sandstone, which is the topmost of the four sandstone bodies, is present in the area between Baldslow and Hazelhurst [TQ 820 129]. The sandstones which occur in the intervening strata are impersistent, may coalesce laterally and are markedly affected by local channelling, as shown, for example, in the outcrop patterns at Fairlight Place [TQ 848 113] and in the area [TQ 856 117] to the west of Fairlight Church.

Near Baldslow red clays were not observed in the beds beneath the Tunbridge Wells Sand. A nearby brickpit [TQ 810 133] formerly exposed the beds at the level of the Cliff End Bone-Bed (White, 1928, p.67), as follows: talus, clay with ironstone, 2.4 m; bone-bed, 0.46 m; lignitic clay and shale, 0.5 m; marl with 'Cyrena' and 'Cypridea', 1.8 m; calcareous sandstone with 'Cyrena' , 1.2 m. In the north-western end of the pit, the talus was noted to thin and a grey laminated silty clay with flat clay-ironstone concretions was observed above the bone-bed. The latter included 'teeth of Lepidotus fittoni Ag. and of Goniopholis crassidens, small polished coprolites, and small phosphatic nodules'.

'Tilgate Stone' debris was noted at several localities in the area of the sandstone outcrop at Silverhill Park. In the southern area, a shallow cutting [TQ 8011 1158]–[TQ 8045 1152] proved clays and sandstones. Some of the sandstones are calcareous, 'with large spiral bodies of the same kind of rock, to 7 ft. [2.1 m] or more in length, some having a dextral, others a sinistral, twist conforming to the law of the logarithmic spiral, characteristic of molluscan shells' (White, 1928, p.66). These forms were named as Dinocochlea ingens gen. et sp. nov. by Woodward (1922, pp.242–248). A nearby quarry in the basal beds of the Wadhurst Clay [TQ 808 113] formerly exposed (White, 1928, p.67) beds with a south-westerly dip of 3 to 5°, as follows: soil, 0.9 m; shale with ironstone nodules and casts of 'Cyrena', about 3 m; sandstone with 'Cyrena', 0.6 m; shale, 0.6 m; calcareous sandstone with 'Cyrena', 0.6 m; marl with 'Cyrena', Viviparus and fish teeth, 0.9 m.

South of the Sandrock Fault in the St Helens district of Hastings, sandstone is well developed in the lower Wadhurst Clay and crops out at the surface over much of the Hastings Borough Cemetery.

South and east of Pett, the Wadhurst Clay crops out between the Pett, Toot Rock and Marsham strike faults and includes a thick sandstone group above the Cliff End Sandstone. 'Tilgate Stone' in the latter was exploited along the outcrop south of Gatehurst [TQ 877 136]. Between the Toot Rock and Pett faults the Cliff End Sandstone is exposed in the higher part of the abandoned cliffs. At one locality [TQ 8915 1412] rippled coarse-grained quartz sand, representing the Top Cliff End Pebble Bed, rests on 6 m of massive buff and grey-white Cliff End Sandstone, the top 0.3 m of which is purplish and rich in plant debris.

To the south-west of Fairlight Place, the lower part of the Wadhurst Clay is exposed in sections in Fishponds Gill. In the highest exposure [TQ 8457 1107] up to 2.4 m of massive, very fine-grained Cliff End Sandstone with occasional small quartz pebbles is present. The base of this sandstone crops out in a minor gully [TQ 8445 1079] below the waterfall which continues the section downward as follows: sandstone, 0.9 m; shale, siderite mudstone and siltstone, 0.43 m; sandstone, 0.5 m; shale and siltstone, 0.7 m; sandstone, 0.25 m.

The Cliff End Sandstone is again exposed in a number of old quarries between Fairlight Lodge [TQ 851 118] and Fairlight. The quarry [TQ 8520 1184] near the lodge exposes the basal beds of the Wadhurst Clay immediately below this horizon, dipping gently south-westward: mudstone and shale, 0.56 m; sandstone, 0.4 m; shale, 0.13 m; shell bed, 0.1 m; shale and siltstone, 0.58 m; Top Ashdown Pebble Bed, 0.05 m; Ashdown Beds, shale, 0.1 m; sandstone, 1.8 m. The roadside quarry [TQ 855 118] to the east exposes up to 5.2 m of massive, fine-grained Cliff End Sandstone with traces of roots, and some streaks of quartz pebbles, and plant debris. A patchy calcareous cement is present near the top of the section which gives rise to hard, dogger-like concretions. Traces of a pebble bed up to 0.04 m thick were noted at the very top of this section.

The Cliff End Sandstone was formerly quarried at two sites near Fairlight. Both now fall within the Hastings Country Park which was set up in 1974. The quarry near Fairlight Church was in use until 1967 and was the site of the BGS Fairlight Borehole [TQ 8592 1173] drilled in 1970–1971. The quarry in which it was sited now forms the car park for the country park, but some faces in the top of the Cliff End Sandstone are still visible. A small face in the northern part of the workings [TQ 8589 1185] formerly exposed the following section: Wadhurst Clay, siltstone and shale, 0.5 m; Top Cliff End Pebble Bed, 0.1 m; Cliff End Sandstone, sandstone with roots and plant debris, c.3.5 m. Elsewhere in this quarry [TQ 8592 1177] the following section was noted: Top Cliff End Pebble Bed, 0.1 m; Cliff End Sandstone, sandstone, locally pebbly with plant debris and roots, c.4.3 m. Combining the thicknesses of the Cliff End Sandstone visible in the quarry and proved in the borehole at Fairlight gives a total of approximately 10 m which is about 0.8 m less than measured in the cliffs at Cliff End. The prominent band of ironstone maintains its position about 0.9 m above the Top Ashdown

Pebble Bed. At Cliff End, the Cliff End Sandstone rests directly on the ironstone, but at Fairlight 0.88 m of shales and sandstone intervene. This suggests that the base of the Cliff End Sandstone is erosional and has cut down more deeply at Cliff End.

The second old quarry at Fairlight lies 0.5 km SSW of the church [TQ 858 115] and now forms part of a nature trail within the Hastings Country Park. The Cliff End Sandstone which is up to 5 m thick, is exposed almost continuously along the north and east sides. At the eastern end of the workings, overburden has been stripped away to reveal the bedding plane at the top of the Cliff End Sandstone; this displays interference ripples, 20 x 7 cm, and trace fossils in some of the hollows. The Cliff End Sandstone shows prominent vertical roots throughout the exposed thickness, especially in the top 0.3 m which approximates to a fossil soil. Relationships between two sections, which are about 50 m apart in the quarry, are summarised in (Figure 14). The black sand with plant debris in section 2, may represent a soil formed in a slight hollow or channel, which thus escaped the erosional episode that preceded the deposition of the transgressive Top Cliff End Pebble Bed. ERST, RDL

Tunbridge Wells Sand

North-western area, around Mountfield, Battle and Sedlescombe

In the area round Mountfield and towards Sedlescombe, the Tunbridge Wells Sand is present in a series of faulted outliers. Excavations [TQ 7200 2095] south of the Darwell Reservoir dam showed up to 5 m of interbedded silts and sandstones with thin clay beds up to 0.3 m thick. Up to 3 m of sandy beds are exposed in the road cutting [TQ 726 208] to the south-east of Taylor's Cottage.

The road cutting at Vinehall [TQ 750 209] in 1969, showed a section in about 7 m of grey sandy silts with sandstone bands, on Wadhurst Clay. ERST

In the area between Penhurst and Battle, silts are the dominant lithology in the lowest part of the Tunbridge Wells Sand, but about 15 m above the base sand becomes dominant and a massive sandstone up to 10 m thick forms a good feature at this level, all over the area. Very few exposures were seen in this area. There are no mappable clay seams within the 30 m of strata which are preserved.

In Creep Wood and Spray's Wood there are 3 m-high crags [TQ 7075 1687] of the massive sandstone which occurs about 18 m above the base of the Tunbridge Wells Sand. RABB

Western area, between Ashburnham Place and Catsfield

In the area between Ashburnham Place and Catsfield the Tunbridge Wells Sand comprises alternating sands and silts with subordinate clayey intercalations. A group of thick sandstones is present between 18 and 23 m above the base. In the immediate vicinity of Catsfield red-mottled silty clays are present in division 2.

The banks of Freckley Hollow [TQ 7100 1480]–[TQ 7100 1423], northeast of Burnt Barns Farm, show an almost continuous section, on the dip-slope, of well bedded, very fine-grained sandstones with silt lenses and partings. Large-scale, southward dipping, cross-bedding is present. Flaggy ferruginous sandstone overlies white massive sandstone in a small roadside exposure [TQ 7098 1357] south-east of Burnt Barns Farm. Most of these exposures lie within the sandstone group described above.

Red-mottled silty clays with a maximum thickness of about 7.5 m are seen at Catsfield. The larger outcrop [TQ 728 141] wedges out southward, probably as the result of channelling. In the areas to the east around Wyland Farm pebbly medium-grained sandstones occur about 15 to 18 m above the base of the Tunbridge Wells Sand. Other exposures at about this stratigraphical level include a road-cutting [TQ 7398 1446] in massive fine-grained sandstone, 1.5 m high, near Powdermill House and a lane bank section [TQ 7480 1495] near Downbarn Farm which shows 2.3 m of sandstone with grey silts.

At the Powdermill Lake outflow channel about 6 m of the lowest beds in the Tunbridge Wells Sand are exposed [TQ 7412 1457]. These include fine-grained sandstones with clayey silts and with lignitic and mud pellet beds. Topley (1875, pp.67–68) described a now obscured section nearby in Powdermill Lane [TQ 744 147]–[TQ 744 144]. 'At the top of the hill is sand and sandstones with two or three feet [0.6–0.9 m] of mottled clay'. Further down, at the bend of the road, he noted the sequence summarised as follows: clay and loam, 1.8 m; sand, 0.3 to 0.6 m; sandstone, 1.2 m; clay, 0.9 m. Topley commented that these beds were apparently faulted but the section here was indistinct; lower down the hill, he noted beds summarised as follows, dipping N at 3°: sand and sandstone, 11.3 m; loam, 0.8 m; sandstone, 1.8 m; clayey loam, 2.4 m.

A trial water well [TQ 7431 1496] south of Battle, proved the sequence: Tunbridge Wells Sand (red-mottled clays in uppermost 3 m), 49 m; Wadhurst Clay with Northiam Sandstone, 56 m; Ashdown Beds, to 55 m. The above classification is based on chipped samples and a gamma-log, kindly provided by the Eastbourne Waterworks Company. The borehole demonstrates that the red clays shown in this vicinity on the 1980 edition of the 1:50 000 Geological Sheet as Wadhurst Clay are in fact, fault-bounded clays within the Tunbridge Wells Sand. The structural diagram (Figure 15) has been modified accordingly.

Central area, around Westfield

In the Westfield area, where up to 30 m of the Tunbridge Wells Sand is preserved, the strata comprise fine-grained sands and silts with thin red-mottled, pale grey silty clays. The highest beds include medium-grained sands. A laneside exposure [TQ 7982 1641] near Platnix Farm shows 1.5 m of cross-bedded ochreous and pale grey sandstones with iron pan development. Clay beds are significantly absent in this vicinity, possibly due to the presence of comparable sandstone-filled channel structures. The Westfield Borehole [TQ 8204 1614] proved 3.32 m of siltstone and sandstone above the Wadhurst Clay.

Ninfield area

Down, only the lowest 30 m of the Tunbridge Wells Sand are preserved. These beds comprise sands and silts and are generally poorly exposed in small road-side sections. An old pit [TQ 7386 1275] at Catsfield Place exposed 1.2 m of flaggy, weakly bedded, medium-grained sandstone.

South-western area, around Bexhill

In the coastal area between Hooe and Bexhill, south of the Whydown Fault, all but the lowest beds crop out. The red-mottled clays of division 2 (p.27) crop out on the slopes below Hooe, where they are interrupted by channels, and extend through Whydown, to Highwood Golf Course [TQ 720 089]. Further outcrops are present at Bexhill Down [TQ 734 081] and at Galley Hill. These beds comprise ochreous and pale grey mottled silty clays, clayey silts and silts; red mottling is impersistent and tends to be preferentially developed towards the top of the more argillaceous beds.

Inland the present exposures are poor and are typically restricted to the sandstone beds. In 1935, Taitt (in manuscript) described the road cutting [TQ 690 078] north-west of Constables Farm as follows: 'The lowest beds exposed are about 6 ft [1.8 m] of white fine-grained sands overlain by about 10 ft [3 m] of flaggy ferruginous sandstone with lignite, then white silty sands, then grey green silty sands with clay lenses — the clay is purplish brown to black in colour — then ferruginous flaggy sands in very irregular bands'.

North-west of Bexhill the brickpit [TQ 720 094] at Turkey Lane (formerly termed the Lunsford Works and now the Ashdown Works) has been extended considerably over latter years. In 1977 a composite section was measured, mainly in the central part of the north face. The strata appear to be mainly channel deposits and are summarised as follows: weathered sandy silt, 1 m; laminated sandy silt, locally lignitic, 2.8 m; sandstone and siltstone, 0 to 1 m; clayey siltstone, 1.6 m; silt with sand laminae, sharp base at floor of channel, 1.3 m; silty clay, sharp base, possibly a channel feature, 2.5 to 3 m; silty mudstone with lignite fragments, c.10 m; lignitic silty sand with laminated grey silty mudstone, possibly a composite channel deposit, 1.4 m; siltstone, 0.8 m; silty clay, red-mottled, c.5 m.

A large channel feature in the top of the north-west corner of the pit was better exposed in 1968 and was seen to cut down northwestwards. Major variations occur in the basal lag deposits of the channels: in some places they comprise lignitic sandstones but elsewhere there is little lithological contrast in the argillaceous beds above and below the channel floors. The structureless red-mottled beds pass laterally into grey clays and silts which have a bedded appearance on weathering. The red clays were formerly mistaken for the top beds of the Wadhurst Clay (White, 1928, p.62) but boreholes sunk by Redland Bricks Limited proved the presence of 13 m of Tunbridge Wells Sand below these beds.

The coastal succession from Cooden to Galley Hill (p.61) is similar to that observed in the Cooden Borehole (Lake, 1975) and progressively lower strata are exposed from west to east, including the upper 80 m of the Tunbridge Wells Sand. RDL

Hastings area

South of the Ore Fault, most of the built-up area of Bohemia down to the coast at White Rock is underlain by Tunbridge Wells Sand. A number of small temporary sections, noted during the survey, showed mostly silty sandstone with silty clay. On the north side of the A21 (Bohemia Road) near Hastings Museum and Hospital [TQ 810 094], up to 6 m of yellowish grey, friable silty sandstones occur. They are well jointed, laminated in part and dip SSE at 5 to 7°. ERST

Weald Clay

In the area between Ninfield and Lunsford's Cross and at Henley's Details of the coastal exposures are given in Appendix 1.

Chapter 5 Structure

The Hastings district lies athwart the main structural axis of the Wealden anticlinorium. Lamplugh (1919) deduced from the results of some early deep boreholes, that the major surface anticline involving Cretaceous formations overlies a deep basin of Jurassic rocks. Subsequently parallels were noted between the apparently inverted structure of the Weald, in which a depositional basin is overlain by a structural anticline, and similar structures discovered during the search for hydrocarbons in the North Sea (Kent, 1975).

The traditional view, summarised by Wooldridge and Linton (1955), that the surface folding of the Wealden rocks represents merely the weak marginal effects of the mid-Miocene Alpine orogeny, has proved increasingly difficult to maintain. It is now generally thought from a study of deep boreholes and geophysical data, most of which is commercially confidential, that structures in the basement rocks have strongly influenced those in the Mesozoic and Tertiary rocks (Lake, 1976), and have also controlled sedimentation to some degree. Thus faults affecting the surface strata may be related to structures in the Palaeozoic 'basement' rocks. The precise relationship and the genesis of the structures, however, await publication of these confidential data.

In the Hastings district there is a well defined fault pattern especially in the central area where the oldest rocks are exposed. The minor faults may be tensional accommodation structures between major faults. Folds seem to be discrete features of limited lateral extent, which are related either to the internal structure of individual fault blocks or to terminal bending against the more important faults. The structural pattern presented here differs from that of earlier authors, who regarded the Weald as a plexus of en-echelon folds with subsidiary faults. In this account greater importance is ascribed to vertical movements, especially faulting, in the genesis of major folds.

The view that the folding of the Weald is of mid-Miocene age needs modification in the light of modern work on basin development and evidence from deep boreholes. Evidence of intra-Jurassic and Cretaceous movements of fault blocks within the Wealden basin and on its margins is accumulating from the study of shallow boreholes. For example at Cliffe in North Kent (Owen, 1971; Shephard-Thorn in Dines, Holmes and Robbie, 1971) a surface anticline in Chalk and Lower Tertiary strata has been shown to overlie an east–west graben which was active at least from Oxfordian to Albian times. Early borings in the Kent Coalfield yielded evidence of overlaps and unconformities in the Jurassic and Cretaceous rocks on the northern margin of the basin (Lamplugh, Kitchin and Pringle, 1923). Workings at Tilmanstone Colliery subsequently proved the presence of a graben comparable with that at Cliffe, which preserves Oxford Clay beneath the overlapping Lower Cretaceous strata (Plumptre, 1959). Allen (1976, 1981) also invoked contemporary movements of fault blocks in the London Platform source area of the Wealden deposits, to explain the periodic influxes of arenaceous sediments into the Wealden 'lagoon' (p.18). Although this evidence supports Kent's (1975) concept of fairly continuous, rather than episodic, crustal movements during the development of the north European Mesozoic basins, it remains difficult to pinpoint the time at which the overall Wealden structure achieved its present inverted form. There is stratigraphical evidence of some deformation and erosion of the Chalk prior to the deposition of the earliest Tertiary formations in southern England, and this deformation may mark the initial stage of the Wealden uplift. On regional evidence the final stage of uplift, when the Wealden structure achieved its present form, is assigned to the mid-Miocene Alpine orogenic period. Apart from minor seismicity and some high level Pliocene deposits there is little evidence of more recent movements.

The main structural features of the district are depicted in (Figure 15). Because of the varying erosional and structural levels across the area it has not been possible to contour a single horizon everywhere and because changes in thickness are not known in detail, no attempt has been made to reduce contours to a single horizon. In some blocks of Ashdown Beds in the eastern part of the district, where the top of the formation has been removed by erosion, conjectural contours have been based on local marker horizons and should be treated with some reserve.

Structural units

The complex pattern of faults and contours depicted in (Figure 15) may be initially confusing but if it is compared with the 1:50 000 geological map, the following structurally positive or negative units may be recognised (Figure 16).

