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Geology of the Alresford district. Sheet description of the British Geological Survey, 1:50 000 Series Sheet 300 (England and Wales)

By A R Farrant, P M Hopson, C R Bristow, R K Westhead, M A Woods, D J Evans, I Wilkinson, A Pedley

Bibliographical reference: Farrant, A R, Hopson, P M, Bristow, C R, Westhead, R K, Woods, M A, Evans, D J, Wilkinson, I P, and Pedley, A. 2011. Geology of Alresford district. Sheet description of the British Geological Survey, 1:50 000 Series Sheet 300 (England and Wales).

Geology of the Alresford district. Sheet description for the British Geological Survey 1:50 000 Series Sheet 300 Alresford (England and Wales)

Authors: A R Farrant, P M Hopson, C R Bristow, R K Westhead, M A Woods, D J Evans, I Wilkinson, A Pedley

Keyworth, Nottingham: British Geological Survey 2011. © NERC 2011. All rights reserved. ISBN 978 0 85272 673 0

The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty’s Stationery Office. Licence No: 1000017897/2011 Maps and diagrams in this book use topography based on Ordnance Survey mapping.

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Acknowledgements

This Sheet Description the published product of the 1:10 000 scale geological mapping of the Alresford district, undertaken by P M Hopson, A R Farrant, C R Bristow, R K Westhead and A Pedley in 1981 and between 1994 and 1997. It has drawn heavily and quoted extensively from the individual map sheet technical and specialist reports compiled by the individual authors and on an unpublished Chalk criteria document by D T Aldiss, C R Bristow, P M Hopson, M D A Samuel, C J Wood and M A Woods. Professor R N Mortimore (Brighton University) is thanked for his support and advice throughout the Survey’s activities in this area.

This Sheet Description was compiled and written by A R Farrant from data held in the open file Technical Reports for this district, and in addition to the collection of data, many individuals have freely given their advice, and provided the local knowledge, including R K Westhead, C R Bristow, P M Hopson and A R Farrant. P M Hopson reviewed early drafts of this document. S Holloway is thanked for his comments on the structure, concealed geology and hydrocarbon sections, and M A Woods for his review of the biostratigraphy.

We acknowledge the Environment Agency (Southern Region) for their support in the field surveying of the Itchen headwaters area in the north-west of the sheet.

Landowners, tenants and quarry companies are thanked for permitting access to their lands.

Cartographers who worked on the diagrams for this Sheet Description are P Lappage and H W Holbrook. The manuscript was edited by A A Jackson and the series editor is J E Thomas.

Notes

The area covered by Sheet 300 Alresford is referred to as the ‘district’. Symbols in brackets for example (LeCk) refer to symbols used on the 1:50 000 scale map.

National grid references are given in the form [SU 1234 1234]; all lie within the 100 km square SU unless otherwise stated.

Boreholes mentioned in the text are identified by a BGS Borehole Registration Number in the form (SU63SE/227).

The number given with plate captions is the registration number in the National Archive of Geological Photographs held at BGS, Keyworth. It is generally in the form P123456.

Digital and other maps at the 1:10 000 scale can be purchased from BGS, Keyworth, where records of the boreholes may also be consulted. This report includes interpretations of data available at the time of writing. Additional information is available in BGS files. Neither the report nor its complimentary 1:10 000 scale geological maps should be taken as a substitute for detailed site investigations. Users should note that the stratigraphicalal nomenclature used in this report is liable to revision.

Geology of the Alresford district—summary

Known more for its literary connections with Jane Austen and the gardens of the naturalist Gilbert White at Selborne, the Alresford district’s typically gentile English countryside seen in the Alresford district is fundamentally a product of the underlying geology. Commencing in the east, a journey westwards begins on the low lying sandy heaths and heavy clay pastureland around Bordon and Woolmer Forest, developed from the Lower Cretaceous sands and clays. Further south-east around Petersfield, the characteristic ridge and vale country is founded on the alternating sands and clays of the Lower Cretaceous Hythe and Sandgate formations.

Rising steeply above the lowlands is the indented and landslipped Upper Greensand scarp, behind which the land slopes gently down to small villages such as Selborne and East Worldham before rising steeply again up the Chalk escarpment which forms perhaps the most striking feature. This scarp, running north-south across the sheet district effectively divides the region into two. Above the scarp the high hills capped by clay-with-flint around Medstead and Four Marks gently descend eastward down the long gentle dip slopes of the Chalk to the headwaters of the Itchen around New Alresford. The majority of the East Hampshire Downs with its dry valleys and gently rolling hills is underlain by the Chalk.

The landscape seen today is the result of a very long geological history which stretches back to the Early Jurassic and beyond. The rocks at surface and those beneath the district give valuable information for the understanding of such major earth history events as the opening of the Atlantic and the Channel Basin, the drowning of most of Europe during the Cretaceous Period, the Alpine earth movements and the wide climatic variations in our most recent past.

These events have also created the conditions for the development of oil and gas and their entrapment in the rocks at depth, a feature which manifests itself in the ‘nodding donkeys’ pumping oil to the surface at places such as Humbly Grove just to the north of the district.

(Table 1) Geological succession. Timescale from Ogg et al, 2008.

Chapter 1 Introduction

Topographical setting

This Sheet Description describes the geology of the western margin of the Weald together with the Chalk downland and primary scarp of north-east Hampshire between Winchester, Petersfield and Alton (Table 1); (Figure 1).

The Alresford district can be divided into two parts; a generally low lying area of ground underlain by Lower Cretaceous strata in the east, and the Chalk downlands which gradually slopes down to the headwaters of the River Itchen in the west (Figure 2) and (Figure 3).

The east of the district forms the western margin of the Weald. The oldest rocks outcrop in the south-east of the district around Petersfield and Liss. Here, the Weald Clay Formation is exposed in the core of an anticlinal structure, around which the Hythe Formation forms a steep, arcuate escarpment. Away from this escarpment, around the western, plunging, nose of the anticline, the topography and strata dip down into the surrounding vales that extend north to Bordon and Sleaford. These vales are underlain by the sands and clays of the Folkestone and Gault formations. Heathland is particularly well developed on the sandier soils on the Folkestone Formation.

The Upper Greensand forms a distinct, well-developed, extensively landslipped escarpment between Petersfield and Binstead. Many springs rise from the Upper Greensand and form the headwaters of the Rivers Rother, Alton Wey and Godalming Wey.

However most of the district is underlain by the Upper Cretaceous Chalk, which forms an extensive area of rolling downland, bounded in the east by the primary chalk escarpment between Alton and Petersfield. Several small anticlines and synclines create an undulating topography, further enhanced by numerous dry valleys, which converge around Alresford and form the headwaters of the River Itchen. The southern edge of the district is structurally more complex along the line of the Winchester Anticline and the Warnford Dome. Much of the higher ground is covered by extensive areas of clay-with-flints, and in the north-east of the district around East Stratton, several small outliers of Palaeogene strata are preserved.

History of research

The district and surrounding sheet areas were first systematically surveyed at the scale of one- inch to one mile (1:63 360) scale in the mid-19th century by H W Bristow, F Drew and T R Polwhele, and published in 1858–1868 on [Old Series] Sheets 8, 9, 11 and 12. The region was resurveyed on the scale of six inches to one mile (1:10 560) scale in 1888–1898 by C E Hawkins, and published in 1898 as Sheet 300 [New Series] with drift. It was reprinted in 1957, and reconstituted from the 1:63 360 scale without geological revision on to a 1:50 000 scale topographical base map in 1975.

The Alresford Sheet district (Sheet 300) was resurveyed at the 1:10 000 scale by P M Hopson, A R Farrant, C R Bristow, R K Westhead, A Pedley and D T Aldiss in 1981 and 1994–1997 (Figure 4), with support from D J Evans (deep geology), I P Wilkinson (microbiostratigraphy) and M A Woods (macrobiostratigraphy).

A part of the Alresford district was briefly described in 1862 by Bristow and Whitaker, in their Memoir memoir on parts of Berkshire and Hampshire (Sheet 12), and in 1875 by W Topley, in the memoir on the Geology of the Weald. A J Jukes-Browne and W Hill recorded some observations on the Lower and Upper Cretaceous rocks of the area in the memoirs on the Cretaceous Rocks of Britain published between 1900 and 1904 (Jukes-Browne and Hill, 1900, 1903, 1904), but no detailed account of the geology of the Alresford district had appeared before Osborne White published the memoir accompanying the first New Series Geological Sheet in 1910 (Osborne White, 1910). All these early memoirs are now out of print.

One of the earliest publications setting out the stratigraphy of the Weald was Gilbert White’s ‘Natural History and Antiquities of Selborne in the County of Southampton’ published in 1789 (White, 1789). Mantell (1822) and Fitton (1824) also described the stratigraphy of the area, but used differing names for the same sequence. Murchison (1826) recognised, but did not name the main divisions of the Lower Greensand, which were also noted by Martin (1828) in a memoir on the strata of western Sussex.

The Lower Greensand has also been studied by Dines and Edmunds (1929), Kirkaldy (1933) and Middlemiss (1962) who proposed various stratigraphic schemes which are shown in (Figure 5). Humphries (1964) studied the Lower Greensand in the area from Storrington westwards to Petersfield and north to Liphook. Various aspects of the sedimentology of the Lower Greensand have been studied; Humphries (1956) discussed the origin of the chert in the Hythe Formation; Wood (1956) examined the heavy mineral suite of the Lower Greensand and Narayan (1963, 1971) and Allen and Narayan (1964) studied the cross-stratification within the Lower Greensand. Casey (1961) reviewed the palaeontology of the Lower Greensand and provided a reliable zonal framework to which the various formations and members could be assigned. Jukes-Browne and Hill (1900) published the first volume of their treatise on the Cretaceous Rocks of Britain (Gault and Upper Greensand). Owen’s (1963; 1971a; 1971b; 1975) studies of the Gault and in part of the Upper Greensand provide a detailed zonal scheme for these formations. Between December 1997 and January 1998, three cored boreholes were drilled around Selborne, through the thickest part of the ‘Selbornian’ sequence. The core penetrated through the lowermost Chalk, the whole of the Gault and Upper Greensand sequence and into the Folkestone Formation of the Lower Greensand Group (Hopson et al., 2001; Woods et al., 2001).

The Chalk was described by Jukes-Browne and Hill (1903; 1904) in their memoirs on the Cretaceous Rocks of Britain. Brydone’s (1912; 1942) descriptions of the Chalk of Hampshire include biostratigraphical details for many individual localities in Hampshire, including some within the present area. Correlation of the Lower Chalk (now the Grey Chalk Subgroup) of south-east England was expounded by Kennedy (1969), whilst the petrology, conditions of deposition, and diagenesis of the Chalk Group were considered by Hancock (1975). Robinson (1986) described in detail the stratigraphy of the Chalk of the North Downs and Mortimore (1979; 1983; 1986a; 1986b; 1987) did the same for the Middle Chalk and Upper Chalk (now the White Chalk Subgroup) of Sussex. Bristow et al. (1995) proposed a new scheme of lithostratigraphical nomenclature for the Chalk Group in the Shaftesbury district of Dorset. The units recognised in Dorset and in Sussex can be traced into Hampshire and Wiltshire (Bristow et al., 1997), and form the basis of the description of the Chalk in this report. Bristow’s scheme was adopted by the Geological Society Stratigraphical Committee with some amendments in 1999 (Rawson et al., 2001; Hopson, 2005) and is shown in (Table 2), where its relationship to the traditional scheme is also given.

Geological succession

The solid formations and superficial deposits mapped during the survey are listed in (Table 1).

Structurally, the district falls within the Weald Basin (Figure 6), an eastward extension of the larger Wessex Basin (sensu Underhill and Stonely, 1998). It comprises a system of post-Variscan extensional sedimentary basins and ‘highs’ that covered much of southern England (and extended offshore) south of the Variscan Front between the London Platform and Mendip Hills during Permian to Mesozoic times. At greater depths lie Palaeozoic strata which were strongly deformed during the Variscan Orogeny, a period of tectonic upheaval and mountain building that culminated at the end of the Carboniferous. The rocks of the ‘Variscan Basement’ are weakly metamorphosed sandstones and limestones of Devonian and Carboniferous age. Several major southward-dipping thrust zones and north-west-orientated wrench faults have been tentatively identified in the basement, principally from seismic reflection data. These are thought to have originated during the Variscan Orogeny. This deformation was followed by a long period of erosion and a major unconformity marks the base of the Permo-Triassic sequence.

In Permian times, subsidence associated with periods of tectonic extension began to affect southern England initiating the development of a number of smaller basins within the Wessex Basin, each bounded by large faults. Sedimentation in the expanding Wessex Basin began to the west of this district. Deposition gradually spread eastwards so that the earliest Mesozoic rocks present, at depth, within the district are a thin sequence of red beds thought to be of Triassic age. Crustal extension was accommodated by reactivation of existing faults in the Variscan basement which show evidence of syndepositional downthrow to the south during Permian and Mesozoic times. The largest of these faults divide the region into a series of structural provinces (Chadwick, 1986) such as the Weald Basin and Channel Basins, separated by the Hampshire-Dieppe High (also known as the Cranborne-Fordingbridge High).

This district lies at the western edge of the Weald Basin which is bounded by the London Platform to the north and the Hampshire-Dieppe High to the south. The Hogs Back–Kingsclere structure marks the boundary between the Weald Basin and the London Platform in the Basingstoke area. The northern margin of the Hampshire-Dieppe High lies in the Portsmouth area and is marked by the Portsdown–Middleton Faults which underlie the northern flank of the Portsdown Anticline (Hopson, 2000).

Syndepositional movement on the major faults resulted in thick Jurassic sequences being laid down on the downthrown (hanging-wall) sides; the beds commonly thin against the tilted fault blocks. Major periods of active extensional faulting occurred during the Jurassic and during deposition of the Wealden Group of the Lower Cretaceous. During periods of tectonic quiescence, the rates of sedimentation increased evenly towards the centre of the Weald Basin.

The sea began to flood the Wessex Basin in Rhaetian (Late Triassic) times, depositing the Penarth Group. The area of deposition increased gradually throughout the Jurassic, although minor periods of erosion occurred, mainly at the basin margins. By Late Oxfordian to Kimmeridgian times, the London Platform was probably entirely submerged. Towards the end of Kimmeridgian times, the London Platform began to re-emerge, probably as a result of global sea-level fall and a reduction in the rate of tectonic subsidence. This resulted in erosion on the margins of the Wessex Basin and the beginning of the development of the Late Cimmerian unconformity. This marine regression continued into Cretaceous times, while the environment of deposition changed from offshore marine (Kimmeridge Clay Formation) to shallow marine (Portland Group), to brackish water and evaporites (Purbeck Group), to fluviatile (Wealden Group). The final period of extensional fault movement, marked by normal faulting, resulted in the accumulation of thick sequences of Wealden Group sediments in the main fault-bounded troughs in the Weald Basin, whereas the intervening exposed highs suffered severe erosion.

A period of regional subsidence followed, and, combined with eustatic sea-level rise, led to a renewed marine transgression of the Wessex Basin. The ensuing deposition of the Lower Greensand, Gault, Upper Greensand, and eventually the Chalk covered all the surrounding high areas including the London Platform.

A global sea-level fall at the end of the Cretaceous resulted in erosion of parts of the higher Chalk units and the development of a pre-Cenozoic unconformity. Later, deposition in Eocene to Oligocene times was followed by the onset of the compressive tectonic regime during mid Tertiary ‘Alpine’ earth movements. These movements effectively reversed the sense of movement on the major bounding faults of the Wessex and Channel basins causing inversion of the basins and highs. Uplift is estimated at about 1500 m (Simpson et al., 1989) for both the Weald and Channel depocentres. Subsequently, erosion has unroofed these inverted basins giving rise to the present-day landscape.

Cross-sections showing the main structures are presented on Sheet 300 (Alresford). The major extensional faults which control the asymmetric en échelon fold structures such as the Winchester–Meon Pericline can be seen beneath Warnford (Section 2, Sheet 300) and are well picked out by the structure contours on the base of the Lower Greensand (Figure 7).

Chapter 2 Structure

The district lies within the Wessex Basin, a broad extensional basin developed during the Jurassic that suffered inversion during the Miocene (Alpine) compressional event (Stoneley, 1982; Lake and Karner, 1987; Underhill and Paterson, 1998). Within the Wessex Basin a series of sub-basins and highs were developed. The broad chalk plain of this district conceals much of this early structure and only the inversion structures of the Miocene are clearly seen in the outcrop. The district lies at the western margin of the east–west trending Wealden Anticline (the Weald Basin), a broad, gentle structure which gently plunges to the west. This gives rise to the broadly arcuate primary Chalk escarpment between Alton and Petersfield and forms the closure of the North and South Downs. Superimposed on this broad structure are several smaller, more acute, east–west trending anticlinal or periclinal structures, shown on (Figure 8), usually associated with east–west faulting within the Jurassic strata at depth.

The largest of the fold structures in this district is the Winchester–Meon–Harting Combe structure. This comprises a series of en échelon periclines which run along the southern margin of the sheet between Rake [Grid square 80 26], Warnford [SU 62 23] and Cheesefoot Head [SU 53 27]. The easternmost part of this structure is the Harting Combe Anticline (Thurrell et al., 1968), in the south-east of the district. This exposes the topmost part of the Weald Clay in its core. It plunges westwards and extends south-west through Petersfield and Stroud. It continues on an east–west trend through East Meon village, just south of the Alresford district, where it is cored by Upper Greensand and the Grey Chalk subgroup. Around East Meon, the structure is divided into two en échelon, west-north-west to east-south-east segments, separated by about 700 m across strike. Strata to the south of the fold dip consistently south or south-south-west at between 2 and 6º, while in a strip up to 500 m north of the fold axis, they dip up to 5º north. North of this, a 500 m-wide belt of steeply dipping strata occurs, with strata dipping up to 11º north-north-west. This belt of steeply dipping chalk runs west-south-west to east-north-east from near West Meon [SU 650 225] to Langrish [SU 700 245]. Farther north, the strata level out to become flat lying or even gently south dipping.

Its westerly continuation is the Warnford Dome, centred on the valley just south of Warnford where the West Melbury Marly Chalk comes to crop. Essentially it is an asymmetric anticline, with the steeper north limb, plunging at a few degrees to both to the east-south-east and west-north-west. The River Meon has excavated the structure so that it now forms a basin-like feature in the landscape. However, only the northern limb of this fold structure extends onto the southern margin of the Alresford district.

To the west, the anticlinal structure extends north-westwards through Lomer [SU 592 233] where the Lewes Nodular Chalk is exposed in two small inliers, and on towards Cheesefoot Head [SU 531 276]. Here, the structure is a large anticline known as the Winchester Anticline, of which only the eastern end is seen in the Alresford district. It is an east–west trending, eastward-plunging, asymmetric anticline with a steeply dipping northern limb. The Holywell Nodular Chalk is exposed in its core just north of Cheesefoot Head, but the Zig Zag Chalk is exposed a short distance to the west around Chilcomb [SU 507 283] in the Winchester district (Booth, 2002). The Winchester Anticline was intensely investigated for hydrocarbons and as a possible gas repository. The information from a few deep wells into the Jurassic was enhanced by additional shallower borings proving the Melbourn Rock (basal Holywell Nodular Chalk Formation) and Glauconitic Marl. Structure contours for these two units show the form of the anticline, and are shown in (Figure 9). Around Winchester, this structure is known to have dips of 10º on its northern limb but as little as 3º to 4º to the south-west on its southern limb.

Several smaller amplitude, also generally east–west trending folds, affect the Chalk across the rest of the district. A minor, gently plunging anticline extends west from Hawkley through West Tisted and on towards Alresford. This corresponds with the ridge of Newhaven Chalk extending through Bramdean Common [SU 635 295]. A second gently plunging anticline extends from Alton, through Medstead and towards Abbotstone Down. The corresponding syncline on the northern limb extends from Preston Candover towards Micheldever, in which is preserved the Palaeogene outlier at East Stratton.

Faulting

There are a number of recognisable, mappable faults at surface in the area, and most of those occur on the primary Chalk scarp where the relative thickness of the chalk formations permit small faults to be identified. Several minor faults associated with the development of the Winchester–Meon–Harting Combe structure have been mapped around Langrish on the southern margin of the sheet.

Many smaller faults with throws of less than a metre or so were seen in several of the disused chalk pits, but could not be traced outside the pits. This minor faulting may well be a ubiquitous feature of the chalk. Instead of discrete faults, the strata may be displaced by several metres by numerous minor shear zones over a distance of several tens of metres, thus smearing the ‘fault’ zone over quite a wide area with little or no surface expression. On seismic profiles, faults that exist within the harder successions beneath the Chalk apparently tend to become attenuated as they propagate upwards. Instead of a discrete fault, displacement can be dispersed into zones of numerous relatively minor faults. Such zones could be several tens of metres wide, and can themselves die out upwards, passing up into anticlines or synclines. Several examples of these minor faults were seen in the railway cutting to the east of Four Marks Station around [SU 6718 3545]. At least five such faults were identified over a 200 m stretch of cutting, throwing down to the east with throws of generally less than a metre. None of these faults can be traced outside the cutting.

Tectonic activity during deposition can affect Chalk lithology on a basin-wide scale. There is growing evidence that tectonic and eustatic movement occurred in phases throughout the Upper Cretaceous (Mortimore and Pomerol, 1991, 1997; Mortimore et al., 1998; Evans and Hopson, 2000; Evans et al., 2003). Four major tectonic phases (demonstrated in Germany and the eastern Anglo-Paris basin) caused local channelling and slumping, and the local formation of hardgrounds and phosphatic chalks, as well as variations in marl development throughout southern England. Some characteristics of the Chalk in the present area may be a result of these continued movements, for example the local presence of a bed of very hard chalks near the top of the Seaford Chalk (the eastern extremity of the Stockbridge Rock Member mapped on the Winchester sheet) and the thin marl seams in the New Pit and Newhaven Chalk.

It is assumed that drainage lines tend to follow major fractures within the Chalk. Although fracture sets may well control valley orientation, there is little direct evidence of significant faulting along the major valley orientations. The general geological structure, topography and regional dip exert a strong influence. Many of the major valleys may follow drainage lines superimposed from the Palaeogene cover.

Chapter 3 Concealed strata

The stratigraphy of the rocks buried beneath the district is known from boreholes sunk primarily for the hydrocarbon industry (Table 3). Those at Humbly Grove [SU 6962 4487] just north of the district, Old Alresford (SU63NW/20) [SU 6244 3707], Lomer 1 (SU52SE/18) [SU 5959 2356], Bordon 1 (SU73NE/48) [SU 7883 3642] and East Worldham (SU73NW/28) [SU 7406 3756] form the basis of this account.

At depth, a thin Permo-Triassic sequence of limestone, siltstone, sandstone and breccia overlies beds of siltstone and orthoquartzite tentatively assigned to the Devonian–Carboniferous ‘basement’. The structural contours (Figure 10) and subcrops of the sub-Permian surface for the southern half of the United Kingdom (Smith, 1985) show a broad band of Devonian rocks flanked to the north by Carboniferous strata stretching from the Mendips south-eastwards into the eastern part of the English Channel and the Weald (Figure 11). A similar map (Sellwood and Scott, 1986) of the sub-Mesozoic floor beneath southern England incorporates the thin and patchy Triassic cover with the older ‘basement’.

Devonian to Triassic

The Devonian and Carboniferous (D-C) rocks proved beneath the district (Table 4) are predominantly cleaved, reddish brown, Devonian siltstones, mudstones and sandstones, and hard recrystallised Carboniferous dolomites and limestones. In the Lomer Borehole, near the southern margin of the district, this pre-Variscan basement consists of beds of siltstone and orthoquartzite tentatively assigned to the Devonian. Similar boreholes to the south ion the Fareham and Portsmouth district (Hopson, 2000) provide further information about these sedimentary rocks. These Devonian continental rocks were deposited on the Brabant Massif to the north of the Cornwall Basin (Ziegler, 1982), a part of the Variscan fore-deep basin; this basin derived much of its sediment from the continent of Laurasia to the north. The Humbly Grove boreholes, on the northern margin of the district, proved hard recrystallised dolomitic Carboniferous Limestone, whereas to the east the East Worldham Borehole penetrated siltstone, originally assigned to the Ordovician, but now thought to be of Devonian age.

A thin Permo-Triassic sequence of limestone, siltstone, sandstone and breccia overlies the pre-Variscan basement in this district. Permo-Triassic red beds and marine Rhaetian (Penarth Group) sedimentary rocks have been identified in some boreholes locally. The Lomer borehole proved 35.4 m of limestone, dolomitic limestone and breccia. These lithologies may be the equivalent to the thicker sequence seen farther south-west in the Portland–Wight Basin (Hamblin et al., 1992), or, more likely, they represent a marginal conglomeratic facies of the Mercia Mudstone Group, analogous to the ‘Dolomitic Conglomerate’ of the Mendip Hills and Glamorgan. There is some evidence to suggest an angular discordance between these beds and the overlying strata.

Jurassic

The whole of the Jurassic System is represented in rocks at depth below the district (Table 5). They are mainly marine in origin and were deposited within the subsiding Wessex Basin. They rest conformably on the Penarth Group, and reflect predominantly shallow marine deposition. The relatively uniform, cyclical sequences of the Jurassic provide evidence for the eastward shift of the area of maximum subsidence in the Wessex Basin as the faults bounding the Hampshire–Dieppe High became active. The Weald and Channel basin depocentres developed at this time. In general these beds thicken into the Weald Basin.

The Purbeck Group is for the most part now considered to be lowest Cretaceous in age with the base of the Berriasian being taken as the boundary in southern Britain. Thus in this district the traditional boundary at the base of the Cinder Bed, that marks the lithostratigraphical change from Lulworth up into the Durlston Formation is some way above the base of the Cretaceous that is placed stratigraphically lower within the Mupe Member known in the Dorset area. This period boundary has not been defined in the deep boreholes in this district.

Chapter 4 Lower Cretaceous

Lower Cretaceous rocks crop out across the eastern third of the Alresford district (Figure 12). The Cretaceous Period is defined in southern Britain at the base of the Berriasian stage (see above) and therefore much of the Purbeck Group known in boreholes at depth beneath this district is now considered to be the lowest part of the Cretaceous. The Purbeck Group rocks are poorly described in most boreholes and it is not possible to define a Berriasian boundary. They represent a period of shallow water limestones probably deposited during a phase of heightened salinity but do contain thin short-lived normal marine deposition which produced for example the characteristic Cinder Bed that marks the base of the Durlston Formation. These are the final marine-influenced rocks of the ‘Jurassic Sea’ and despite renewed subsidence at this time, clastic deposition in the Weald Basin was maintained in non-marine facies by the abundant sediment supply derived from the uprising London–Brabant Ridge to the north, Armorica to the south, and other landmasses to the west and south-west. These early Lower Cretaceous sediments are formally called the Wealden Group (W) here and include the informal ‘Hastings Beds (Group)’ and Weald Clay Formation (WC). The latter is the lowest exposed subdivision in this district and it crops out in the south-east, near Petersfield.

The Lower Cretaceous strata in southern Britain comprise an important sequence that shows considerable vertical and lateral variation in both thickness and facies: the sequence generally being fullest and thickest towards the basin centres (Whittaker et al., 1985). In the Alresford district, the Lower Cretaceous strata are poorly understood with little published regarding their distribution and development. This is particularly so of the lowermost Wealden Group, generally lying concealed at depth beneath the Lower Greensand (LGS), Gault, Upper Greensand (UGS) and Chalk of the district. However, a series of deep hydrocarbon exploration wells drilled across the Alresford and surrounding districts provide valuable information on the subsurface nature and distribution of the concealed ‘Wealden Series’ and other Lower Cretaceous rocks. Geophysical logs over the Lower Cretaceous interval were run in a number of these boreholes and the various stratigraphical intervals reveal characteristic log signatures that can be widely correlated between boreholes. The concealed Lower Cretaceous strata including the whole of the Weald Clay are summarised on (Table 6).

Rising sea level in Aptian times flooded the Wessex Basin and eventually led to the re-establishment of a marine connection with the North Sea Basin around the western end of the London–Brabant Ridge. The boundary between the lower, nonmarine sequence, the ‘Wealden Group’, and the upper marine sequence, the Lower Greensand Group, is marked by the Late Cimmerian Unconformity. The unconformity represents a gap in the sequence that is greatest at the margins of the Weald Basin, where much of the Lower Cretaceous is missing, and reduces progressively towards the centre of the basin. In the central Weald, the unconformity is represented by a number of closely spaced minor erosion surfaces, close to the boundary between the ‘Wealden Group’ and the overlying Lower Greensand Group (Chadwick, 1986; Ruffell, 1992).

Tidally influenced shallow-marine and shoreline sands and clays form the Lower Greensand. Thicker sequences were deposited in the Weald Basin which subsided faster than the London–Brabant Ridge. Deepening of the basin continued into Albian times when the Gault, a sequence of deeper water marine clays, was deposited. By Late Albian times, the London–Brabant Ridge had been overstepped by the Gault. The Upper Greensand is, in part, the lateral equivalent of the Gault and represents a shallow-water nearshore environment. It increasingly replaces the Gault towards the western part of the Wessex Basin.

Wealden Group (W)

These beds were deposited in predominantly freshwater conditions, in a large shallow lake or lagoon that occupied much of the present area of Hampshire and the Weald (Radley, 1999). Some indications of periodic erosion and shallow-water brackish conditions occur, suggesting minor flood events from the ‘East Anglian Sea’ to the east (Allen, 1975). Alluvial and lagoonal mud plains were periodically covered by braided rivers carrying coarser material. Some of the major siltstone–sandstone bodies are thought to have formed by lateral accretion from migrating channels, but the thickest sand units are attributed to accretion of sediment transported into the basin as a result of erosion on a rejuvenated block-faulted source area.

At this time, the Channel and Weald basins are thought to have been separated by the ‘Portsdown Swell’ (the successor to the Hampshire–Dieppe High), and the ‘Wealden Group’ is known to thicken northwards away from this structure.

The correlation of the Lower Cretaceous Wealden Group presented here is based upon the published geophysical log interpretations of similar sequences encountered in the Collendean Farm Borehole in the Weald Basin (Whittaker et al., 1985). North–south and east–west correlation diagrams of the Lower Cretaceous sequences (Figure 13) and (Figure 14), illustrate that considerable lateral variations exist in the individual members units. This is seen not only in the thinning of units to the north and west, but also in the gamma-ray and sonic log responses which reflect lithological variations. However, despite the thinning of the Wealden Group towards the basin margins, there appears to have been no northerly or westerly overstepping of the earlier Wealden Series sequences by the succeeding sequences. This is illustrated by the fact that the main sands and clays, including the basal Fairlight Clay unit and the (thin) Lower Tunbridge Wells Sand, can be identified in all boreholes. Indeed, the Fairlight Clay is thought to be present as far as the Farley South and Odiham boreholes, beyond which the entire Wealden and Lower Greensand may be truncated beneath the Gault and Upper Greensand.

The lateral change in borehole log character is most clearly seen in the Weald Clay succession and seems directly attributable to lateral facies/lithological variations. In thicker more basinward locations the gamma-ray response of the Weald Clay is high, the log signature being of a finely and highly serrated character. This changes to the north and west, becoming more deeply serrated (‘ratty’), with increasingly thick units of lower gamma-ray values giving a blocky character. There are also indications of higher gamma-ray units decreasing gradually upwards in a cyclic nature. These responses are indicative of a passage to siltier and ultimately sandier facies. This probably reflects an increasingly closer proximity of basin margins to the north and west, beyond Odiham and Stockbridge as the basin filled. It also serves to make the distinction between the Upper Tunbridge Wells sands and the sandier Weald Clay increasingly difficult towards the basin margins.

Weald Clay Formation (WC)

Within the Alresford district, only the uppermost 25 m of the Weald Clay are present. It crops out over a small area in the bottom of Harting Combe, north of Rogate, at the western margin of the Vale of Fernhurst. This formation is less varied than the Wealden Group, but two major sequences occur, the lower with thin limestones containing small forms of Paludina and the upper with large forms of the same gastropod. The mudstones are pale to dark grey and yellow–brown, locally variegated in greyish green and brick-red colour and contains sandstones and rare limestones (some dolomitic) particularly near its base. A thin sideritic mudstone has been worked for iron in the past, marked by a series of bell-pits. Generally the mudstone appears at the surface as mottled orange, red and grey clay in a much weathered condition. The red mudstones still retain their red colour when weathered.

The oldest recognisable datum is a sideritic mudstone traceable by the bell-pits which have been sunk through the overlying clay down to the ironstone. For the most part, this ironstone rests on mottled orange and grey silty mudstone, but at least locally, fine-grained buff sandstones lie only a short distance below the ironstone in the adjacent Haslemere (301) district [SU 819 266] (Thurrell et al., 1968, p. 32). Above the ironstone comes some 15 m of dominantly of mottled orange and grey silty mudstone, but with some red, and red and grey mottled mudstone. These clays are succeeded by an impersistent bed of fine-grained yellow sand in the west of the district. A further 5 m of mottled orange and grey silty mudstone separates this sand from a higher one, up to 5 m thick, which forms the local top to the Weald Clay Formation.

In the adjacent Haslemere (301) district, it was thought that the overlying beds of the Weald Clay had been removed by erosion prior to the deposition of the Atherfield Clay Formation. The recent mapping has shown, however, that the basis for this assumption is erroneous. Whilst the Atherfield Clay may rest on a sandstone within the Weald Clay, there is no direct correlation of this sandstone to other such arenaceous units farther east. Furthermore, much of the sandstone soil brash thought to be in situ sandstone units of the Weald Clay Formation, is in fact derived and incorporated in the head deposits. Thus, the postulated unconformable overstep of the Atherfield Clay Formation across the various members of the Weald Clay in this part of the Vale of Fernhurst is not proved.

The sand bodies within the Weald Clay are interpreted by Allen (1975; 1981; 1989) as fluviatile deposits in braided channels within a ‘normal’ environment of a variable variable-salinity coastal mudplain. There is a major component of western (Amorican–Cornubian) detritus. Molluscan evidence (Radley, 1999) reflects a range of lagoonal, lacustrine and alluvial environments, with freshwater and fluctuating brackish water conditions. Both the sedimentology and molluscan faunas suggest both Boreal and Tethyan marine influences during the most saline episodes.

Depending on the amount of erosion of the topmost Weald Clay, only the upper part of the Cypridea clavata and/or the base of the C. valdensis ostracod zones are present within the Alresford district (Thurrell et al., 1968). The clavata Zone extends up to the topmost sand of Bed 7, whilst the valdensis Zone ranges from the top of Bed 7 to the base of the Atherfield Clay Formation.

Details

The lowest mappable horizon of the Weald Clay within the present district is an ironstone. It can be traced readily through Lower Common Wood [SU 8190 2650] to [SU 8225 2665] in the adjacent Haselmere (301) district by the number of bell-pits which have been sunk through the overlying mudstone into the ironstone. A stream section [SU 8190 2651] on the west side of the wood reveals sideritic ironstone nodules, 0.3 m diameter and 0.1 m thick, set in mottled orange, and grey silty clay.

Farther west, the outcrop of the ironstone is largely hidden under head but at the margins of the head, or where the bedrock is exposed, bell-pits can again be found [SU 8076 2665], [SU 8063 2664], and [SU 8097 2704]. The overall impression gained from tracing this ironstone bed around the closure of the Fernhurst Anticline is that the dip on both limbs is very gentle. Above the ironstone, there occurs about 15 m of mottled orange and grey silty mudstone. These mudstones were formerly extensively worked for bricks by the Rogate to Rake road [SU 8027 2728] and [SU 8040 2701], but no section remains. Osborne White, (1910), page 7) recorded a section there as:

Possibly the ironstone noted in this section, and also in another one 90 m to the east, belong to the ironstone horizon recorded above. Mottled red and grey mudstones were also noted in this pit, and have been recorded at a number of localities at about the same stratigraphical level during the present survey [SU 8025 2666]; [SU 8022 2692]; [SU 8028 2692]; [SU 8050 2700]. Reddish brown and grey silty mudstone was also found at a higher level beneath an impersistent sand bed [SU 8002 2677] and [SU 8015 2654]. This fine-grained yellowish orange sand, which lies about 10 m below the base of the Atherfield Clay Formation, can be followed for about l km, around the valley sides, between [SU 7995 2680] and [SU 8030 2650].

There are many springs issuing from the base of this sandstone. Above the sandstone are some 5 to 8 m of stiff mottled orange and grey silty mudstone. This in turn is succeeded by a 4 to 5 m impersistent bed of fine-grained yellowish orange sandstone on which the Atherfield Clay Formation rests locally. This highest sandstone forms the top to the Weald Clay Formation over a two kilometre tract on the south side of the Fernhurst Anticline, being generally thicker in the west than in the east. On the north side of the anticline it appears to be absent in the area of Birch and Rough copses [SU 801 271], but reappears north of the brick-field [SU 8035 2720]. It is not seen to the east of this locality.

Lower Greensand Group (LGS)

Within the Weald Basin the Lower Greensand Group is divided into four formations which crop out in the south-east of the district. The Sandgate Formation is further divided into three members. The stratigraphical nomenclature is given in (Figure 5). The lateral variations in the thickness of the Lower Greensand Group in the Petersfield area are shown schematically in (Figure 15).

Atherfield Clay Formation (AC)

The Atherfield Clay Formation consists of stiff dark grey or brown clay, fossiliferous, variably glauconitic silty, and locally sandy, clay and of early Aptian age. The formation is about 20 m thick around Petersfield, reflecting a generally thickening into the Weald. The Atherfield Clay is poorly exposed in the Alresford district, and as a consequence is poorly known. The weathered surface deposits are generally mottled orange and grey, locally reddish brown, silty clays or clayey silt. Glauconite is present in variable quantities and on the south side of the outcrop, the Atherfield Clay is a highly glauconitic sandy clay. No fossils have been recorded from the Petersfield area but on general considerations the Atherfield Clay probably belongs to the forbesi Zone of the Lower Aptian (Bristow et al., 1987).

Details

Nowhere is there any exposure of the Atherfield Clay Formation of the Alresford district. It was formerly exposed in the northern part of the Harting Combe brick-yard [SU 8033 2731], but no significant records exist of any exposures. By the Harting Combe crossroads, the deposits consist of a fine-grained sandy glauconitic clay and clayey sand around [SU 803 262]. Similar glauconitic sandy clay can be found in the fields north of Combe Hill around [SU 797 2651] to the north of Birch and Rough copses around [SU 8010 2705] and to the south of Rake around [SU 8035 2735]. Eastwards of this last locality, the dominant lithology is a mottled yellowish brown sandy clay; red-brown mottling was noted at two points [SU 8087 2717] and [SU 8124 2724].

Hythe Formation (H)

The Hythe Formation comprises medium-grained, glauconitic sandstones with some thin siliceously cemented units and pebble beds. These beds form the bulk of the rounded upland between Rogate, Sheet, and Rake. Several exposures are described in Bristow, (1991). The glauconite imparts the characteristic ‘pepper and salt’ texture to the deposit. Locally there are fine-grained pebble beds which coarsen towards the top of the unit. Thin siliceously cemented sandstones and chert beds are a common feature. Fuller’s earth, found at many localities the adjacent Chichester (317) district, has not been noted in this area. Cross-bedding occurs, but much of the bedding is in tabular units. A variety of sedimentary structures, including those resulting from dewatering have been noted locally. Fossils, other than sponge spicules, have not been encountered during the present is survey, but they are probably locally common.

The Hythe Formation spans the Lower Aptian/Upper Aptian boundary and ranges from the deshayesi Zone up to possibly to the martinides Zone at the top, although on in the Chichester Sheet district there are indications that this zone is absent and that the bowerbanki Zone is the highest zone of the Hythe Formation (Bristow et al., 1987).

The thickness of the Hythe Formation varies from 10 m to about 92 m, but the beds thicken markedly eastwards into the Weald, and at outcrop in the east of the Alresford district range from 64 m to about 95 m.

Details

North of Rogate, the higher beds of the Hythe Formation form long dip slopes inclined at about 4º south or south-south-west. The north-facing scarp is between 30 and 45 m high. Exposures of the lower strata on the scarp face are rare, but appear to consist dominantly of orange–brown or yellowish brown, glauconitic, fine to coarse-grained sands.

There is a small, but interesting, roadside section [SU 8012 2582], on the Rogate to Rake road which exposes about 8 m of horizontally bedded sands (Plate 1).

The upper 6 m of the section consists of orange and buff, fine- to medium-grained sandstone, cross-bedded in horizontal units. Some of the cross-bedding is picked out by glauconite. About 4 m from the top is a thin (5 cm) siliceously cemented sandstone rich in sponge spicules; the beds above this layer are intensely bioturbated. A metre below this thin siliceous sandstone is a layer of impersistent siliceous doggers which rest with marked disconformity on the underlying unit.

The underlying unit consists of 2 m of buff to yellowish orange, glauconitic, cross-bedded, fine- to medium-grained, friable sandstone. Some of the foresets are steeply dipping (up to 35º) and some of these appear to be slumped. A number of dewatering structures are visible.

A thin section of the siliceous sandstone in this exposure was described by R W Sanderson (in Bristow, 1991) as porous pale yellow, rough-textured silicified glauconitic sandstone. It consists of moderately well-sorted, angular to subangular quartz grains (0.15 to 0.35 mm) with common rounded or lobately ovoid pellets of glauconite and glauconitic mudstone, some of which exhibit fibro-concentric veneers of more highly birefringent material, dispersed in a microcrystalline chalcedonic matrix. A few silicified simple, sponge spicules are present, together with rare grains of zircon, muscovite, colourless pyroxene and plagioclase as accessories.

Some 550 m east-south-east of the road-side exposure section above, an outcrop of horizontally bedded, buff, fine- to medium-grained sandstone was seen in the bank at [SU 8065 2565]. There are poor sections of the higher strata in the woods to the north of Rogate Lodge. One of the old degraded quarries [SU 8060 2515] has poor exposures of buff, medium- to coarse-grained, nonporous, siliceously cemented spicular sandstone. The sponge spicules are particularly evident on the weathered surface. Another quarry [SU 806 250] 15 m to the south of the above has poor exposure but there are many blocks of medium grained, nonporous, fine- to medium-grained, siliceously cemented sandstone on the quarry floor. The sandstone weathers orange and is very friable. Blocks of medium-grained spicular sandstone are to be found on the path [SU 8017 2508] in the wood on the south-west side of the Rogate road. The Hythe Formation hereabouts form a long dip slope inclined at about 4º to the south. Continuing southwards and stratigraphically higher in the sequence, yellowish orange and ferruginous brown, medium- to coarse-grained sand appears to be the dominant lithology.

Farther west, the Hythe Formation has a total thickness of about 84 m in a borehole (SU72SE/23) at [SU 7906 2396]). Just north of this borehole, greenish yellow clayey medium- to coarse-grained sand is commonly augered at the surface. Blocks of siliceous sandstone are also locally common on the surface at [SU 7974 2486] and [SU 7910 2455]. Large dip slope surfaces south and south west of Durford Wood around [SU 776 246], [SU 781 248] and [SU 785 246] dip at about 4º just west of south. The dip appears to decrease westwards to about 2º around [SU 763 243], [SU 770 245] and [SU 773 245] and to swing round to south-south-west. To the south at Ryefield [SU 7761 2230] the Hythe Formation, mostly fine- to medium-grained, yellowish green sands, are is 94 m thick.

There are several excellent sections in the sunken lane [SU 7622 2440] to [SU 7640 2436] on the east side of the River Rother near Sheet, showing up to 4 m of medium-grained, orange to ferruginous brown, glauconitic, friable sandstone, with a few thin (2 to 3 cm) seams of siliceous sandstone. Thin coarse-grained sandy pebbly beds with scattered quartz pebbles up to 8 mm diameter, also occur, together with some buff glauconitic beds. This section is stratigraphically high within the Hythe Formation. Beds at a similar stratigraphical position were formerly exposed in the road bank by the railway bridge [SU 7570 2485] north of Sheet (Osborne White, 1910 p. 9) and described as brown, ferruginous glauconitic sand with cherty concretions, resting on bright orange sand.

In the borehole at the Petersfield Waterworks (SU72SE/37), [SU 7529 2480] 400 m west of the railway bridge, the Hythe Formation is 85 m thick. This compares with the 88 m in the Itshide Rubber Co. Ltd Borehole, Petersfield (SU72SW/12), [SU 7465 2374], and 90.7 m at the Petersfield Laundry (SU72SW/45), [SU 7417 2344].

About 3 m of horizontal orange glauconitic friable sandstone is exposed in the bank of the River Rother at [SU 7620 2517]. Some 600 m to the north-east, yellowish brown, medium-grained, friable sandstones, with silicified concretions 0.5 m thick towards the top, occurs in the lane bank [SU 766 257] south of Tankerdale Farm. Hawkins (Osborne White, 1910 p. 9) noted brown sandstone dipping 3º to the north-east in the railway cutting [SU 7680 2615] west of Stodham Park (formerly Stodham House). Nearby in the deeply cut lane [SU 7710 2605] south of Stodham Park there is 3 to 4 m of orange medium-grained, friable sandstone interbedded with layers of buff, glauconitic, coarse-grained siliceously cemented sandstone. Medium- to coarse-grained ferruginous sand can be augered in the bank of the sunken lane [SU 7720 2620] to [SU 7775 2645]. All these occurrences, from the River Rother to this locality, are in the uppermost Hythe Formation. The junction with the Sandgate Formation (Rogate Member) in Stodham Lane is described under the Rogate Member. Stratigraphically lower beds to the east consist dominantly of coarse-grained yellowish brown sand.

The total thickness of the Hythe Formation at a borehole near Greatham (SU72NE/11), [SU 7785 2964] is 64 m, if the 1.5 m of clay at the base of the hole is correctly identified as the Atherfield Clay Formation.

Sandgate Formation (SaB)

The Sandgate Formation occurs in the east and south-east of the Alresford district between Bordon and Petersfield. It consists of a variety of lithologies, and in Petersfield area, Bristow (1991) divided the Sandgate Formation into three members, these being the Rogate Member, the Pulborough Sandrock Member and the Marehill Clay Member. In the north-east of the district around Bordon, the Rogate Member is replaced by the Bargate Sandstone Member. In this area, the Sandgate Formation is for the most part mapped as a single unit and it is only in the extreme south-east of sheet SU73SE around Longmoor Camp (Sheet SU73SE) that the tripartite succession that Bristow recognised becomes evident. On sheet SU83SW to the east, the Marehill Clay dies out northwards and the beds between the base of the Folkestone Formation and the Rogate Beds are mapped as Sandgate Formation undivided. At least 10 m of undivided Sandgate Formation are shown on the north-eastern part of sheet SU73SE, around Woolmer Forest (Sheet SU73SE), whilst to the south of that sheet, around Liss, the upper 5 to 10 m of the sequence is identified as Marehill Clay.

In the Petersfield area, the lowest unit is the Rogate Member which is overlain by the Pulborough Sandrock Member. Locally this unit is separated by the Lower Marehill Clay Member (LMhC) into Lower and Upper beds (UPSk, LPSk). The Upper Marehill Clay (UMhC) caps this sequence. The two members cannot be traced farther north than Longmoor Camp, where the Sandgate Formation is mapped as undivided. The Sandgate Formation is of Late Aptian age and probably falls within the single ammonite zone of Parahoplities nutfieldensis with the exception of the uppermost Marehill Clay Member, which may be up to the Hypacanthoplites jacobi Zone in age.

Details

West of the River Wey, small exposures, scrapes and auger holes consistently prove silty and clayey, poorly sorted, quartz sand with a few scattered limonitised ooids. Knowles and Middlemiss (1959) noted small exposures of pale-coloured, banded and ferruginous, clayey poorly sorted sand with lenses of fossiliferous, highly ferruginous, soft, cross-bedded sandstone. Fossils collected from the ferruginous sandstone nodules set in poorly sorted sand yielded Parahoplites sp. and other fossils including Toucasia lonsdalei, indicative the cunningtoni Subzone of the nutfieldensis Zone. The fauna and lithology suggest a strong link with the Pulborough Sandrock Member to the south and south-east (Bristow, 1991, 1998).

Glauconitic, clayey, fine-grained sand was augered at several localities around Bordon (Bristow, 1998). The cored Hollywater Farm Borehole (SU83SW/67), [SU 8085 34304] proved 28.22 m of the Sandgate Formation, consisting of a dominantly sandy upper unit 13.5 m thick (possibly the Pulborough Sandrock Member) over a dominantly argillaceous unit 14 m thick (of possible Rogate Member affinity). The base of the borehole comprises 0.7 m of sandstone assigned to the Bargate Member (Bristow, 1998).

Around Round Hill [SU 8018 3373], very fine-grained to fine-grained buff sand and sandstone was noted which may be the Pulborough Sandrock Member, although it is not possible to map it in this area. Similarly, mottled orange and grey sandy clay augered near Hollywater Clump [SU 8038 3341] just below the Folkestone Formation may be the Marehill Clay Member. Just east of the Alresford district, the old railway cutting on the north-western slopes of Holm Hills [SU 8207 3261] revealed about 6 m of fine- grained ferruginous, locally silty, sand. This may be the Pulborough Sandrock Member. A trial borehole nearby (SU83SW/47), [SU 8223 3219] proved this sandy unit and passed into an underlying clayey unit, which may be the Rogate Member.

The Sandgate Formation (undivided) is mapped on the eastern margin of sheets SU73SE and NE and within the broad flat-bottomed valley south of Whitehill village. From Brimstone Inclosure [SU 779 325] northwards to Fern Hill [SU 799 332] the top of the Sandgate Formation is marked by a strong negative break of slope beneath the Folkestone Formation scarp. Drains cut into this heavily wooded area at the base of the scarp, show thin impersistant dark grey sandy clays within the generally sandy bedrock and these may well be the most northward expression of the Marehill Clay.