Unit 1: North of the Brede Valley Fault and its westward continuations

Here Ashdown Beds and Wadhurst Clay strata are up-faulted relative to those in Unit 2.

Unit 2: Between the Brede Valley and Guestling Green faults

This is a graben-like block extending from Westfield to Pett Level, in which Tunbridge Wells Sand and Wadhurst Clay strata are preserved.

Unit 3A: Around Brightling, Netherfield and Battle

Here Purbeck Beds are exposed in a horst-like anticlinal block. The anticlinal lineament is offset by 2 to 3 km from that in Unit 3B.

Unit 3B: Between the Guestling Green and Ore faults

In this up-faulted block, which extends from Crowhurst to Fairlight, Ashdown Beds with cappings of Wadhurst Clay occur. This unit includes the major Fairlight Anticline, with a prominent line of steeply dipping strata and reversed faults on its northern side, which may reflect a major eastward-trending basement structure.

Unit 4: Between Battle and Bexhill

Here, in the south-west of the district, down-faulting and the general southerly dip have preserved the Tunbridge Wells Sand and basal Weald Clay.

Unit 5: South of the Ore Fault

In this block the strata are faulted down to the south, preserving Tunbridge Wells Sand around St Leonard s.

There is broad agreement between the structural units outlined above and the patterns of gravity and aeromagnetic anomalies shown in the insets on the 1:50 000 sheet. The structural lineament from Netherfield to Fairlight is emphasised by a belt of positive Bouguer gravity anomalies. On the ground, horsts and reversed faults have been recognised locally along this belt. Major faults, with displacements of more than 60 m, are concentrated in the area between Battle and Fairlight. RDL, ERST.

Details

The Purbeck inliers

The major structures in the north-west of the district (Unit 3A in (Figure 16)) are strike faults, trending WNW–ESE, with which folds are intimately associated. Bending of strata against fault planes is most marked close to the northern boundary faults of the inliers, where the fault throws are generally greatest. This indicates that the faults, rather than the folds, are the control structures. Reverse faults have been postulated by Bazley (in Anderson and Bazley, 1971, pp.6–7) but, with the exception of the fault proved in Liassic strata in the Brightling No. 1 Borehole [TQ 6726 2182], about 1 km north-west of Brightling, the evidence is ambiguous. Apart from this exception, Howitt (1964) thought that all the faults discovered in the Ashdown Beds–Portland Beds succession were normal. It is possible, however, that the inclination of the faults may alter at depth in the lower part of the Jurassic sequence. The minor faults may locally pass laterally into monoclinal 'roll' structures.

South of Battle

This northern part of structural Unit 4 (Figure 16) is a zone of accommodation between the Catsfield Stream and Whydown strike faults, trending E–W, and the elements of Unit 3B which trend ESE–WNW. Subordinate folds are also present, more particularly in the Battle–Catsfield area where a syncline, trending NE–SW, seems to mark the western termination of the Battle Ridge structure.

A fault complex which trends N–S to the east of Caldbec Hill, Battle seems to link the zone of Purbeck inliers to the Fairlight Anticline. Another weak synclinal structure is present in the Brede valley at the eastern end of the zone of Purbeck inliers.

The Bexhill coastal section

Minor flexuring seen in the Weald Clay adjacent to the fault on the foreshore at Cooden suggests, in conjunction with evidence from the Cooden Borehole [TQ 7043 0641], that a complex of faults is present. This complex has been represented schematically on section AB of the 1:50 000 geological map. To the east, in the area which includes the Galley Hills, undetected faults may complicate the stratigraphical sequence. Structural repetitions of the sequence may explain the unusually extensive sandstone reefs at a relatively low level in the Ashdown Beds, east of Glyne Gap. RDL

North of the Brede Valley Fault

This up-faulted area, which corresponds to structural Unit 1, is broadly anticlinal and is limited to the north on the adjacent

Tenterden (304) Sheet by the Peasmarsh Fault (Shephard-Thorn and others, 1966). The structural trend is east–west. The group of strike faults, including the Footlands, North and South Powdermill, Reyson's and Stonestile faults, are considered to be tensional along the crest of the anticline. The conjectural Brede Valley Fault, which throws down to the south, seems to run into the Archer Wood and other faults which form the northern boundary of the Purbeck inliers, but which throw down to the north.

Westfield to Pett Level

This corresponds to structural Unit 2 (Figure 16) which lies between the Brede Valley and Guestling Green faults. Here Wadhurst Clay and Tunbridge Wells Sand strata are preserved in a graben-like structure, which is thrown down about 60 m relative to the rocks to the north and south. Internally the graben is cut by a number of oblique minor faults, several of which trend south-westwards, for example the Westfield and Three Oaks faults. A gentle anticlinal structure which trends ENE–WSW has been traced between Guestling Thorn and Winchelsea, and is cut by the Icklesham and Wickham Manor faults. The Pannel and Pickham faults trend approximately from E–W roughly parallel with the Brede Valley and Guestling Green faults. A block of Ashdown Beds, north and east of the junction of the Three Oaks and Guestling Green faults is thrown up in an apparently anomalous fashion.

Crowhurst to Fairlight

The area between the Guestling Green and Ore faults corresponds to structural Unit 3B (Figure 16). It is dominated by the major Fairlight Anticline, which in detail seems to be a horst-like structure rather than a simple fold. The intensity of strike and oblique faulting within its axial zone supports the theory that it resulted from the rejuvenation of a major fracture in the Palaeozoic basement. High northerly dips are present between the Coghurst and High Lankhurst faults and also between the Marsham and Bachelors Bump faults. These, together with the reversed faults on the coast at Haddock's and Fairlight Cove, make up a strong lineament on the northern flank of the anticline (Figure 15). Vertical dips in the Ashdown Beds at the Marsham Fault [TQ 8369 1333] between Old Coghurst and Rock Farm are probably due to fault movements. The Wilting Fault has a reverse throw and pivotal dip-faults occur to the north of this.

Bexhill to Ecclesbourne

In this coastal block which corresponds to structural Unit 5, the strata are thrown down to the south by the Wilting and Ore faults. The block is affected by two sets of oblique faults which trend respectively NW–SE and NE–SW. Tunbridge Wells Sand is preserved between two of these faults in the St Leonards–Hastings area, where a minor anticlinal flexure brings up an inlier of Wadhurst Clay. ERST, RDL

Chapter 6 Quaternary

The Quaternary deposits of the Hastings and Dungeness district occur mainly on the low ground east of Winchelsea and Rye, over the southern part of Romney Marsh, at Bulverhythe [TQ 775 090] and Hooe Level [TQ 690 070], and in the valleys of the main streams such as the Brede and Tillingham. These include peat, river and marine alluvium, (the latter varying from clay to sand), storm beach gravel and blown sand. Solifluction deposits (Head) have been mapped on some of the slopes of the river valleys while the effect of the cold Quaternary climate can locally be seen in such phenomena as valley-bulges and landslips. (Table 6) summarises the most probable relative dating of the deposits and events of the Quaternary of the district. (Figure 18) illustrates the nature and thickness of the Flandrian deposits around Rye and at Dungeness.

In the present district the periods of glaciation experienced north of the Thames are indirectly recorded by periglacial phenomena and by sea-level changes consequent on the waxing and waning of the ice-sheets. Despite the multiple nature of these events, none of the Quaternary deposits of the district can be assigned with certainty to stages earlier than the Devensian, the latest cold stage, and the succeeding Flandrian warm stage.

It is probable that local icefields or permanent snow may have occupied the higher ground at times during cold periods when widespread solifluction also gave rise to Head deposits while large-scale valley-bulges, together with cambers and gulls on the valley sides and interfluves, probably also originated in these cold periods.

Although there may have been a long-term eustatic fall in sea level thoughout the Quaternary, its effects were overshadowed by the considerable fluctuations of sea level consequent on the growth and waning of polar ice-sheets in this period. Direct evidence of the position and elevations of early coastlines is, however, scanty. To the west at Black Rock, Brighton, there is a raised beach at about 7.5 m above OD, which has been generally believed to be of Ipswichian (Last) interglacial age. Recent amino acid assays of shells from this raised beach (Davies, 1984) refer it to Stage 5 in the palaeotemperature curve of Shackleton and Opdyke (1973). In the present district, at Cliff End [TQ 8877 1303] an elevated sea cave (now destroyed by coast erosion) provided the only local evidence for the position of an early possibly, Ipswichian, coastline; the floor of the cave was at 18.2 m and it yielded signs of Mesolithic occupation (Palmer, 1972; 1977). In view of its greater height, it may represent a high sea level earlier than that of the Black Rock raised beach. More obvious evidence of sea level changes in the later Quaternary is supplied by the variations of base-level of the rivers, as revealed by boreholes and the radiocarbon-dating of organic sediments. In cold stages the rivers would respond by downcutting to the lower base-level but during the interglacial periods they aggraded their lower reaches, filling the 'buried valleys', and laid down spreads of gravel in their floodplains. Surviving remnants of terrace gravel in the Brede and Tillingham valleys lie at 15 to 18 m above OD (7 to 10 m above the alluvium) and possibly grade to the level of the supposed Ipswichian raised beach.

At the beginning of the Flandrian period 10 000 years ago, sea level in the English Channel stood at least 40 m below its present level. As the climate ameliorated, the melting of the ice-sheets caused a rapid rise of sea level, the Flandrian transgression. This saw the final filling of the Devensian 'buried valleys' and the deposition of the earliest marine sands and gravels of the Dungeness–Romney Marsh complex. Brief regressions or still-stands of sea level, possibly augmented by the growth of coastal shingle barriers, led to peat formation at several horizons. The most notable example of this is the submerged forest bed of Pett Level, which lies at about present low water mark and has been dated at about 5000 years old. Since its formation, sea level in the Channel has remained at or about its present level. The later Flandrian saw the formation of coastal shingle barriers by eastward longshore drifting; in the lee of these barriers estuarine salt marshes developed and have been reclaimed and drained in historical times.

Periglacial phenomena and deposits; river deposits

Valley-bulges and cambers

These superficial structures are not depicted on the geological map but are probably present in and along most of the valleys that are underlain by relatively incompetent Wealden and Purbeck strata. The presence of valley-bulges is suggested by steep dips of variable direction in some streams, and accurate sections of such bulges have been recorded in two valleys that have been closely investigated during the construction of dams. At Powdermill Reservoir [TQ 800 195], north-west of Brede, the Wadhurst Clay crops out on the valley sides, but the floor of the reservoir is on relatively permeable sandstones, silts and clays of the Ashdown Beds. The cut-off trench encountered a bulge beneath the alluvium that extended for 100 m across the centre of the valley and had an amplitude of approximately 10 m (Walters, 1971, fig. 24, p.79). A similar structure was proved in the cut-off trench for Darwell Reservoir [TQ 720 213], 2 km west of Mountfield (Kellaway, 1972). Here the valley is floored entirely by Wadhurst Clay, but the bulge has crumpled strata over a zone 100 m wide in the centre of the valley, bringing Ashdown Beds sandstones close beneath the surface. It is apparent from the section (Figure 17) that much of the upper part of the bulge was removed by erosion before the present valley fill of gravel and alluvium was laid down. The original amplitude of the bulge may have been as much as 30 m.

Few clear examples of cambering and gulling have been noted during the recent survey, though infilled joint cavities have been observed in the highest Ashdown Beds sandstone near Hastings Castle and in the Cliff End Sandstone in the old Fairlight Sand Quarry [TQ 859 115], which suggests some movement of joint blocks downslope. In a roadside at Chick Hill [TQ 8871 1361], Pett, massive joint blocks of Cliff End Sandstone have been rotated backwards into the slope during cambering.

Landslips

In the inland parts of the district there are a number of small-scale landslips, chiefly involving slopes in Wadhurst Clay strata. Much larger landslips occur along the coast between Hastings and Cliff End and also at the foot of the abandoned Cadborough Cliff, west of Rye. These slips are developed mainly in Ashdown Beds strata, particularly where clays are exposed at the foot of the cliffs. They range from rotational slips involving 50 m or more of strata to minor mud-flows. Several of the slips are compound in nature having a rotational style on their landward side and passing into debris flows and mud slides seaward. Locally, as at Cliff End, smaller slips are present at the cliff top, where basal Wadhurst Clay slips over the Cliff End Sandstone on to the beach. Most of the landslips appear to have originated during the Devensian or early Flandrian periods.

Head

Silty loams are common on the lower slopes of many of the valleys. Typically they are uniform in texture, and dark brown in colour. They probably result from periglacial solifluction and from more recent hillwash preferentially generated at spring-lines, such as that at the base of the Tunbridge Wells Sand. Locally, however, a tendency for this material to be located on north- and east-facing slopes suggests the possibility of a wind-blown loessic component.

In places it is difficult to distinguish the Head from deeply weathered bedrock particularly where the latter is silty, because weakly consolidated silts and poorly sorted arenaceous deposits seem to be highly susceptible to de-structuring by permafrost. All gradations thus exist between in-situ deposits and their soliflucted derivatives. An arbitrary minimum thickness of 1.4 m was adopted for mapping these deposits. Where the nature of the silty material is uncertain, as on the Tunbridge Wells Sand of the Bexhill area, it has been considered to be solid.

Local deposits of angular rock debris with a brown sandy matrix have been noted on the steep sides of the coastal glens between Ecclesbourne and Fairlight, though they have not been shown on the map. They appear to represent fossil screes.

River gravels

Small patches of First Terrace River Gravels occur in the Brede and Tillingham valleys at about 7 to 10 m above the alluvial floodplain; they represent a single period of aggradation, probably during the Ipswichian interglacial. The gravels are dominantly of local origin, and their main components are pebbles of Wealden sandstones and siltstones in a ferruginous sandy matrix. They have been exploited on a small scale for local aggregate use.

Alluvium

Freshwater alluvium is present in the floodplains of the Ash Bourne and of the rivers Asten, Brede and Tillingham, and their tributaries. It consists mainly of mottled greyish brown silts and clays, commonly with a basal lag gravel of local materials and some small developments of peat. In minor tributary valleys the composition of the alluvium strongly reflects the rocks that crop out nearby. The alluvium passes seawards into Marine Alluvium. The passage between the two is imperceptible and in most instances the boundary has been taken at the farthest upstream extent of the old seawalls built for reclamation. Beneath the present floodplain and contiguous coastal marshland there are deep buried channels which were filled with alluvium as sea level rose during the Flandrian. Since the valleys were then probably tidal, the distinction between freshwater and Marine Alluvium within the channels is as arbitrary as it is at the surface.

Peat

Peat occurs near the surface only in the Tillingham valley, where it has a thin cover of recent silts. In a riverbank section [TQ 8683 2005], 1.2 m of dredged material was noted above 0.9 m of grey clay with plant fragments, which rested on a bed of peat at least 1.2 m thick. This bed continues under clay cover of 1.4 m for about a kilometre upstream and downstream of this mapped outcrop. In addition thin peat has formed locally in the patches of freshwater alluvium in the coastal marshland and in the slacks between shingle ridges of the Dungeness complex; none of the latter occurrences is thick enough to have been mapped.

Buried peats have been proved in trial boreholes at a number of localities. These are discussed separately below. ERST, RDL, JGOS

Flandrian coastal deposits

The deposits of Marine Alluvium, Storm Beach Gravel and Blown Sand, that have been mapped at the surface of the coastal marshlands of Hooe Level, Combe Haven (between Bexhill and Hastings), Pett Level and Romney Marsh, together with the shingle spreads of Rye Harbour and Dungeness, represent only the latter half of the Flandrian period. Boreholes have proved sequences extending down to nearly 40 m below OD (Figure 18) in the coastal marshlands and the buried channels beneath the river floodplains. A comparison of the available borehole records suggests much lateral variation with few widespread marker horizons, such as peats, except perhaps in the buried channels. This variability may reflect penecontemporaneous erosion and reworking in coastal environments that were exposed to the full effects of storms and tides.

(Table 7) shows the available radiocarbon datings for Flandrian deposits in the Channel coast area and is based on Shephard-Thorn (1976). Most of these samples were collected through the good offices of site investigation contractors and were not critically selected to date specific horizons or events. It is thus unwise to attempt to draw any definite conclusions on correlation with other areas.

The submerged forest of Pett Level and the widespread peat of the Rother, Brede and Tillingham valleys (Figure 18) have all yielded dates of around 5000 years old, which fall within the period of a regression of sea level between the transgressive phases Thames II and Thames III of Devoy (1979, 1982). These dates are, however, considerably older than those from the surface peats of Romney Marsh, dated at about 3000 years old, which Green (1968) suggested were equivalent to the submerged forest. It would seem that the submerged forest and its inland extensions have been preserved in the area west of Rye, but were either eroded away or not deposited in the Romney Marsh area, prior to the accumulation of the surface peats during the Bronze Age.

It appears that sea level rose sharply after the formation of the earliest peats about 9500 years ago until a major regression about 5000 years ago gave rise to the submerged forest of Pett Level and Bexhill, and related peat horizons in the river valleys. Subsequently sea level oscillated at or about its present level, with some signs of a transgressive phase in post-Roman times. During the last 1000 years, man has played an important geological role by reclaiming coastal marshlands and building sea defences. The district, unlike the Thames estuary, appears to have escaped any major subsidence towards the North Sea basin.

Marine Beach Deposits and Tidal Flats

The overriding factor in coastal development in the district is the eastward longshore drift, caused by the prevailing southwesterly winds. This drift has transported flint shingle in vast quantity from the nearest Chalk outcrops at Beachy Head more than 50 km to Dungeness. Shingle ridges thrown up by storms often form relatively permanent features and build up into complex spits and barriers, as at Rye Harbour and Dungeness, some of which are capped with dunes of sand blown off the lower beach. Shingle does not extend far below high water mark and most longshore transport takes place in the relatively narrow zone where waves break on the beach. The lower beach of the intertidal zone comprises quartzose, shell-sand which becomes finer seawards and passes into interlaminated dark clays and fine sands. A schematic section through a typical Dungeness beach is shown in (Figure 19) which demonstrates how apparent horizontal stratification is produced by the seaward accretion of beach deposits.

Salt marshes of the tidal Rother below Rye show many typical features such as the trapping of sediment by colonising plants and intricate tidal creek patterns. They typify the sedimentary environment in which much of the reclaimed clayey Marine Alluvium was deposited.