Rogate Member (RoB)

The lithologically variable Rogate Member is a heterogeneous sequence of coarse-grained pebbly sands, very glauconitic clayey pebbly sands, glauconitic pebbly and sandy clays, calcareously cemented pebble beds and coarse-grained pebbly sands with many polished limonite pebbles. A dominantly clayey unit is thick enough to map in the middle of the unit. The member is up to 47 m thick around Greatham and probably lies within the subarcticum Subzone. No diagnostic faunas have been found.

Details

In the Rogate area, the Rogate Member forms a small but prominent scarp, with a dip slope descending to the south at about 4º. Poor exposures of glauconitic yellowish brown clayey pebbly sand and sandy pebbly clay can be seen in Garbitts Lane [SU 8095 2345] south-south-east of Rogate. Augering reveals the lithological complexity of this unit, with medium- to coarse-grained ferruginous sands, locally clayey and glauconitic. West of Rogate, much of the outcrop is hidden beneath superficial deposits, but poor exposures of coarse-grained ferruginous and glauconitic orange–brown medium- to coarse-grained sand occur around [SU 7995 2420]. Kirkaldy (1933) recorded 2.4 m of coarse-grained shelly and pebbly glauconitic sandstone in this area.

There are good exposures in the sunken lane north of Durleighmarsh Farm [SU 7877 2427] (Bristow, 1991). This lane section displays a series of small exposures with coarse-grained pebbly sands, coarse-grained ferruginous, pebbly sands and coarse-grained pebble clayey sand. A little further south [SU 7858 2382] glauconitic coarse-grained well-sorted, friable sandstone is overlain by a coarse-grained buff sand with many polished ironstone pebbles.

Poor exposures of coarse-grained, pebbly sand with much polished ironstone, are visible in a road cutting west of Durleigh Marsh Farm [SU 7775 2385] (Bristow, 1991). To the west, the Rogate Member is largely covered in with superficial deposits, but small exposures of coarse-grained clayey pebbly sand occur near Westmark Farm at [SU 768 241] and [SU 773 238].

There is an extensive outcrop of the Rogate Member around Sheet. Road bank exposures around the area [SU 7575 2435] to [SU 7555 2410] show coarse-grained glauconitic clayey pebble sand with ironstone fragments. Osborne White (1910) recorded 9 to 12 m of fine- to coarse-grained, cross-bedded, reddish brown ferruginous sand with coarser beds including brown pebbles at the road junction nearby at [SU 7555 2410], and at another section half a mile west-north-west of Sheet Chruch, at least 5.63 m of white, yellow and reddish ferruginous sandstone.

On the east side of the River Rother around Liss, glauconitic sandy clay is present at the top of the Rogate Member. The roadside bank north-east of Stodham Park has 2.5 m of yellowish orange, slightly glauconitic pebbly sand over yellowish orange sand without pebbles, marking the contact between the Hythe Formation and the Rogate Member. Coarse-grained, locally glauconitic, pebbly sands and friable sandstones are seen in many roadside exposures around Liss, notably at [SU 777 267]; [SU 7840 2705]; [SU 7847 2725]; [SU 7848 2733]; and [SU 7846 2726]. In addition to the road sections there were several old pits from which a ‘Bargate Stone’ was extracted. These are now mapped as the Rogate Member. In a pit at [SU 7875 2785] near Ciddy Hall, Osborne White, (1910) recorded about 3 m of coarse-grained cross-bedded calcareous sandstone with pebbles of quartz, ironstone and glauconite. Another pit [SU 784 277], now built over, formerly exposed about 3.6 m of uncemented calcareous grit, which was heavily piped into by a brown earthy sand. Other old pits in the area have gone unrecorded [SU 7860 2775] and [SU 789 279]. Similar sandstones are exposed in road sections nearby at [SU 7847 2768] and [SU 7915 2816] (Bristow, 1991).

North-east of Liss, the top of the Rogate Member is marked by a highly glauconitic sandy clay which can be augured and seen in road sections and banks at [SU 7808 2713] and [SU 7808 2737]. The railway cutting [SU 8002 2907] to [SU 8100 2906] was described by Drew (in Topley, 1875) who recorded a sequence of clayey sands with bands of ferruginous nodules and fossiliferous ‘Bargate Stone’ at the base. Nearby, coarse-grained clayey glauconitic pebbly sand occurs in Reeds Lane [SU 7952 2864]. Clayey ferruginous, poorly sorted, sand was augured north-west of Forest Mere [SU 8123 3030] (Bristow, 1998).

Borehole evidence (Bristow, 1991) suggests the thickness of the Rogate Member ranges from 31.5 m in the Itshide Rubber Borehole (SU72SW/12), [SU 7465 2374], and 28.05 m in the Petersfield Laundry Borehole (SU72SW/45), [SU 7417 2344] in the Petersfield area, thinning to 21.8 m at Stroud in borehole (SU72SW/4), [SU 7225 2360] and 13.8 m at Flexcombe in borehole (SU72NE/3), [SU 7684 2692].

Bargate Member (Bt)

The Bargate Member crops out in the north-east of the district and is best developed in the Guildford district. It consists of friable calcareous glauconitic sandstones and cemented flagstones with a maximum thickness of 35 m. Pebbles of quartz and chert (or ‘lydite’) up to 6 mm across are locally common. The Bargate Member only has only a very small outcrop in the extreme east of the district.

Details

It is poorly exposed in the river bank at Headley Mill, near Bordon [SU 8111 3575] to [SU 8115 3575] where there is much sandstone debris. The contact between the Bargate Member and the rest of the Sandgate Formation is defined by a fairly sharp feature around Prospect Hill Farm [SU 825 354].

Pulborough Sandrock Member (PSk)

The grey Pulborough Sandrock Member consists of uniformly fine-grained, friable, well-sorted, fossiliferous sandstone, rarely cross-bedded, grey when fresh, yellowish brown when weathered. Sparse coarse sand grains, including polished limonite, may be present near the base. Coarse ferruginous sand is locally present at the top in the Steep Marsh area, and around Pulborough cemented ironstone up to 0.3 m thick is locally present. There are thin clay beds in places. Locally, the beds are richly fossiliferous; the fauna includes Parahoplites cunningtoni, the subzonal index fossil at the top of the P. nutfieldensis Zone. Other fossils recorded include the rudist Toucasia lonsdalei, which is indicative of warm Tethyan waters.

In the south-east, east of Petersfield, the member divides into upper and lower sandstone units, separated by the Lower Marehill Clay. Around Ryefield, [SU 7761 2230] the upper and lower sandstones are 12 and 20 m thick respectively, whilst at Elstead, [SU 8422 2093], they are 8 and 10 m thick respectively.

Details

Low cliffs of the Lower Pulborough Sandrock Member are present on the south side of the River Rother as far as Durford Bridge [SU 7825 2330]. Many small exposures show up to 2 m of dark grey or orange, fine-grained, glauconitic sandstone. The river cliff at Haben Bridge [SU 8080 2292] in the extreme south-east corner of the district exposes some 3 to 4 m of flat-lying, soft, friable, fine-grained sandstone, locally cemented by iron. Some of the beds are richly fossiliferous with the fossils occurring as clustered moulds. The fauna was listed by Casey (1961) and in an appendix in Bristow (1991), and is indicative of the Parahoplites cunningtoni Subzone of the P. nutfieldensis Zone. North of the river, the lower Pulborough Sandrock Member is exposed in the lane leading to Rogate [SU 8075 2379]. The higher beds consist of glauconitic, clayey, fine-grained friable sandstone, although towards the middle of the outcrop, a pebbly horizon was noted (Bristow, 1991). A poor section in the basal sandstone occurs on the main road at [SU 7787 2379].

Much of the outcrop of the upper Pulborough Sandrock Member is obscured by superficial deposits. Buff and grey loose cross-bedded sands were noted beneath yellowish ironstone (marking the contact with the upper Marehill Clay Member). Trial pits at Petersfield Sewage works [SU 769 229] proved 2 m of greenish black, fine- to medium-grained, clayey sandstone.

The upper and lower units of the Pulborough Sandrock Member merge just east of Petersfield. North of the town, low crags of orange sandstone, locally cemented by iron, dipping 4º south-west crop out on the side of the road at [SU 745 241]. Boreholes in the town indicate thickness of 11.89 m at borehole (SU72SW/5), [SU 7491 2334], 11.28 m at borehole (SU72SW/48), [SU 7413 2330], 9.75 m at borehole (SU72SW/12), [SU 7465 2374] and 9.45 m at (SU72SW/46), [SU 7417 2344]. The farthest west occurrence of the Pulborough Sandrock Member is in the Stroud Borehole (SU72SW/48), [SU 7225 1236] where it is 14.63 m thick.

Blocks of ironstone with shell moulds, noted in fields near Bedale’s School [SU 7438 2456], yielded a limited fauna indicative of the cunningtoni Subzone. An old pit south of Boyer’s Common [SU 7563 2537] proved a thin unit of coarse-grained ferruginous cross-bedded, sparsely fossiliferous sandstone above fine-grained yellowish buff friable sandstone, from which the gastropod Anchura (Perissoptera) robinaldina was obtained. This unusual coarse-grained sandstone was also noted in an old pit, now backfilled, 700 m to the north-east [SU 7607 2519]. This may be the locality where Fitton (1836) collected an extensive fauna indicative of the cunningtoni Subzone.

A good exposure of up to 6 m of horizontally-bedded, fine-grained, orange, friable sandstone can be seen in the stream bed or old lane leading north-west from the Harrow Inn [SU 7530 2532]. Some cross-bedding and iron cementation occurs locally. Surface brash at [SU 7645 2610] yielded Pterotriginia mantelli and Yaadia nodosa indicative of a late Aptian age.

Around Liss, the Pulborough Sandrock Member is largely buried by superficial deposits, but small scattered exposures of fine-grained grey sand and dark grey clayey fine-grained sand occur at [SU 7727 2725] and [SU 7735 2732]. At Greatham Pumping Station [SU 778 296], thicknesses of 16.76 and 12.85 m of fossiliferous fine-grained sandstone are recorded in boreholes (SU72NE/11), (SU72NE/12) and (SU72NE/17).

Marehill Clay Member (MhC)

The distinctive Marehill Clay Member consists of dark grey to purplish grey, locally glauconitic, silty clay. It is sparsely fossiliferous, containing only undiagnostic foraminifera. In the south-east of the district, the member is split into two parts by the Upper Pulborough Sandrock, which dies out westwards near Petersfield. The upper and lower clays are around 5 and 8 m thick respectively, but these thicken north-eastwards. In the Stroud Borehole, (SU72SW/48), [SU 7225 1236], the most westerly occurrence, it is 23.78 m thick, increasing north-eastwards to 36.74 m at Flexcombe (in borehole (SU72NE/3), [SU 7668 1269] and 32.61 m in the Greatham pumping station [SU 778 296] boreholes (SU72NE/11), (SU72NE/12) and (SU72NE/17). The lithology varies little over the outcrop, although north-east of Steep, glauconite becomes more common, and it becomes increasingly sandy towards the north-east. Around Longmoor Inclosure [SU 793 296] there is much coarse-grained pebbly sand, but it still forms a mappable unit, although north of here, the Marehill Clay ceases to be easily identified as a separate unit.

Details

There are few good exposures in the south-east of the district, as much of the outcrop is covered in superficial deposits. The Marehill Clay can be augered in many places (see Bristow 1991 for details), and occasionally seen in ditches south of the River Rother. The junction of the lower Lower Marehill Clay with the underlying Pulborough Sandrock Member can be seen in the river cliff 600 m south of Wenham Manor Farm [SU 7843 2322], where 0.6 m of fine-grained sandy black and glauconitic clay rests on friable, greyish brown and fine-grained sandstone. The Upper Marehill Clay can be seen in ditches around West Heath, where it was formerly well exposed in the railway cutting [SU 7850 2305]. The cutting exposed the basal ironstone bed of the Folkestone Formation resting on 3 m of dark clay and 1.6 m of more sandy clay overlying the iron-cemented top of the Upper Pulborough Sandrock Member.

The Upper Marehill Clay was exposed in trial pits for the Petersfield Sewage works [SU 769 229] where 2.5 m was formerly exposed. Drew (in Topley, 1875) noted over 3.6 m of dark coloured sandy clay with pyrites in a railway cutting just north-east of Petersfield railway station.

The Stroud Borehole (SU72SW/48), [SU 7225 1236], is the farthest west that the Marehill Clay has been proved in the Weald, where it is 23.78 m thick and described as silty clay, olive-grey, locally greenish and with a very minor sand content. Between Petersfield and Liss, there are very few exposures, but dark grey clay and clayey silts can be augered at many points and seen in ditches (see Bristow, 1991, for more details), and in river bank exposures near Flexcombe [SU 7721 2697]. Evidence from these small exposures indicates that the Marehill Clay becomes increasing glauconitic and sandy to the north-east. In the Flexcombe Borehole (SU72NE/3), [SU 76681269], [SU 7684 2692] the Marehill Clay comprises 36.74 m of dominantly olive-black clay with only a minor sand content. North of Liss, again, very few exposures are present and where seen or augered, the member comprises a glauconitic dark grey clay, and is increasingly sandy north-east of Greatham. In the extreme north-east, around the Longmoor inclosure, the Marehill Clay Member and Pulborough Sandrock are mapped, for the most part beneath head. Here purplish grey silty clay and poorly cemented fine-grained sandstone have been noted in auger holes, drainage ditches and incorporated into the overlying head (Hopson, 1998). The dominant lithology is of a glauconitic clayey coarse-grained sand or glauconitic sandy clay. North of here the member cannot be mapped separately and is included with the undivided Sandgate Formation. Glauconitic sandy clay was augered in the Weavers Down area [SU 8065 3000] and springs mark the base of the overlying Folkestone Formation in several places.

Folkestone Formation (F)

The Folkestone Formation crops out along a narrow south-west to north-east tract between Petersfield and Liss Forest, where the outcrop widens significantly between Longmoor Camp and Bordon. Here it occupies a broad (2.5 to 3.5 km wide) north-south tract of sandy heathland and woodland from Greatham, Blackmoor, Borden through to Kingsley. At its maximum in this district the Folkestone Formation is estimated to be between 75 and 85 m thick, although the succession thins to a minimum of 10 m in the south of the district at Stroud.

The formation consists of yellow-orange, friable, cross-bedded, fine- to coarse-grained, sands and sandstones. The upper part of the succession contains common white, grey or lilac clay partings. Parts of the sequence, especially towards the base contain many seams of small pebbles which consist chiefly of quartz and dark siliceous rocks. The sand is more or less ferruginous throughout, and especially so in the middle parts, where much of it is irregularly cemented.

Much of the succession is exposed in the West Heath Sand Pit [SU 785 228] (Plate 2), where it consists of 25 m of cross-bedded, yellow to yellow–brown, medium- to coarse-grained sand showing an overall dip of about 4° to the south. These sands characteristically occur in large-scale cross-beds, in units up to 3 m thick, but the upper part of the succession consists of 6 m of tabular, friable sandstones, each about 0.1 m thick and separated by thin (10 mm) grey clays. Allen and Narayan (1964) describe in detail the nature of the cross-bedded sets, which are up to 5 m in thickness. Narayan (1971) in a wider study of palaeocurrents throughout the Lower Greensand Group across the Weald and northern France, demonstrated a strong unidirectional preferred orientation towards the south-east, and suggested the Folkestone Formation was deposited by the lateral migration of sandwaves in a shallow sea, possibly under tidal conditions. Wood, (1956), noted a significant increase in the amount of kyanite in the heavy mineral fraction, and suggested Amorica as a possible source. However, given the palaeocurrent direction, the Caledonides or Scandinavia may be a more likely origin, as suggested by Juignet et al. (1973).

At the top of the Folkestone Formation, a thin brightly coloured, sandy ironstone, the ‘Iron Grit’ (up to 0.1 m thick), is well developed in the Chichester district to the south-east. The most westerly exposure in the Weald was noted near Petersfield around [SU 725 236] (Osborne White, 1910).

Very few fossils have been found in the Folkestone Formation in this district. Occasional ironstone casts of wood and of marine molluscs have been recorded. The formation is thought to span the Upper Aptian to Lower Albian boundary (Bristow, 1991). The topmost part of the Folkestone Formation was penetrated by the BGS Selborne boreholes (Hopson et al., 2001). Three cored boreholes were sunk, between December 1997 and January 1998 around Selborne. Selborne No 1. (SU73SW/22) was drilled at Frenchmare Copse [SU 7320 3494]; Selborne No 2 (SU73SE/39) at Priory Farm [SU 7540 3435] and Selborne No 3. (SU73SE/40) on Honey Lane at [SU 7583 3400]. Together these boreholes go through the lowermost Chalk, the whole of the Gault and Upper Greensand sequence and into the Folkestone Formation of the Lower Greensand Group.

Details

Petersfield–Rogate–Liss area

South-east of Rogate, the Folkestone Formation is 54 m thick in the Elsted Borehole (SU82SW/20), [SU 8422 2093]. South of Rogate, just beyond the present district, there are excellent roadside exposures [SU 8068 2248] to [SU 8055 2238] and old quarry sections near the aptly named Sandhill Farm. Up to 10 m of cross-bedded fine-, medium- and coarse-grained buff sandstone can be seen with southward- dipping foresets.

West of Rogate, there are good exposures of the Folkestone Formation in the West Heath Sand Pit [SU 785 228], where up to 25 m of cross-bedded, yellow, buff and locally pink medium- to coarse-grained sandstone dipping south at 4º are exposed. On the west side of the pit, close to the entrance, large-scale cross-beds in units up to 3 m thick with foresets dipping at 28º to the south, typify much of the sections. On the south side of the pit, the uppermost beds consist of 6 m of tabular units, each about 10 cm thick, of brown medium- to coarse-grained friable sandstone separated by thin (10 mm) beds of buff and grey clay. The cross-bedding in this pit has been described in detail by Allen and Narayan (1964) and Narayan (1971). The junction of the Folkestone Formation and the Marehill Clay Member could formerly be seen in the railway cutting to the north. South-west of this pit, the Ryefield Borehole (SU72SE/7), [SU 7761 2230] proved 30 m of Folkestone Formation.

Several small exposures occur on the outskirts of Petersfield, notably at [SU 7546 2285] where 1 m of finely stratified coarse-grained, orange-yellowish friable sandstone is exposed; in an old pit [SU 7405 2310] now built in at Borough Hill, where up to 3 m of coarse-grained buff cross-bedded friable sandstone occurs with forests dipping at 26º south; and north of the railway line at Tilmore Road [SU 7446 2380] where up to 2 m of coarse- to very coarse-grained cross-bedded, yellow sandstone can be seen.

Sand was formerly extracted from a number of pits around Stroud [SU 725 236]; [SU 7244 2370]; [SU 7255 2405]. The Gault-Folkestone Formation contact was recorded by Osborne White, (1910) at the first of these pits. Here 2.13 m of yellow and white cross-bedded sandstone with iron staining and occasional some wood fragments is overlain by 1.75 m of stiff sandy dark greenish clay with small rounded quartz pebbles. Another section across the Gault-Folkestone contact can be seen in a pit 200 m west-north-west of Aldersnapp Farm [SU 7276 2435]. This may be the pit referred to by Topley (1875) as at the south corner of Steep Common. It is also recorded by Osborne White (1910) and Bristow (1991). Here, over 2.5 m of medium- to coarse-grained, thinly bedded, micaceous sandstone with thin clay wisps and drapes is overlain by 0.96 m of grey glauconitic clay, with a ferruginous, coarse-grained, locally pebbly sand at the base.

A section behind Aldersnapp Farm [SU 7304 2425] exposed the junction of the Folkestone Formation and the Marehill Clay, and a road cutting nearby [SU 7295 2445] proved 1.5 m of buff medium- to coarse-grained thinly bedded friable sandstone. In this area, the Folkestone Formation is only 10.37 m thick. At Steep, a partially overgrown pit exposes 8 m of yellow, cross-bedded, friable sandstone, overlain by 2 m of angular flint gravel set in a clay matrix (older head). Another small section with very coarse-grained friable sandstone occurs at [SU 747 252]. A section formed by a waterfall 500 m south-west of Steep Marsh [SU 7517 2581] exposes some 6 m of coarse-grained, buff-brown, friable, soft, well bedded sandstone. The bedding planes are picked out by thin ironstone bands and dark grey silty clays up to 3 cm thick, which proved barren of microfossils (Bristow, 1991).

In the Flexcombe Borehole (SU72NE/3), [SU 7684 2692], the Folkestone Formation is 10.77 m thick, but much of the outcrop is obscured by superficial deposits. Osborne White, (1910) recorded a section in a pit 400 yards south-south-west of Liss Church around [SU 7690 2837) where 3.8 m of white and yellow cross-bedded, micaceous sand with seams of brown and grey clay occurred beneath 2.4 m of soil and slope wash. In woods north of the water works at Liss Forest, an old pit [SU 7795 2968] reveals 1.5 m of orange, coarse-grained, cross-bedded friable sandstone. An old quarry [SU 7897 2995] on the north side of Longmoor Enclosure is situated close to the base of the Folkestone Formation. Here, 2 m of thinly bedded tabular cross-bedded, fine- to medium-grained, buff-yellow friable sandstone and thin (10 mm) clays occur. The clays occur in beds 0.4 m thick with thin sand partings.

Bordon–Woolmer area

Throughout the Bordon area, small exposures of yellow to white fine- to medium-grained sand and sandstone of the Folkestone Formation can be seen in ditches and low bluffs along roads and tracks. Numerous exposures of some thickness were noted from the aerial photographs within the confines of the military ranges but access was not possible at the time of the survey. The most notable of these exposures are north of Longmoor Road in the area of the Woolmer Down Rifle Ranges [centred on 791 316] and in Cranmer Bottom Rifle Ranges [SU 792 329].

Up to about 5 m of cross-bedded, friable, white to dark purplish brown, fine- to medium-grained sandstone can be seen in the cutting [SU 7975 3017] to [SU 7993 3059] along the dismantled railway south-east of Longmoor Camp. The section provides a typical weathering profile of the Folkestone Formation which commences with a thin (5 to 20 cm), dark, humic, acid, sandy soil with a heavy tree and bracken root mat at its base. The Folkestone Formation beneath this soil layer is often very weakly cemented or loose sand and bleached white. Underlying this loose sand and in places replacing it is a layer of secondarily iron-cemented sandstone which is commonly very strongly coloured. In general this loose sand/cemented sandstone horizon is confined to the uppermost 1 to 1.5 m of the section but in places the iron-cementation was noted to the base of the section particularly along near vertical discontinuities (?joints) and where thick cross-bedded units come to the surface. Elsewhere thin ironstone partings were noted above thin (2 to 10 mm) clay partings between cross-bedded units, and along individual coarser-grained foreset beds. The remainder of the section is predominantly in cross-bedded units interspersed with some planar bedded units, each of which are about 0.5 to 1.5 m in thickness.

Similar sandstones were also seen in the small pit [SU 780 310], now used as a mobile home park, in Greatham, although access to the face is difficult. Here the upper part of the face stands proud as a single, indurated, cross-bedded unit between 2 and 2.5 m thick. This unit rests on loose or poorly indurated yellow sand much obscurred by talus and landscaping for parking lots. A small (10 m across) pit at [SU 7887 3135] off Woolmer Road shows 2 to 3 m of yellow, partially secondarily iron-cemented, fine- to medium-grained sand. This pit is notable because the iron-cementation appears to pick out cryoturbation involutions within the sand.

Numerous degraded and partially overgrown exposures of yellow, fine- to medium-grained sand and friable sandstone were noted in the cutting beneath the Petersfield Road [SU 7925 3395] to [SU 7910 3430] at Whitehill. Similar yellow sands were visible in the pit [SU 7855 3535] north of the caravan site off Hogmoor Road.

The most notable exposures of the Folkestone Formation are in a series of active pits south and west of Kingsley [SU 788 382] where sequences (2 to 8 m in thickness) of sand and partially indurated sandstone towards the top of the formation can be seen. Extraction in this area has been continuous from at least the turn of the century and pits were noted in the Alresford Memoir (Osborne White, 1910). Abandoned quarries are being reclaimed, principally by domestic landfill, and new greenfield sites, were being developed during the survey.

Sleaford–Frensham area

In the Sleaford area, the Folkestone Formation has been worked in several large pits [SU 800 384], [SU 805 384] and [SU 809 385] but no section remains. Osborne White (1910) refers to a pit near Trottsford Farm [SU 8080 3845] which exposed 6 m of orange and pale brown, coarse-grained sand with pebble beds. The sand is described as being stained black in places, and contains, in addition to the usual quartz pebbles, some angular and rounded lumps of grey and brown laminated clay. Knowles and Middlemiss (1959) noted coarse-grained pebbly sand in the pits in this area.