Marine Alluvium

Tidal flat and saltmarsh deposits have accumulated extensively in the lee of the coastal shingle barriers. These marshlands include Hooe Level, Combe Haven, Pett Level, the lower flood-plains of the Brede and Tillingham rivers, East Guldeford Level, Broomhill Level, Denge Marsh and other patches which lie between the major shingle spreads of Dungeness Foreland. The sediments, which range from fine sand to stiff grey clays, have accumulated up to the level of high tides over the past 3000 years or so. The sands may represent beaches passing seawards into tidal flats, as in the present Camber Sands, and the clays may represent salt marshes, as in the tidal reaches of the Rother. Reclaimed lands are lower on the landward side of an old sea wall because no sediment has accumulated after the embanking and the earlier deposits have compacted. Thus some of the oldest reclaimed areas are at, or below, present mean sea level. Silt-filled creeks locally stand up in inverted relief in reclaimed salt marshes because of differential compaction after drainage, giving rise to a dendritic pattern of creek-ridges.

Green (1968) described the soils of Romney Marsh, paying particular attention to the reclamation history as it had affected soil development. He distinguished areas of old decalcified marshland from younger calcareous marshland and suggested the following sequence to be typical of the marsh deposits:

The Young Alluvium corresponds to the surface deposits of Marine Alluvium; the underlying deposits are rarely exposed, except in deep drainage ditches. Areas of sand within the Marine Alluvium have been shown separately on the geological map; they include two patches of Green's Midley Sand which rise through the alluvium to 2 to 3 m above OD, near Broomhill [TQ 995 197] and west of Lydd [TR 025 208]. Green suggested that the Midley Sand is fairly continuous below the marshland east of Rye and that the presently exposed patches may represent remnants of an old sand-spit coastline. ERST, RDL

Storm Gravel Beach Deposits

These gravels consist of beach shingle that has been thrown up above mean high water mark by storm waves, where it forms semi-permanent ridges or 'fulls' that may accrete one on another, building up extensive spreads of shingle, which reach a height of 6 m or more above sea level, for example at Rye Harbour and Dungeness. The older shingle deposits are entirely natural features, but those formed over the last few centuries may have been subject to human influence, such as the construction of groynes, sea walls, harbour works and gravel working.

The shingle consists almost entirely of rounded flint pebbles, ranging in size from pea gravel to medium cobbles, with a relatively small proportion of sand and 'fines' in the ridges themselves. A small proportion of hard Wealden and erratic rocks accounts for less than 1 per cent of the whole. Beneath the Wealden cliffs of Bexhill and Hastings to Cliff End a higher proportion of local rocks is present, but the softer lithologies do not survive transport by longshore drift to Dungeness.

Excavations (Hey, 1967) and trial boreholes for the nuclear power stations at Dungeness have demonstrated that the shingle there is extremely thick and extends from 6 m above OD to 10 m or more below OD.

Blown Sand

The largest sand dunes within the district are those at Camber Sands, which rise to over 8 m above OD. Smaller patches have been mapped at Rye Harbour [TQ 935 193], Broomhill [TQ 990 192], where they overlie Midley Sand, and around Lydd. These dunes chiefly result from the deflation of intertidal sand flats and become stabilised by colonisation by marram grass and other sediment binding plants.

When White (1928) described the district, the dunes at Camber were encroaching landward and engulfing buildings. Subsequent efforts have been made to stabilise the dunes by planting marram grass but new dunes are still forming in the area east of Rye Harbour entrance. ERST

Coastal evolution and reclamation of the marshland

Most of the coastal Flandrian deposits that are exposed at the surface have accumulated in salt-marsh and shore environments during the last two or three thousand years, since sea level became relatively stable at about its present position. At first the coastline evolved naturally but, possibly from Roman times onwards, Man has influenced development by constructing sea defences and other reclamation works. The first written records of such works appear after the Norman Conquest: records become more plentiful thereafter and maps were produced at intervals from the 15th century onwards.

These sources together with air photography and accurate surveying have been used in reconstructions of the evolution of Dungeness Foreland and Romney Marsh. Gulliver (1897) suggested tidal eddies as the cause of the form and location of the foreland, and also tried to extrapolate, from the old shingle ridges, former positions of the coastline. Lewis (1931) studied the configuration of shingle beach ridges under the kind of conditions prevailing at Dungeness, and deduced that successive ridges would build out in a progressively more southerly-facing alignment, giving rise to fan-like ridge complexes, like that west of Rye Harbour. He later (1932) applied this concept to the study of the formation of the main foreland, considerably modifying Gulliver's theories in the process. This was followed by a detailed survey by Lewis and Balchin (1940) of the heights of successive ridges in the major shingle spreads in order to see whether any large oscillations of sea level could be deduced. The ridges west of Rye Harbour were studied by Lovegrove (1953). The evolution of the shingle barrier beaches between Fairlight and Hythe was further reviewed by Eddison (1983). A detailed record of changes in the immediate vicinity of the mouth of the Rother below Rye Harbour following the extension seaward of a protective pier was given by Chater (1930). Sections in the beach gravels exposed in excavations for the Dungeness nuclear power station were described by Hey (1967). Accounts of the reclamation of the marshlands in adjoining districts have been given by Smart (in Smart and others 1966; in Shephard-Thorn and others 1966). The distribution of coastal Flandrian deposits in the eastern part of the district is summarised in (Figure 20), which highlights the major complexes of old shingle ridges west of Rye Harbour and at Dungeness Foreland. The stages of development of Dungeness and Romney Marsh are summarised as follows (Figure 21):

  1. Early Flandrian marine and tidal deposits accumulated in Rye Bay, between about 10 000 and 5000 years ago, as sea level rose from a Late Glacial minimum to about its present level. The sediments, seen in boreholes, mainly comprise sands, silts and clays with only a minor proportion of flint gravel. It would seem that flint derived from the Chalk cliffs west of Beachy Head was not reaching the district in great quantity at this time.
  2. As sea level stabilised, a spit grew north-eastwards across Rye Bay from a point near Fairlight Head enclosing a lagoon which opened to the sea between Hythe and New Romney (Figure 21)a. Lewis (1932) argued that the Dungeness Foreland beaches evolved from this bar after breaches allowed the Rother to enter the sea near the site of New Romney and the Brede and Tillingham rivers to enter northeast of Fairlight Head. The isolated portion of the ridge became starved of shingle and so was progressively eroded and re-orientated to face the prevailing winds (Figure 21)b. This theory assumed that the early bar across Rye Bay was built of shingle, but, in view of the limited supply of shingle that appears to have been available, it could have consisted in part of coarse sand with scattered pebbles. Green (1968) regarded the Midley Sand, as the oldest deposit exposed at the surface within the marshland, because other deposits can be demonstrated to rest on it or overlap it. The present exposed remnants of the Midley Sand fall approximately along a straight line between Broomhill and Hythe (Green, 1968, fig. 6), which, if extrapolated south-westwards, extends to the seaward of Fairlight Head. Fairlight Head has figured in most previous reconstructions as the point of origin of the early shingle bars crossing Rye Bay; it is doubtful however that it could have retreated as far as has been suggested during the time available. It is now suggested that the surviving surface outcrops of Midley Sand are the remnants of a once continuous sandy bar which was built across Rye Bay enclosing a lagoon before shingle arrived in quantity from Beachy Head. Gradually this lagoon became at least partly silted up with blue grey 'buttery' clay containing Scrobicularia. Later, either because of the sheltered location or a minor regression of the sea, vegetation colonised the surface of the clay giving rise to a widespread peat bed with trees, which constitutes the submerged forest of Pett Level. The relationship between the submerged forest, which is radiometrically dated at 5300–5200 years old (Table 7) and the near-surface peats of the marshland east of Rye, which are dated at about 3000 years old, is not clear. They could represent either separate regressions or a diachronous onset of peat growth from west to east. The Wittersham Bridge Borehole (Figure 18) proved 3 m of peat, just below OD, which has yielded radiocarbon dates spanning the period, so it seems probable that peat growth and preservation may reflect the occurrence of a suitably sheltered environment rather than specific major fluctuations of sea level.
  3. The supply of shingle coastwise grew and was maintained under a prevailing eastward longshore drift so that the cuspate foreland formed and began to migrate eastward, as interpreted by Lewis (1932, fig. 1), with new ridges being partly built from the destruction of older ridges. The shingle ridges extending through Scotney Court [TR 015 200] had been formed prior to 2740 years ago, which is the radiocarbon date obtained from roots penetrating the 'buttery' clay beneath peat near Scotney Court Farm (Table 7). The more easterly ridges were added later. Surveys of the heights of the tops of the storm beaches that make up several major shingle spreads of Dungeness Foreland (Lewis and Balchin, 1940) showed an eastward rise in average height, which could indicate a gradual rise in sea level during the period of deposition. The average heights recorded were as follows: west of The Midrips, 4.1 m above OD; west of The Wicks, 4.2 m above OD; Holmstone Beach, 4.3 m above OD; Lydd Beach, 4.7 m above OD; Denge Beach, 5.3 to 6.3 m above OD. By Roman times the foreland was big enough for large areas of salt marsh to form in its lee. Saxon charters tell of various landholdings and settlements at Lydd, Rye and Old Winchelsea, which all later became members of the Cinque Ports. There is no clear written evidence of reclamation work prior to the 12th century, but it had almost certainly begun long before that.
  4. The settlement of Old Winchelsea lay on a sand or shingle promontory which lay roughly at the present position of the mouth of the Rother (Cooper, 1850), possibly a remnant of the original bar across Rye Bay (Figure 21)c. A period of severe storms during the 13th century culminated in the virtual destruction and abandonment of Old Winchelsea in 1287, and the establishment of the New Winchelsea on its present site; the old settlement of Broomhill was also abandoned at this time. The River Rother had entered the sea near New Romney prior to 1287 but changes following the storms blocked this mouth, and the river subsequently flowed out near Camber (Figure 21)d. A low grassed-over shingle ridge extends for more than 2 km NNE from Broomhill Farm [TQ 979 184]; 'recurves' on this spit are turned in the wrong direction for a prevailing eastward drift and it is suggested here that this spit and the truncated remnants near Black House Farm [TQ 949 208] represent the wide mouth of the Rother after the storms of 1287. Recent work near Hayling Island has shown that local reversals of longshore drift can occur at harbour mouths (Harlow, 1979), especially in the lee of an offshore island. Possibly a similar mechanism operated here while remnants of the Old Winchelsea promontory or island affected the coastal regime of tides and currents. The Northpoint Beach shingle also seems to have grown between the 13th and 16th centuries by local westward drift at the Rother mouth.
  5. Since 1287 the history of coastal changes and reclamation of the marshland is fairly well known from contemporary documents and maps. It is thus hard to improve on the coastal reconstructions of Lovegrove (1953) and Lewis (1932) for this final period. During this time the influence of man has been greatest, both in building coastal defences and harbour works and in reclamation. For example the successive works to keep Rye Harbour open have contributed largely to the retention of shingle west of the harbour and the depletion of shingle supply to the east at Camber and Broomhill (Chater, 1930; Du-Plat Taylor, 1930). In Romney Marsh the reclamations appear to have progressed from east to west. Most published versions are based on the map of Elliot (1847) which was reproduced by Steers (1964); his attribution of reclamations in the 8th century to parts of Denge Marsh and ground north of Lydd is unsupported by written evidence and has been questioned by Green (1968) and others. To the west, most of the area as far as East Guldeford was reclaimed between the 12th and 17th centuries. The valleys of the Rother, Brede. and Tillingham have been reclaimed in more recent times but are still partly tidal. West of Rye Harbour reclamation by means of short interconnecting sea walls appears to have kept pace with the growth of successive beaches. ERST

Details

River gravels

A small pit [TQ 7972 1833] to the south of Powdermill reservoir showed 0.8 m of brown sandy gravel with subangular siltstone, ironstone and chert fragments. The deposits have a slight depositional dip to the south.

In the Tillingham valley two small terrace remnants occur north of Udimore, [TQ 869 199]; [TQ 876 196], at about 15 m above OD. Here up to 1.2 m of brown sandy gravelly loam and ferruginous gravel overlie bedrock.

Landslips

The Covehurst Wood landslip [TQ 850 103] is a major rotational slip, extending along the coast for 800 m, as far as the mouth of Fairlight Glen. The cliffs which form the backwall of the slip rise to about 100 m above OD. and drop steeply to the undercliff area, up to 250 m wide, which comprises a mass of slipped and fallen rock waste. The strata include competent sandstones of the upper Ashdown Beds overlying the incompetent 'Fairlight Clays'. The curved slip planes apparently originated in the clays and extended into the competent backwall rocks via joint planes and fractures. Marine erosion is attacking the toe of the slip, forming a low cliff with exposures of a 'melange' of mottled clays with sandstone boulders. Here also, disturbed beds in the foreshore indicate that the effects of the slip extend well below present sea level. It is probable that like other major landslips on the channel coast, e.g. at Folkestone Warren (Hutchinson, 1969) and at Beachy Head, it originated during a period of reduced sea level at the end of the Devensian. At present it seems to be broadly in equilibrium, with only minor movements at the toe being apparent.

On the eastern side of Fairlight Glen [TQ 860 110], below the Coastguard Station, the upper cliff is much affected by landslipping, over a distance of 600 m. The movements which are chiefly rotational with some mudflows at the toe, extend down to the sandstone unit in the Ashdown Beds, which rises in the cliff towards the crest of the Fairlight Anticline. The slip thus hangs above the beach here and mudflows at its toe constantly drop rock waste on to the beach, where it is rapidly dispersed by wave action. The steep backwall of the slip is cut in upper Ashdown Beds sandstones.

The landslipped area between Goldbury Point [TQ 877 114] and Fairlight Cove [TQ 880 120] presents a rather confused appearance. The dominantly clayey strata have been affected by rotational movements with back-tilting of foundered blocks, as well as mud-flows of varying scale. Polished grooved surfaces are often visible in the toe areas and emphasise that these slips are very active. As at Covehurst Wood, the toe comprises a 'melange' of multi-coloured clays with sandstone fragments.

Marine Alluvium

Hooe Level

This forms an extension eastward of the Pevensey Levels of the Lewes district. The surface deposits are regarded as freshwater alluvium that accumulated behind the coastal shingle barrier, but the subsurface deposits have been laid down under tidal influences. The typical sequence, which has been derived chiefly from boreholes on the adjacent Lewes Sheet, is as follows: clay, 1.5 to 2 m; peat, 0.6 to 1.8 m; clay with shells, 2 to 9 m; clayey silt, 0.5 to 2 m. A basal peat horizon lying 6.4 m below OD was proved in a borehole [c.683 062] at the Star Inn pumping station. A radiocarbon age of 3715 years BP was obtained by B. Moffat from a peat at 2.8 m depth in the tributary valley [TQ 696 085] south of Hooe (see (Table 7)). In Hooe Level stumps of oak and birch rooted in sandy soil, which were observed about 3 m below high water-mark (Curteis, 1814) are probably equivalent to the submerged forest of Pett Level.

Bexhill coastal area

Greenish grey sands with peaty fragments were exposed in 1968 on the foreshor [TQ 7392 0696] south of Egerton Park. These deposits relate to the short tongue of alluvium which extends through the park. The submerged forest noted by White (1928, p.79, fig. 7) at the east end of Little Galley Hill [c.769 080] was not exposed in 1967 and may have been entirely removed by erosion. Peaty silts with wood fragments, which were noted on the foreshore to the east [TQ 777 083] near Bulverhythe, are related to the alluvial fill of the Combe Haven (Asten) valley. Boreholes in the Combe Haven valley, at the landfill site, have proved up to 17 m of alluvium, extending down to at least 15 m below OD [TQ 7773 0965], with a peat layer extending from OD to about 3 m below. Locally peats are also present lower in the sequence. Up to 12 m of clay and peat were recorded in the foundations of the former railway viaduct [TQ 763 103] (Sweeting, 1925, p.409). RDL, ERST

Pett Level

The coastal shingle barrier protecting this low-lying area has been eroded by the sea over the last century, possibly because of a reduction in the supply of shingle on the shore. During the 1939–45 war the area was flooded as a defence measure but a new sea wall and groynes were constructed after the war. The submerged forest is well exposed at low tide for more than 2 km along the shore northeast of Cliff End. A bed of compact brown woody peat 0.6 to 1 m thick forms ledges. Tree boles in a growth position and recumbent trunks lie on its upper surface. The peat bed rests on soft blue-grey clay more than 1.5 m thick, into which rootlets penetrate. Samples for radiocarbon analysis which were collected about 1.5 km northeast of Cliff End [TQ 899 140], gave ages of about 5205 years for wood from an in-situ tree and about 5300 years for the peat (Table 7). Excavations by Mrs J. Eddison on the foreshore at Cliff End have revealed the presence of two peat horizons below the submerged forest bed.

Grey-brown silty clay has been proved by augering to extend down to depths of more than 1.4 m below the surface over most of the area of Pett Level. Immediately south of the Dimsdale Sewer and east of Winchelsea, 1.4 m of silty clay rests on grey silty sand. No sign of the submerged forest or a near-surface peat has been noted during the survey in this area, although it may be present some 5 to 6 m below the marsh surface.

Marine Alluvium deposited between the shingle banks west of the mouth of the Rother between Camber Castle and Rye Harbour is similar in character to that of Pett Level, with up to 1.3 m of grey brown silty clay overlying grey fine-grained sand.

The Brede valley

The River Brede was navigable upstream to Brede Bridge well into the present century and is still tidal over most of this distance. Thus much of the floodplain alluvium has been laid down in an estuarine environment. In general 1.0 to 1.4 m of silty clay, commonly containing cockles, rests on fine-grained shelly sand. The surface bears many traces of old creeks and runnels. Trial boreholes for a railway electricity substation [TQ 882 178] proved more than 15 m of Flandrian deposits above bedrock (Figure 18), with a bed of peat lying between 2 and 4 m below OD. This peat may be equivalent to the submerged forest of Pett Level.

Tillingham Level

Marine Alluvium has been traced up the Tillingham valley as far as an old sea wall at Tillingham Bridge [TQ 883 198]. It is slightly higher than the freshwater alluvium upstream of the wall: more than 1.4 m of grey-brown silty clay have been augered.

A site-investigation borehole at Tilling Green, Rye, [TQ 915 206] (Figure 18), proved a drift sequence down to more than 25 m below OD. A peat near the bottom of this sequence yielded an early Flandrian date. A later peat bed, approximately 1.5 to 4.0 m below OD., has not been dated, but is probably equivalent to that proved in the Brede valley and near Wittersham Bridge (Figure 18).

East Guldeford Level, Camber and Broomhill Level

This is an area which has undergone major coastal changes in historical times and most of the Marine Alluvium is comparatively young. For example the curving tongue of sand shown on the geological map between East Guldeford and Broomhill Level is marked as a tidal inlet, called the Wineway Channel, on Poker's map of 1617 (Green, 1968, pl.X). It is composed of fine-grained sand with some shells. To the west of an old sea wall [TQ 950 205] even younger salt-marsh clays overlie the sand. An early channel course within this sand area is marked by a broad depression roughly parallel to the present Northpoint Sewer, 1 km east of Rye.

Grey-brown silty clays lie at the surface of most of East Guldeford Level. Near The Hoppets [TQ 9535 2138], levees of fine sand mark the rim of a former tidal inlet that is now filled with freshwater alluvium. Old shingle ridges which rise above the marsh surface near Moneypenny House [TQ 9433 2105] are associated with some marine sand. Dry creeks and runnels are common features of the marshland surface.

On the clay marshland south of the Wineway Channel and north of Northpoint Beach and the Camber sand hills, some 1.0 to 1.3 m of grey-brown silty clay overlies fine sand with shells. Trial boreholes at Camber [TQ 965 190] proved the following sequence in an area mapped as sand: sand, 1 m; silty clay, 2 m; clayey silt, 5 m; silty sand, 2 m. A well east of Camber [TQ 9735 1872] proved drift to 24 m below OD., without penetrating solid rocks.

In Broomhill Level, grey-brown silty clays, which have been augered to depths of 1.0 to 1.3 m, overlie shelly fine sand. The large tract of sand which runs north-eastwards between [TQ 985 185] and [TR 005 205] is a remnant of the Midley Sand (Green, 1968).

In the marshland west of Lydd, sections in the banks of the Jury's Gut Sewer and other dykes show complex overlapping relationships within the alluvial deposits between old shingle ridges. A peat sample and roots extending into underlying clay, from Scotney Court Farm [TR 023 202] (Table 7) gave approximate ages of 2050 and 2740 years respectively, giving a minimum age for the shingle ridges hereabouts.

The Marine Alluvium between the major shingle banks of Dungeness Foreland is similar to that elsewhere in the marshland, with silty clays being predominant at the surface and local traces of peat at depths of 1 m and below.

Denge Marsh

This comprises the area of marshland south and east of Lydd and west of the shingle of Dungeness. In the northern half an extensive spread of sand is present, with buff sandy loam soils overlying fine sand at about 1 m below the surface. In the south, around Dengemarsh Farm, up to 1.5 m of grey-brown silty clay overlies fine sand or occasionally shingle. Similar deposits are present in the hollows between shingle ridges. ERST, JGOS

Chapter 7 Economic geology

A review of the economic geology of the Weald was given by Highley (1976) and extractive industries in Kent were summarised by McRae and Burnham (1973).

The varied pattern of agriculture in the Hastings and Dungeness district reflects the range of soil series developed on the solid rocks and superficial deposits, together with such factors as climate, water supply and drainage.

In the past, bulk minerals were extracted on a small scale for local use, including ironstone, 'Tilgate Stone' , silica sand, brick clay, building stone, marl and limestone. The widespread scatter of old quarries and pits reflects the extent of this former activity. In the 1980s only three major extractive industries operate within the district: gypsum is won from the basal Purbeck Beds at Mountfield (with roadstone from the top of the Portland Beds as a useful by-product), clay from the Tunbridge Wells Sand near Bexhill and Head deposits near Guestling are worked for brickmaking, and beach deposits near Rye Harbour, Rye and Lydd provide sand and aggregate for the construction industry.

Minor surface oil seepages and shows of natural gas in mine workings and boreholes were noted in the past from Wealden and Purbeck rocks, but have not led to any discoveries of commercially exploitable oil or gas deposits. Renewed interest has been shown in the possibility of finding hydrocarbons in Jurassic rocks at depth, aided by modern techniques of seismic prospecting.

Soils and agriculture

The soil types of the Weald were broadly reviewed by McRae and Burnham (1975) and a detailed report on the Soil Survey mapping of Romney Marsh was made by Green (1968). There are obvious contrasts between the soils developed on the upland areas of Wealden and Purbeck rocks and on the reclaimed marshland areas. The rapid variations in outcrop lithology, give rise to equally variable soil types in the district. The occurrence of drift deposits has lead to the development of soils quite unrelated to the underlying solid rocks in some cases.

According to McRae and Burnham (1975) the soils of the upland areas of Wealden and Purbeck rocks all suffer to some degree from impeded drainage and fall within the stagnogley group, some with brown earths. The marshlands have alluvial gley soils; those of the Pevensey Levels, Combe Haven and Brede and Tillingham valleys are decalcified and are comparable to Green's (1968) Decalcified (old) Marshland, which occurs in the district north-east of Broomhill, towards Lydd. Very poor soils are developed on the raw sands and shingle of Rye Harbour, Camber and Dungeness.

The sandy and silty facies of the Hastings Beds tend to develop stagnogley soils with brown earths, since minor developments of clay and other impervious horizons near the ground surface cause widespread impeded drainage. Better soils develop where the sandstones are more friable and free-draining. The Wealden clays and Purbeck shales tend to have stagnogley soils. In the marshland, careful drainage and regulation of water levels is essential for successful farming.

In spite of these seemingly poor soil conditions the district is fairly intensively farmed and woodland tends to be restricted to the poorer soils and more dissected terrain or areas formerly mined by bell-pits for ironstone. A range of mixed farming is carried on with grain and root crops doing well in favoured locations. Fruit growing is well established around Icklesham and Winchelsea and several successful hop gardens are sited on deep soils flanking the Brede valley. Sheep rearing has been a traditional occupation in the marshland, with the animals being wintered on drier upland pastures. More recently parts of the better drained marshland have successfully been put to arable crops. Dairying and stock raising are also carried on.

Aggregates

'Tilgate Stone' from the lower part of the Wadhurst Clay was worked in the early 1900s for road dressing in the district, for example near Brede. Blocks of the hard, blue-hearted, calcareous siltstone, were broken with hammers by the local roadmenders, on site. Small patches of terrace gravels were also exploited for hoggin.

The only working sources of aggregate within the district in the 1980s are the wet pits in the Storm Gravel Beach Deposits west of Rye Harbour and around Lydd. The Rye Harbour deposits are nearing exhaustion, but appreciable quantities still remain around Lydd and Dungeness, where working is of course subject to planning and conservation restraints. In addition to material marketed directly to the construction industry, a considerable amount is used annually for coastal defence measures between Pett Level and Dungeness.

A recent development has been the successful exploitation for roadstone, of the topmost 1.5 m of the Portland Beds, which forms the floor of the old pillar-and-stall workings in the Mountfield gypsum mine. Beneath the No. 4 gypsum seam, the fine-grained sandstone at the top of the Portland Beds has a strong calcite cement, and yields a stone suitable for crushing into aggregate and prepared asphalt dressings. Quantities of waste rock from the gypsum mines have been sold locally for hard core.

Limestone

Beds of limestone within the Purbeck Beds were worked in the 19th century for lime burning (Topley, 1875). In their restricted surface outcrops, in the high dissected country around Heathfield and Mountfield, they were widely exploited by means of bell-pits.

Silica sand

This term, in industrial usage, describes sands containing a high proportion of silica (as quartz). These are used principally as foundry moulding sands and glass sands. The Cliff End Sandstone was exploited near Fairlight (Highley, 1977), as a moulding sand, up to about 1970. The small proportion of chromium in the sand, renders it unsuitable for glass manufacture, due to the strong colour it imparts (Boswell, 1918)

Building stones

Traces of old workings for building stone survive in many places and these formerly supplied a variety of stone for local use. Stone was used chiefly in the construction of churches and fortifications in mediaeval times, but was later used in domestic architecture especially in Victorian times.

Among the stones exploited were sandstones from the Hastings Beds, including the calcareous 'Tilgate Stone', from the Wadhurst Clay, and occasional slabs of distinctive red-brown shelly clay ironstone from the same formation. Yellowish brown sandstones from the Tunbridge Wells Sand were widely used for garden walls in the Victorian suburbs of Hastings and St Leonards, but are now sadly decayed. Fairlight Church is built of Cliff End Sandstone quarried nearby. This stone is soft and easily worked when first quarried, but the exposed surfaces harden on weathering. Ironstone slabs were used to decorative effect in the Landgate at Rye. Udimore Church contains much 'Tilgate Stone' of local origin and this material was also used extensively in Winchelsea for the church, town walls and gates. Hastings Castle, built soon after the Norman Conquest, includes in its fabric a variety of local stones used in random masonry. Among these are sandstones and sphaerosideritic siltstones from the Ashdown Beds, together with 'Tilgate Stone', bone-bed, ironstone and silicified Tempskya from the Wadhurst Clay as well as cobbles of flint and igneous rocks derived from the seashore nearby. A small amount of imported oolitic limestone (?Caen Stone) was incorporated in the arch of the Collegiate church within the castle.

Brick-making, pottery and refractory clays

Bricks and tiles were formerly produced from a variety of clays and other materials, dug within the district, mostly for local or estate use. Potteries using local clays were once active near Brede and Rye, but the modern potters of the district use imported clays.

Silts from the Ashdown Beds and the overlying hillwash were dug for brick-making at Ashburnham [TQ 685 161]. Clays within the Ashdown Beds were exploited by small brickworks near Ore [TQ 838 123]; [TQ 836 118]. The Wadhurst Clay was worked for brick-making at a number of localities including Marlpits near Ninfield [TQ 710 132], Battle [TQ 768 147], Baldslow [TQ 797 131], Hollington [TQ 792 124], near Brede Bridge [TQ 828 174] and at Doleham Halt [TQ 836 162]. Red-mottled clays of the Tunbridge Wells Sand have been worked at Sidley [TQ 732 092] and were formerly used for the manufacture of engineering bricks in the Ashdown Works, Turkey Lane [TQ 722 094]. This latter plant has now been modified to produce domestic stock-bricks using the red clays and the siltier beds above. Head deposits are dug at Guestling Brickworks [TQ 841 158] for the manufacture of specialist hand-made bricks. The Head, which here is a brown sandy loam, is dug and allowed to weather for a winter, before further processing.

Certain overbank clays within the Ashdown Beds seem to have refractory properties and, following the geological survey, a series of mineralogical tests was carried out by BGS, with ceramic tests being made by the British Ceramic Research Association. Samples of potential refractory clays were collected from the coast sections near Fairlight and from the cores of the Fairlight Borehole. The test samples were specifically selected to exclude sphaerosiderite-bearing rocks, which are intimately intermixed with the supposed fireclays. Thus, although the results were marginally encouraging in terms of ceramic and shrinkage properties, it might be very difficult to apply the same degree of selection on a commercial basis in a working pit. This, and the reddish brown colour developed on Tiring, effectively rules out these clays for most present industrial purposes.

Gypsum

Although the pioneer Sub-Wealden boreholes (Chapter 2), which were sunk near Netherfield in about 1873–6, failed to find their main objective, coal, they incidentally discovered valuable gypsum deposits, at workable depths in the basal Purbeck Beds. This discovery was quickly exploited by the opening of the Mountfield Mine [TQ 7200 1935] in 1876. A modern mine has been developed at Brightling [TQ 6765 2175], just outside the present district to the north-west, where production started in 1963.

Within the area of the Sussex Purbeck inliers (Howitt, 1964), there are four consistent evaporite seams in the lower 15 m or so of the Purbeck Beds, which constitute the Gypsiferous Beds Member (p.13). These seams are numbered from 1 to 4 in descending order. The No. 4 seam, which averages over 3.5 m in thickness, has been widely mined by pillar-and-stall methods at both mines. The other, lesser, seams have been worked on a smaller scale (Highley, 1976).

Trial boreholes have confirmed the presence of basal Purbeck Beds evaporites at depth around the inliers and elsewhere in the district (Howitt, 1964). In general, at depths greater than 250 m below the surface, anhydrite rather than gypsum is present. In the Fairlight Borehole five gypsum/anhydrite seams were proved (Holliday and ShephardThorn, 1974), but none was of commercial quality.

Hydrocarbons

Commercial discoveries of oil or natural gas have not been made in the district, but a number of oil seepages and shows have been noted and natural gas has been encountered in boreholes and mine workings. The best known discovery is that of natural gas in a water bore at Heathfield in 1896, which was used for many years to light the railway station. The gas at Heathfield was discovered near the Ashdown Beds–Purbeck Beds junction and contained methane and hydrogen. A similar discovery was made during the drilling of the Fairlight Borehole in 1971, when gas was first noted in the drilling mud return from a depth of about 270 m (Plant and Bone Beds Member) and subsequently at about 335 m (Gypsiferous Beds Member). Analysis of gas collected by displacement in an inverted jar, by the London Research Centre of the Gas Council, showed the sample to consist mainly of air with 0.25 per cent hydrogen and 0.16 per cent methane and traces of higher hydrocarbons. It would seem that the air was probably entrapped in the drilling mud and, making allowance for the makeshift sampling method, the composition and pressure of the gas at Fairlight is comparable with the Heathfield occurrence. Tests were carried out on core samples from the Portland Beds to establish their porosity and permeability but the results were so low as to suggest that the gas was transmitted and stored in fissures rather than the inter-granular pores of the host rock.

Gas has also been detected in the Brightling mine workings, so that it is now officially a safety lamp mine. Oil seepages have been noted at the surface in the vicinity of faults in the Purbeck inliers (Anderson and Bazley, 1971) and also in the gypsum mine workings. Traces of oil were recorded from the cores of the Tunbridge Wells Sand in the Cooden Borehole [TQ 7043 0641] (Lake, 1975). Most of these occurrences are probably derived from sources in the Kimmeridge Clay via fissures and fault planes.

Wealden iron industry

The Hastings district has been an important centre for the extraction of iron ore since Roman times. The industry was developed by the Romans, subsequently fell into decline and then grew again in importance in the Middle Ages. The forge and furnace works at Ashburnham was probably the largest in the Weald and the last to close in the early nineteenth century (Straker, 1931, pp.364–370). The ironstone, which in this district was almost exclusively dug from the Wadhurst Clay, was worked in bell-pits or obtained as a byproduct of the excavation of clay for marling from open pits. A full documentation of the working, production and history of the industry was published by Straker (1931). He recorded Roman bloomeries at Beauport Park, Footlands and Oaklands Park. Later bloomeries were at Baldslow Place, Buckholt, Bynes Farm (near Crowhurst), Coghurst, Conster Manor, Crowhurst Park, Ellenwhorne, Fairlight, Fore Wood, Guestling (North Wood), Icklesham (two sites), Loneham Farm (near Powdermill Reservoir), Peppering Eye, Pickdick, Platnix, Roughter Wood (Udimore) and Sidley. Furnaces were subsequently developed at Ashburn-ham, Beckley, Brede, Buckholt, Crowhurst, Darwell and Panningridge. Additionally, forges were situated at Hodes-dale (Woodsdale near Whatlington), Kitchenham, Mount-field, Potmans and Westfield. Straker also suggested the presence of works at Barnhorn, Battle Park, Beech Mill (near Battle), Hastings (Blacklands) and Rackwell Gill (Crowhurst).

Further researches by the Wealden Iron Research Group, updating Straker's survey, were presented by Cleere and Crossley (1985). ERST, RDL.

Water supply

The demand for water for the area around Hastings grew with its development as a resort and, from the mid-1850s underground supplies were developed by the drilling of boreholes. This demand has continued to rise, especially seasonally, with the summer influx of visitors to the coast and the yield from underground sources is now decreasing. The main sources now come from surface storage such as Powdermill [TQ 800 195] and Darwell [TQ 715 212] reservoirs, which each supply about 21 000 m3/day. By contrast groundwater abstraction provides about 7500 m3/day.

Average annual rainfall varies from less than 700 mm in the Bexhill and Dungeness areas to more than 850 mm in the north-west of the district. River flow is measured at two localities, both situated at the western side of the district. The River Darwell, gauged at Darwell Reservoir [TQ 722 213], has a drainage area of 9.63 km2 and a mean flow of 0.03 m3/sec. The Ash Bourne, gauged at Hammer Wood Bridge [TQ 684 142], has a drainage area of 18.7 km2 and a mean flow of 0.23 m3/sec.

Previous publications dealing with the hydrogeology of the area include Whitaker and Reid (1899), Whitaker (1911) and Edmunds (1928). A Well Catalogue (Cole and others, 1965) includes abstracts and information on the majority of recorded wells in the district. The major hydrogeological features of the formations within the district are as follows:

Jurassic

The Purbeck Beds are of little significance for water supply. Water entering the gypsum mines from fissured limestones has to be pumped out and pumping rates as high as 10 l/sec have been recorded. Due to the presence of limestone and gypsum the water is extremely hard.

Cretaceous

Most groundwater is extracted from the upper sandstones of the Ashdown Beds, with smaller amounts from the less widespread Tunbridge Wells Sand. The Wadhurst Clay forms an effective aquiclude between these two water-bearing formations. Both aquifers are poorly known and their yields are affected by lithological variation and faulting. It is probable that fissure flow makes an appreciable contribution to the yield of most wells. The abstraction of water from such aquifers is best achieved by means of large-diameter boreholes, which offer a larger surface area of aquifer and lower entrance velocities. Problems of siltation are inherent in wells penetrating these formations and careful design of screens and filter packs is essential to obtain maximum yields over a period. These aquifers have occasionally been developed by blasting to enhance the fissure flow.

Ashdown Beds

The lower, clayey part of the Ashdown Beds (formerly the Fairlight Clays), is of no importance as an aquifer. Surface springs are usually only sufficient to supply local domestic needs. A rare example of a significant spring supply comes from the Military Road Waterworks, Rye [TQ 923 210] where the yield was 10.1 l/sec whilst in use.

The upper, sandy part of the Ashdown Beds by contrast forms a major aquifer which gives the highest yields of any of the Hastings Beds. It is predominantly arenaceous although fine grained, and water-movement is mainly by inter-granular flow giving low permeabilities. Hence large-diameter wells, with a large surface area may obtain useful yields where boreholes have failed. Past attempts to increase yield by boring in the base of the well have also failed. In addition to intergranular flow, fissure-flow associated with fault fracturing probably contributes to the yields of most wells sited in valleys. The heterogeneity of the beds has caused major problems. At Hastings Tramway Power Station [TQ 823 108] one bore yielded no water when drilled in 1934. The Fairlight Hall Well [TQ 855 117] encountered water at a depth of 3.5 m, which however disappeared when the bore reached 9.0 m. Brede Valley Pumping Station [TQ 826 174] is a rare example of artesian conditions and a borehole here overflowed at 126 m3/day on completion in 1892.

Saline intrusion into coastal boreholes has occurred. At the Rock-a-Nore Well [TQ 828 095], sunk in 1901, brackish water was originally abstracted and piped to houses as a form of 'spa water'. When this became unpopular the water was used for refrigeration purposes. The West Marina railway station borehole [TQ 787 089], drilled in 1915, consisted of a 76 m borehole sunk at the base of a 14.5 m dug well. The well water was saline but the borehole water was fresh.