On the north bank of the River Wey, a small pit [SU 8117 3884] still exposes 4 m of medium- to coarse- grained, cross-bedded, friable sandstone with much secondary iron cementation. To the east, just outside the Alresford district, a large working pit exposes about 20 m of cross-bedded yellow sand [SU 815 389]. The lowest part of this pit exposes dark grey silty clay similar to the Marehill Clay, but given that the Folkestone Formation is about 83 m thick in this area, it is more likely to be a clay bed within that formation.

Selborne Borehole

The upper 7.28 m of the Folkestone Formation was cored at the base of Selborne 2 Borehole (SE73SE/39) [SU 7540 3435] (Figure 16). It comprises pale greyish brown medium- to coarse-grained, moderately sorted, micaceous, quartz sand with regularly spaced thin (up to 7 cm thick), pale grey, plastic clay seams and laminae. The beds are generally cross-stratified. The uppermost 0.25 m (between 60.52 m and 60.77 m) beneath a conspicuous burrowed surface consists of dark greenish grey medium- to coarse-grained, sparsely glauconitic, muddy sandstone with fine small pebbles of polished and subrounded quartz, phosphatic nodules and limonite clasts. Biostratigraphically this material is considered to be of D. mammillatum Superzone (sensu Owen, 1992) age by analogy with the exposure at the nearby Selborne Brickworks.

Gault Formation (G)

The Gault crops out over a roughly south-west to north-east tract from just west of Petersfield to Blacknest near Alice Holt Forest. It forms a low-lying tract of ground beneath the Upper Greensand scarp and is dominantly covered in pasture. There are very few good exposures of the Gault, although it has been worked for bricks at several localities. Most of these brickworks are now disused and offer no exposure. The contact between the Gault and the Upper Greensand is also affected by landslides (see Chapter 7).

The Gault Formation consists mainly of pale to dark grey fissured soft silty clay with scattered phosphatic nodules up to 15 mm across. The basal bed of the Gault consists of dark greenish grey loamy sand about 0.9 m thick with common phosphatic and ferruginous concretions. The weathered profile of many natural exposures shows a gradation up into very soft, pale yellow-brown, plastic clay beneath the active soil layer. Its maximum thickness is 115 m at the southern edge of the district (Figure 17), thinning to about 100 m in the Petersfield area, around 95 m in the BGS Selborne boreholes (Figure 17)a (SU73SW/22), [SU 7320 3494]; (SU73SE/39) [SU 7540 3435]; and (SU73SE/40) [SU 7583 3400] and about 45 to 60 m thick in the north-east of the district.

The Gault Formation has been closely studied at many localities in the North Downs, using the Copt Point section at Folkestone as the type succession. The work of H G Owen (1958; 1960; 1963; 1971a; 1971b; 1975; 1988; 1992; 1996a; 1996b) is paramount in those studies. The BGS Selborne boreholes (Hopson et al., 2001) provide a more complete record of the Gault succession in the Alresford area (Figure 18). A simple correlation of the Selborne succession with the Folkestone section and other notable successions along the outcrop around the Weald is presented here (Figure 19).

Lithologically, the Gault within the Selborne boreholes can be simply divided along traditional lines with the Lower Gault comprising dark grey mudstone of Mid Albian age and a paler more calcareous Upper Gault mudstone of Late Albian age. In terms of thickness the succession as a whole is greatly expanded compared to the Folkestone type site with the greatest expansion thickness within the Lower Gault (Middle Albian). The Upper Albian is likewise expanded but 43% per cent of that succession is in Upper Greensand facies. The Selborne boreholes can more readily be compared to with the thick successions encountered along the southern outcrop of the Weald than the thinner successions along the northern outcrop. Outline isopachyte maps for the combined Upper Greensand and Gault (Figure 17)c derived from analysis of logged boreholes and downhole geophysical log responses (principally data from released hydrological and hydrocarbon wells) that have penetrated the full thickness of the Albian demonstrate that the Selborne area is centred over the thickest exposed Middle and Upper Albian succession in south-east England.

Fossils, particularly bivalves and ammonites, are locally common, especially in the phosphatic nodules. These allow the Gault Formation to be divided into a number of zones and subzones (see Owen, 1971). The range of strata seen in the Alresford area spans the H. dentatus to M.(M.) inflatum Zones.

Details

The Blacknest–Oakhanger–Greatham area

Numerous small exposures of Gault were identified during the survey. These were generally on meander bluffs of streams traversing the Gault outcrop, and usually beneath a thin cover of head or alluvium. For example in the headwaters of the River Rother around Hawkley [SU 760 306]; in Oakhanger Stream between Priory Farm [SU 755 345] and Chapel Farm [SU 768 353]; and in the headwaters of Kingsley Stream to the west and north-west of Lode Farm [SU 776 378].

A temporary exposure at Frithend (Bristow, 1998) in 1996 [SU 8120 3910] exposed 6.5 m of blue-grey clay. The upper 4 m was mostly slipped and or covered in talus. The base of the section was marked by a layer of red, fossiliferous siderite nodules. An extensive fauna included Hoplites dentatus, H. spathi, H. paronai and H. vectensis, all indicative of the dentatus Zone, spathi Subzone. The base of the Gault is probably 1–2 m below the section.

A notable exposure at [SU 7601 3255] near Bradshott Wood and very close to the contact with the overlying Upper Greensand showed 0.5 m of an unusual lithology comprising black fine-grained sandy, silty, waxy clay with a blocky fracture. An auger hole beneath this section penetrated another 2.3 m of the same material before touching soft sticky pale grey silty clay of more typical Gault lithology. Micropalaeontological analysis of this unusual material proved it to be from the late upper C. auritus or earliest lowermost M.(M.) rostratum Subzone (i.e. late upper M.(M.) inflatum or early lower S. dispar Zone). The samples also contained abundant radiolaria, making this a unique locality onshore in the UK (Wilkinson, 1997a).

The Selborne Brickworks [SU 767 343] off Honey Lane, Selborne exposes about 11.5 m of very dark blue-grey to grey silty clay that weathers to a pale yellowish brown near the surface and along some larger joints. A prominent brown-tinged bed approximately 3 m up from the base of the section acts as a useful marker in the quarry and has been equated (Woods, 1996a) with Bed 4 in Owen’s (1963) description of this exposure. The outline lithological log shown in (Figure 20) is derived from a number of small, apparently in situ, sections around a small area of open water. Drainage channels on the eastern margin of the pit (in 1996), cut below the level of the water, excavated very dark grey, micaceous, silty clay with pockets of fine- to medium-grained glauconitic sand. Associated with this excavated material are pyritic wood fragments and abundant phosphatic, glauconitic, ironstone nodules which often may have an impregnated surface of polished quartzitic coarse sand and fine pebbles up to 5 mm in size. Many of these nodules appear to be coprolitic and are fossiliferous. The excavated material represents the basal bed of the Gault locally. This basal unit was observed during the survey in a freshly dug drainage ditch 200 m south-east of the quarry, see also (Figure 21). Biostratigraphically the Selborne Brickworks section spans the D. mammillatum Superzone (sensu Owen, 1988) and the Hoplites dentatus Zone (H. spathi Subzone) (Woods, 1996a).

Selborne boreholes

The Gault Formation was proved in all three Selborne boreholes. The overlap and outline classification for each is shown in (Figure 21). Traditionally this formation has been divided into the Lower Gault comprising dark grey mudstone of Mid Albian age, and Upper Gault, made up of paler, more calcareous mudstone of Late Albian age. The boundary between the Lower and Upper Gault is placed at 12.50 m within Selborne 2 and at 44.97 m in Selborne 3. In general terms the Gault can be divided into three units based on lithology. The correlation between the geophysical and lithological logs in the boreholes is shown in (Figure 22).

An upper unit of the Upper Gault encountered between 51.92 m and 56.18 m in Selborne 1 comprises silty and very fine-grained sandy mudstone with pyrite (as bright grains, nodules and disseminated throughout the rock), mica and fine-grained glauconite. The silt and sand constituents pick out pale grey laminations and heavy bioturbation in a generally darker grey matrix. The unit is significantly more argillaceous than the basal Upper Greensand Formation above, and the core characteristically breaks up into short 3 to 5 cm lengths as it dries. A particularly well-laminated bed was noted between 53.86 m and 54.17 m.

The remainder of the Upper Gault (sampled between 56.18 m and 87.89 m in Selborne 1, from 4.90 m to 12.50 m in Selborne 2 and 24.90 m to 44.97 m in Selborne 3) comprises generally strongly bioturbated silty mudstone, with pyrite (as bright grains, nodules and disseminated throughout the rock), silt and fine sand-sized mica flakes, glauconite, and some phosphatic nodules, the latter more common in the lower part. Bioturbation is generally coarse but fine burrowing attributed to Chondrites is noted at several horizons. Less strongly bioturbated horizons demonstrate distinct fissility and are generally darker grey than surrounding beds. Shell fragments are common throughout the succession, but are particularly common above or below surfaces marked by concentrations of pyrite and phosphate nodules. One such horizon at 35.45 m in Selborne 3 is a burrowed contact with associated phosphatic nodules overlain by concentrations of Actinoceramus concentricus and represents the division between the Hysteroceras orbignyi Subzone (below) and H. varicosum Subzone (above). The base of the Upper Gault is marked by a burrowed contact overlain by beds (about 10 m thick) with fine sandy and coarse silt laminations, a number of burrowed surfaces and the last appearance downhole of the bivalve Actinoceramus sulcatus.

The Upper Gault proved in the three Selborne boreholes includes the Dipoloceras cristatum Subzone to Callihoplites auritus Subzone of the Mortoniceras (M.) inflatum Zone of the Upper Albian (Woods, 1998a).

The Lower Gault was proved in its entirety in Selborne 2 between 12.5 m and 60.52 m (47.92 m) and the uppermost Lower Gault between 44.97 m and 66.82 m in Selborne 3 (Figure 21). The upper part of Selborne 2, to a depth of about 20 m, is considered to be unreliable for thickness determinations due to the obviously sheared nature of the beds within landslide-affected ground. The Lower Gault comprises dark grey, becoming greenish dark grey downwards, bioturbated, sparsely silty mudstone, with some beds of more silty and fine-grained sandy mudstone with phosphatic nodules, mica, glauconite and pyrite. Regular concentrations of phosphatic nodules and Chondrites burrowing are a common feature. The lowest part of the Gault in Selborne 2 (below 58.31 m) is a bioturbated, glauconitic, fine- to medium-grained sandy mudstone with coarse-grained sand and fine, subrounded, quartz pebbles.

The macro- and microbiostratigraphy of these beds is discussed in Woods (1998a), Woods et al. (2001) and Wilkinson (1997b; 1998) they are considered to span the Hoplites dentatus Zone to Euhoplites lautus Zone of the Middle Albian.

Petersfield–Liss area

There are very few good exposures of the Gault clay in this area. Calcareous blue clay with phosphate and pyrite nodules were formerly exposed in a pit at Stroud [SU 721 235], together with a few fossils indicative of the Middle Albian Hoplities dentatus Zone (Osborne White, 1910). Two pits at Steep Marsh [SU 752 262] and [SU 756 262], exposed dark grey silty clay with selenite and phosphatic nodules Osborne White, (1910) recorded Hoplities interruptus in both pits.

Another section at West Liss [SU 759 286] exposed 4.5 m of poorly stratified, stiff, bluish grey, calcareous clay with a few phosphatic nodules, becoming more silty, micaceous and greyish brown towards the southern end. Fossils collected from this pit (Osborne White, 1910) include Hoplities interruptus, Inoceramus concentricus, Lima (mantellum) gaultina, Pecten (syncyclonema) orbiclaris and P. (neithea) quinquecostatus, indicative of the dentatus Zone.

Upper Greensand Formation (UGS)

The Upper Greensand Formation (Figure 23) crops out in a broad outcrop from Binstead in the north where it forms a prominent spur over the Gault clay plain, south through East Worldham, Selborne and Hawkley. In this area it forms a well-developed cuesta. From here southwards the outcrop narrows markedly, often in places less than 500 m wide and tucked up beneath the Chalk scarp, as it passes through Steep and Langrish.

The Upper Greensand Formation consists of bedded, pale yellow-brown, pale grey and greenish grey, bioturbated siltstone and silty very fine-grained sandstone with variable amounts of mica and glauconite. The beds show a characteristically wispy-bedded structure due to small lenses of clay and sand. The characteristic small blocky brash weathers quickly to a greenish hue. In this district, there occur apparently lenticular masses of uniform siltstone that are very hard, grey to bluish grey, calcareous with a porcellanous texture and weather to a buff or white colour. These siltstones have been worked for building stone and are colloquially known as the ‘bluestone’ or ‘malmstone’. The latter term has also been used for the local facies of the Upper Greensand as a whole. The Upper Greensand forms a distinct, often landslide-affected, scarp along its crop from Petersfield to Binstead. It is between 35 and 40 m thick to the south of the district but thickens markedly northward to an estimated 50 to 60 m. The full thickness of the Upper Greensand was cored in a series of boreholes near Selborne (Hopson et al., 2001; Woods et al., 2001). In the Selborne 1 Borehole the Upper Greensand has a complete thickness of 45.8 m (Figure 24).

The Upper Greensand has been closely studied in its northern outcrop along the North Downs (Jukes-Browne and Hill, 1900; Dines and Edmunds, 1929, 1933; Dines et al., 1969) and by other authors (Hinde, 1885; Gossling, 1929). Osborne White (1910) describes the Upper Greensand of the Alresford district and notes that the ‘Malmstone appears to attain its greatest thickness - about 200 feet [about 61 m] - in the neighbourhood of Selborne’ but also that it ‘admits of no satisfactory division’.

A correlation based on the sections in the North and South Downs with that seen in the Selborne boreholes is given in (Figure 25). This clearly demonstrates that the Selborne Upper Greensand succession is between three and five times thicker in comparison with the northern and southern outcrops. In the northern outcrop, Owen (1975; 1996b) considers his unit A to be principally of Mortoniceras (M.) rostratum Subzone age whilst his units B to D are of M. (D.) perinflatum Subzone age (or possibly younger). Since macrofossil and microfossil evidence suggests that the comparable subzonal boundary in the Selborne 1 Borehole is at about 31 m, a correlation of units B to D of Owen with units Ai, Aii and B in Selborne 1 would seem appropriate. Whilst much of the Selborne 1 sequence contains sparse glauconite grains, a conspicuous ‘glauconite-rich event’ occurs a short distance above this biozonal change; similarly glauconite is apparent from lithological descriptions by Owen (1975; 1996b) and within the Chanctonbury Borehole (Young and Lake, 1988). In the absence of good biostratigraphical control in the sparse faunas of the Upper Greensand Formation this ‘perinflatum glauconite-rich event’ might prove reliable as a local chronostratigraphical marker.

It is tempting to equate Owen’s scheme (units A to D) with the crudely fourfold division in Dines and Edmunds (1933, fig. 11). Such comparisons would suggest that the ‘Passage Beds’ of the older literature equate to unit A of Owen and units C and D herein.

It would appear from the scant biostratigraphical information available that a second ‘event’ rich in glauconite grains at 44.65 m in Selborne 1 can be associated with the subzonal change from Callihoplites auritus to M.(M.) rostratum and can therefore be correlated with such a ‘glauconitic event’ in Gault facies at Folkestone (Bed XII) (Owen, 1975, 1996b; Morter and Wood, 1983; Owen, 1996b).

Details

Selborne 1 Borehole

The full succession of the Upper Greensand was cored from depths of 6.10 m to 51.92 m in Selborne 1 (SU73SW/22). Its top is marked by a strongly burrowed surface beneath the glauconitic sandy chalk of the Glauconitic Marl Member (Cenomanian) (Woods, 1998a). Its base at 51.92 m is placed at a low angle erosive surface separating generally ‘silty’ sediments from more argillaceous lithologies below.

Within the Upper Greensand Formation, five ‘members’ were identified in Selborne 1 Borehole; each distinguished by slight variations in lithology, glauconite and mica content, and colour. The succession is summarised in (Figure 24) and (Table 7). Photographs showing representative sections of core from the five Upper Greensand lithological units are shown in (Plate 3), (Plate 4), (Plate 5), (Plate 6) and (Plate 7).

In general terms the Upper Greensand comprises calcareous, strongly bioturbated, very fine-grained sandy siltstones and silty sandstones, which become more argillaceous with depth. Petrological analysis (Lott, 1999) demonstrates that the coarse silt and fine sand constituents are of biogenic silica and calcite, with glauconite and detrital quartz in variable proportions and that these grains are set in a variably argillaceous, siliceous, and micritic matrix. Pyrite nodules and fragments (up to about 20 mm diameter) are present throughout, and detrital mica is also common. The upper part of the succession is very pale greyish yellow-brown becoming progressively (in distinct bands) grey downwards. Below 26.64 m the Upper Greensand is pale grey becoming dark grey towards its base.

The sparse fauna (Woods et al., 2001) indicates the uppermost Mortoniceras (M.) inflatum Zone, Callihoplites auritus Subzone at the base of the formation up to the Stoliczkaia dispar Zone, Mortoniceras (M.) rostratum Subzone and (?) Mortoniceras (Durnovarites) perinflatum Subzone. The boundary between the zones is tentatively placed between 44 and 45 m. This places the Upper Greensand of the Selborne area within the Upper Albian.

Binsted area

The Upper Greensand is commonly exposed in the banks of many of the roads and lanes which radiate from the village of Binsted. Several small quarries occur in the area. A small disused quarry at Mill Court [SU 7561 4165] exposes up to 9 m of massive, firm, calcareous, bedded, pale yellow-brown, pale grey and greenish grey, bioturbated siltstone and silty, very fine-grained sandstone interstratified with soft laminated sandstone in the upper part. According to Osborne White, (1910) ‘Pecten (Syncyclonema) orbicularis J. Sow. is fairly common here, and P. (Neithea) quinquecostatus J. Sow. also was noted.’

Between River Hill Farm and Binsted Place, a quarry on the south side of the road [SU 7873 4110], shows about 10 m of beds approximately 20 to 30 m above the top of the Gault. The section displays 10 m of light grey to white, massive bioturbated siltstone and silty very fine-grained sandstone, with hard blue lenticles, interbedded with grey to brown, soft silty bioturbated fine-grained sandstone with clayey seams and small brown phosphatic nodules. Two other exposures nearby were recorded by Osborne White, (1910); one a poor exposure of massive fine-grained sandstone in the road cutting by River Hill Farm, whilst higher beds can be seen in the side of the same road, between Binsted Place and the sunken cross-roads in Binsted village.

A small exposure in a disused quarry near Wheatley [SU 7856 4058] exposed 6 m of well-bedded pale sandy siltstone, becoming more marly towards the base.

East Worldham–Selborne area

There are many good exposures of the Upper Greensand in roadside banks throughout the district most notably around Empshott [SU 752 313], east of Stairs Hill Farmhouse [SU 757 314], on the broad dip slope east of Selborne, at [SU 7515 3598], west of Hartley Wood [SU 7515 3598], near East Worldham House [SU 7515 3805] and on the extensive dip slope area around East and West Worldham. Osborne White, (1910) noted about 20 m of Upper Greensand in a road section (Plate 8) north-west of Candover’s Farm, 1 km south-east of West Worldham [SU 7519 3597], mostly consisting of grey, flaggy ‘malmstone’ with occasional concretions and beds of harder, blue cherty stone. The Upper Greensand was also noted from road sections between here and West Worldham.

The banks of Hollow Lane, Selborne (now known as Honey Lane) around [SU 74 33] provides a good section of grey and grey-brown silty very fine-grained sandstone about 10 m below the base of the Chalk. Near the middle of the section, Osborne White, (1910) noted a bed of hard, blue to blue-grey calcareous stone with casts of tubular borings and fragments of Ostrea and Pecten (Syncyclonema) orbicularis. In the softer calcareous beds below, specimens of Exogyra and Schloenbachia (probably a misidentification of Callihoplites as Schloenbachia is a Cenomanian form) were obtained. The upper part of the Upper Greensand can be seen in several small road sections around Selborne.

Langrish–Hawkley area

Around Langrish, the Upper Greensand forms a prominent dip slope sloping gently to the west at around 2º to 3º. North of Langrish the outcrop becomes much narrower, possibly due to a steepening of the dip. An old quarry at [SU 7323 2549] shows up to 8 m of buff, blocky weathering siltstone. Small lane-side exposures occur around Steep at [SU 7380 2593] and around [SU 738 261]. South of Ashford Farm is a section which spans the Upper Greensand - Chalk boundary at [SU 7442 2647]. The upper surface of the greensand here is burrowed and infilled with glauconitic pebbly sand of the Glauconitic Marl.

The sunken lane from Steep Marsh to Hawkley [SU 7517 2690] to [SU 7532 2683] has intermittent poor exposures of blocky buff and grey bioturbated clayey siltstone. In the small quarry at the road junction [SU 7518 2691], Osborne White, (1910) noticed that the greensand here contained a considerable proportion of quartz sand in addition to glauconite.

Between Wheatham Farm and Hawkley, the outcrop widens. In the lane just east of Middle Oakshott Farm, Osborne White, (1910) recorded a rough-faced bluish bed of stone. Good exposures of some 2 to 4 m of blocky weathering buff and grey siltstone occur in the lane south-west of Hawkley [SU 7400 2876] to [SU 7430 2892]. An old quarry at Combe Hangar [SU 7495 2870] still reveals 2–3 m of blocky buff and grey clayey siltstone in beds up to a metre thick.

Chapter 5 Upper Cretaceous

Chalk Group

The Upper Cretaceous Chalk Group underlies much of the district, and is up to about 440 m thick. This unit forms the extensive scarp which extends north-south across the district (linking the prominent scarps of the North and South Downs) and the extensive downland to the west. Traditionally in this area the Chalk has been discussed in terms of its biostratigraphical zonation related to two conspicuous hard bands in the succession that divide the Chalk into three unequal parts. These are referred to as the Lower, Middle and Upper Chalk formations on the map. Subsequent to the printing of this map the terminology was developed further and this tripartite formational division has been superceded. The Chalk members shown on the map are now considered as formations within a Grey Chalk and White Chalk Subgroup and Chalk Group hierarchy. The current nomenclature is a development of the lithostratigraphical schemes devised by Mortimore, (1979; 1983; 1986a; 1986b; 1987) and by Bristow et al., (1995; 1997) and adopted by the Geological Society Stratigraphical Committee in 1999 (Rawson et al., 2001; Hopson, 2005). The nomenclature for the Upper Cretaceous utilised in this district is shown in (Table 2) where its relationship to the traditional scheme is also given.

A correlation chart for the inceptions and extinctions of microfossils (foraminifera), a zonal scheme based on those fossils and its relationship to the lithostratigraphical scheme and known markers is given in (Table 8).

In Cenomanian times, emergent land masses were present in south-west England, Wales, Scotland and Northern Ireland, and farther afield in Brittany and elsewhere. Southern Britain lay approximately 10º of latitude farther south than at present. Chalky sediments accumulated on the outer shelf of an epicontinental subtropical sea of normal salinity with little terrigenous input.

Grey Chalk Subgroup

This is essentially equivalent to the Lower Chalk of Bristow et al., (1997) but the youngest unit, the Plenus Marls is now included with the overlying Holywell Chalk. This unit, between 79 and 87 m thick comprises two formations, namely the West Melbury Marly Chalk Formation which is overlain by the Zig Zag Chalk Formation. The base of the West Melbury Marly Chalk Formation is marked by the Glauconitic Marl Member, an arenaceous, glauconitic, marly sandstone which provides a distinctive positive gamma-ray peak in downhole geophysical logs throughout southern England. The top of the Grey Chalk Subgroup is taken at the surface below the lowest marl of the Plenus Marls Member.

West Melbury Marly Chalk Formation (WMCk)

The West Melbury Marly Chalk Formation crops out in the area of gently sloping low ground directly in front of the main Chalk escarpment. Between Langrish and Selborne, the outcrop is quite narrow, in places less than 200 m wide. North of Selborne the outcrop widens to almost a kilometre to the west of Chawton where the basal feather edge climbs the Upper Greensand dip slope. It consists of buff, grey and off-white, soft, marly chalk and hard grey limestone arranged in couplets, forming a cyclic sequences of soft, pale to medium grey, marly chalks and thin, grey to brown limestones. The base of this succession is marked by a grey marl with a variable glauconite content, which rests on an eroded surface of the Glauconitic Marl and Upper Greensand. The thickness estimated from the outcrop, ranges from approximately 15 to 35 m. The basal marl with conspicuous glauconite is only a metre or so in thickness but sparse glauconite ranges up to 2 to 3 m into the overlying strata. A hard sponge-rich limestone, or closely spaced series of such limestones occurs 1 to 2 m above the basal bed and these may also contain sporadic glauconite grains.

A characteristic, pale greyish brown, rough textured, thin (10 to 30 cm) limestone packed with Schloenbachia marks the middle of the West Melbury succession. Woods (1994) tentatively equated this bed with the ‘M3 limestone’ at Folkestone (Gale, 1989). Above and below this limestone, a number of thin, grey poorly fossiliferous limestones occur. In general those below the distinctive limestone contain sponges. These limestones vary in hardness. Some appear locally as ‘cemented lenses’ and all are laterally impersistent, so that individual beds cannot be identified reliably by ‘counting up’ (or down) the sequence.

The Tenuis Limestone, where present, at the top of the sequence is similar in appearance to the ‘M3 limestone’. It is a pale greyish brown, rough textured calcarenitic limestone with Schloenbachia and is distinguished by the presence of I. tenuis and by its uneven hackly fracture (particularly after frost action). The West Melbury Marly Chalk includes all the chalk of the Cenomanian M. mantelli, M. dixoni and C. inerme zones and the basal part of the T. costatus Subzone (A. rhotomagense Zone). Biostratigraphically the Tenuis Limestone is placed at the base of the Turrilites costatus Subzone of the Acanthoceras rhotomagense Zone. The West Melbury Marly Chalk generally forms an aquitard between the Upper Greensand and the Zig Zag Chalk due to its high clay content.

Details

Large exposures of the West Melbury Chalk are rare and only small sections are seen in this district, principally along sunken tracks leading up to the scarp. A temporary exposure in road works near Holybourne [SU 7378 4092] showed up to 3 m of pale to dark grey marly chalk and thin limestones.

Osborne White, (1910) notes a pit 700 m south of Barleywood Farm, Upper Farringdon [SU 7283 35722] which showed about a metre of whitish grey marly chalk with Schloenbachia varians overlying the Glauconitic Marl and Upper Greensand.

A small degraded pit near Vann Farm, Empshott, a few metres stratigraphically above the Glauconitic Marl exposed about 0.5 m of pale greyish brown chalk marl with a thin bed of hackly fractured, spongiferous, limestone containing Inoceramus debris and Schloenbachia varians.

The degraded and partially water-filled pit near to the site of the Selborne 1 Borehole (SU73SW/22) at Frenchmare Copse exposes a small section [SU 7318 3491] of very pale greenish white, fine- to very fine-grained calcarenite with some phosphatic nodules. This section must be stratigraphically close to the level of the Glauconitic Marl. The Selborne 1 Borehole itself penetrated 6.10 m of the Chalk succession (Figure 27) of which the uppermost 4.29 m was uncored. From 4.29 to 4.69 m the core is green tinged very pale brown highly bioturbated argillaceous chalk (marl), speckled with very fine to coarse sand-grade glauconite grains which are estimated to constitute only 5 to 10 per cent of the deposit. The concentration of glauconite increases downwards to the sharp apparently planar base of this bed.

From 4.69 to 6.10 m depth, the lowest part of the West Melbury Marly Chalk Formation is composed of sand that is very pale brown speckled green becoming dark olive-green with depth; the sand is weakly cemented, heavily bioturbated, very fine- to medium-grained and consists of glauconite and quartz grains in a calcareous matrix (‘marl’). Phosphatic nodules were noted below 5.08 m with a concentration between 5.60 and 5.80 m. This bed is the Glauconitic Marl Member herein. Thin section analysis (Lott, 1999) shows that the detrital grains are dominantly coarser subrounded to rounded dark green glauconite (46 per cent), subangular to subrounded quartz (15 per cent) and globular silica (21 per cent), with minor amounts of muscovite mica, feldspar and phosphate as well as foraminifera and ostracod tests. The matrix is composed of micrite and detrital clay usually in patches or laminae with a sparse ferroan calcite cement (10 per cent).

Glauconitic Marl Member (GM)

The Glauconitic Marl Member comprises up to 2 m of partly indurated fine- to medium-grained, calcareous sand with black phosphatic nodules, 2 to 20 mm in diameter. It is bright olive green, highly glauconitic and bioturbated. This friable rock weathers to loose, dark green clayey sand. It consists of sand grade glauconite grains, up to 15 per cent quartz (mostly fine fine-grained sand) and accessory amounts of muscovite and feldspar in a poorly cohesive mix of clay minerals. Clay minerals including smectite make up 15 per cent of the marl. Dark green glauconite grains make up about 25 per cent of the rock, and range in size from 0.4 to 0.03 mm.

The Glauconitic Marl Member is apparently not present everywhere but this or the superposed ‘marl’ with glauconite grains (the basal part of the West Melbury Marly Chalk) was consistently augered during surveys. Mapping suggests that there are two closely spaced sedimentary breaks in the succession at this level. The lower is the well-burrowed surface, associated with phosphatic nodules, at the base of the Glauconitic Marl Member and the higher at the base of the ‘marl’ with glauconite grains. It is erosion represented by this upper surface that cuts out the underlying Glauconitic Marl Member in places.

The disconformable and possibly erosional, contact with the underlying Upper Greensand can be observed in a quarry at [SU 7442 2647] where the upper surface of the greensand is burrowed and infilled with glauconitic pebbly sand of the Glauconitic Marl Member.

Palaeontological evidence shows that the Glauconitic Marl Member is of Cenomanian age but its base is probably very close to the Albian-Cenomanian boundary (Wilkinson, 1994; Woods, 1994). The contact of the Glauconitic Marl Member with the underlying Upper Greensand generally lies in low ground between the dip slope of the Upper Greensand and the primary Chalk escarpment. The contact between it and the overlying West Melbury Marly Chalk is generally proved by augering.

Details

The Glauconitic Marl Member is exposed and has been augered in a number of localities along the outcrop. A good exposure of the Glauconitic Marl was seen in the roots of a fallen tree next to a shallow pit at Stirvill’s Copse [SU 7503 4007] near Alton. This showed about 1 m of heavily bioturbated glauconitic sandstone containing marl clasts and phosphate nodules. The Glauconitic Marl was also well exposed in a 700 m-long stream section 100 m west of Stirvill’s Copse towards Neatham. It is seen again 350 m further farther downstream, in a stream bank section at [SU 7448 4102] where 1.5 to 2 m of highly bioturbated glauconitic sandstone is overlain by grey marly chalks, with blocks of greensand at the base.

A notable exposure south of Alton occurs at Water Lane [SU 7315 3810] to [SU 7330 3800] (Figure 26). The strongly burrowed surface associated with phosphatic nodules between beds 5 and 6 represents a major widespread hiatus and has been noted commonly around this part of the Weald and Woods (1996b) suggests that this burrowed horizon is also the Albian-Cenomanian boundary. The youngest Albian Praeschloenbachia briacensis Subzone has been removed over most of southern England at this event.

Osborne White, (1910) noted a pit 700 m south of Barleywood Farm, Upper Farringdon [SU 7283 35722], where just over a metre of firm micaceous glauconitic sandy marl with brown phosphatic nodules was observed, sandwiched between the West Melbury Marly Chalk and the underlying Upper Greensand into which the glauconitic material was piped.

In the Selborne 1 Borehole [SU 73200 34940], see (Figure 27) the Glauconitic Marl Member rests on a strongly burrowed surface developed in the Upper Greensand and the glauconite-rich ‘marl’ lithology is found down to at least 6.40 m within the Upper Greensand. Isolated pockets of glauconitic sand thought to have been carried deeper by concealed burrowing were encountered to 7.40 m. The macrofauna here and at the Water Lane section is dominated by the bivalves Aucellina gryphaeoides, Aucellina sp. (with a striate umbonal ornament), Pliculata minuta, Entolium orbiculare and Cucullaea obesa, and the brachiopods Grasirhynchia grasiana, Gemmarcula canaliculata and Terebratulina protostriatula (Woods, 1998a). These indicate that the beds are Lower Cenomanian Mantelliceras mantelli Zone, Neostlingoceras carcitanense Subzone. Owen (pers. comm., 2000) noted that a local amateur collector obtained much material including ammonites from a road widening section within Selborne village, unequivocally confirming this subzone.

Thin-section analysis from a sample taken at 5.48 m in Selborne 1 Borehole shows that the Glauconitic Marl Member is dominated by poorly sorted subangular to subrounded detrital monocrystalline quartz, together with some coarser subrounded to rounded glauconite grains in a micritic and argillaceous matrix (Plate 9). Some muscovite, feldspar, phosphatic grains and common foraminifera also occur.

The contact of the Glauconitic Marl Member with the remainder of the overlying Chalk Group was recorded by Osborne White (1910) in a small road section in Gracious Street, Selborne [SU 7387 3362]. He recorded approximately a metre of dark grey-green speckled marly glauconite sand with brown phosphate nodules overlying 1.2 m of dull brown-grey, flaggy silty sandstone and brown grey malmstone. Osborne White (1910) reported the following fauna ‘Pecten (Syncyclonema) orbicularia., Plicatula sp., Pleurotomaria perspective, Schloenbachia varians and Lamna appendiculata’ from this locality.

Augering proved glauconitic sand at intervals from near [SU 7507 3150] Grange Farm, Empshott to Ketcher’s Farm [SU 7443 3300] in Selborne. The Glauconitic Marl-Upper Greensand contact was formerly exposed in the cutting immediately to the south of Ketcher’s Farm but this section is now degraded. The water supply memorial to Gilbert White opposite the farm must be built on the Glauconitic Marl. The degraded and partially flooded pits either side of Hall Lane [SU 732 350] 500 m east of Norton Farm must have exposed the lowest part of the Grey Chalk Subgroup including the Glauconitic Marl Member. This sequence was sampled in Selborne 1 Borehole (SU73SW/22), see (Figure 24) and (Figure 27) and the glauconitic sand was augered locally during the survey.

The contact between the Upper Greensand and the Glauconitic Marl was also seen in a drainage ditch [SU 7405 3003] 500 m due south of Vann Farm and olive green glauconitic sand was augered at intervals from there northwards along crop to just east of Quarry Farm, Empshott Green [SU 7430 3105].

West of Langrish, the Glauconitic Marl Member is buried beneath head, but it was augered at many localities between here and Steep Marsh, especially along the lane around [SU 2428 2677]. Here an old pit may have once worked the Glauconitic Marl Member as a building stone. Around Wheatham Farm [SU 7511 2717], the clay is pebbly. Between Wheatham Farm and Oakshott, the Glauconitic Marl Member can be readily seen and augered in road banks and fields. The junction of the Glauconitic Marl Member with the Upper Greensand can be identified in a number of the sunken lanes around Oakshott and Hawkley at [SU 7452 2784]; [SU 7410 2786]; [SU 7402 2802] and [SU 7404 2811] and by augering almost continuously to Empshott.

Zig Zag Chalk Formation (ZCk)

The Zig Zag Chalk Formation is composed of mostly firm, pale grey to off-white blocky chalk and the lower part is characterised by rhythmic alternations of marls and marly chalks with firm white chalk. Thin gritty, silty chalk beds act as markers in the sequence. The lower part is more marly and contains some thin limestones. In this district the Zig Zag Chalk is estimated to be between 30 and 75 m thick.

The Zig Zag Chalk outcrops along the face of the main Chalk escarpment between Alton and Langrish. The crop is particularly narrow around Steep and Wheatham Hill but widens significantly around Selborne where it forms the floor of several deep valleys. Around Alton, it forms a gently sloping bench at the foot of the escarpment, possibly created by the River Wey. The formation is seen again in the south of the district around Warnford, where it crops out in the Warnford Dome. In the north of the district around Alton and Chawton, part of the outcrop of the formation is obscured by superficial deposits.

The base of the Zig Zag Chalk Formation is commonly at a strong negative slope break at the base of the Chalk escarpment, especially in the south of the district. This abrupt change in slope appears to correspond with the incoming of thick beds of firm to hard blocky chalk above the gently sloping ground underlain by the West Melbury Marly Chalk. Around Chawton this feature is less apparent, but can still be recognised locally. The top of the formation is placed below the Plenus Marls Member of the succeeding formation and this is frequently identified as a weak negative slope break beneath the strong bluff developed on the Melbourn Rock Member.

The base of this formation is taken at the erosional contact at the base of the ‘Cast Bed’ (in the Southern Province). The Cast Bed (Bristow et al., 1997) is a very fossiliferous silty chalk immediately above the Tenuis Limestone (where this is present), and is the direct equivalent of Bed C1 of Gale (1995).

The lower part of the formation has a greater marl content and contains some thin limestones. Some distance above the base of the formation, hard, pale grey, splintery limestones with conspicuous Sciponoceras may occur. The upper part of the Zig Zag Chalk tends to be less marly, pale grey to white, firm, marly chalk with common Inoceramus pictus and the echinoid Holaster subglobosus. This colour change is thought to occur at the level of ‘Jukes-Browne Bed 7’ (a calcarenite bed with phosphatic nodules). No flints are recorded in this area. The upper limit of the Zig Zag Chalk is taken at the base of the Plenus Marls Member. The base of the formation falls within the basal Turrilites costatus Subzone and the top is coincident with the top of the Calycoceras guerangeri Zone.

Details

Brash associated with the Cast Bed was noted adjacent to the River Wey at [SU 7321 4024], on the A31 roundabout at [SU 7343 4010] and in a field 200 m south-west of Neatham Manor [SU 7397 4043].

Small sections along the Zig Zag Path, Selborne [SU 741 332], expose levels of the Zig Zag Chalk throughout the sequence and give an overall perspective of the change from grey interbedded limestones and marls at the base up through off-white soft to moderately hard marly chalks up to the large blocky creamy coloured chalks immediately below the Melbourn Rock. Despite its title this is not the locality from which the Zig Zag Chalk derives its name (which is from Zig Zag Hill, near Shaftsbury in Dorset). The name is that coined by Gilbert White who created and planted the hedges along this switchback path up to one of his favourite lookout points.

Field brash examined to the north-east [SU 7411 3919]; [SU 7410 3921] of Clay’s Farm, East Worldham included an extensive fauna of principally bivalves and brachiopods. The collection included very common Entolium orbiculare and Oxytoma seminudum as well as the brachiopods Capillithyris squamosa and Kingena sp., which are particularly indicative of the Cast Bed at the base of the Zig Zag Chalk. The association of this fauna with a buff coloured, silty chalk and the presence of internal moulds of gastropods, from which the Cast Bed derives its name, confirms the stratigraphical horizon.

A degraded quarry at Northfield Hill [SU 7320 3400] showed about 4 m of discontinuously exposed pale grey, marly chalk overlain by a prominent bed of hard, gritty, calcarenite chalk. The fauna in the marly chalk included Plicatula inflata, Pycnodonte vesiculare and Entolium orbiculare together with a questionable Turrilites costatus, and in a stratigraphically lower section, Inoceramus tenuis. Only fish teeth, an indeterminate terebratulid and phosphatic clasts were collected from the calcarenite. Woods (1996a) suggests the T. costatus subzone and tentatively equates the calcarenite with part of the Cast Bed somewhat akin to the Totternhoe Stone. Interestingly, Jukes-Browne and Hill (1903) also identify similar calcarenites in pits south-south-east of Alton Station around [SU 727 390] and north-north-east of Farringdon [SU 714 361] which they also noted as similar to the Totternhoe Stone. They suggested that this bed was some 60 to 65 feet (about 18.3 to 19.8 m) below the Melbourn Rock.

About 12 m of greyish massive chalk with occasional pyrite concretions were formerly exposed in a lime works quarry at Wilsom 0.5 km south of Alton Station (Osborne White, 1910). The contact with the overlying Holywell Nodular Chalk was identified here. The strata dip to the south-east at between 10º and 3º. Zig Zag Chalk was also formerly exposed in a small quarry near Farringdon [SU 7085 3564], where about 6 m of strata was observed (Osborne White, 1910).

The Watercress Line cutting section at Mount Pleasant [SU 717 388] to [SU 720 391] is greatly overgrown but shows blocky smooth moderately hard cream to white and flaggy soft to moderately hard chalk in brash and small sections. Inoceramid fragments, possibly Inoceramus pictus, indicative of a level high in the Zig Zag Chalk were found beneath the Windmill Hill bridge.

A poor exposure of the Zig Zag Chalk is exposed in a pit at the base of the eastern spur of Wheatham Hill [SU 7091 2704]. This section was formerly noted by Osborne White, (1910) who identified 16.5 m of interbedded bluish grey marly chalk. He also noted about 20 m of unfossiliferous strata exposed in a quarry on Farrow Hill, near Hawkley around [SU 736 290]. Jukes-Browne and Hill (1903) noted some gritty chalk in this quarry similar to that seen near Alton and Farringdon (see above), about 18 m below the base of the Holywell Nodular Chalk.

A pit 250 m north-west of St John’s Church, Langrish [SU 7020 2403] exposes about 20 m of massive-bedded, pale grey, very poorly fossiliferous chalk with thin marly horizons. Fossils identified from the upper part of the sequence include Inoceramus pictus and thin-shelled echinoids suggesting the higher part of the formation above the lower part of the A. jukesbrownei Zone.

The Zig Zag Chalk crops out along the lower slopes of the inward facing Warnford Dome, but there are no significant exposures although exposures are known to the south in the Fareham (316) district (316) (Hopson, 1996).

White Chalk Subgroup

The White Chalk Subgroup is essentially the combined Upper and Middle Chalk Formations of Bristow et al. (1997). In the Southern Province, it is defined as the succession from the base of the Plenus Marls Member of the Holywell Nodular Chalk Formation up to the youngest chalk beneath the unconformity at the base of the overlying Palaeogene or Quaternary deposits (Hopson, 2005). The base of the Holywell Nodular Chalk Formation in present practice includes the Plenus Marls Member. In general the White Chalk Subgroup is characterised by white chalk with numerous flint seams, with nodular chalks in the lower part. The White Chalk is divided into seven formations (Table 2), six of which occur in this district with the omission through erosion of the youngest Portsdown Chalk Formation. Up to 340 m of the White Chalk is estimated to outcrop in this district.

Holywell Nodular Chalk Formation (HCk)

The Holywell Nodular Chalk Formation (Holywell Chalk Member on the map) comprises generally hard, nodular chalks with flaser marl seams throughout. Three units can be identified. In ascending stratigraphical order, these are the Plenus Marls Member, the Melbourn Rock Member and an unnamed succession of hard nodular and grainy chalks with abundant shell debris most notably species of Mytiloides. It crops out along the face of the primary Chalk escarpment between Alton and Langrish and on the northern side of the Warnford Dome around Warnford. South of Hawkley, the outcrop is very narrow, often usually less than 200 m wide. It also crops out in a small inlier in the deep valley just north of Cheesefoot Head [SU 530 282], and is between 15 and 30 m thick based on field estimates. The Melbourn Rock Member generally forms a strong positive feature and characteristic brash that can be traced around the outcrop.

The Plenus Marls Member is rarely well exposed but is present along the whole outcrop of the Holywell Nodular Chalk Formation. The Plenus Marl Member consists of an alternating succession of blocky white chalk and medium grey silty marl beds, mostly between 1 and 20 cm thick, though the highest, Jefferies’ Bed 8 (Jefferies, 1963), can be up to 50 cm thick (Bristow et al., 1995). The Plenus Marls, coextensive with the greater part of the Metoicoceras geslinianum Zone, contain common Inoceramus pictus, as well as the eponymous belemnite Praeactinocamax plenus.

Overlying the Plenus Marls is the Melbourn Rock Member, a very hard, grainy nodular chalk generally lacking in shell detritus. The top of the Melbourn Rock is recognised by the incoming of abundant bivalve shell debris. It is a feature-forming unit up to 3 m thick. The overlying shell detrital and grainy chalks form a narrow outcrop in the face of the primary scarp. In places, mainly on the less steep slopes, they form a positive feature. The top of the Holywell Nodular Chalk Formation is characterised by the transition to smoother, softer New Pit Chalk, but in practice is taken at the highest recognisable shell-detrital chalk during surveying.

The Holywell Nodular Chalk spans the Cenomanian-Turonian boundary with that boundary close to the top of the Melbourn Rock Member. The greater part of the Holywell Nodular Chalk is in the Mytiloides spp. Zone (this usage follows Hopson, 1996). The base of Gaster’s ‘I. labiatus Zone’ coincides with base of the Melbourn Rock. The formation covers the Metoicoceras geslinianum Zone, the Neocardioceras juddii Zone (entirely in Melbourn Rock facies) and much of the Mytiloides spp. Zone.

Details

The Plenus Marls Member at the base of Holywell Nodular Chalk was identified in field brash immediately beneath the Melbourn Rock at a number of localities [SU 734 310] near Goleigh Farm, at [SU 737 314]; [SU 742 314]; [SU 7405 3175]; [SU 7470 3205] (including an example of P. plenus)] in the vicinity of Noar Hill, near Hale Copse [SU 7320 3205] and north of Newton Farm [SU 716 339]. At each locality, yellow or green marl fragments were identified within a generally creamy white, smooth, blocky chalk brash.

The Plenus Marls was formerly exposed in an old chalk pit at Wilsom [SU 7250 3932], 0.5 km south of Alton Station (Osborne White, 1910). Here, about 2.5 m of dark grey laminated marl containing rounded fragments of grey massive marly chalk and grey marly chalk with ‘A. plenus’overlies greyish massive chalk (Zig Zag Chalk). The marls are in turn overlain by 2–3 m of hard white nodular chalk with small bored nodules of hard brown chalk. The Plenus Marls were also noted in a road cutting around [SU 7290 4174], north-west of Holybourne Church, and in a section in a lane bank [SU 7281 3013] 2 km north-west of Hawkley Church. Here 0.3 m of grey marly chalk is overlain by 0.6 m of pale yellowish grey, firm blocky, chalk with ferruginous staining and 0.3 m of dull, greenish grey to buff laminated marl (Osborne White, 1910).

There are few exposures of the Holywell Nodular Chalk north of Alton, but locally it produces a very conspicuous brash, and occasional some exposures in the road cuttings north-west of Holybourne church. Osborne White (1910) noted a good section in a pit at [SU 7211 4056]. Here, 4 m of hard nodular chalk is interbedded with thin, greyish white, laminated marly chalk dipping at 5º to the north-east.

The characteristic intensely hard, nodular chalk of the Melbourn Rock Member at the base of the Holywell Nodular Chalk is easily traced from north of Alton to the west of Farringdon around Selborne and Old Noar hills and southwards to Hawkley. It also forms outliers at Neatham Down [SU 734 394], underlies south Alton [centred on 722 388 (Windmill Hill)], to the east of Chawton House [SU 711 371], north of Farringdon [SU 711 357], capping the ridge from Annett’s Farm [SU 706 347] to Bush Down [SU 727 343] and near Noar Hill Hanger [SU 746 315]. The summit of Noar Hill [SU 7413 3188] is pock-marked by a large number of shallow pits with some exposures of rough, nodular chalk (Osborne White, 1910).

The Watercress Line cutting between Mount Pleasant and Newtown [SU 715 387] exposes the top of the Melbourn Rock and the lower part of the remainder of the Holywell Chalk. At the time of survey this cutting was heavily overgrown with no clear sections, however, brash from numerous small scrapes and burrows confirmed the characteristic intensely hard nodular chalk of the Melbourn Rock overlain by grainy hard nodular and flaggy chalks with a few pink inoceramid shell fragments. Osborne White, (1910) noted a 3 m section of hard, iron-stained nodular and flaggy chalk in a pit by the railway line, probably at [SU 7023 3768], faulted against soft white homogenous chalk (New Pit Chalk).

A small exposure [SU 7391 3195] about 100 m east of Charity Farm exposes about 6.5 m of interbedded hard nodular chalk and thick marls (Figure 28). Comparison of lithologies and the contained fauna with the standard Sussex succession suggest that this section covers the interval between the Pilot Inn Marl and the top of the sequence containing the Meads Marls.

Higher beds within the Holywell Nodular Chalk were seen in new exposures for silage pits at Newton Valence Place Farm [SU 722 334]. Here sections up to a maximum of 5 m high showed hard grainy nodular chalks overlain by similar chalks packed with pink Mytiloides sp. shell debris. These probably equate with the first up-sequence acme of this inoceramid and therefore upper Holywell Chalk can be inferred.

Much of the Holywell Nodular Chalk and the transition to the overlying New Pit Chalk was formerly seen in many small roadside sections on the lane between Newton Valence and Hawkley around [SU 731 317] and [SU 727 323] (Osborne White, 1910). Another exposure at [SU 7149 3240] yielded hard nodular chalk with Mytiloides mytiloides.

Field brash on the Holywell Chalk throughout the district suggests that there is a northwards reduction in the incidence of very shelly chalks in the higher part of the Holywell sequence. Northwards, outside the district, shelly chalks again form a significant part of the Holywell sequence (Farrant, 1997).

In the west of the district, shelly, hard, grainy chalk brash has been identified on the floor of the coombe [SU 530 244] beneath Cheesefoot Head, and around Warnford [SU 6167 2324], but there are no exposures.