Over-abstraction from the Ashdown Beds has led to falls in water-levels and declining yields from many boreholes. By 1917 the yields of some sources had declined to a serious extent and since then increases in demand have been met from surface sources. Many of the older boreholes fell into disuse, but since 1951 both the Filsham Well [TQ 778 092] and to a lesser extent the Fore Wood Well [TQ 746 132] were pumped during dry summers to supplement the supply.

Investigations into the resources of the Ashdown Beds were begun in 1975 by the Eastbourne Water Company aimed at siting new abstractions of groundwater from the Ashdown Beds, remote from areas previously exploited. It was planned to site new boreholes to penetrate the top 50 m or so of the Ashdown Beds sandstones in confined, down-dip or synclinal situations.

Initial results of drilling and testing such boreholes were encouraging. Mean values for transmissivity (T) of 120 m2/-day were obtained in the Ashburnham area with a corresponding storage coefficient (S) of 1.4 X 10–4. Although very high yields were not expected, the aim is to use groundwater to augment stream flow and allow abstraction further downstream.

Wadhurst Clay

Although this formation behaves primarily as an aquiclude, because of its impermeable nature, minor yields can be obtained from thin sandstones which are developed at several horizons. Water from this formation tends to have a high iron content and can be impotable. Recharge to the sandstone horizons is limited and some boreholes tend to silt up during pumping so that most have small, reducing yields. At Eastland Farm [TQ 721 133] the yield was 0.33 l/sec whilst at Cobbs Hill Farm [TQ 736 106] the yield was 0.15 l/sec. Consistent supplies of groundwater cannot be expected from every borehole drilled in the Wadhurst Clay. A trial bore at Crowhurst [TQ 757 135] yielded no water. Most private boreholes for domestic use were abandoned when mains supply became available.

Tunbridge Wells Sand

There is no major abstraction from the Tunbridge Wells Sand, which comprises silts with interbedded mottled silty clays and sandstones. These generally give low yields which are sufficient only for domestic supplies. As in the Wadhurst Clay, the water is often iron-rich and impotable. At Crowham Manor [TQ 816 167] a spring issues from a permeable horizon above a clay seam and supplies a farm. Water has generally been taken from shallow wells at low rates. At Whatlington [TQ 761 202] attempts to pump a 45 m borehole at 0.32 l/sec resulted in its silting up and abandonment, but a borehole 40 m distant and 14 m deep was pumped for 12 years at the rate 0.05–0.06 l/sec without difficulty.

Drift

In the area of Lydd attempts have been made to abstract water from the Storm Gravel Beach Deposits. In most cases the water was either saline, as in the case of Holmstone Range [TR 041 200], or unsuitable due to pollution, as at The Ripe [TR 043 206]. Yields can however be quite substantial. The Brewery Well [TR 040 209], now disused, had a yield of 11.37 l/sec of hard but potable water. Good yields up to 25 l/sec were obtained from Denge Beach Pumping Station [TR 068 201]. The estimated yield for all the wells at this station was in order of 1590 m3/day. MAP

Appendix 1 Coastal exposures

The cliff-sections of the present district provide excellent exposures in the Hastings Beds group of the Wealden and are the type area for these beds. This account provides details of the major sections along the 20 km coastline between Norman's Bay [TQ 690 058] and Rye, which include a sequence of rocks from low Ashdown Beds to the basal Weald Clay, although no formation is completely exposed.

The sections are here described geographically from west to east as seen in the cliffs, rather than in stratigraphical order, and so provide a convenient guide (Figure 7), (Figure 8), (Figure 9), (Figure 22), (Figure 23), (Figure 24), (Figure 25). Earlier accounts of these sections have largely become outdated because of cliff recession and changes and corrections to stratigraphical nomenclature. For example, between Cooden and Bexhill, where the stratigraphy has been extensively revised during the present survey, marine erosion has greatly changed the sections visible and coastal protection works have obscured others. However, the older accounts are of some interest for their descriptions of vanished features and also give an impression of the extent of coastal changes over the years.

Visitors to the sections may find the special 1:25 000 geological sheet 'Hastings–Rye' (in the 'Classical areas of British geology' series) a useful complement to the descriptions given below. Some parts of the sections are only accessible at certain states of the tide and it is essential for intending visitors to consult tide tables and to plan their excursions with an adequate safety margin to reach a suitable access point. In addition some of the higher cliffs are dangerously unstable, so that it is not advisable to work close to the foot of the cliffs without prior inspection; protective headgear is strongly recommended. ERST, RDL

Cooden to St Leonards

To the south-west of the fault at Cooden [TQ 7026 0615] red-mottled clayey silts within the Tunbridge Wells Sand crop out on the reefs and these are cut by a system of silt-filled channels, floored by a mud pellet bed which locally reaches 0.3 m in thickness. This pellet horizon is very similar to those noted in the Cooden Borehole at depths of 71.6 and 83 m (i.e. at least 58 m below the top of the formation) and the throw of the fault is estimated to be of a similar order.

On the inshore reefs east of this fault a variety of dip and strike directions were recorded in the shaly mudstones of the Weald Clay indicating a markedly undulating structure. Milner and Bull (1925, p.302) suggested a shallow synclinal structure for this tract with local disturbance at the west end of the cliff-section. The mudstones contained ferruginous silty beds and bioturbated silty beds and showed little variety in lithology.

The sea-defence works have almost totally obscured the cliff-section but landslips in 1968 revealed sections in greenish grey and pale grey mudstones with tabular ironstones [TQ 7125 0651]. Small exposures west of the hotel showed finely laminated mudstones [TQ 7068 0639] and laminated siltstones overlying mudstone [TQ 7087 0643]. White (1928, p.55) recorded a bed of greenish grey clay which was divided into polygonal blocks by fissures filled with dark green claybreccia at a point 0.5 km ESE of the old Coastguard Station about [TQ 714 063].

The contact of the Weald Clay with the Tunbridge Wells Sand, described by White (1928, p.54 and fig. 11) as blue shales resting conformably on soft laminated yellow sandstone, was no longer visible in the low cliffs at Cooden at the time of the survey in 1968. The shales, which White erroneously described as Wadhurst Clay, were noted to pass upwards into weathered silty beds with close-set seams of clay-ironstone and ferruginous sandstone. On the foreshore reefs below, in 1968, medium grey silty mudstones with ironstone beds, striking at 130° were seen [TQ 7162 0648] in close proximity to the topmost bed of the Tunbridge Wells Sand.

From this area eastwards to Galley Hill there are intermittent exposures of beds in the Tunbridge Wells Sand. The sequence is comparable to that observed in the Cooden Borehole (Lake, 1975) and some 80 m of the beds cut in the borehole are probably represented at outcrop where the overall dip is eastwards.

The first cliff exposure [TQ 7180 0660] of Tunbridge Wells Sand to the east of the Weald Clay outcrop noted in 1968 was south of the junction of Beaulieu Road and Hartfield Road. This showed about 4 m of sandstones and silts with lignitic bands.

From south of Beaulieu Road to the Richmond Avenue slipway, sandstones were less evident and the low cliff displayed sections, up to 10 m high, in well laminated, pale grey, variably clayey silts with local sandy and lignitic partings. The presence of channels was suggested by a slight discontinuity of bedding in the sections west of Veness Gap [TQ 7227 0672] and south of the road known as South Cliff [TQ 726 068]. The weak anticlinal structure apparent in the cliffs at the former locality (described by White 1928, p.53) may be a purely sedimentary feature.

The section [TQ 7307 0685] at Richmond Avenue slipway, which in 1968 was somewhat degraded, was described by White (1928, fig. 9) as showing two discontinuities due to channelling. The lower sandstone was still exposed and contained burrows. Saurian footprints have been reported from the foreshore near this locality (Beckles, 1854, p.460). From Richmond Avenue to Galley Hill the foreshore shows several reefs of fine-grained sandstone, commonly lignitic and bioturbated.

The section observed at Galley Hill is shown in (Figure 22) which incorporates additional information from White (1928, fig. 8) for faces obscured by talus in 1968. The following composite section was measured in the fault block: sandy siltstone, 1.8 m; sandstone, pellets at base, 0.8 m; three silty pellet beds with gastropods and plant fragments, 0.2 m; silty clay and mudstone, 1.35 m; sandstone, 0 to 0.8 m; silts and clay, red-mottled locally, 3.6 m; talus to beach level, c.3.7 m. Apart from the easternmost fault, the correlation between the fault blocks suggested by previous authors is not convincing. Similarities exist between the second and fourth fault blocks suggesting a net downthrow to the west. On the foreshore south and west of this face, three channel structures are observed, all cutting down south-westwards; red-mottled clays are present within the third fault block.

East of the point, higher beds, consisting predominantly of variably indurated silts with very subordinate sandstones appear. Red and green mottled clayey silts are evident on the foreshore below and these crop out as far east as the inferred line of the Old Town Fault (see below).

Proceeding eastwards, the next cliff-section at Little Galley Hill [TQ 769 081] exposes strata which are inferred to lie in the Ashdown Beds. This cliff is not so well exposed as when described by White (1928, pp.47–50). The following section which is composite, is based on White's description and on recent observations and summarises the beds from the headland westwards: silts with sandstone bands, locally lignitic, c.9.6 m; sandstone with lignite at top (forms ledge at foot of east end of cliff), c.2.4 m; silts and sandstones, 2.4 m; pellet bed, 0 to 0.3 m; siltstone, c.4.5 m; marly clay, c.4 m;

sandstone, c.3 m; pebble bed, 0.15 m; sandstone with ?saurian footprints, 3.7 m. The strata in the cliff-section generally seem to be planar-bedded, in contrast to the large-scale channel structures which are present in the Tunbridge Wells Sand at the western Galley Hill.

White (1928, pp.49–50) inferred the presence of a fault, the Glyne Gap Fault, from evidence seen in the reefs south-west of Little Galley Hill. He took this fault to separate the two successions of the Galley Hills both of which were then regarded as being in the Ashdown Beds. Seaward of the above section he observed in the foreshore a sequence of sandstone, shale, siltstone and clay, the last locally mottled red and occupying a wide belt south of Glyne Gap and Galley Hill. This sequence is still visible under amenable conditions of season and tide, although the upper clay sequence is discontinuously exposed. White grouped all but the topmost shale with the 'Fairlight Clays' and postulated that the Glyne Gap Fault occupies a 'gap' below. The author is of the opinion however, that a lower 'gap' offers a better position for the line of the fault, which is now termed the Old Town Fault. The beds below therefore belong to the Tunbridge Wells Sand, as described above.

Between Glyne Gap and St Leonards there is an extensive spread of alluvial deposits which is flanked on the seaward side by Storm Gravel Beach deposits. Small sandstone and siltstone reefs are patchily exposed on the foreshore as far east as [TQ 7752 0832]; thereafter Flandrian peaty silts are intermittently exposed (see p.56).

Parts of the Ashdown Beds–Wadhurst Clay sequence have, at various times been exposed in the former cliff-line to the east of the West Marina. RDL

St Leonards–Hastings

Near the coast at St Leonards, the base of the Wadhurst Clay falls eastward to lie between high and low water marks at the foreshore reefs known as Goat Ledge [TQ 802 087]. These reefs are formed by the

outcrop of a bed of massive 'Tilgate Stone', which is probably equivalent to the sandstone in the West Ascent section (p.39). It lies low in the Wadhurst Clay, and is flexed into a minor fold plunging west. The bed of 'Tilgate Stone' is 1.5 m thick and consists of blue-grey calcareous siltstone with small scale cross-bedding; it is partly decalcified to brown rottenstone. The upper surface has the characteristic rounded mammillated form first described and illustrated by Webster (1829).

The 'Tilgate Stone' reefs are abruptly terminated by a fault trending WNW–ESE which crosses the promenade [TQ 8025 0885] and throws down about 50 m to the NE, bringing beds low in the Tunbridge Wells Sand to foreshore level.

The White Rock Fault crosses the coast at the landward end of Hastings Pier, trending NE–SW and throwing down to the NW. In the old sea cliffs behind White Rock Place [TQ 8132 0925] the section recorded by Fitton (1836, pp.167–168) is now much degraded and is partly obscured by protective masonry. The following sequence was visible in 1970: Wadhurst Clay, Cliff End Sandstone, up to 6 m; shales (obscured by masonry), up to 4 m; Ashdown Beds, 4 m.

The Wadhurst Clay shales below the Cliff End Sandstone became known as the 'Endogenites' Beds and yielded to Fitton remains of the tree fern Endogenites erosa (now Tempskya schimperi (Gorda)) and the small bivalve Cyclas media (now Neomiodon medius).

The White Rock locality takes its name from a former promontory of basal Wadhurst Clay 'Tilgate Stone' which was shown on Webster's (1829) section, drawn in or before 1824, but was destroyed by marine erosion prior to the publication of Fitton's paper in 1836.

Hastings Castle is built on crags of top Ashdown Beds sandstones which rise to over 60 m above OD at the southern extremity of the West Hill spur. Just north-east of the castle ruins, at Ladies Parlour [TQ 821 095], the hill is capped by a thin remnant of the basal Wadhurst Clay comprising weathered siltstones and mudstones with traces of clay-ironstone. The tree fern Tempskya was noted from these strata by Tylor (1862), The underlying top Ashdown Beds sandstone has a hardened ferruginous surface but the top pebble bed is not developed. Around the castle and in the old quarry exposures to the east, 20 m or more of massive well jointed sandstones dipping gently south-westwards are exposed. These are medium-grained, white and buff, with very flat easterly-directed foresets and frequent thin bands of mud-flake conglomerate at the bases of minor channels.

Hastings to Ecclesbourne

The mouth of the Bourne, on which Hastings Old Town lies, is blocked by a 150 m-wide ridge of shingle that has accumulated against the two breakwaters in recent times.

East Hill rises steeply on the east of the Old Town; it is ascended by a cliff railway in a cutting [TQ 827 095] which displays top Ashdown Beds, similar to those of Hastings Castle, overlain by thin basal shales of the Wadhurst Clay, from which fossils of the tree fern Tempskya were noted by Fitton (1836) and Tylor (1862), and the massive Cliff End Sandstone about 7 m thick. The latter forms a near-vertical feature on East Hill and adjacent cliff tops. A section at the southern end of the row of houses at High Wickham [TQ 8296 0999] shows a well developed pebble bed, 8 cm thick with quartz and rare chert pebbles up to 7 mm in diameter, overlying 4 m of friable white fine-grained sandstone (Cliff End Sandstone) with vertical root traces.

The top Ashdown Beds sandstones and Cliff End Sandstone are clearly exposed in the abandoned sea cliffs behind Rock-a-nore Road to the eastern breakwater, as are the gently eastward-dipping foresets in the former. The old caves above the scree at the foot of the cliff are man-made.

Beyond the eastern breakwater eastwards to the Foul Ness Fault the top 50 m of the Ashdown Beds and the Cliff End Sandstone are well exposed above a mass of slipped and fallen rock debris which lies at the cliff foot. A composite section of the Ashdown Beds compiled from overlapping sections recorded at East Cliff [TQ 8305 0961], [TQ 8311 0966] and [TQ 8326 0970] is as follows:

Thickness m

WADHURST CLAY

Shales and siltstones with ironstone nodules

seen

ASHDOWN BEDS

Sandstone, fine- to medium-grained, massive, gently dipping cross-bedding; thin bands of ferruginous mud-flake conglomerate,

estimated 17.0

Clay, dark grey, throws out ferruginous springs

0.1

Sandstones and siltstones, thinly interbedded, much iron pan on joints

3.5

Mudstone, silty, grey

1.0

Sandstone, fine-grained, silty, laminated, massive,

well jointed, with some iron pan

1.7

Sandstone and siltstones, grey and ochreous, local cross-bedding; iron pan on joints

5.5

Mudstone, dark grey, ochreous, with much plant debris and lignite streaks; roots up to 7 mm in diameter penetrate bed below

0.1

Siltstone, pale grey and ochreous, with interlaminated fine-grained sandstone and ferruginous ribs which weather out to give honeycomb effect on cliff face; plant debris; local roots

2.3

Sandstone, very fine-grained, silty, grey-white and ochreous; much iron pan throughout in very irregular forms; plant debris on bedding. Some red and ochreous staining in top 0.6 m; 'boxstone' nodules near base

2.4

Siltstone, dark grey, planty, laminated

0.4

Mudstone, silty, grey-green, with sphaerosiderite

2.2

Sandstone, fine-grained, pale grey, with sphaerosiderite, silty laminae and much iron pan

0.45

Mudstone, silty, pale grey-green to pale grey; sphaerosiderite in top 0.6 m, shaly and dark olive-grey below; massive below 0.9 m

2.4

Alternating siltstones, grey, ferruginous, locally sphaerosideritic, and mudstones, silty, grey, with plant debris near the bases of some units

4.75

The Foul Ness Fault crosses the cliff top at an acute angle at [TQ 8325 0970] trending WNW–ESE and throwing down about 17 m to the NE. This has the effect of juxtaposing in the cliff top, the Cliff End Sandstone to the SW and shales somewhat higher in the Wadhurst Clay to the north-east. The shales are unstable and slip across the fault-plane on to the beach. The section in the backwall of the resulting slip scar [TQ 8328 0977] revealed two sandstones 1.0 m (upper) and 2.4 m (lower) thick, the lower being about 12 m above the top of the Cliff End Sandstone.

Between Hastings eastern breakwater and Foul Ness, the lower part of the cliff is largely concealed by rock debris that has fallen or slipped from above. The soft clays and shales have been rapidly removed by wave action leaving boulders of the more resistant sandstones strewn over the beach and wave-cut platform. Several interesting varieties of calcareous 'Tilgate Stone' from the basal Wadhurst Clay are present including some with mammillated forms, others with shells and bones, and a spectacular form where the calcite has crystallised in radial aggregates giving a spotted 'pseudo-igneous' appearance.

Continuing eastward beyond the Foul Ness Fault towards the mouth of Ecclesbourne Glen, a sequence closely similar to that of East Cliff is seen, but older beds appear in the foot of the cliff because of the gentle south-westerly dip. Below the equivalents of the lowest silty mudstones of the East Cliff section a massive cross-bedded unit, up to 5 m thick, of grey siltstone with ribs, laminae and irregular pods (pseudonodules) of white sandstone rich in fine-grained plant debris is seen. The foresets of this unit dip NE at about 10°. They have been deformed by dewatering and differential compaction producing minor faults and folds, pull-aparts and loading structures. Stewart (1981b, fig. 3.13; 1983) has published detailed profiles of the sedimentary structures hereabouts and farther east and has suggested that the large scale cross-sets are point-bar deposits produced by migrating fluvial channels, which carried a high suspended load.

The base of this cross-bedded unit is obscured by talus and beach material at the foot of the cliff below Ecclesbourne Glen. However, on the wave-cut platform outcrops of grey massive silty fine-grained sandstone with sphaerosiderite, plant debris and traces of mud-flake conglomerate are visible beneath it [TQ 837 099]. Similar siltstones and sandstones with sphaerosiderite occur in the wave-cut platform east of Ecclesbourne Glen, where some cross-bedding is apparent.

The characteristic massive facies of the top Ashdown Beds sandstones, with flattish easterly-facing foresets and strong jointing, as seen in the crags below Hastings Castle is maintained across East Cliff and Foul Ness almost to the western rim of Ecclesbourne Glen. The aspect of this sedimentary unit undergoes a major change from west to east across the mouth of the glen. On the western side [TQ 8360 0992] the lowest massive sandstones are replaced by a set of cross-strata, up to 12 m thick, with alternating foresets of sandstone and siltstone. On the eastern side the massive character is entirely lost and here thinly interbedded sandstones and siltstones with some silty mudstone occur. The upper 7 m of the unit seems to be flat-bedded but cross-bedding, inclined at 5–10° SW is clearly visible in the lower 4 to 6 m of strata, which can be traced for a few hundred metres east of the glen. These changes in facies are shown graphically in (Figure 23). Sections lower in the Ashdown Beds, and accessible from the beach, have been measured and are portrayed together with those from East Cliff in (Figure 9). This shows that, in spite of some lateral lithological variation, fairly close correlation of the several sections is possible by means of the few marker beds illustrated.

At the cliff top, about 100 m ENE of the mouth of Ecclesbourne Glen [TQ 8378 1000], a fine section in upper Ashdown Beds and lower Wadhurst Clay strata may be examined with the aid of field glasses, although it is quite inaccessible. The thicknesses quoted in the following summary are thus, of necessity, estimated. It is not possible to confirm the presence of the Top Ashdown Pebble Bed: Wadhurst Clay, shales with thin siltstones and 'Tilgate Stone' bands, c.3 m; Cliff End Sandstone, sandstone, 6 m; shales, 1 m; 'Tilgate Stone', 1 m; shale and clay-ironstone, 1 m; sandstone, 0.45 m; shale and clay-ironstone, 1 m; Ashdown Beds, sandstones and siltstones, 11 m.

Ecclesbourne to Lee Ness

Proceeding ENE from the mouth of Ecclesbourne Glen, the foot of the cliff is much obscured by talus for the next 500 m. At the cliff top the distinctive outcrop of the Cliff End Sandstone can clearly be seen to rise gently north-eastward. Immediately beneath, the basal shales and 'Tilgate Stones' of the Wadhurst Clay form a sloping grassy ledge. The top Ashdown Beds sandstones maintain their character and thickness of about 10 m for some distance. Beneath them, 30 m of well stratified sandstones with minor silty and argillaceous beds crop out in the cliff forming vertical joint-bounded faces. The cross-bedded unit of grey siltstones with sandstone laminae that appeared in the foot of the cliff east of Foul Ness is at a higher elevation beneath these stratified sandstones. Some 500 m east of the mouth of the glen [TQ 841 100] the cross-beds give way to a saucer-like channel, 60 m wide by 10 m deep, which was first noted and figured by Topley (1875, fig. 3, p.41). This apparent example of large-scale, trough cross-stratification may represent a complex channel-fill. On the east the channel intersects planar-bedded sandstones, 2 to 10 m thick, which in turn rest on a massive sandstone bed, 2.5 m thick, that forms a ledge at the foot of the cliff. This prominent bed of pale grey silty sandstone has a hardened ferruginous crust on its upper surface, which incorporates a mud-flake conglomerate with plant debris, from which rootlike protuberances, associated with abundant sphaerosiderite, extend down for 0.3 m. The hardened surface probably results from a period of emergence and plant colonisation. Below, the sandstone is fairly uniform for 0.45 m and then becomes highly sphaerosideritic with iron-staining for 0.55 m, in which a crude lamination is apparent before passing downwards by alternation into olive-grey silty mudstone. This bed was figured by White (1928, plate IIB) who used it to mark the junction of the 'Ashdown Sand' and 'Fairlight Clays', a division that can no longer be upheld.

About 750 m ENE of Ecclesbourne Glen, beneath Hastings Downs, a sizeable landslip [TQ 845 101] extends for some 200 m along the cliffs. Beyond this slip the cliffs are stable for a short distance of 50 m or so whence the major landslipped area of Covehurst Wood is reached. Between the two slips the cliffs show an Ashdown Beds sequence which is generally similar to that described near Ecclesbourne Glen overlain by basal Wadhurst Clay and a prominent crag of Cliff End Sandstone in the cliff top. The summary description of the estimated sequence visible in the inaccessible cliffs [TQ 846 101] is as follows: Wadhurst Clay, sandstone, 2 m; shales, 2.5 m; Cliff End Sandstone, sandstone, 8 m; Ashdown Beds, sandstone, 5 m; siltstone and sandstone, 6 m; laminated sandstone, 10 m; mudstone with thin sandstone bands, 10 m. The Covehurst Wood landslip is a major rotational slip, which extends north-eastwards along the coast for 800 m as far as the mouth of Fairlight Glen. The cliffs which form the backwall of the slip rise to about 100 m above OD and drop steeply to the tumbled and roughly vegetated undercliff area, which is up to 250 m wide (see also Chapter 6).

Midway along the slip, the rocks of the backwall are disturbed by the Ore Fault which crosses the cliff in a small re-entrant [TQ 8490 1042] and disappears beneath the undercliff. The fault trends ESE–WSW and has a throw of about 15 m down to the SSW here. The Ore Fault and the dip combine to bring older rocks up into the cliff foot, notably the chiefly argillaceous rocks of the Ashdown Beds, which are an important factor in the slip movements. The rocks of the backwall cliff are largely inaccessible, but the Cliff End Sandstone continues to form a distinctive feature at the cliff top. Beneath it a grassy slope marks the outcrop of the basal Wadhurst Clay. The topmost Ashdown Beds still consist mainly of thinly bedded silty sandstones, about 10 m thick, which overlie more massive sandstones about 20 m thick beneath, the latter being underlain by argillaceous beds concealed beneath the undercliff.

Fairlight and Warren Glens are short steep-sided valleys that drop about 120 m in half a kilometre from the Fairlight ridge to the sea, where their small streams 'hang' above the beach due to rapid cliff recession. The Cliff End Sandstone forms a good feature around the rim of the two glens. The valley sides are cut in Ashdown Beds and are much obscured by hillwash, but the sandstone features are sufficiently prominent for them to be mapped separately from the clays. In the ravine at Dripping Well [TQ 8504 1109] and in the adjacent old quarry, near Place Farm, the following ,sequence was measured: Wadhurst Clay, Cliff End Sandstone, sandstone, 8 m; clay-ironstone, up to 0.15 m; shales with 'Tilgate Stone' bands, 2.6 m; gap, 0.9 m; Ashdown Beds, sandstone, 3 m. The spring which gives Dripping Well its name rises at the base of the Cliff End Sandstone. No trace of the Top Ashdown Pebble Bed was seen above the sandstone, which forms a small waterfall in the stream.

The Cliff End Sandstone is also exposed in crags near Lover's Seat [TQ 854 108] and here it contains internal channelling structures, streaks of small quartz pebbles and lignitic plant debris, silty bands and shows local calcareous cementation.

Several outcrops, which appear to be undisturbed, protrude through beach deposits at the north-east end of the Covehurst Wood landslip. At Black Rock [TQ 8526 1055], below the mouth of Fairlight Glen, siltstones and silty sandstones, with red-stained coarser sand picking out ripple sets, dip west at 5°. The reefs 120 m to the northeast [TQ 8537 1060] are of massive fine-grained sandstone with reddish iron staining, associated with cross-laminated siltstones and these apparently dip north-west at 20°; but this may be a foreset dip.

Marine erosion has truncated the spur between Fairlight Glen and Warren Glen, exposing alternating clays and sandstones of the Ashdown Beds over a 500 m length of coast known as Willowpit Wood. The relative incompetence of these strata is reflected by the fairly gentle stepped profile of the cliffs here, which are much affected by minor mud-flows.

Around the mouth of Warren Glen [TQ 858 108] the rocks at beach level are in situ and are well exposed. On the west [TQ 8555 1068] a mainly sandy unit rises into the bottom of the cliff and thence eastward. The following sequence can be made out: tumbled sandstone blocks of upper cliff; sandstone, c.5 m; mudstone, 1.5 m; sandstone with plant debris, 4 to 5 m; siltstone with cross-bedding and minor slumping, 3 m. These beds can be traced eastward for 100 m or more and it is apparent that the siltstone and sandstone in the lower part of the section represent proximal and distal end members of a set of cross-strata up to 10 m thick. The cross-beds have an apparent dip of up to 10° WNW. They probably resulted from lateral accretion in a broad fluvial channel environment similar to that suggested for the cross-bedded unit seen near Ecclesbourne Glen. However, some of the sedimentary structures seen in the basal siltstone suggest comparisons with a tidal flat environment with migrating channels. Several examples of small three-toed foot-prints, up to 0.2 m long, were seen hereabouts on the undersides of fallen sandstone blocks.

On the eastern side of Fairlight Glen, below the Coastguard Station, the upper cliff is much affected by landslipping, over a distance of 600 m (Chapter 6).

Lee Ness to Fairlight Cove

At Lee Ness Ledge [TQ 867 108] a distinctive bed, the Lee Ness Sandstone, forms a flat reef and can be clearly traced in the cliff for 1 km eastward, picking out the Fairlight Anticline. The bed is up to 2.3 m thick and displays a number of interesting sedimentary and faunal features. It is best seen in the reefs below the cliffs at Goldbury Point [TQ 876 114]; this latter place name was used by White (1928) although it does not appear on the Ordnance Survey maps. The Lee Ness Sandstone is characterised by small-scale lateral variations which are generally caused by loading structures or internal erosion; the following section is fairly typical:

Thickness m

Sandstone, fine-grained, whitish grey, massive, becoming medium greenish grey below with traces of faint lamination and bioturbation and small clasts of grey silt. Some secondary ochreous staining associated with sphaerosiderite. Top of bed, as exposed on beach is irregular and is penetrated by vertical cylindrical trace fossils (roots or burrows?) up to 7 cm in diameter and 20 cm deep. Gradational base

0.45

Siltstone, olive-grey, laminated with white fine-grained sand; bioturbated (burrows with meniscus fills up to 20 mm in diameter); slightly irregular burrowed base

0.15 to 0.23

Sandstone, fine-grained, whitish grey, faintly laminated, as above; gradational base

0.08 to 0.15

Sandstone, silty, with greenish grey silt laminae; slight bioturbation; gradational base

0.05 to 0.10

Siltstone, pale grey, with wavy greenish grey to dark grey laminations

0.10 to 0.15

Siltstone, grey, uniform

0.10 to 0.13

Siltstone, pale grey, with olive-grey laminae.

Bioturbation and load-casts abundant; partly erosional base

0.10 to 0.25

Sandstone, silty, grey to olive-grey above, with irregular laminations and wisps and burrow-fills of white fine sand. Passing down below about 0.45 m into pale grey silty sandstone with faint laminations

seen 1.25

The underside of the Lee Ness Sandstone has an irregular contact with underlying grey silty mudstone, and carries frequent casts of the three-toed footprints of Iguanodon up to 0.5 m in length (Plate 3). These suggest a phase of lower water level or even emergence immediately prior to the transgressive event which laid down the Lee Ness Sandstone and infilled the footprints, preserving them as casts. It is difficult to interpret the sedimentary environment of the Lee Ness Sandstone, which appears to be out of context with the beds above and below. The frequent load-casts and the almost complete bioturbation of the sandstone by burrowing organisms suggests that it may represent a brief estuarine incursion up a major embayment or channel. Stewart (1981b, p.3.20), however, interpreted the Lee Ness Sandstone as a small lacustrine delta.

The axis of the gentle Fairlight Anticline crosses the cliff about 600 m ENE of Lee Ness Ledge [TQ 8715 1120] trending about E–W. The 10 m of strata which are exposed below the Lee Ness Sandstone on the crest of the anticline, are the lowest seen in the cliff-sections between Hastings and Cliff End. They comprise alternating beds of red-mottled grey and green silty mudstones and fine-grained sandstones and siltstones with plant debris; sphaerosiderite is abundant throughout. The harder sandstones and siltstones form a series of linear curving reefs on the shore platform.

The cliffs between Lee Ness and Goldbury Point are cut in alternating thin sandstones and mottled silty mudstones and rise to a fairly uniform height of about 55 m above OD. For the most part the beds above the Lee Ness Sandstone are inaccessible and partly obscured by talus and minor mud-flows, but Stewart (1981b, fig. 3.14) illustrated a possible point-bar sequence 7.5 m thick, high in the cliff. At Goldbury Point [TQ 877 114] frequent cliff falls have left a clean, but inaccessible section:

Estimated thickness m

HEAD

Sandy loam, brown

1.1

ASHDOWN BEDS

Mudstone, silty, grey-green

1.1

Siltstone, ferruginous, hard

0.8

Mudstone, silty, grey-green; red-mottled at base

1.5

Sandstone, massive, ferruginous, irregular weathered surface

2.0

Mudstone, silty, olive-green with hard ribs of siltstone.

Becomes more massive and silty near the base with harder ferruginous bands projecting

4.6

Mudstone, dark grey and olive-grey; some purplish red mottling at base

5.5

Sandstone, fine-grained, massive, jointed

0.8

Mudstone, silty, banded dark grey and grey-green, ochreous staining

3.7

Siltstone, ferruginous, hard

0.3

Mudstone, silty, pale olive-green with red-mottled bands and patches of ochreous staining

3.0

Miidstone, silty, dark grey-green; brown ferruginous band at top

2.0

Siltstone, massive, with much iron-staining and iron pan on vertical joints

2.4

Mudstone, silty, dark grey and grey-green with some dark red mottling

4.6

Siltstone, ferruginous, banded, hard

1.1

Mudstone, silty, grey and red mottled

3.0

Lee Ness Sandstone: exposed on shore at foot of cliff

2.3

Nodular spheroidal aggregates of sphaerosiderite up to 0.3 m in diameter are seen weathering out of mottled red and dark grey-green mudstones at the foot of the cliff, west of the point. Small three-toed reptilean footprints have been noted on fallen blocks of sandstone and siltstone nearby. Stewart (1981b, p.3.20, fig. 3.15) has equated the variegated mudstones on the Goldbury Point section with overbank deposits with pedogenic horizons and has also identified possible point-bar deposits and crevasse splays.

At Goldbury Point, the cliff line turns to NE–SW. Strata similar to those seen west of the point continue for 700 m as far as the Fairlight Cove Reversed Fault but they are much affected by landslips and mud-flows. The Lee Ness Sandstone passes out to sea at Goldbury Point. At an horizon a few metres above the Lee Ness Sandstone, another cross-stratified unit is intermittently exposed at the foot of the cliff, north-east of the point. The cross-beds face north-east and comprise ferruginous sandstones and siltstones with lignite (fossil drift-wood), sphaerosiderite and mud-flake conglomerates. These rocks acquire a reddish brown skin on exposure but are grey and grey-green on freshly broken surfaces. Stewart (1981b, fig. 3.16) has interpreted this unit as a point-bar deposit.

The landslipped area between Goldbury Point and Fairlight Cove, displays rotational movements with back tilting of foundered blocks, as well as mud-flows of varying scale (Chapter 6).

A thin sandstone which is present between Fire Hills and Fairlight Cove was exposed in 1970 in the backwall of a slip [TQ 8786 1179], 250 m south-west of the Fairlight Cove Reversed Fault, where there is a section in about 6 m of the Ashdown Beds, comprising mudstones, sandstones and siltstones with lignite and plant debris.

Fairlight Cove to Haddocks's Reversed Fault

The Fairlight Cove Reversed Fault crosses the coast [TQ 8806 1197] in a re-entrant in the cliff which provides convenient access to the shore; the fault plane intersects the cliff dipping at about 60°, to the south-west. In the absence of a suitable marker bed the throw cannot be precisely determined, but it is thought to be about 60 m down to the NNE.

In the low cliffs between the Fairlight Cove and Haddock's reversed faults, a distance of 800 m, the strata exposed are chiefly sandstones with interbedded silty mudstones, which are roughly equivalent to beds from 50 to 80 m below the top of the Ashdown Beds. The dominant feature, is a cross-bedded unit which Stewart (1983, fig. 4) has named the 'Haddocks Rough Unit'. This extends for 500 m north-east of the Fairlight Cove Reversed Fault (Allen, 1976, p.394 and pl.I; Stewart, 1981b, p.3.20, fig. 3.14). The unit is up to 10 m thick and rises from the base of the cliff at the fault to the top near Haddock's Cottages [TQ 883 124]. The base of the unit is erosional and cuts down deeply into the underlying strata. The foresets dip south-westwards, generally at about 10° but with a maximum dip of 19°. The rocks between the two faults are arched into a gentle fold. A composite section of the beds exposed in this tract [TQ 8806 1197]–[TQ 8857 1251] is given below. These beds show great lateral variability and contain several erosion surfaces. The higher beds at the north-eastern end of the section are inaccessible but can be seen to comprise alternating foresets of fine-grained sandstones and silts with occasional mudstone bands, up to 1.5 m in thickness:

Thickness m

ASHDOWN BEDS

Haddock's Rough Unit:

Major cross-bedded unit (cuts across lower strata to the top of the distinctive sandstone bed marked 'X' below) comprising alternating thin interbeds of fine-grained sandstone, siltstone and silty mudstone with much black plant debris; mud-flake conglomerate at base. Overall tendency for cross-beds to get finer distally, i.e. to the south-west up to about

10.00

Silt and silty mudstone, grey

1.1

Sandstone, fine-grained, massive, white with dark shale band

2.0

Silt and silty mudstone, grey, iron pan on joints

3.7

Mudstone, silty, sphaerosideritic with white fine-grained sandstone at top, 0.6 m thick

1.7

Sandstone, fine-grained, grey and buff, with much iron pan on oblique joints, sphaerosiderite in patches

1.8

Silt, massive, grey with iron pan on joints; thin sphaerosideritic clay over band of lignitic plant debris at base

2.9

Silt, grey, much iron pan on joints; thin grey sphaerosideritic clay at base

1.5

Sandstone, fine-grained, ochreous

0.1

Mudstone, silty, grey, more silty at top; iron pan on joints

1.8

Sandstone, silty, massive, buff, much iron pan; sphaerosiderite in top 0.9 m, with lignite in band 0.3 m above base; silty with plant debris at base

2.4

Mudstone, silty, grey, with sphaerosiderite

1.3

Sandstone, silty, yellowish buff, with prominent vertical trace fossils which branch upwards and are picked out by brown sphaerosiderite aggregates. More silty with much plant debris at base [X]

2.4

Variable cross-stratified unit consisting of grey-green sphaerosideritic silty clay with much plant debris and lenses of pebbly coarse sandstone, up to 1 m thick

2.4

Siltstone, grey, hard

0.4

Clay, silty, grey

0.2

Sandstone, silty, sphaerosideritic, with iron pan on joints

0.9

Clay, silty, pale grey

0.5

Sandstone, fine- to medium-grained, grey, with thin

lenses of coarse pebbly sand near base seen to

1.4

Gap-obscured by beach material

—

Cross-bedded siltstones and sandstones with plant debris exposed on foreshore platform

—

Stewart (1981b, p.3.20; 1983, p.377) has drawn attention to the presence of siltstone and sandstone drapes in the Haddock's Rough Unit and to the disturbance of individual foresets by burrowing organisms which indicate significant variations in discharge. A probable sedimentary model is that of a point-bar, accreted laterally by small increments of sediment into a deep channel, rather than that of a giant sand-wave in a high-energy braided stream environment, as suggested by Allen (1976, p.394). Possible brackish water influences are suggested by dinoflagellate assemblages which have been extracted from the Haddock's Rough Unit (Batten and Eaton, 1980).