New Pit Chalk Formation (NPCk)

The New Pit Chalk Formation, between 25 and 45 m thick, consists of smooth, white, firm to moderately hard chalks, massively bedded, with regularly spaced pairs or groups of marls, each up to 15 cm thick. Locally, sporadic small flints occur in the uppermost part of the succession. It crops out towards the top of the primary Chalk escarpment between Alton and Langrish, capping the spur around Newton Valence, but in many places its outcrop is masked by superficial deposits, chiefly the clay-with-flints and older head. South of Hawkley, the outcrop is very narrow, often in places less than 200 m wide. It also crops out on the northern side of the Warnford Dome around Warnford and north of East Meon, and in a small inlier in the deep valley just north of Cheesefoot Head [SU 530 282] in the west of the district.

The top of the New Pit Chalk (as defined by Hopson, 2005 in Sussex) is conformable at the base of Glynde Marl 1 in Sussex, but with one of the higher marls elsewhere although invariably it occurs in the interval Glynde Marls to Southerham Marls in the Southern Province. The mapping boundary is placed at the appearance of nodular chalks and significant flint development that generally occurs between Glynde Marl 1 and Southerham Marl. In this district, flints are confined to the upper half of the succession although elsewhere they are known to occur sparsely even down to within a few metres of the base of the formation. The New Pit Chalk forms sloping ground within the primary Chalk escarpment, above the first positive feature. It is usually softer than both the Holywell and the Lewes Chalks, below and above respectively, and it may form a slight negative feature in the scarp.

The base of the New Pit Chalk is marked by the upward disappearance of inoceramid-rich (M. mytiloides) nodular chalk at the level of the Gun Gardens Main Marl. The fauna is much sparser than in the Holywell Chalk and mostly comprises brachiopods (both terebratulids and rhynchonellids) rather than abundant inoceramid bivalves. Thin shelled Mytiloides hercynicus/subhercynicus are present but tend to be flattened and preserved as chalky moulds. The New Pit Chalk belongs to the uppermost part of the Mytiloides spp. Zone and all but the highest part of the Terebratulina lata Zone.

Details

There are many small pits throughout the outcrop but most are degraded or show only a few metres of poorly fossiliferous blocky white chalk. A small exposure near Cadnam Farm, Alton [SU 7205 4139] shows 2.3 m of firm, slightly marly chalk with occasional small flints, bisected by a 20 cm-thick pale grey brittle marl seam with Lewisceras peramplum and other fossils diagnostic of the upper T. Lata Zone (Figure 29). The prominent marl seam is likely to be one of the typically thick New Pit Marls.

A small exposure at [SU 7015 3395], near Pelham Place, East Tisted, showed 1.3 m of large blocky, soft to moderately hard, smooth, white, chalk with a 15 cm marl seam. The fauna includes the brachiopod Terebratulina lata, the inoceramid bivalves Inoceramus cuvieri and I. lamarcki as well as the echinoids Conulus subrotundus and Discoides minimus that indicate the T. lata Zone (Woods, 1996a). The faunal and lithological association suggest a level around the New Pit Marl 1 at which level the fossils are known to be common.

There are limited exposures of the New Pit Chalk in the west of the district. Numerous scrapes and burrows on the steep lower slopes of Cheesefoot Head Coombe [SU 528 280] and as field brash beneath Telegraph Hill [SU 524 282], both show soft to firm white blocky chalk with only rare flint nodules.

An exposure [SU 6844 2294] in an old pit 1 km north of East Meon reveals 4 m of soft, greyish white to white, blocky chalk containing a few beds of nodular flints and a marl seam 1.7 m above the base. Inoceramus cuvieri and Terebratulina lata were noted from here; the co-occurrence of T. lata and I. cuvieri suggests assignment to the upper T. lata Zone (Mortimore, 1986a) in the higher part of the New Pit Chalk.

Around Warnford, several exposures within the upper part of the New Pit Chalk were seen (Figure 30). A section at Well Bottom [SU 6084 2327], exposes around 6 m of soft white blocky and flaggy chalk, from which Inoceramus cuvieri, which characterises the higher part of the T. lata Zone was obtained. Osborne White, (1910) recorded just over 10 m of chalk in a pit 350 m east of Warnford Bridge at [SU 6270 2312]. The section consists mainly of soft to firm white chalk, locally iron stained and with a few small phosphatic concretions with a 10 cm thick marl seam just below the top of the section, and another thinner marl seam at the base. The very top of the section above the thick plastic grey marl is very hard and nodular, tentatively suggesting basal Lewes Chalk which would therefore equate the marl to the Glynde Marl 1 or the Southerham Marl of the standard Sussex succession (Mortimore, 1986a). The chalk dips at 15º to the north and is in the T. lata Zone, specimens of which were found here.

A heavily overgrown and degraded cutting, adjacent to Hayden Barn [SU 6335 2292] on the southern margin of the district, for the now disused Meon Valley railway line, must have shown a complete section through the New Pit Chalk but only small exposures of large blocky white chalk were seen during the survey. Both these sections have been assigned to the Terebratulina lata Zone principally on the basis of their lithology and relative position in respect to the overlying Lewes Chalk. The railway cutting is almost certainly the one recorded by Osborne White, (1910), who noted a considerable thickness of firm, white closely jointed chalk with thin layers of light- grey marl dipping 20º north-east. Small asteroid ossicles were reported by Osborne White (1910) together with ‘T. lata and Ostrea vesicularis’ from here.

Lewes Nodular Chalk Formation (LeCk)

The Lewes Nodular Chalk Formation comprises interbedded hard to very hard nodular chalks and hardgrounds with soft to medium/hard chalk and marls and some griotte chalks. The nodular chalks are typically lumpy and iron-stained, this iron-staining usually marking sponges. Brash is rough and flaggy and tends to be dirty. The first regular seams of flint appear near the base. The flints are typically black or bluish black with a thick white cortex. Sheet flints are common.

In the standard Sussex succession the Lewes Nodular Chalk includes the strata from the Glynde Marl 1 to the base of the Shoreham Marl 2 (Mortimore, 1986a) but this was subsequently modified in Mortimore and Pomerol (1996, fig. 2), where the Lewes Nodular Chalk commences above the marl at the inception of nodularity. In exposed sections the Lewes Nodular Chalk can be divided informally into two units. The lower is mainly medium- to high-density chalks and conspicuously iron-stained hard nodular chalks whilst the upper is mainly low to medium-density chalks with regular thin nodular beds. Between the two informal units the boundary is marked by the Lewes Marl and an extensive system of black cylindrical burrow-form flints called the Lewes Flints. The upper Lewes Nodular Chalk is further distinguished by the occurrence of the bivalve Cremnoceramus (Mortimore, 1986a). There are several levels of sheet flint within an interval of 4 or 5 m in the lower part of the upper Lewes Chalk. The Lewes Chalk includes the top of the Terebratulina lata Zone, and all of the Plesiocorys (Sternotaxis) plana (formerly Sternotaxis plana) and Micraster cortestudinarium zones. The higher beds of the Micraster cortestudinarium Zone contain carious, ‘rinded’ flints.

The mapping base coincides with the incoming of hard nodular chalks just above the top of the New Pit Chalk. The first persistent seams of flint appear near the base. The flints are typically black or bluish black with a thick white cortex. The formation is generally between 50 and 55 m thick over much of its crop, but it may be as little as 40 m over the Warnford Dome and up to 70 m in the north-west of the district. The top of the formation is placed at the highest recognisable bed of nodular chalk below the incoming of smooth white chalks with Platyceramus. This part of the succession is also marked in this district by a belt of large nodular and carious black and grey flints that span the boundary between the Lewes Nodular Chalk and Seaford Chalk formations.

In this district, the Lewes Nodular Chalk Formation outcrops along the top of the primary chalk escarpment between Alton and Langrish, but much of its outcrop is masked by the clay-with-flints and older head. In places it also forms the dip slope behind the escarpment crest, particularly between High Cross [SU 711 265] and East Tisted [SU 701 318], and around Shalden [SU 698 417]. Its outcrop also extends a considerable distance up some of the dry valley networks that drain to the headwaters of the River Wey in Alton. The Lewes Nodular Chalk also outcrops on the northern side of the Warnford Dome between East Meon and Warnford, in a pair of inliers near Lomer [SU 590 235] and [SU 572 234], and in the core of the Winchester Anticline around Cheesefoot Head [SU 531 276].

Details

Numerous small chalk pits occur throughout the Lewes Nodular Chalk outcrop, but most are now degraded, only showing thin sequences of generally hard nodular chalks with flint seams. A section, in the lower part of the Lewes Chalk was logged near Becksteddle Farmhouse, East Tisted [SU 6980 3018] (Figure 31). The thicker and lower of the two marls in that section contained abundant specimens of the foraminifera Coskinophragma, a name used in Mortimore (1986a), but now called Labyrinthidoma, which suggests a correlation with the Southerham Marl 1 of Sussex. The fauna also included Spondylus sp. and Neithea quinquecostata within the marl, Spondylus spinosus, Plagiostoma hoperi, Inoceramus cuvieri and I. lamarcki, an assemblage that indicates the upper part of the T. lata Zone. Higher in the Lewes Chalk succession, a section near Plain Farm, East Tisted [SU 6920 3188] (Figure 31) included a fauna dominated by the bivalve Cremnoceramus (including ? C. denselamellatus) and with Micraster cortestudinarium indicating the Coniacian M. cortestudinarium Zone.

Small exposures at Greenwood Copse [SU 6897 3620] and near Wood Barn [SU 6923 3672] contain faunas indicative of the T. lata Zone low in the Lewes Chalk, whilst another degraded pit on the southern edge of Theddon Copse [SU 6913 3957] yielded Plesiocorys (Sternotaxis) plana the zonal index for part of the middle Lewes Nodular Chalk.

Numerous small exposures of very hard nodular or grainy chalk occur on the steep valley sides between Shalden and Alton, but there are very few large exposures. Of these, most occur in a series of small often overgrown pits. A pit south-east of Bentworth Lodge at [SU 6881 4047] shows 1.7 m of moderately to intensely hard highly nodular chalk with well-developed cone-in-cone structures. A short distance above the base of the section is a rich horizon of Micraster normannaie, indicative of the lower M. cortestudinarium Zone. Other exposures nearby [SU 6855 4081] contain fauna from the Plesiocorys (Sternotaxis) plana Zone in very hard blocky white chalk. A composite section (Figure 32) in a pit near Crossing Cottage [SU 6786 4133] displays about 5 m of very hard nodular chalk with a locally intensely hard phosphatised and spongiferous hardground near the base (Woods, 1997), and several large flint horizons. A marked change from strongly nodular to weak nodular chalk is possibly correlated with the Hope Gap hardground in Sussex (Mortimore, 1986a; Woods, 1997). The occurrence of M. normannaie and Cremnoceramus suggest assignment to the lower M. cortestudinarium Zone.

A pit [SU 6832 2980] adjacent to the old railway line 100 m south of Woodside Farm, near Monkwood provided a 2.45 m section. The lower part of the section exposed mostly soft, Zoophycos-rich chalk, overlain by conspicuously nodular, flinty, spongiferous chalk. Fossils include Plesiocorys (Sternotaxis) plana, S. placenta and Micraster normanniae, indicative of the Lewes Nodular Chalk, upper Plesiocorys (Sternotaxis) plana Zone. The pit was being filled in 1996. The Zoophycos-rich bed at the base of the section probably equates with the Cuilfail Zoophycos bed of Sussex, and thus the overlying nodular chalk probably represents the lower part of the complex of hardgrounds below the main Navigation Hardground.

A 4.6 m section of firm, locally weakly nodular and spongiferous chalk with regularly 40 cm-spaced, prominent horizons of mostly carious flints was exposed in a pit 550 m north-east of Basing Home Farm, near West Tisted [SU 6838 2880]. The fauna consists mainly of the bivalve Cremnoceramus, including C. brongniarti, (note: this species is now generally regarded as a synonym for other species defined within palaeontological work that post-dates this determination) indicating Lewes Nodular Chalk, probably M. cortestudinarium Zone. Material collected by Brydone (1912, locality no. 147), probably from the same or nearby locality, includes Micraster turonensis indicative of the upper Lewes Nodular Chalk or lower Seaford Chalk, upper M. cortestudinarium Zone or lower M. coranguinum Zone.

The Lewes Nodular Chalk was also exposed in a pit at the junction of Barnet Side and Kings Lane, Froxfield [SU 7041 2746]. Here, interbedded soft to firm and hard, spongiferous, nodular chalk yielded a fauna including abundant Terebratulina lata, and various Mytiloides and echinoid species, indicative of the upper T. lata and Plesiocorys (Sternotaxis) plana Zones of the Lewes Nodular Chalk. This is Brydone’s (1912) locality number 125. Several other small pits were noted by Brydone (1912), but only small exposures of hard to firm, nodular chalk can be seen today. A pit at Rodder’s Dell, Froxfield around [SU 710 269] (Brydone, 1912, locality no. 126) yielded Micraster leskei (large form) and M. precursor indicative of the middle and upper Plesiocorys (Sternotaxis) plana Zone of the lower to middle Lewes Nodular Chalk.

The pit 600 m south-east of the church at Froxfield Green [SU 7089 2515] exposes 6 m of nodular, iron-stained, gritty flinty chalk with an uneven fracture, and with 1 to 5 cm thick, very hard, phosphatic, nodular beds rich in shells and 1 to 5 cm thick. Several scattered nodular flint beds occur near the top of the section. The chalk here has a gentle apparent dip to the north-west. Fossils collected include Plesiocorys (Sternotaxis) plana, S. placenta, Micraster normanniae, possible M. precursor and Echinocorys aff. gravesi?, indicating the middle Lewes Nodular Chalk, upper Plesiocorys (Sternotaxis) plana Zone. Previous collections by C E Hawkins in 1889, (see Osborne White, 1910) and Brydone (1912, locality no. 127) also include M. precursor, M. normanniae and Plesiocorys (Sternotaxis) plana.

On the southern margin of the district, a series of small exposures in a track cutting from [SU 6666 2296] to [SU 6641 2249] south of Drayton Mill reveal up to 1 m of hard to quite hard, grey to white, nodular, locally gritty chalk. Brydone (1912, locality no. 128) collected Micraster leskei ? (small form) from the higher part of this cutting around [SU 671 229] which is tentative evidence for the lower to middle Plesiocorys (Sternotaxis) plana Zone of the Lewes Chalk (Mortimore, 1983, 1986a). Numerous small exposures, principally in nodular or grainy hard chalk were noted along the abandoned Meon Valley railway line, north of Hayden Barn [SU 6335 2292], Warnford.

The north face [SU 6938 2418] of a pit at Lower Bordean exposes up to 2.85 m of variably hard, iron-stained, nodular chalk with significant beds of nodular flint at 0.5 m (Flint A) and 2 m (Flint B) above the base of the section, and a conspicuous marl bed at 2.1 m above the base of the section (Figure 33), (see Woods, 1996b). Fossils collected below Flint B are mostly indicative of the Turonian uppermost Plesiocorys (Sternotaxis) plana Zone, and include Plesiocorys (Sternotaxis) plana, Echinocorys gravesi and Micraster normanniae. Those collected above Flint B, including Cremnoceramus rotundatus?, indicate the basal part of the Coniacian M. cortestudinarium Zone. The boundary of these two zones lies in the middle part of the Lewes Nodular Chalk.

Fragmentary and questionably identified inoceramid fauna, including Cremnoceramus, Platyceramus ? (shell fragments) and ? Volviceramus involutus (shell fragments), were collected from another pit at Lower Bordean [SU 6917 2447], suggesting assignment to the lower part of the M. coranguinum Zone. Micraster aff. coranguinum and M. turonensis ? were also collected, again suggesting the lower part of the M. coranguinum Zone. Where visible, the morphology of the periplastron in the Micraster specimens is coarsely ornamented, which is consistent with a level at or above the M. coranguinum Zone (Drummond, 1983). From this interpretation the lower Seaford Chalk of Mortimore (Mortimore, 1986a) might be inferred, but field evidence suggests assignment to the top of the Lewes Nodular Chalk.

Field brash near a filled-in pit [SU 6887 2459] west of Lower Bordean contains Micraster spp., with periplastron morphology suggesting assignment to an horizon in the upper part of the M. cortestudinarium Zone (Lewes Nodular Chalk), or even basal M. coranguinum Zone (Drummond, 1983), higher Lewes Chalk or basal Seaford Chalk.

Brash in a chalk pit just north-east of Bereleigh House [SU 6810 2379] contains the inoceramid bivalve Cremnoceramus sp., mostly indicative of the M. cortestudinarium Zone in the higher part of the Lewes Chalk (Mortimore, 1986a), although undescribed species also occur in the basal M. coranguinum Zone of the Seaford Chalk. However, the association of Cremnoceramus with terebratulid brachiopods also collected at the locality favours the M. cortestudinarium Zone. Brash around another pit 400 m east of this [SU 6842 2358] contains Cremnoceramus sp. (shell fragments), Mytiloides? and Micraster sp., suggesting the upper Plesiocorys (Sternotaxis) plana Zone and M. cortestudinarium Zone, upper Lewes Nodular Chalk.

In the west of the district, the Lewes Nodular Chalk is mapped extensively around the Chilcomb inlier. Hard to very hard, uneven fractured, dirty, nodular and grainy textured chalk brash with numerous large nodular flints are the main feature of Chilcomb Down [SU 523 288], Temple Valley [SU 536 283], Longwood Warren [SU 525 266] and Telegraph Hill [SU 523 282], but there are no significant exposures.

Seaford Chalk Formation (SCk)

The Seaford Chalk is composed mainly of soft white chalk with seams of large nodular and semi-tabular flint, some of which are very large and tracable over large distances. Near the base, thin harder nodular chalks also occur, associated with seams of carious flints, giving this lower part of the formation a similar appearance to the upper part of the Lewes Chalk. Therefore the boundary is not clear-cut in mapping terms. The base is conformable at the base of Shoreham Marl 2 in Sussex, that marks the change from regularly spaced nodular and grainy chalk beds of the upper Lewes Nodular Chalk Formation to smooth white chalks. Typical brash from the lower part of the Seaford Chalk contains an abundance of fragments of the bivalves Volviceramus and Platyceramus (Mortimore, 1986a). In the absence of these bivalves, the smoothness, flaggy-bedded nature and pure whiteness of the soft chalk serve to distinguish it from the Lewes Chalk below. The top of the formation is conformable at the Buckle Marl 1 in the Sussex succession.

Higher in the succession, the flints are black and bluish black, mottled grey with a thin white cortex, and they commonly contain shell fragments. Towards the very top of the unit (5 to 10 m below the Newhaven Chalk), a thin discontinuous horizon of intensely hard porcellanous silicified chalk, the Stockbridge Rock Member, can be identified in the extreme west of the district, but is not shown on the map. This unit becomes much more extensive and continuous farther west in the neighbouring Winchester district. It contains abundant sponge spicules, most commonly as moulds, together with some complete sponges and rare echinoids. This lithology is readily identifiable in the brash (forming equant, hard, blocky fragments up to about 5 cm across) and forms a useful marker horizon. Field evidence suggests that there might may be several thin, hard bands between 5 and 10 m below the base of the Newhaven Chalk, each separated by thin intervals of white chalk. Its patchy distribution in the Alresford district might be explained by variations in the level of cultivation, and therefore exposure, but it is also likely to be due to lateral changes in the degree of sedimentation/silicification. It occurs at a level less below the Barrois’ Sponge Bed and the Clandon Hardground of the North Downs (Robinson, 1986) and may equate with the Whitway Rock of the Newbury area (Sumbler, 1996). In Kent, Rowe’s Echinoid Band, a bed of about 30 cm containing an acme occurrence of Conulus sp. with other echinoids, occurs just above Barrois’ Sponge Bed and is inferred to occur above the Stockbridge Rock Member. Across this district the Seaford Chalk is estimated to range between 45 and 80 m thick.

Biostratigraphically, the Seaford Chalk is co-extensive with the Micraster coranguinum Zone and crosses the Coniacian-Santonian boundary, which is placed at the Michel Dean Flint (Mortimore, 1986a). This boundary is also marked by the incoming of Cladoceramus. Foraminifera are common in the formation and foraminiferal zones BGS14 to 17 can be recognised (Table 8).

Much of the outcrop is controlled by the underlying structure and the formation underlies much of the central and eastern part of the sheet. The Seaford Chalk principally crops out on the dip slope behind the primary Chalk escarpment (here developed mainly on the Lewes Nodular Chalk), and in the Alresford area where the headwater valleys of the River Itchen have cut through the overlying Newhaven Chalk, particularly around Bighton, Ropley and Bramdean. It also crops out along the line of the Winchester–Meon Pericline and around the margins of the Warnford Dome. However, across large parts of the district, particularly along the crest and the dip slope of the primary escarpment, much of the outcrop is obscured by extensive deposits of clay-with-flints. In these areas, the chalk is often exposed in pits dug for liming the surrounding clay soils.

Details

Around Bentworth, Medstead and Four Marks, the Seaford Chalk crops out in a band several kilometres wide on the dip slope behind the primary chalk escarpment, indented by several deep valleys. However, here the exposure is generally poor, often masked by clay-with-flints and restricted to field brash and isolated chalk pits. Many of these pits are degraded and only provide small exposures.

A series of pits around Bentworth, Medstead and Beech all show similar soft white chalk sequences with well developed flint seams. They all show close associations of the bivalve Platyceramus sp. and the echinoid Conulus sp., and in a number of cases M. coranguinum and the crinoid Bourgueticrinus sp., this indicates that all the sections are within the Santonian part of the M. coranguinum Zone. The largest exposure in the district north-east of Bentworth [SU 6691 4125], shows 4 to 5 m of smooth blocky white chalk with occasional Platyceramus. This pit is however, not logged in detail as much of the face was inaccessible. Due east of Bentworth are a couple of large pits; one at [SU 6743 4050] has no exposure, but the largest at [SU 6716 4034] displays 4.75 m of soft, white, flinty chalk with sponge beds, a prominent Platyceramus acme and occasional Conulus, suggesting the higher part of the M. coranguinum Zone. This is Brydone’s Locality 377 (Figure 34). Close by, a section adjacent to the Sun Inn, Bentworth, displays about 1 m of soft blocky white chalk. North of Bentworth, at Haley Firs [SU 6648 4184], 2.4 m of soft white blocky chalk with prominent large flattened nodular flints and a sponge bed is exposed in a small chalk pit. Based on the fauna, Woods (1997) ascribes this to the M. coranguinum Zone. Another pit at [SU 6588 4209] exposes about 4 m of soft blocky white chalk with four minor flint bands, with an acme of Cladoceramus unduloplicatus and Platyceramus, suggesting the middle M. coranguinum Zone.

(Figure 35) shows outline logs for the following sections: HP16, [SU 6763 3892] 500 m west of Gadwick Cottages; HP17 [SU 6708 3782] south-south-west of Warren Farm House, Wivelrod; HP18 [SU 6750 3814] south of Wivelrod Cottages; HP19 [SU 6649 3796] north-west of Redwood Farm; HP20 [SU 6713 3884] east-south-east of Bentworth Hall; HP21 [SU 6716 3909] east of Bentworth Hall; HP24 [SU 6583 3785] near Medstead Grange; and HP25 [SU 6532 3520] at Lower Soldridge Farm. All are in soft white chalk with well-developed flint seams and have yielded the bivalve Platyceramus sp. and the echinoid Conulus sp., occasionally M. coranguinum and the crinoid Bourgueticrinus sp.

Two sections, HP22 at [SU 6641 3981] south-east of Hall Farm, Bentworth and HP23 at [SU 6530 3877] south-east of Gaston Grange (Figure 36), both show a conspicuous seam of Conulus-rich chalk together with Platyceramus sp, Bourgueticrinus sp. and a thick thick-tested form of Echinocorys scutata. This acme association is a good indicator for the higher part of the M. coranguinum Zone at about the Rowe’s Echinoid Band, above Barrois’ Sponge Bed, in East Kent. The proximity of these sections to the base of the Newhaven Chalk (i.e. Uintacrinus socialis Zone) is indicated by the presence of Micraster aff. rostrata and Cretirhynchia plicatilis in the section near Hall Farm.

At Upper Soldridge Farm [SU 6494 3543], a small pit exposes a 1.8 m section in patchily hard chalk with a sponge bed and a nodular flint horizon. The fauna is again indicative of the upper M. coranguinum Zone (Woods, 1998b). Two sections, HP9 at [SU 6693 3538] and HP 10 [SU 6707 3545] (Figure 37) in the cutting immediately east of Four Marks and Medstead Station on the Watercress Line included specimens of Micraster coranguinum and Echinocorys sp. indicative of the M. coranguinum Zone. A specimen of Cladoceramus undulatoplicatus found in a loose block beneath the most easterly section indicates level within the Santonian part of that zone.

To the south-west of Four Marks and Medstead Station five closely spaced sections were logged in the railway cutting which runs parallel to the Winchester Road, Four Marks (Plate 10). These are HP11 [SU 6612 3489], HP12 [SU 6593 3477], HP13 [SU 6583 3471], HP14 [SU 6575 3466] and HP15 [SU 6571 3464]. They expose soft to firm, white chalk with numerous conspicuous semicontinuous flint seams (Figure 38). The fauna includes large amounts of thick shelled Platyceramus at some levels and the echinoid Conulus albogalerus an association which indicates the Santonian part of the M. coranguinum Zone.