Immediately south-west of the Haddock's Reversed Fault a distinctive sandstone bed ('X' in section above), with ferruginous root-like structures, crops out at beach-level and rises gently to reach the cliff top just south of Haddock's Cottages where it is cut out by the Haddock's Rough Unit. The rocks of the foreshore platform between Haddock's Cottages and the Haddock's Reversed Fault exhibit large-scale trough cross-bedding of low amplitude. At least three superimposed orders of cross-strata may be discerned with dips of between 2 and 10° on the flanks of the troughs (Figure 24). These seem to be the cross-strata which Stewart (1981b, p.3.17) has interpreted as laterally accreted point-bar deposits. Some earlier workers (Milner and Bull, 1925, p.309) mistakenly interpreted these cross-strata as tectonic structures, which could not be traced into the adjacent cliffs. They therefore postulated a fault running parallel to the coast to complete the picture.

Haddock's Reversed Fault to Cliff End and Toot Rock

The Haddock's Reversed Fault (Plate 4) crosses the coast in a reentrant in the cliff about 200 m north-east of Haddock's Cottages [TQ 8857 1251] with a trend parallel to that of the Fairlight Cove Reversed Fault. The fault plane dips at 60° to the SSW. Here again, in the absence of a convenient marker bed, it is not possible to determine the precise throw of the fault, but it would appear to be of the same order as that of the Fairlight Cove Reversed Fault, with a downthrow of about 55 to 60 m to the north. The fault plane is well exposed on the north side of the re-entrant, where it intersects the Cliff End Sandstone. The surface shows an intricate pattern of corrugations which are not slickensides, but rather the effect of imbrications produced within a compound fault zone about 0.3 m wide, which is occasionally visible in section at beach-level.

Beyond the Haddock's Reversed Fault, the cliff-line swings around to the NNE with a general height of 20 to 30 m as far as Cliff End. The upper part of the cliff is cut in soft Wadhurst Clay shales that give rise to a strip of densely wooded, slipped terrain from which material occasionally falls to the beach. The Cliff End Bone Bed occurs within these shales a few metres above the top of the Cliff End Sandstone, which stands out prominently, in the upper cliff. A 1 m band of shales with a 0.1 m bed of clay-ironstone at the top, lies beneath the base of the Cliff End Sandstone, giving rise to a notch in the cliff which conveniently marks the junction of the Wadhurst Clay and the Ashdown Beds. Beneath the notch up to 15 m of sandstones with thin silty mudstone bands are exposed above the beach. In this stretch of coast the rocks form part of a gentle anticlinal flexure which causes the base of the Cliff End Sandstone to fall almost to beach-level at the Cliff End Fault [TQ 8875 1300] (Figure 25).

In dry weather the re-entrant at the Haddock's Reversed Fault provides convenient access to the foreshore but the slipped Wadhurst Clay material can be treacherous in wet conditions. At the cliff top [TQ 885 125] there are scattered exposures in the Wadhurst Clay comprising about 16 m of shales and subordinate siltstones with clay-ironstone nodules, and with fish and plant debris and bivalve moulds at some horizons. These strata overlie the Cliff End Sandstone.

Although the lenticular Cliff End Bone-Bed is absent in this section, it is present, up to 0.2 m thick, at its type locality about 400 to 500 m NNE of the reversed fault [TQ 887 129] (Plate 5). Here it consists for the most part of coarse subangular quartzose sandstone with a calcareous cement; pebbles of pinkish quartz and fine-grained siliceous rocks are also present, together with rolled nodules of clay-ironstone. Faunal remains include many fish teeth and scales (Patterson, 1966) with some 'reptilean' bone fragments and teeth; early mammals are represented by a small suite of teeth recovered after careful collecting and laborious separation processes (Woodward, 1911; Clemens, 1963; Clemens and Lees, 1971; Kermack, Lees and Musset, 1965). Both the mammalian remains (Clemens and Lees, 1971) and sharks (Patterson, 1966) provide valuable data for the determination of the evolutionary lineages within these groups. The mammalian species from the Cliff End Bone-Bed listed by Clemens and Lees include: Loxaulax valdensis (Woodward), Sphalacotherium tricuspidens Owen, Melanodon hodsoni Clemens & Lees, Aegialodon dawsoni Kermack, Lees & Musset. Among the Wealden sharks reviewed by Patterson, the following species have been recorded from the Cliff End Bone-Bed: Hybodus ensis Woodward (common), H. parvidens Woodward (common), H. brevicostatus Patterson (rare), Lonchidion breve breve Patterson (moderately common), L. rhizion Patterson (uncommon), L. heterodon Patterson (rare). Other fish remains, notably species of Lepidotus, and 'reptilean' teeth and bones occur fairly commonly, as do pieces of fossil drift-wood.

At the type locality, the bone-bed occurs at the cliff top and is not easily accessible. Past collections were made from fallen slabs at the foot of the cliffs among beach gravel, which gave rise to some stratigraphical confusion. During the present survey it has been conclusively demonstrated that the bone-bed occurs in shales about 2.9 m above the top of the Cliff End Sandstone and is supplied to the beach by intermittent cliff falls (Shephard-Thorn in Clemens and Lees 1971).

In 1965 a new road-cutting through the Wadhurst Clay at Cliff End [TQ 888 137] showed:

Thickness m

Topsoil and slipped clay with siltstone fragments

0.82

WADHURST CLAY

Clay, shaly, olive-green, with siltstone laminae; clay-ironstone occurs as small scattered nodules and in a double band 150 mm thick, 0.3 m below top

1.00

Siltstone, pale grey, cross-bedded, with some grey-green shale partings

0.10 to 0.15

Clay, shaly, olive-green with silt laminae and some small ironstone nodules

0.40

Siltstone, decalcified, ferruginous, with traces of bone

0.05

Shales, olive-green with silt laminae and bands; loose fragments of 0.1 m thick silt bed with horizontal and vertical rootlets

3.00

Clay, shaly, dark greenish grey, with white partings of shell debris, scattered ironstone nodules in middle

0.50

Siltstones, thin, cross-bedded, with shale partings

0.53

Shell band with grey-green clay and ironstone nodules

0.08

Siltstones, laminated, cross-bedded, with shale partings

0.68

Shales, olive-green, with siltstone laminae Cliff End Bone-Bed:

0.18

Sandstone, coarse-grained, pebbly, with ironstone nodules

0.1 to 0.25

Clay, grey-green

0.12

Clay-ironstone, nodular

up to 0.15

Siltstones, hard, grey, cross-bedded, shelly at base

0.15

'Tilgate Stone': irregular slumped shelly calcareous siltstone with uneven loaded base

0.45

The sequence below, and north of the Cliff End Fault, in the beds down to the Ashdown Beds and including the Cliff End Sandstone is as follows:

Thickness m

WADHURST CLAY

'Tilgate Stone' (as in previous section)

0.45

Clay, grey-green, with lenticles of siltstone and shells

0.15 to 0.25

Sandstone, ochreous, shelly, uneven base

0.12

Siltstone, finely laminated

0.08

Clay, shaly, blue-grey

0.12

Siltstones, cross-bedded, thin decalcified layer with shells at base

0.33

Clay, grey-green, with brown clay-ironstone nodules in lower 70 mm and shelly layers

0.16

Sandstone, fine-grained, silty, ochreous, cross-bedded, decalcified in part, shelly

0.33

Clay, shaly, grey-green, with shells and ostracods; band of clay-ironstone nodules at top

0.18

Siltstones, pale yellowish grey, cross-bedded, with shells; brown indurated layer at top

0.50

Top Cliff End Pebble Bed:

Sand, coarse-grained, quartzose with few scattered pebbles in ripples

up to 0.03

Cliff End Sandstone:

Sandstone, fine- to medium-grained, massive, grey-white, dark mauve-grey in top 200 mm due to presence of fine lignitic plant debris, with traces of vertical roots extending below. Thin streaks of coarse sand with quartz pebbles at 1.07 and 1.55 m below top. Signs of trough cross-bedding below; 0.15 m band of coarse sand with pebbles at base

3.10

Sandstone, coarse-grained, with pebbles at base, fining upwards

0.33

Sandstone, medium-grained

0.38

Sandstone, coarse-grained, pebbles up to 12 mm; cross-bedded, with lenses of finer sand

0.76

Sandstone, fine- to medium-grained, white to buff, cross-bedded. Frequent lignitic debris partings down to 0.76 m. Hollow moulds of bivalve shells

(?Neomiodon) pick out bedding structures

3.05

Sandstone, fine-grained, brown

0.05

Sandstone, fine-grained, cross-bedded, with 'slump' structures

0.25

Sand, fine-grained, finely laminated, packed with hollow moulds of Neomiodon valves

up to 0.20

Sandstone, medium-grained, cross-bedded; several streaks of hollow shell moulds pick out cross-bedding

2.36

Silt, brown, ?decalcified, weathers as notch in cliff

0.10

Sandstone, fine-grained with some grey silt, white, cross-bedded; ferruginous patches; passing into grey siltstones at base

0.60

Basal beds of Wadhurst Clay:

Clay-ironstone, nodular, brown-skinned, blue-hearted

0.12

Shales, grey-black, with pale siltstone laminae, cross-laminated; some shells and trace fossils; thin brown silt at base

0.53

Top Ashdown Pebble Bed:

Sandstone, medium-grained, buff, ripple-bedded; irregular top; coarse-grained with scattered chert and quartz pebbles at base

up to 0.20

ASHDOWN BEDS

Sandstone, very fine-grained and silty, ferruginous

0.33

Sandstone, massive, coarse-grained at top, finer below becoming silty and ferruginous in basal 0.2m

0.92

Distinctive grey-white band. Alternations of silty fine-grained sandstone and grey silt. Thin silty shale at base

0.90

Sandstone, medium-grained, yellowish grey. Upper surface is rippled and has a ferruginous crust

0.75

Siltstone, pale grey, massive

0.18

Sandstone, fine- to medium-grained, cross-bedded; much ferruginous staining especially at top; becoming silty and finer at base

1.72.

Siltstone, grey, interlaminated with ochreous fine-grained sand. Ferruginous crust on upper surface; more silty at base which has a thin mud-flake conglomerate

0.70

Sandstone, fine-grained, silty, yellow, with hard ferruginous crust, up to 25 mm, at top

seen to 1.25

The bone-bed, a coarse grit up to 0.15 m thick, occurs in the soft shaly beds at the cliff top. The Cliff End Sandstone, 10 m thick, below is separated from the Ashdown Beds by shales 1 m thick, marked by the head of the standing figure (A11377)

The upper Ashdown Beds are represented by up to 15 m of strata in the foot of the cliff, between the Haddock's and Cliff End faults (Figure 25). A pale band of alternations of fine-grained sandstone and silt below the top of the formation can be traced between the faults. A distinctive unit of well jointed, trough cross-bedded sandstone with silt laminae up to 7 m thick, occurs at the foot of the cliff north of the Haddock's Reversed Fault. About 350 m NNE of the Haddock's Reversed Fault [TQ 887 128] a broad channel is cut into this sandstone unit. It is about 50 m wide and 3 m deep and is filled with pale grey silty mudstone. The upper surface of the sandstone has a ferruginous crust, possibly indicating brief emergence before the channel was filled in. Some crumpling of strata is apparent on the south (upthrown) side of the Cliff End Fault.

The thin band of shales with ironstone nodules below the Cliff End Sandstone yielded an ostracod fauna indicative of the 'C-phase' of the Rye Cycle of the basal Wadhurst Clay to the late F. W. Anderson. These beds are the equivalent of the Endogenites' Beds of the Hastings district. The Cliff End Sandstone is thus established to be a sandstone body within the Wadhurst Clay, and not the topmost Ashdown Beds as concluded by previous workers. This sandstone includes a succession of channel-fills; Stewart (1981b, fig. 3.18) suggested that the lower part of the Cliff End Sandstone may represent a delta, whereas the upper part may represent a fluvial, braided stream environment.

Anderson was also able to show from his studies of ostracod faunas that the Cliff End Bone-Bed lies approximately at the horizon of the 'S-phase' of the Lydd Cycle, in the Cypridea tuberculata beds (C. paulsgrovensis Zone) of the Wadhurst Clay (Anderson, Bazley and Shephard-Thorn, 1967, p.27).

The well known submerged forest of Pett Level can be traced as far south as the Haddock's Reversed Fault and north-eastwards for several kilometres towards Winchelsea Beach. At low water it extends seaward for 100 m or more from the foot of the shingle beach below the Pett Level sea wall. In-situ tree boles and recumbent trunks occur on a bed of woody peat, 0.6 to 1.0 m thick, which rests on blue-grey 'buttery' clay, seen up to a thickness of 1 m. Roots from the peat bed penetrate the underlying clay. The peat forms a low ledge or reef just above the low water line which is much colonised by boring molluscs.

At Toot Rock, a small island of solid rocks rises steeply out of the reclaimed marshland. It lies between the eastward-trending Toot Rock and Marsham faults and the strata dip at 7 to 20° to the north. A sequence of upper Ashdown Beds and basal Wadhurst Clay, which is generally similar to that at Cliff End, is visible in the old south-eastward facing sea cliffs [TQ 892 137]. Other exposures in the old sea cliffs bordering Pett Level, Winchelsea and Rye are described with the inland exposures in Chapter 4. ERST

Appendix 2 Aspects of the clay mineralogy of the Wealden and upper Purbeck rocks

Introduction

The clay mineralogy of the Wealden and upper Purbeck strata has hitherto received little attention, apart from an early paper by Tank (1962) and some records by Perrin (1971). Clay mineralogical studies have been carried out within BGS and at the University of Reading for differing purposes. Dr C. P. Sladen has provided this resume of his work on the clay mineralogy of the Hastings Beds–Purbeck Beds sequence of the Hastings–Cliff End coast section and of the Fairlight Borehole, with his conclusions on the sources and depositional environments of these rocks. A comparable and complementary study on Fairlight Borehole specimens was carried out within the BGS Petrology Unit; these results are retained on file at Keyworth. Ceramic testing of clays from the Ashdown Beds of the coast sections and the Fairlight Borehole was also carried out by the BGS Applied Mineralogy Unit. The results of these several studies of clay mineralogy are closely comparable. ERST

Results

Samples were collected from the Hastings–Cliff End coastal exposures and the Fairlight Borehole, representing a stratigraphical interval from just above the basal Purbeck Gypsiferous Beds Member to the Cliff End Bone Bed (lower Wadhurst Clay). In addition, possible source rocks for these sediments were sampled from a number of boreholes.

All the samples examined contained kaolinite and illite. In addition, there is a quantity of clay mineral which is collapsible to 10A after heating to 375°C. This may take the following forms: a) illitesmectite, where a discernible peak forms around 17A upon glycollation, b) degraded illite, where a wide range of spacings up to 30A is formed upon glycollation, c) vermiculite, which has a 14A air-dried peak which is unaffected by glycollation.

Samples from below the Cinder Bed horizon (taken here as the base of the Cretaceous) are dominated by illite and randomly inter-stratified illite–smectite but at this horizon, kaolinite rapidly becomes more abundant. The Purbeck Beds above the Cinder Bed, and the Ashdown Beds are dominated throughout by kaolinite and illite. Most commonly, degraded illite and vermiculite are also present. Randomly interstratified illite–smectite is common in the uppermost Purbeck Beds and above the Cliff End Sandstone but otherwise it occurs only sporadically. Chlorite is confined to minor amounts in the beds immediately above the Cinder Bed.

In the Cretaceous strata, an antipathetic relationship commonly exists between the proportions of kaolinite and the minerals collapsible to 10A after heating to 375°C. The coastal sections show few variations in the proportions of clay minerals but the overbank clays are an exception as these commonly contain more kaolinite. No significant lateral qualitative or quantitative variations were found in beds that could be traced laterally for up to 0.5 km. Size grading of clay minerals is not apparent. This is seen when comparing the proportion of clay minerals to the grain size of the host rock , for mean values are almost identical. In addition, different size-fractions show little variation, although vermiculite and illite–smectite tend to be more concentrated in the finer fractions.

The 1Md illite polymorph is dominant throughout and constitutes more than 80 per cent of the total illite. The remainder comprises 2M illite, with only a trace of the 1M polymorph being present. Illite sharpness ratios are consistently under 2.0. Kaolinite crystallinity measurements indicate that a disordered form is most abundant.

Scanning electron microscopy revealed authigenic clay in very few samples; nos. FB8, FB13 and CS7 contain some authigenic kaolinite. These are all medium-grained sandstones which occur within thick clay sequences. Cementation is always limited, and the cement is normally a small amount of hydrated iron oxides. Where quartz cements are present, they take the form of isolated overgrowths with well developed crystal faces which pre-date the formation of authigenic kaolinite.

Discussion

The lack of authigenic clays in most samples indicates that the clay minerals are usually wholly detrital in origin. Alteration by burial and diagenesis was very limited, as shown by the illite sharpness ratios and polymorphs which indicate the zone of early to middle diagenesis (Foscolos and Stott, 1975). The detrital clays therefore reflect the climates, source rocks and environments during erosion and deposition.

During deposition of the uppermost Jurassic beds the principal source of the detrital clays was peneplained earlier Jurassic carbonates and calcareous muds (Allen, 1967; Howitt, 1964). The climate was semi-arid, as shown by the various lithofacies and biofacies (Holliday and Shephard-Thorn, 1974). Weathering of the source rocks under these conditions would have yielded illite and illite–smectite. Hence, these are the dominant detrital clay minerals. Evidence for the neoformation of clay minerals in the depositional basin due to the high salinities was not found but warrants further searches.