A poor degraded section [SU 6823 3391] on the golf course near Akhurst Farm, Four Marks, shows soft, white, powdery chalk with a single large nodular flint seam. The flint and the adjacent chalk were packed with inoceramid bivalve fragments (including hinge and umbonal area fragments), some of which were very thick and identified as Volviceramus involutus. The association of flint and this inoceramid suggests the Seven Sister’s Flint. A small section, HP3 [SU 6735 3299], remaining in an otherwise much deeper pit 300 m south-east of Kitwood Farm (Figure 39) exposes 5.5 m of soft to moderately hard, smooth, blocky white, chalk with numerous well-developed nodular flint seams. Above the most prominent of these flint seams a single large tabular flint was noted. The fauna included M. coranguinum and Echinocorys sp. suggesting a level within the M. coranguinum Zone. The lithology and its proximity to the conjectural basal Newhaven boundary would suggest that the sequence seen here is in part equivalent to the Haven Brow Beds of the Sussex Coast.

The largest section in the district at Dudman’s agricultural lime quarry [SU 6570 3050] off Soames Lane between Ropley Dean and West Tisted includes the top of the Seaford Chalk and the lower part of the Newhaven Chalk (Figure 40).

The full section will be described here despite the upper half of the quarry being in Newhaven Chalk. The presence of thick shelled Platyceramus, M. coranguinum and a ‘tea-cosy’ morphotype of Ecinocorys scutata suggest a level for the base of the pit at about the Whitaker’s Three-Inch Flint and below Barrois’ Sponge Bed. This high M. coranguinum Zone level is confirmed by Conulus albogalerus and Actinocamax versus found towards the top of the lower face (sections 1, 2 and the base of 3). A prominent marker flint seen in the section could therefore be equated with the Exceat Flint. Above this level the chalk in this quarry is lacking in marls and the correlation with the standard marl-bed-rich Sussex succession is less reliable. However, the biostratigraphy of this section suggests some broad correlations.

Possible brachial plates of Uintacrinus were collected from the section immediately below the ‘marker flint’, however, the first unequivocal Uintacrinus socialis plates were found in the base of Section 4 in 1996 (some 8.5 m above the ‘marker flint’). Subsequent collecting in the spring of 1998 revealed U. socialis plates, 2.5 and 5.5 m above this ‘marker flint’. On the Sussex coast this crinoid first appears at the level of the Buckle Marl 1, which is between the Exceat Flint and Buckle Flint 1 (flints spaced ‘9 ft’ apart according to Rowe, 1900). An Echinocorys sp. rich band is also known at this level in Sussex. The incoming of U. socialis, the Echinocorys-rich band and the spacing between (about 3 m) the ‘marker flint’ and ‘flint 2’ (see section) taken together would suggest that ‘flint 2’ in the section would equate with Buckle Flint 1. Mortimore (1986a) identified acmes of Uintacrinus socialis and Echinocorys scutata var. elevatus in the interval above (up to the Hawks Brow Marl in Sussex) and this would seem to equate with the sequence logged in Section 4 at this site. The incoming of small smooth calyx plates of the crinoid Marsupites testudinarius at this site would suggest correlation with a level just below the Brighton Marl of the Sussex coastal sections. Further correlations for this site are negated by the inaccessibility of the highest part of the section but the 6 m of soft, white chalk with discontinuous flint seams would suggest that a level equivalent to the Kemptown Marl may be reached at the top of the face.

Around Northington, north of Alresford, a small exposure of chalk occurs at the entrance to the Grange Estate, near Swarraton [SU 5691 3647]. Here, a 3 to 4 m deep cutting exposes a section through about 6.5 m of soft blocky white chalk with large nodular and tabular flints and sponge beds (Figure 41). The fauna includes Cladoceramus undulatoplicatus and similarly is indicative of the upper M. coranguinum Zone. The flint 0.25 m above the spongiferous beds may be Bedwells Columnar Flint which is coincident with the highest acme of C. undulatoplicatus.

Locally around Northington, a thin horizon of intensely hard porcellanous silicified chalk, the Stockbridge Rock Member, occurs in the topmost Seaford Chalk, about 5 m below the Newhaven Chalk. This is readily identifiable in the brash, especially south-west of ‘The Grange’ [SU 5570 3550]. Farther west, around Winchester, this hard bed becomes more prominent and widespread and forms a useful marker horizon.

Around Alresford there are a number of exposures within the Seaford Chalk. Near Park Farm on the river bluff on the south bank of the River Itchen near Itchen Abbas, a small pit [SU 5454 3253] exposes about 6.5 m of heavily jointed, white, soft chalk with apparently in situ but often commonly shattered flint seams (Figure 42). The upper part of the section has suffered considerable solution and pipes filled with orange and reddish brown flinty, very sandy, silty clay penetrate to a depth of nearly 3 m. This material is related to the older head mapped at a higher level a short distance to the south of this exposure (see Older head 1 description). The fauna collected here is zonally undiagnostic and contains the bivalve Platyceramus, the crinoid Bourgueticrinus ellipticus and an unspecied echinoid Micraster. The crinoid is, however, most common in the M. coranguinum Zone where the bivalve is also common and the association with regular seams of large flints strongly suggests assignment to the Seaford Chalk.

Three exposures in and around Alresford are noteworthy. To the west of Fobdown Farm, near Alresford, in Andover Water Plantation, a small quarry [SU 5690 3380] (HP31) used as a source of track hardcore and cattle-barn flooring, exposes about 4 m of white blocky and flaggy soft chalk with large flint nodule seams (Figure 43). The fauna collected from the level of the sponge bed contains the bivalves Platyceramus sp., Mimachlamys cretosa and Spondylus spinosus and the crinoid Bourgueticrinus ellipticus. A single complete, uncrushed Echinocorys amongst a number found in the interval beneath the very large tabular flint seam has a morphology comparable to specimens from Barrois’ Sponge Bed and would therefore place this section within the higher Santonian part of the M. coranguinum Zone. A second exposure in this valley east of the bridge at Abbotstone (Osborne White, 1910 p. 49) [SU 565 345] is now degraded and overgrown. It is thought to be the pit described on page 49 of the old memoir (Osborne White, 1910) where chalk with regular seams of flint nodules demonstrating a slight southerly dip was noted.

North-east of New Alresford on the interfluve between the River Alre and a small north bank tributary, a large degraded pit [SU 5950 3324] exposes 3 to 5 m of soft, white, smooth, very heavily jointed chalk with many disrupted nodular flint seams. The appearance of the chalk here is the same as that seen at Park Farm to the west. Both sites have the same geomorphological position, being on steep northward facing river bluffs, the mode of formation and preservation of this intrinsically weak chalk is unknown but it may be postulated that the destructured chalk is a remnant of a formerly more extensive periglacially shattered blanket of rock.

South of Grange Farm, Tichborne a large riverside quarry (HP33) [SU 5734 2995] (Figure 43) exposes 10 m of soft to firm white, blocky chalk with regular seams of large nodular flint. The chalk here contains the bivalve Platyceramus and the echinoids Echinocorys scutata (large high domed morphotype), Hirudocidaris hirudo (spines) and Micraster coranguinum. The biostratigraphically important bivalve Cladoceramus undulatoplicatus is tentatively identified from a fragile uncollected specimen suggesting that the quarry spans the Coniacian-Santonian boundary in the higher part of the M. coranguinum Zone.

A large pit (HP34) [SU 6408 2765] (Figure 43) identified as Brydone’s (1912) pit 427, shows soft to moderately hard white blocky chalk with regular flint seams, one of which forms a level of interlocking nodular flints which can be traced across the face. Brydone considered this locality to be in the M. coranguinum Zone.

There are few exposures in area north of East Stratton. Brydone’s (1912) locality 263 at around [SU 5275 4225] yielded a M. coranguinum Zone fauna, and brash from the surrounding area yielded the bivalve Platyceramus and Conulus, indicative of the upper part of the Seaford Chalk.

In the southern part of the Alresford district, the Seaford Chalk is exposed in several disused pits and railway cuttings around Bramdean, Privett and West Meon. Blocky white chalk with common Platyceramus fragments is exposed in tree roots in the upper part of a chalk pit 400 m south of Basing Home Farm [SU 6891 2809]. Hard, coarsely nodular chalk brash is found in the bottom of the pit, suggesting that the junction of the Seaford and Lewes Nodular chalks passes through the middle of the section.

A chalk pit in Hurst Bottom, Privett [SU 687 270] (Brydone, 1912, locality 148) exposes numerous small faces of soft to quite hard chalk, with large nodular flints. The fauna, including Micraster turonensis, M. bucaillei and Conulus albogalerus suggests the upper (Santonian) part of the M. coranguinum Zone, around the middle of the Seaford Chalk. M. bucaillei was also identified in a poorly exposed pit 300 m north of Upper Bordean Farm [SU 6904 2566] by Brydone (1912, locality no. 437), his fauna included the brachiopod ?Gibbythyris ellipsoidalis suggesting the basal Santonian, Seaford Chalk, ?upper M. coranguinum Zone.

Brydone’s (1912) locality 420, probably in a pit at [SU 6756 2676] near Privett included the echinoids Conulus albogalerus and a ‘tall-domed’ morphotype of Echinocorys scutata, together indicating the upper Seaford Chalk, upper M. coranguinum Zone. Nearby chalk exposed in fallen tree roots is white, brittle, with common Platyceramus fragments. Another Brydone locality (435), 400 m south-east of Laydean Farm, Froxfield [SU 6968 2605] yielded quite hard to firm, uneven, hackly, locally nodular chalk, with common thick- and thin-shelled inoceramids, including Platyceramus and possible Volviceramus, consistent with a position low in the Seaford Chalk.

One of the best sections in the middle Seaford Chalk around Privett is in the disused railway cutting at southern portal of the tunnel 500 m east of Stock Farm, Privett [SU 6708 2695]. Here, around 20 m of soft, white chalk with common flint beds is exposed (Figure 44). Fauna from the lower part of the section include the bivalve Volviceramus involutus and echinoid Micraster (Isomicraster) gibbous indicating the lower (Coniacian) part of the Micraster coranguinum Zone. Cladoceramus undulatoplicatus was collected 7.5 m m above the base of the section, indicating the basal part of the Santonian in the middle M. coranguinum Zone. M. coranguinum, Conulus and thick-shelled Platyceramus in the higher part of the section indicates the upper M. coranguinum Zone. The Seven Sisters flint may occur just below the exposed section. Brydone (1912, locality no. 419) also collected Bourgueticrinus ellipticus(?) and M. ex gr. coranguinum from this cutting, indicating the M. coranguinum or U. socialis Zone, of the Seaford or basal Newhaven chalks.

Two chalk pits in soft white chalk typical of the Seaford Chalk, one at the southern corner of Common Copse, East Meon [SU 6832 2620] (Brydone, 1912, locality 436), and the second at The Jumps, West Tisted [SU 6679 2820] (Brydone, 1912, locality 416), yielded Micraster coranguinum.

A small pit [SU 6404 2320] 450 m south-east of Brocklands Farm, West Meon exposes about 4 m of soft smooth white chalk with four flint seams (the middle two associated with a brittle grey marl seam). Its position low in the Seaford sequence and the presence of a significant marl seam, and despite the absence of a Platyceramus faunal element, tentatively suggests that the beds exposed can be correlated with the Belle Tout Beds of the standard Sussex succession. Nearby, there are numerous exposures, generally showing soft, white, smooth, blocky chalk with flint seams, along the course of the abandoned Meon Valley railway line, particularly for 0.5 km south-west of West Meon Station [SU 6418 2361].

Newhaven Chalk Formation (NCk)

This formation is composed of soft to medium-hard, smooth, white chalk with numerous marl seams and flint bands, including abundant Zoophycos flints (notably at levels near the base). Typically, the marls vary between 20 and 70 mm thick. They are much attenuated or absent locally, over positive synsedimentary features, where the distinction between the Seaford and Newhaven formations is lithologically difficult. Channels with hardgrounds and phosphatic chalks have been recorded elsewhere within the formation (Mortimore, 1986b; Hopson, 1994; Aldiss et al., 2002; Jarvis, 2006).

In this district the Newhaven Chalk is estimated to be 40 to 70 m thick. The base is defined as the Buckle Marl 1, and the upper boundary us placed at the Castle Hill Marl 2 at the type locality at Seaford Head. The field brash is composed of soft to medium-hard, smooth, angular, flaggy fragments of white chalk similar in appearance to that of Seaford Chalk. The incoming of abundant flints with Zoophycos (a spiral trace fossil often commonly preserved in flint) and crinoid debris near the base of the formation serves as a useful marker for mapping the lower boundary. Individual plates of the zonal index crinoids Uintacrinus socialis and Marsupites testudinarius occur in numerous small pits, track exposures and occasionally rarely, brash. There are abundant Echinocorys, oysters and Bourgueticrinus in the testudinarius Zone in exposures, but otherwise macrofossils are rarely seen in the brash.

Biostratigraphically, the Newhaven Chalk covers the whole of the Uintacrinus socialis, Marsupites testudinarius and the Uintacrinus anglicus zones and most if not all of the Offaster pilula Zone and foraminiferal zones BGS18 and 19 (Table 8). It crosses the Santonian-Campanian stage boundary, which is placed at the Friars Bay Marl in Sussex (Mortimore, 1986a) and this also marks the top of the range of Marsupites testudinarius. In the standard Sussex succession the formation includes the strata from the base of Buckle Marl 1 to the Castle Hill Marls.

The Newhaven Chalk Formation outcrops extensively across the Alresford district, covering much of the central and western parts of the sheet except where erosion has incised into the underlying Seaford Chalk, such as in the headwater valleys of the River Itchen around Alresford, the upper Bramdean valley and along the line of the Winchester–Meon Pericline. Much of the outcrop is obscured by an extensive cap of clay-with-flints and other superficial deposits. Exposures are generally poor and restricted to a few pits, mainly concentrated at the margins of the clay-with-flints plateau, which suggests that they were dug for agricultural lime for the dressing of the heavy clay land on the plateau, but it is possible some depressions may have originated as solution hollows. However, the identification of Uintacrinus socialis, Marsupites testudinarius and more rarely Offaster pilula within small exposures and field brash confirms the presence of the Newhaven Chalk at a large number of localities. In addition, both Brydone (1912) and Osborne White (1910) identified many localities with these zone fossils, which have been used to confirm field observations. Around East Stratton, the Newhaven Chalk is locally overlain by Palaeogene strata.

Details

Medstead, Bentworth and Upper Wield

Several small exposures of Newhaven Chalk occur in disused pits between Medstead, Bentworth and Upper Wield. Three pits (Figure 45) occur very close to each other at Gaston Grange, near Medstead, all of which contain Newhaven Chalk. The first [SU 6480 3912] exposes 6.2 m of soft flinty chalk, with a fauna indicative of the basal Newhaven Chalk (U. socialis Zone); the second, 400 m to the north [SU 6482 3948] shows 3.6 m of soft flinty chalk, again with a U. socialis Zone fauna. The third, another 200 m to the north [SU 6485 3968] displays 3.8 m of soft white blocky powdery chalk with occasional rare small spiky and nodular flints. All are described in Woods (1997) and shown in (Figure 45). Their presence and the degraded pits in the shallow valley northward from Holt End, helps to delimit the subcrop of the Newhaven Chalk in the north-west of sheet SU63NE.

At Upper Farm, Bradley, 1.9 m of soft chalk with locally large nodular flints and (?)Zoophycos flints with Marsupities testudinarius is exposed in an old overgrown chalk pit [SU 6420 4004], (Figure 45). Several other degraded pits nearby also have small degraded exposures of soft blocky white chalk from the M. testudinarius Zone. To the west, opposite Blue Ridge Farm [SU 6325 3990], lies another overgrown pit with a weathered 2 m exposure. The soft flinty chalk contains an acme of crushed Echinocorys, which are similar in form to types found in the M. coranguinum Zone. However, given the northerly dip and the proximity to pits in the M. testudinarius and U. socialis zones, it is more likely that this form of Echinocorys is from the Newhaven Chalk.

Several pits occur to the west of Upper Wield. The largest [SU 6228 3852] shows a poor section of very blocky soft smooth white chalk with M. testudinarius. Similarly, this zone fossil was found in a small pit [SU 6215 3860] to the north-west, and in another poorly exposed 10 m deep pit [SU 6214 3790] to the south-south-west.

Candover valley and East Stratton

On the north side of Abbotstone Down, near Swarraton Farm [SU 5836 3680] an overgrown pit displays three small (2–3 m) sections (Figure 45). The soft flinty white chalk is assumed to be correlative across the pit, but this cannot be proved. The record of Uintarcrinus socialis agrees well with the position of the pit a short distance above a major negative break of slope which marks the base of the Newhaven Chalk.

The best exposures of Newhaven Chalk in the district occur to the west of Preston Candover, where three pits have been actively worked on a small scale. The first of these is on the Preston Farm Estate at [SU 5988 4169]. Here, a deep sheer-sided pit exposes a 12 to 13 m succession of soft blocky white chalk with four major nodular flint seams. The chalk (Figure 46)c contains M. testudinarius and Echinocorys elevata in the basal 4 m, overlain by more blocky soft white chalk with possible Uintacrinus, suggesting the higher part of the pit may be in the U. anglicus Zone. Several solution pipes and conduits can be seen in the upper part of the pit, infilled with dark brown clay and flint.

To the north, on the same estate, lies the second pit near Preston House [SU 5927 4230] which has been worked recently on two levels, the deeper level has been partially infilled. The lower section exposes 4 m of soft white blocky chalk with 2 or 3 flint seams (Figure 46)a. Near the top of the section is an acme of M. testudinarius, including a crushed entire calyx. Another acme occurs 0.86 m below Flint 1. Another pit, still farther north [SU 5815 4248] contains 3 to 4 m of undistinguished soft blocky white chalk with inconspicuous horizons of small and medium sized nodular flints and thin marly partings. The presence of Echinocorys depressula and E. tectiformis led Woods (1998) to assign the sequence to the middle Newhaven Chalk (U. anglicus to O. pilula zones).

The third is an actively worked pit close to the crest of the hill overlooking Brown Candover at Robeys Farm [SU 5704 3911] that exposes 6 m of soft locally spongiferous chalk with small nodular flints and three thin marls (Figure 46)b. Several acmes of Echinocorys tectiformis and E. depressula are present indicating the middle to upper Newhaven Chalk. Further to the south-east, another freshly worked but much smaller pit at [SU 5607 3860] contains about 2 m of almost flintless soft white chalk. The chalk also lacks a diagnostic fauna, but the oysters present probably equate with the middle-upper Newhaven Chalk. The exposure also shows solution pipes 2 m deep filled with clay-with-flints. East of Micheldever, Brydone (1912, locality 918) and Osborne White, (1910) recorded an E. depressula Subzone fauna from an old pit at [SU 5292 3916], including E. scutatus and Ostrea vesicularis. A small pit on the edge of Lawn Copse [SU 5394 3773] exposes 0.3 m of red brown clay above 2 m of firm white chalk with a few scattered knobbly flints and a possible specimen of E. depressula and Acutostrea incurve.

In the east of the area, a pit on Northington Down [SU 5530 3770] displays 4 m of highly weathered chalk with numerous large finger flints (10 to 15 cm across). The deep weathering is probably due to the location of the pit close to the valley floor. However, the section was too overgrown and weathered to identify any marker horizons.

At West Stratton, Brydone (1912, locality 1031) identified Echinocorys scutatus var. truncata and Offaster pilula in an old pit [SU 5302 4061]. Osborne White, (1910) identified various other fossils including Porosphaera nuciformis, Clausa globulosa, Onychocella lamarki, Rhynchonella reedensis and Ostrea vesicularis. At East Stratton, the old brickpit [SU 544 399] formerly exposed the junction of the Newhaven Chalk and the Reading Formation. The chalk is described as soft with small subspherical and fusiform flints and yielded amongst others Echinocorys scutatus (gibbous form) and Ostrea lateralis, regarded by Osborne White, (1910) as being typical of the higher part of the Offaster pilula Zone. A deep overgrown pit at [SU 5480 3982] (Brydone, 1912, locality 921) and a degraded pit at Burcot Farm [SU 5485 3865] yielded specimens of Echinocorys depressula.

Four Marks, Ropley and New Alresford

Several good exposures of the Newhaven Chalk occur around Four Marks, Ropley and New Alresford. The sequence of Newhaven Chalk at Dudman’s agricultural lime quarry is discussed fully in the Seaford Chalk section, see above and (Figure 40).

To the west of Dallmer Pond, a pit [SU 6527 3016] exposes about 3.5 m of soft, white, blocky chalk with regularly spaced small nodular flint seams. Above a conspicuous continuous horizontal sheet flint, a crushed partial calyx composed of eight large (up to 3 cm), highly ornamented, individual plates of the crinoid M.testudinarius was found. This find at approximately the same level as the highest beds exposed in Dudman’s Quarry suggests that the acme of this large form of the crinoid might well be exposed in the highest part of this pit also.

A section at Westfield Copse [SU 657 318] of about 5 m of very soft, low density and powdery, white chalk with a single large nodular and rusty stained flint seam at its centre included specimens of the echinods Echinocorys depressula and E. tectiformis, which indicate the lower part of the Offaster pilula Zone. Much of the lower part of the Newhaven Chalk, up to and including chalk in the Marsupites testudinarius Zone, can be seen in the road cutting between Gilbert Street and Kitwood known as Swelling Hill [SU 659 327]. Uintacrinus socialis and Marsupites testudinarius were collected from these sections by Brydone.

A small cut [SU 5358 3042] for a barn at Avington Manor Farm shows crisp, white, small blocky chalk with a single small flint seam. The macrofauna was sparse and undiagnostic but the foraminifera (Wilkinson, 1998) indicate a level within the middle of the Uintacrinus socialis Zone at the base of the Newhaven Chalk.

The largest exposure of the Newhaven Chalk in the district is within the Alresford Station Cutting [SU 5938 3238] (Figure 47). A composite section based primarily on the exposure on the south side of the cutting shows 15.5 m of soft to moderately hard, large blocky chalk with regularly spaced flint seams. Towards the base of the section Platyceramus becomes abundant with an acme of large-plated strongly ornamented Marsupites testudinarius above. The association of Echinocorys aff. elevata and Micraster rostrata with the large-plated crinoid suggests a level within the central part of the Marsupites testudinarius Zone in the lower part of the Newhaven Chalk. This would suggest a level at and above the Kempton Marl of the Sussex succession but the absence of distinct marls in this section preclude a definitive correlation.

A small degraded and partially backfilled quarry section (HP32) at [SU 5476 3070] (Figure 48) 250 m north-east of Hampage Farm, Ovington, shows a thin clay-with-flints overlying about 2.5 m of soft, powdery, low density chalk. Two distinct anastomosing marl seams are associated with an acme of Echinocorys truncata and Offaster pilula. Together this fauna indicates the ‘lower belt’ of O. pilula in the Subzone of abundant O. pilula (O. pilula Zone) in the higher Campanian part of the Newhaven Chalk. The sequence lies above the Old Nore Marl, and below the Peacehaven Marl in the standard Sussex succession.

South of the obvious windpump north of Itchen Stoke, a small section [SU 5586 3312] of about 3 m of soft to firm, white, blocky chalk without flint contains an abundant oyster and inoceramid bivalve fauna including Gryphaeostrea canaliculata. In addition the crinoids Bourgueticrinus sp. and importantly Uintacrinus socialis indicate the lowest Zone of the Newhaven Chalk. The U. socialis Zone was also identified in a poor degraded exposure [SU 5997 3290] east of New Alresford. Here in a few metres of very low density, soft blocky chalk at the top of a degraded section thin shelled inoceramid bivales and a crushed Conulus sp. were found together with the zonal index U. socialis.

Two small pits at [SU 6029 3306] and [SU 6059 3316], (Brydone, 1912, sites 822 and 821 respectively) are attributed to the Marsupites testudinarius Zone, both are now degraded. The railway cutting [SU 6075 3255] to the south also contains this zonal index. Another of Brydone’s localities (950) off Whitehill Lane, Bishop’s Sutton, also identified as the partially backfilled pit [SU 6001 3167] in this survey (HP30) (Figure 48), proved 3.5 m of white, soft to very soft blocky chalk. Associated with an anastomosing marl in the middle of the sequence is an acme of the echinoid Echinocorys depressula; the subzone of this echinoid is in the lower part of the Offaster pilula Zone of Campanian age. The base of the Newhaven Chalk is presumed to be just below the floor of an excavation for silos at Manor House Farm [SU 6196 3118] (Figure 48) where the zonal index Uintacrinus socialis was found within 1.5 m of soft locally spongiferous chalk. The same zonal index was found in a roadside scrape [SU 6477 3494] adjacent to Brydone’s 682 pit near Upper Soldridge Farm. East of Ropley Dean Station a section [SU 6322 3254] (HP8), (Figure 48) excavated for a new engine shed, exposed 3.5 m of large blocky, soft white chalk containing a fauna including Cretirhynchia exsculpta, Echinocorys elevata and coarsely ornamented calyx plates of the crinoid Marsupites testudinarius, the zonal index. This indicates the Santonian part of the lower Newhaven Chalk.