The appearance of abundant detrital kaolinite at the Cinder Bed horizon matches observations in Dorset (Cosgrove, 1975) and has also been detected in other boreholes in the Weald e.g. in the Broadoak Borehole which lies 30 km to the north-west and also in the Warlingham Borehole, south of London (author's unpublished results). Mineralogical criteria can therefore help to define the Jurassic–Cretaceous boundary in southern England. The early Cretaceous tectonism rapidly increased the relief in the source areas, the rainfall, the clastic sediment input and the variability of source rock mineralogy.

The Hastings Beds samples all contain more kaolinite than the source rocks suggested by Allen (1967). This indicates considerable weathering prior to burial. Little of this weathering was at the depositional site for the clay minerals vary little with sedimentary environment. There was little size grading of different clay minerals because there is negligible variation in particle size. Erosion and deposition were rapid, and the distance of transport was short. The lack of halmyrolysis infers an absence of saline sedimentary environments.

The presence of vermiculite provides more information on the weathering conditions in the source areas during the early Cretaceous. Chemical treatments indicate that the vermiculite is a potassium-deficient alteration product of illite (Tank, 1962, 1964). The reaction illite–vermiculite requires a strong, rapidly leaching environment which allows the removal of interlayer cations before the structure can be broken down. The frequent absence of smectite suggests that the weathering sequence was illite–vermiculite–hydroxy–A1 interlayered vermiculite. The latter is equivalent to a secondary aluminous chlorite. Kaolinite was the next weathering product. This weathering sequence points to acid soils in temperate or subtropical climates. The presence of abundant quartz would have inhibited the further weathering of kaolinite to gibbsite (Marion and others, 1976). From the evidence available, and by comparison with the mineralogy of present-day soils, podsolisation was the main soil-forming process in the source area. Mean annual rainfall probably lay between 600 and 1200 mm. A slightly more arid climate may account for horizons rich in illite–smectite, for example above the Cliff End Sandstone.

In the soil environment postulated, most chlorite in the source rocks would weather to vermiculite. The evidence suggests that the total percentage was very small, probably less than 2 per cent.

Acid leaching conditions also appear to have prevailed within the Wealden depositional basin, but were less severe than in the source area. This would account for the slight alteration of clay minerals in the overbank clays. Greater hydromorphy is suggested by the development of sphaerosiderite and, occasionally, lepidocrocite. Other depositional environments lack the leaching potential required to alter the clay minerals.

The lack of diagenetic alteration may be principally due to the mature mineralogy. Pore-water movement within the Hastings Beds has been inhibited, not only by the interbedded clays, but also by the thick overlying Weald Clay. Because of this and the shallow depth of burial, which may have been only about 1200 m or less in the early Tertiary, pressure solution features are predictably rare. The formation of quartz cements may have been further inhibited by the poor sorting of most sands, as clay particles tend to inhibit their development. Significantly, quartz overgrowths and authigenic kaolinite are restricted to those sands which must have received large volumes of pore-water expelled from the thick clay sequences, for example the channel sands in the basal Ashdown Beds.

Conclusions

Inferences from numerous climatic indicators which suggest that the Wealden Basin moved from a semi-arid zone during the Purbeck to a warm temperate zone in Hastings Beds times (Allen, 1976), are reinforced by data on the clay mineralogy. Vertical variations in clay minerals, which are characterised by long periods of uniformity followed by abrupt change, indicate rapid topographical changes and suggest that faulting may have been the main tectonic mechanism. No evidence for contemporaneous volcanic activity is indicated in the clay mineralogy in this area. CPS

Appendix 3 Six-inch geological maps and photographs

Six-inch geological maps

The following is a list of six-inch National Grid maps included, wholly or in part, in Sheets 320 and 321, with the dates of survey. The surveyors were R. A. B. Bazley, E. A. Edmonds, R. D. Lake, E. R. Shephard-Thorn and J. G. O. Smart.

Manuscript copies of the maps are deposited for public reference in the libraries of the British Geological Survey. Uncoloured dye-line copies of these sheets are available for purchase.

TQ 60 NE

R.D.L.

1968

TQ 61 NE

R.A.B.B.

1965

TQ 61 SE

R.D.L.

1967–68

TQ 62 SE

E.A.E., R.A.B.B.

1960, 1965

TQ 70 NW

R.D.L.

1968

TQ 70 NE

R.D.L.

1967

TQ 71 NW

R.A.B.B.

1965

TQ 71 NE

R.A.B.B., R.D.L., E.R.S.T.

1965–67

TQ 71 SW

R.D.L.

1967

TQ 71 SE

R.D.L.

1967

TQ 72 SW

E.A.E.

1960

TQ 72 SE

E.A.E.

1960

TQ 80 NW

E.R.S.T.

1969–70

TQ 81 NW

E.R.S.T.

1965–6

TQ 81 NE

E.R.S.T.

1965–6

TQ 81 SW

E.R.S.T.

1969–70

TQ 81 SE

E.R.S.T.

1969–70

TQ 82 SW

J.G.O.S.

1959

TQ 82 SE

J.G.O.S.

1957

TQ 91 NW

E.R.S.T.

1965–69

TQ 91 NE

E.R.S.T., J.G.O.S.

1956–57, 1967

TQ 91 SW

E.R.S.T.

1965–69

TQ 92 SW

J.G.O.S.

1957–58

TQ 92 SE

J.G.O.S.

1956–57

TR 01 NW

E.R.S.T., J.G.O.S.

1956, 1967

TR 01 NE

E.R.S.T., J.G.O.S.

1956, 1967

TR 02 SW

J.G.O.S.

1956–57

TR 02 SE

J.G.O.S.

1956–57

Geological photographs

Copies of photographs illustrating the geology and landscape of the district are deposited for reference in the library of the British Geological Survey at Keyworth. The numbers of all the photographs are in Series A. Black and white prints and slides can be supplied at a fixed tariff and colour prints and transparencies are also available for all the photographs.

Appendix 4 Borehole records

(Appendix 4)

Records of boreholes which are not confidential may be consulted on open file at BGS Keyworth, by arrangement. Enquiries should be addressed to: Head, Information and Central Services, National Geosciences Data Centre.

The following is a list of selected boreholes for which records are available. The table indicates their stratigraphical range. Those marked with an asterisk are cored boreholes drilled for BGS.

References

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Figures, plates tables

Figures

(Figure 1) The topography of the Hastings and Dungeness district.

(Figure 2) Generalised solid geology of the Hastings area.

(Figure 3) Biostratigraphical correlation of Upper Jurassic formations in boreholes.

(Figure 4) Sections in the Purbeck Beds.

(Figure 5) Ostracod faunicycles recognised in the Purbeck Beds sequences.

(Figure 6) Graphic sections of the upper Ashdown Beds proved in boreholes.

(Figure 7) Generalised lithostratigraphical section of the rocks exposed in the Hastings–Cliff End coast section.

(Figure 8) Sketch section of the cliffs between Hastings and Cliff End.

(Figure 9) Sections in the Ashdown Beds between East Cliff, Hastings and Ecclesbourne Glen.

(Figure 10) Schematic diagram showing the Wadhurst Clay sequence.

(Figure 11) Wadhurst Clay sequences proved in boreholes.

(Figure 12) Sections in upper Ashdown Beds at Harrow Lane.

(Figure 13) Sections in the upper.Ashdown Beds and basal Wadhurst Clay at Winchelsea.

(Figure 14) Lithology and plant colonisation of the Cliff End Sandstone in the old quarry near Fairlight church.

(Figure 15) Structural contours on selected stratigraphical horizons.

(Figure 16) Broad structural units of the Hastings district.

(Figure 17) Section through the cut-off trench of the Darwell Reservoir.

(Figure 18) Flandrian deposits proved in trial boreholes.

(Figure 19) Schematic section through a typical beach at Dungeness.

(Figure 20) The former shorelines and reclamation of the area near Rye Bay.

(Figure 21) Some hypothetical stages in the development of Dungeness Foreland.

(Figure 22) The Tunbridge Wells Sand in the Galley Hill section. See also Topley (1875).

(Figure 23) Sketch section of cliffs at Ecclesbourne Glen. WdC: Wadhurst Clay, CES: Cliff End Sandstone, TA: Top Ashdown Beds, a, b, d, e: horizons in upper Ashdown Beds as in (Figure 9), p.26..

(Figure 24) Map of large-scale trough cross-bedded units A, B and C exposed in the foreshore between the Fairlight Cove and Haddock's reversed faults

(Figure 25) Sketch of the cliff section between Hadock's Reversed Fault and Cliff End (after a drawing by Mr. A. R. Tingley.

Plates

(Front cover).

(Rear cover).

(Geological sequence).

(Plate 1) Cliffs in Ashdown Beds and Wadhurst Clay, east of Hastings [TQ 830 095]. The upper part of the cliff is in low Wadhurst Clay strata, including the Cliff End Sandstone (c.8 m). Below, thick, well jointed sandstones of the upper Ashdown Beds are seen for about 50 m. At the foot of the cliff 5 m of silty mudstones of Fairlight Clays' facies occur. (A11316).

(Plate 2) Iguanodon footprint preserved as a cast on the underside of the Lee Ness Sandstone, Ashdown Beds, Lee Ness, 1 km SW of Fairlight Cove [TQ 871 112]. The footprint was made in the mudstone underlying the sandstone during a dry or shallow-water episode and subsequently infilled as a cast when the sandstone was deposited. (Photo E.R.S.T.).

(Plate 3) Trough cross-bedding in Ashdown Beds, Fairlight Cove [TQ 882 117]. The sandstones exposed on the foreshore exhibit trough cross-bedding. A major cross-bedded unit, the 'Haddocks Rough Unit', about 10 m thick, is seen in the cliffs behind (A11360).

(Plate 4) Haddock's Reversed Fault, 1 km SSW of Cliff End [TQ 885 125]. Ashdown Beds sandstones in the lower cliff are thrown up relative to the Wadhurst Clay and topmost Ashdown Beds. The fault plane is clearly seen where it cuts the massive Cliff End Sandstone (A11366).

(Plate 5) Type locality of the Cliff End Bone-Bed, Wadhurst Clay, Cliff End [TQ 887 129]. The bone-bed, a coarse grit up to 0.15 m thick, occurs in the soft shaly beds at the cliff top. The Cliff End Sandstone, 10 m thick, below is separated from the Ashdown Beds by shales 1 m thick, marked by the head of the standing figure (A11377)

Tables

(Table 1) Summary of sequences below the Purbeck Beds proved in boreholes.

(Table 2) Generalised sequence proved in trial boreholes at Dungeness.

(Table 3) Comparison of stratigraphical divisions of the Purbeck Beds in the Sussex inliers

(Table 4) Ostracod zones of the Purbeck Beds in the Sussex inliers.

(Table 5) Ostracod zones of the Wealden.

(Table 6) Correlation of Quaternary deposits and events.

(Table 7) Radiocarbon dates from coastal Flandrian deposits in the south-eastern Weald.

(Borehole records) Appendix 4 Borehole records

Tables

(Table 1) Summary of sequences below the Purbeck Beds proved in boreholes

Borehole

Mountfield No. 1

Mountfield No. 2

Battle*

Fairlight**

[TQ 7195 1931]

[TQ 7195 1931]

[TQ 7573 1706]

[TQ 8592 1173]

Thickness m

Depth to base m

Thickness m

Depth to base m

Thickness m

Depth to base m

Thickness m

Depth to base m

Portland Beds

33.5

88.4

32.3

83.5

43.0

290.2

33.71

373.53

Kimmeridge Clay

221.6

—

420.0

503.5

c.319.4

c. 09.6

23.17

—

Corallian Beds

—

—

77.4

—

c. 21.6

—

—

Total depth

310.0

580.9

631.2

396.70

* original depths given in feet only

** original depths given in feet and inches

(Table 2) Generalised sequence proved in trial boreholes at Dungeness

Thickness m

Lower Cretaceous

Wealden (Hastings Beds)

Tunbridge Wells Sand

proved up to c. 35

Wadhurst Clay

c. 15

Ashdown Beds

c. 115

Upper Jurassic

Purbeck Beds

c. 55

Portland Beds

c. 13

Kimmeridge Clay

proved up to c. 25

(Table 4) Ostracod zones of the Purbeck Beds

Zone

Characteristic species

Purbeck

Upper

Cypridea setina

C. aemulans, C. alta s.l.,

C. lata latissima, C. penshurstensis

C. propunctata, C. setina s.l.,

C. tuberculata adjuncta, C. wicheri

Middle

Cypridea vidrana

C. darvelensis, C. lata senilis

C. tuberculata langtonensis,

C. vidrana

Cypridea granulosa

C. coelnothi, C. delicatula,

C. dunkeri dunkeri,

C. granulosa fasciculata,

C. granulosa granulosa,

C. granulosa protogranulosa,

C. lata lata, C. peltoides eurygaster,

C. posticalis, C. sagena,

C. swanagensis,

C. tumescens praecursor,

C. tumescens tumescens

Lower

Cypridea dunkeri

C. dunkeri carinata,

C. dunkeri inversa,

C. dunkeri papulata,

C. peltoides peltoides,

C. primaeva

C. tumescens acrobeles

(Table 5) Ostracod zones of the Wealden

Ostracod zone

Lithostratigraphical unit

C. valdensis

Weald Clay

C. clavata

C. marina

C. tuberculata

C. dorsispinata

C. aculeata

Tunbridge Wells Sand

Hastings Beds

Upper Wadhurst Clay

Middle Wadhurst Clay

C. paulsgrovensis

Lower Wadhurst Clay

C. brevirostrata

Ashdown Beds

(Table 6) Correlation of Quaternary deposits and events

Environment

Stage

River valleys

Marine

Periglacial

5000yr*

Alluvium of floodplains

Erosion of cliffs; landslips Peat beds

Accumulation of coastal marshes Formation of coastal barriers Submerged forest

FLANDRIAN (Post Glacial) 10 000yr*

Infilling of buried channels

Accumulation of older marine sands and gravels of Dungeness

Solifluction (Head)

(Late Glacial) 14 000yr*

Final deepening of buried channels

Origin of coastal landslips Low sea level

Solifluction (Head) Cryoturbation

DEVENSIAN (Last Glaciation)

Cutting of buried channels

Low sea level

Solifluction (Head) Aeolian deposits Cryoturbation

IPSWICHIAN (Last Interglacial)

?Aggradation of 1st Terrace of Brede and Tillingham valleys

Sea level c. + 7.5 OD Brighton Raised Beach Cliff End sea cave + 18.2 m OD

WOLSTONIAN (Penultimate Glaciation)

Downcutting (possibly limited by presence of ice or permafrost)

Low sea level

Formation of valley-bulges, gulls and cambering. ?English Channel Glaciation

* Approximate age before present based on radiocarbon dating

(Table 7) Radiocarbon dates from coastal Flandrian deposits in the south-eastern Weald

Laboratory No.

Type of material, locality and level, where known

National

Grid reference

Date B.P.

Published reference

NPL 25

Shells from creek filling, Old Romney, Kent (c. + 3 m OD)

[TR 024 237]

1550 ± 120

Radiocarbon, 6, 25–30

NPL 91*

Peat overlying clay, Scotney Court Farm, Lydd, Kent

[TR 023 202]

2050 ± 90

Radiocarbon, 8, 340–7

NPL 92*

Roots extending from peat into clay, Scotney Court Farm (c. + 3 m OD)

[TR 023 202]

2740 ± 400

Radiocarbon, 8, 340–7

NPL 23

Peat, Higham Farm, Warehorne, Kent (c. + 3 m OD)

[TQ 977 308]

3020 ± 94

Radiocarbon, 6, 25–30

NPL 24

Tree-trunk in peat, Court Lodge, Old Romney, Kent (c. + 3 m OD)

[TR 032 243]

3340 ± 92

Radiocarbon, 6, 25–30

Peat, Lewes No. 2 Borehole, Lewes Brooks, Sussex (–2.3 m OD)

[TQ 413 092]

3190 ± 125

(Jones, 1971)

Birm.167

Peat, Lewes No. 2 Borehole, Lewes Brooks, Sussex (–5.5 m OD)

[TQ 413 092]

5670 ± 170

Radiocarbon, 12, 385–9

Birm.168

Peat, Lewes No. 1 Borehole, Lewes Brook, Sussex (–8.2 m OD)

[TQ 413 013]

6290 ± 180

Radiocarbon, 12, 385–9 (see also Jones, 1971; Thorley, 1971)

IGS/C14/13

Peat, Wittersham Bridge Borehole, Kent (c.–1.5 m OD)

[TQ 885 258]

3560 ± 110

Radiocarbon, 13, 26–8

IGS/C14/14

Peat, Wittersham Bridge Borehole, Kent (c.–2.8m OD)

[TQ 885 258]

4845 ± 100

Radiocarbon, 13, 26–8

SRR/918*

Peat, south of Hooe, Pevensey Levels

[TQ 694 087]

3715 ± 80

IGS/C14/190

Peat from trial borehole for Lewes by-pass (–1.9 m OD)

[TQ 426 093]

4346 ± 40

IGS/C14/191

Peat from trial borehole for Lewes by-pass (–2.0 m OD)

[TQ 426 093]

4305 ± 40

IGS/C14/192

Peat from trial borehole for Lewes by-pass (–2.4 m OD)

[TQ 426 093]

5000 ± 40

IGS/C14/55*

Wood, from in-situ tree, Submerged Forest, Pett Level, Sussex

[TQ 889 140]

5205 ± 105

Radiocarbon, 14, 331–5

IGS/C14/56*

Peat of forest bed (approx. at OD)

[TQ 899 140]

5300 ± 100

Radiocarbon, 14, 331–5

SRR/379

Peat from trial borehole, Langney Point, Sussex (–24.9m OD)

[TQ 642 011]

8760 ± 75

Radiocarbon, 21, 223–4

SRR/380

Peat from trial borehole, Langney Point, Sussex (–27.3 m OD) (Peat bed extends between 24.8 and 28.3 m below OD)

[TQ 642 011]

9510 ± 75

Radiocarbon, 21, 223–4

IGS/C14/15

Peat from base of buried channel of Cuckmere R., Arlington Reservoir, Sussex (approx. at OD)

[TQ 538 074]

9435 ± 120

Radiocarbon, 13, 26–8

IGS/C14/116*

Peat from trial borehole, Tilling Green, Rye, Sussex (–22.5m OD)

[TQ 915 206]

9565 ± 120

Radiocarbon, 16, 95–104

*radiocarbon date from this district