Cheriton and Bramdean

At Rabbit Copse off Balls Lane, a small section [SU 5695 2655] exposes about 4 m of soft to firm, white, blocky chalk with irregularly spaced small spiky and nodular flints. The fauna is dominated by oysters including Acutostrea incurva and Pseudooperna boucheroni and includes the echinoid Echinocorys depressula. This indicates a level from the middle of the Marsupites testudinarius to the lower part of the Offaster pilula zones. A large shallow temporary exposure [SU 5915 2920] for a new cattle shed and dairy at Middle Farm, Cheriton shows up to 2.5 m of soft, white, blocky chalk with a few flints, which includes the zonal index U. socialis. An old chalk pit (at [SU 5782 2892]) now much degraded shows only a metre or so of very gritty soft white chalk with the oyster Gryphaeostrea canaliculata striata and the echinoid Echinocorys depressula with common fragmentary echinoid spines and test, bryozoans, asteroid plates, Pseudoperna boucheroni, Neithea sp. and a large example of Spondylus sp. This indicates the lower-middle Newhaven Chalk.

West Meon–Warnford–West Tisted area

The northern portal of the disused West Meon railway tunnel exposes about 20 m of the Newhaven Chalk but only the lowest 7 m of the section [SU 6485 2534] (Figure 48) was accessible during this survey. Extensive collecting included small- to medium-sized ornamented plates of Marsupites testudinarius, Conulus sp., Pycnodonte vesiculare, Pseudoperna boucheroni and a small form of Echinocorys elevata all indicating Santonian aged lower Newhaven Chalk of M. testudinarius Zone. North-west of Daylesford, a section [SU 6485 2975] exposing up to 4 m of soft chalk included Marsupites testudinarius and Bourgueticrinus papilliformis together with oyster and inoceramid bivalve fragments.

Several outcrops, mostly degraded occur in the south of the district around West Meon. Brash specimens collected [SU 6501 2354] 1 km south of West Meon are of the echinoid Offaster pilula and Offaster pilula aff. planatus, suggesting the top of the ‘upper belt’ of O. pilula in the subzone of abundant O. pilula. Abundant O. pilula were also collected [SU 6502 2353] nearby, again suggesting the upper part of the O. pilula Zone, subzone of abundant O. pilula. A cutting [SU 6662 2409] behind a barn at Riplington exposes white flinty chalk containing calyx plates of the crinoid Marsupites testudinarius, indicative of the M. testudinarius Zone in the lower part of the Newhaven Chalk (Mortimore, 1986a). Calyx plates of Marsupites testudinarius were also collected from several small exposures [SU 6741 2382] and [SU 6743 2386] along a lane cutting west of Bereleigh House. Brydone (1912, locality 853a) also collected M. testudinarius calyx plates from this cutting, as well as from a number of localities around Westbury: an old pit around [SU 652 238] and excavations for Westbury Pavilion [SU 6561 2431].

A chalk pit 250 m north of Marland Pond, West Tisted [SU 6573 2945] (Brydone, 1912, locality 50) in soft white chalk with pink shell fragments yielded a calyx plate of Uintacrinus socialis indicating the U. socialis Zone. Similarly, calyx plates of Marsupites testudinarius, indicating lower Newhaven Chalk were found in a chalk pit 700 m west of Peak Farm, East Meon [SU 6600 2534] (Brydone, 1912, locality 855), a road cutting about 300 m west of The Old Wheatsheaf Inn [SU 656 274] (Brydone, 1912, locality 859), and in an old pit near Filmore Hill [SU 6539 2743] which exposes several metres of blocky, white chalk with 10 cm nodular, scattered flints.

An old pit 400 m south of Filmore Hill Farm, Filmore [SU 6600 2698] exposed 4 m of blocky, smooth, white chalk with beds of nodular flints, up to 30 cm in diameter, with a gentle apparent dip to the south-west. Fossils collected include Uintacrinus socialis indicative of the U. socialis Zone of the basal Newhaven Chalk. Brydone (1912, locality 712) also collected U. socialis from this pit.

Osborne White, (1910) recorded a pit by an old limekiln at the south-eastern end of Baybridge [SU 5294 2308] with soft white chalk and small flints with Echinocorys scutatus.

A pit adjacent to a grain silo at Garretts Farm [SU 6497 2445], see (Figure 49) exposes a section in the lower part of the Newhaven Chalk. The fauna (Woods, 1996c) includes Echinocorys depressula and E.tectiformis which co-occur in the Uintacrinus anglicus and Offaster pilula zones. In the absence of both zonal indices the common occurrence of Pseudoperna boucheroni indicates that the fauna can be no younger than the basal part of the O.pilula Zone.

Two exposures at the south and north portals of the Meon Valley railway tunnel [SU 6457 2483] and [SU 6485 2534] respectively are shown in (Figure 50). The northern section includes large highly ornamented Marsupites testudinarius and Echinocorys elevatus together with Conulus sp. indicating an horizon in the middle of the M. testudinarius Zone. The fauna included two rare examples of almost complete M. testudinarius calices (PMH 2418 and 2422).

The southern section included the fauna Micraster simpsoni associated with abundant Pseudoperna boucheroni which in the absence of the testudinarius zonal index suggests that the section is somewhat higher stratigraphically in the lower part of the Offaster pilula Zone.

Culver Chalk Formation (CCk)

The Culver Chalk, up to 70 m thick, includes the Tarrant Chalk Member and the overlying Spetisbury Chalk Member each of approximately the same thickness. Only the lower part of the Tarrant Chalk Member occurs in the Alresford district, and comprises soft, white chalk without significant marl seams. A particular concentration of large nodular and semitabular flints, the Castle Hill Flints, occurs above the base of the Culver Chalk Formation (Mortimore, 1986a) and above the Castle Hill Marls that contain the base of the formation These units are a little above the Arundel Sponge Bed (Mortimore, 1986a). The maximum estimated thickness of the Tarrant Chalk is 35 m locally but only the basal part occurs in a small outcrop in the extreme south-west of the district around Baybridge where it caps the secondary escarpment. Elsewhere in the Alresford district, most of the sequence above the upper Newhaven Chalk (Offaster pilula Zone) has been removed by erosion prior to the deposition of the Reading Formation.

Biostratigraphically, the Culver Chalk lies mostly or entirely within the Gonioteuthis quadrata Zone, with the base possibly extending downwards into the Offaster pilula Zone in some areas, and foraminiferal zone BGS20. It is entirely within the Campanian stage (Mortimore, 1986a; Bristow et al., 1997). There are no exposures recorded in this district.

Chapter 6 Palaeogene

Although much of the once extensive cover of Palaeogene material has been removed by erosion, several small areas of Palaeogene strata are preserved as a series of small outliers around East Stratton in the north-west of the district. The succession consists predominantly of clay, silt and sand belonging to the Reading Formation. These were laid down in latest Thanetian times, by a series of braided rivers traversing a warm, swampy lowland.

Lambeth Group

The Lambeth Group (LMB) corresponds to the strata formerly described as the Woolwich and Reading Beds. Two formations are recognised in this district, the Upnor and Reading formations (Ellison et al., 1994). In mapping it has proved impractical to delineate these separately because the former is very thin and is therefore described as the basal bed of the Reading Formation herein.

Reading Formation (Rea)

The Reading Formation occurs as a series of small outliers capping the interfluves around East Stratton. It rests unconformably on the eroded surface of the Newhaven Chalk, and is generally very thin, often less than 5 m thick, although locally thicker deposits may occur where the sediment has been ‘piped’ down into the Chalk. Laterally it grades into a thin veneer of clay-with-flints. The Reading Formation consists of mottled, bright red and grey clays and silty clays, but also in shades of purple, brown and orange. The complex mottling has been ascribed to pedogenic processes with multiple overprinting of palaeosols (Buurman, 1980). The basement bed of the Reading Formation (equivalent to the Upnor Formation) comprises a reddish brown or greenish sand or interbedded sand and clay with abundant sub-angular to rounded, corroded and pitted glauconite-stained flint pebbles with locally glauconitic sandy clays, analogous to the ‘Bottom Bed’ of the London Basin. This basal bed is usually less than 1 m thick, at maximum up to 2 m in places. It gives rise to a very pebbly brash with locally common glauconite-stained flints.

Details

The most complete section in the district was that formerly exposed in the East Stratton brick pit [SU 544 398]. There, beneath 3 m of topsoil and clay-with-flints, occurred 3 m of brown and greenish yellow sand and loam with dull red mottling, passing down into grey-brown loam with rusty stains. These deposits rested on the ‘Bottom Bed’, composed of 15 cm of dark green, glauconitic, calcareous loamy sand with small black and green flint pebbles and nodules, and a few small pebbles of white quartz, all resting on a very irregular surface of Newhaven Chalk. Augering proved that up to a metre of glauconitic pale grey clay occurs in several places. The contact with the underlying Chalk is very uneven, the Reading Formation having being extensively piped into dissolution cavities (Figure 51).

A trial pit for the M3 [SU 5337 3975] proved 1.5 m of greenish brown clayey silt above the Chalk. Elsewhere, the common occurrence of small well-rounded flint and quartz pebbles associated with small glauconitised pebbles, for example around Parkhill Farm [SU 535 410], East Stratton [SU 5445 4045] and [SU 5460 3935] indicates the presence of the basal Reading Formation.

An auger hole in Dodsley Wood at [SU 5362 3882] proved 1.1 m of buff-brown clay on 0.2 m of glauconitic clay over Chalk. A small sand pit occurs near the centre of the wood [SU 5391 3855] where an auger hole proved 1.3 m of fine grained, orange brown sand.

A possible degraded outlier of the Reading Formation may occur farther east to the north-west of Preston Candover at [SU 5990 4210]. Here a series of large very degraded interconnected wooded depressions no more than 3 to 4 m deep, mark the site of a former brickpit. The limited exposures show iron-stained orange sandy clay, but no glauconite-stained flints were found. The area is mantled by clay-with-flints.

Chapter 7 Quaternary

About 60 Ma is estimated to have elapsed between the deposition of the youngest preserved Palaeogene and the oldest Quaternary deposits in the region. During this time younger Palaeogene and Neogene strata were deposited across the whole of southern Britain, and subsequently removed following uplift along the Wealden axis (as part of the general inversion of the Wessex Basin). During the Quaternary, a further break in deposition occurred after the accumulation of the clay-with-flints and before the deposition of the younger Pleistocene and Holocene superficial deposits.

During the Pleistocene, sea level rose and fell in relation to the quantity of water locked up in ice caps. At times of glacial maxima, a periglacial environment was established in this district. There was enhanced erosion and mass- movement both by solifluction and by rivers flowing to much lower base levels. Evidence for at least three such glacial maxima can be seen in southern England; the most severe was of Anglian age. (Figure 52) summarises the principal Quaternary deposits and events of Hampshire and West Sussex.

The following descriptions of the deposits are grouped on the basis of their origin. Mass movement deposits are described first, followed by fluviatile and aeolian deposits. Their order does not imply relative age.

Residual deposits

Clay-with-flints

The clay-with-flints is composed typically of orange-brown or reddish brown clays and sandy clays containing abundant flint nodules and pebbles. At the base of the deposit, the matrix is often generally stiff, waxy and fissured (slickensided), and dark brown in colour. Relatively fresh nodular flints are stained black and/or dark green by manganese compounds and/or glauconite. The deposit gives rise to a stiff, red-brown, silty clay soil strewn with flints. This is primarily a remanié deposit resulting from the modification of the original Palaeogene cover and dissolution of the underlying chalk. The thickness of the clay-with-flints is estimated at about 5 to 6 m at its general maximum but this may rise to over 10 m in limited areas, usually where dissolution of chalk is most pronounced.

The margin of the clay-with-flints is sharply defined on the scarp edge but the boundary may be diffuse on the chalk dip slope. This downslope feather edge is locally obscured by a lateral passage into late-stage solifluction deposits or head gravel. These deposits have a more sandy matrix and a surface brash composed principally of gravel-sized broken angular flints.

The clay-with-flints rests on the underlying chalk with a very gentle angular unconformity, and lies across a range of chalk formations, from Holywell Nodular Chalk in the east to Newhaven Chalk in the west.

A generalised structure contour map of the base of the clay-with-flints (Figure 53) shows that they were deposited on a surface with considerable relief. In particular it can be seen that many of the major valleys were at least partly incised prior to the formation of the clay-with-flints. Several outliers of clay-with-flints occur at the base of the primary Chalk escarpment around Alton, indicating that the Chalk escarpment was in existence by this time. This suggests that some uplift had occurred prior to, and probably drove, the removal of the Palaeogene cover. To what extent the clay-with-flints reflects the true extent of the depositional surface upon which the Palaeogene cover was deposited is unclear. Clearly, the deposit has undergone significant Quaternary modification and solifluction to form some of the head deposits mantling the valley sides.

Details

The clay-with-flints has an extensive outcrop in the Alresford district, overlying over half of the chalk outcrop. The most extensive spreads occur along the crest of the primary chalk escarpment between Bentworth, Four Marks and High Cross, but the deposit also caps many of the interfluves around Alresford, East Stratton, Upper Wield, Cheriton and Bramdean. The margin of the deposit is often commonly marked by a series of old chalk pits, dug to obtain agricultural lime to treat the acidic clay-with-flints soils. Many of these pits show thin reddish brown flinty clay, overlying the chalk with an uneven irregular rock-head. The clay-with-flints is often commonly preserved where it has subsided into dissolution pipes and karstic cavities (often developed along sheet flint horizons and bedding planes) within the chalk. These dissolution pipes can penetrate several metres into the underlying bedrock.

Numerous exposures in the roots of fallen trees, animal burrows and pits show thin dark orange-brown and red-brown stiff waxy clay with stained orange nodular flints. In the north-west of the district high on the interfluves to the north and south of Itchen Abbas and Avington, around Brown Candover, Preston Candover and East Stratton, the clay-with-flints also contains appreciable quantities of well-rounded, chatter-marked flints and more rarely glauconite-stained rolled subangular flints. These are regarded as indicators of the proximity of the Reading Formation. Whilst orange, clayey, fine- to medium-grained sand has been seen in pockets within the clay-with-flints in this district, with the one exception of the Reading Formation mapped around East Stratton, there were no further traceable deposits attributable to the Reading Formation identified during the survey.

Around the margins of the Reading Formation, the contact between the sands and glauconitic clay and the adjacent clay-with-flints is very diffuse. In many places, particularly around Thorny Down Wood and Preston Candover, the clay-with-flints may rest directly on the thin basement beds of the Reading Formation; indeed much of the clay-with-flints in this area may simply be cryoturbated and weathered Reading Formation.

Structural contours drawn for the base of the clay-with-flints demonstrate that it forms a planar surface, folded very gently along the major fold axes affecting the Chalk. This suggests that movement across this axis may have persisted into the Quaternary. The dips on the clay-with-flints are more gentle than the Chalk, giving rise to gentle angular unconformity, representing a period of erosion between the end of the Cretaceous and the start of the Quaternary that may or may not be in addition to the pre-Palaeogene erosional event.

There are very few exposures of the clay-with-flints, but a small exposure near West Meon [SU 6630 2502] reveals 1.5 m of red clay supporting 1 to 10 cm subangular and some 5 cm nodular flint clasts, overlying chalk. Over 3 m of red sandy clay with matrix-supported angular flint clasts occurs in an exposure [SU 6841 2470] at Mare Pond.

The clay-with-flints contact with the underlying Newhaven Chalk was seen in an excavation behind a barn [SU 6528 3858] on Jennie Green Lane, near Medstead. The contact was highly irregular with many small dissolution pipes in the chalk infilled with clay-with-flints (Plate 11)

An exposure [SU 6669 2909] in the bank of an old chalk pit 1 km east of West Tisted reveals 0.5 m of angular flint gravel, with abundant fractured flints, overlying 0.5 m of red flinty clay, with abundant slightly fractured flints, packed together and forming up to 60 per cent volume of the deposit. The upper gravel layer may represent thin older head.

Mass movement deposits

Older head 1

The older head 1 consists of soliflucted slope deposits ranging from flinty gravels to reddish brown, sandy clays containing abundant flint nodules and pebbles which are generally much more shattered than those within the clay-with-flints. They are typically derived from the solifluction of the clay-with-flints and represent part of the genetic continuum of superficial mass movement deposits between the remanié clay-with-flints deposits and the fluviatile river terrace deposits downstream. They represent an earlier phase of solifluction prior to the formation of the main head deposits along the valley bottoms. Several large sheets of older head occur in this district, often generally no more than a few metres thick. The deposits are most widespread on north- and east-facing slopes and commonly grade laterally into areas with only a thin flinty veneer. Downslope and downstream, these deposits become better sorted and eventually grade into river terrace deposits.

Details

Two distinct areas of older head deposits which may represent either degraded river terraces or the intermediate stage in a continuum from valley head to river terrace were identified. The first occurs in the valley draining south-east from Lasham to the head of the Wey in Alton. Here, flinty gravels, mapped as ‘older head’, occur up to 10 m above the valley floor. Disused overgrown gravel pits indicate the gravels must be at least 3 to 4 m thick. Downstream, these gravels probably grade into the true river terrace deposits downstream of Alton, but the crucial section is obscured by urban development. Similar gravels occur in the valley south of Chawton, which are exposed in a small pit 400 m south-west of Chawton House [SU 7074 3663] (Plate 12). Here between 3.2 and 3.5 m of structureless, clast supported, orange-stained, fine- to coarse-grained flint gravel with a matrix of dark reddish brown coarse sandy silty clay is exposed. There is slight indication of imbrication in the upper part of the pit but this structure is unclear due to the nodular nature of the flint clasts.

The second occurrence is in the Candover valley between Brown Candover and Chilton Candover. Here, gravel with abundant small rounded pebbles derived from the clay-with-flints and Palaeogene deposits, set in an orange clay-rich matrix, mantle the valley sides up to 20 m above the valley floor. There is no clear geomorphological expression of a ‘terrace’, but there is a distinct lithological difference between this deposit and the older head on the sides of the tributary valleys to the south, which have far fewer rounded pebbles set in a much darker brown clay matrix, as demonstrated at [SU 5954 3951]. Only farther down the Itchen do the true river terraces become apparent.

Numerous small pits are known throughout the outcrop but they are generally degraded and apart from the section noted above, very few exposures were seen.

Older head 2

The older head 2 deposits are comparable to the last described, but generally contain fewer flints and they occur on the Lower Cretaceous strata in the south-east of the district. The clast lithology generally reflects the underlying host rock, but with variable amounts of flint. On the Lower Greensand deposits, they generally consist of brown sandy and flint clay, changing to a flinty clay on the Gault clay outcrop. They are most extensive in the area west of Petersfield and north-west of Liss. Here they also contain much chalk debris. They are thought to have originated as solifluction lobes during periglacial episodes during the Devensian glaciation.

Details

In the sand pit on the east side of Bedales School [SU 746 251], up to 2 m of angular flint gravel set in a brownish grey clay matrix overlies the Folkestone Formation (Plate 13). The older head consists of angular flints set in a grey clay derived from the Gault. The Folkestone Beds are medium- to coarse-grained, locally cross-bedded, friable sandstones.

Head

Head deposits accumulated largely by solifluction and hillwash, mainly under periglacial conditions during the Quaternary glaciations. They are heterogeneous but are typically composed of very gravelly silty, sandy clay or diamicton, ranging to clayey sandy gravel, all with variable proportions of coarser material and with an earthy texture. The composition of head varies according to the local sources of material and details of landscape evolution. In the Alresford area, head is mostly derived by erosion of the Chalk and Palaeogene strata, but may well include material reworked through older Quaternary deposits such as clay-with-flints, older head deposits and, probably, older fluvial deposits (some of which may be locally absent now due to erosion). The clasts are thus primarily nodules and frost-shattered fragments of flint of a wide range of sizes, commonly cobble or coarse gravel sized. In comparison with the clay-with-flints, head generally includes a greater proportion of shattered and transported flints. A small proportion of the very well-rounded flint pebbles derived from the Palaeogene is commonly present but proportionally this tends to be less than in the clay-with-flints.

However in the east of the district, the head deposits are derived from the Lower Cretaceous strata. Much of the head on the Gault clay has a dominantly clay matrix but with significant content of chalk, either as pebbles or finely disseminated sand-grade particles, and flints. In contrast, head material derived from the Rogate Beds is dominantly clayey, while that derived from the Folkestone Formation is very sandy and hard to distinguish from the parent material.

The head deposits derived mainly from the chalk were formerly mapped as ‘dry valley deposits’ or ‘coombe deposits’ and in part as ‘River and Valley Gravel’ or ‘Valley Gravel’. While these terms are accurate, they are imprecise and are not used in the current BGS scheme of nomenclature for superficial deposits.

The head deposits form part of the continuum of superficial deposits from the remanié clay-with-flints capping the interfluves and the alluvium in the major river valleys. The most important difference between head and clay-with-flints is that the former has undergone gradual downslope movement. The Chalk bedrock on which head lies is thus less likely to be part of an ancient landscape surface which has undergone extensive karstic dissolution. Although the composition of the two types of deposit can appear similar, their significance to engineers and hydrogeologists is thus quite different. The irregular, piped chalk surface commonly found beneath clay-with-flints has been considerably denuded within the modern valleys and as a consequence head deposits generally rest on a chalk surface, which shows significantly less irregular topography.

Head in the chalk dry valley bottoms underlies very gently sloping ground, which is commonly relatively poorly drained. This is generally delimited against the valley side by a slight negative break of slope, taken to mark either the edge of the deposit or a significant decrease in its thickness. In arable fields, ground underlain by head deposits is seen to be much more stony than the adjacent slopes; the soil contains an abundance of angular flint fragments, with some broken nodules and, rarely, very well-rounded ‘Tertiary’ flint pebbles. It is likely that the deposit originally included a component of chalk debris, which has now been dissolved, at least from the surface layers. The soil is commonly a darker brown or reddish brown than on nearby slopes, although the colour contrast is not marked where those slopes are themselves masked by head.

The downstream limit of the head deposits occurs where they have been predominantly reworked by fluvial processes, and so merge into alluvium or terrace. In the lower reaches of the dry valley networks, the finer fraction of the head deposit can sometimes be winnowed out by ephemeral stream flow during periods of groundwater flooding. This leaves behind very coarse flinty lag gravel with little or no fine-grained matrix.

Details

Across much of the Alresford district, the head deposits are almost entirely confined to the dry valley bottoms although some more extensive areas of head occur around Woolmer Forest. Head deposits are very rarely exposed, and due to the considerable flint content cannot easily be penetrated with a soil auger. The thickness of most head deposits in the area is therefore unknown. Borehole records and old gravel pits suggest that the head is mostly less than 2 m in thickness, but could locally attain 5 m or more.

In Lasham Bottom, north of Alton, a thick deposit of head extends along the floor of the valley from the neighbourhood of Herriard (Sheet 284) down to Alton, and has been dug for railway ballast and other purposes in many pits, in most cases now, disused. Several old gravel pits occur [SU 6647 4209]; [SU 4662 4211]; [SU 6865 4086]; [SU 6772 4133] along the floor of the valley (Osborne White, 1910).

Osborne White, (1910) noted good exposures at the old Lasham level-crossing, north of Wadgett’s Copse [SU 6772 4133] and at Old Woman’s Piece [SU 6865 4086], nearly half a mile north-west of Warren Farm. The head here consisted of generally coarse-grained flint gravel, and seldom showed any bedding except in its lowest parts, which were chalky and tufaceous. Small blocks of white and buff sandstone (sarsen) and iron-sandstone were common, as were fragments of silicified Inoceramus in the sandy matrix. The gravel is not, however, confined to the floor of this valley, several small terraces of gravel occur above the valley floor, which are probably equivalents of the river terraces seen further farther downstream. They may represent former infills of valley-bottom head, which have been incised into during periglacial periods during the late Quaternary. These have been mapped as older head.

In the Candover valley, about 3 m of coarse to fine flinty gravel, chalky in places, and showing signs of bedding, was exposed in a small field pit [SU 6009 4082] near the tumulus, 900 m south-west of Preston Candover Church (Osborne White, 1910).

In the Alre valley, coarse-grained flint gravel has been worked in a series of old pits for example, at and north of Old Alresford, at North Street near Ropley, and at Ropley Dean, between Ropley and Bishop’s Sutton. A little to the west of the crossroads at the western end of Alresford a cutting for a new road showed (in 1908) about 3 m of red-brown loam and clay, containing many small angular flints arranged in regular bands (Osborne White, 1910).

Similarly, head deposits have been extensively worked in the Itchen valley (Osborne White, 1910). Numerous small excavations occur throughout the Bramdean valley between Privett and Tichbourne. A few metres of rather fine, stratified gravel was exposed in a small pit [SU 6584 2606] in the wood south-west of the crossroads 850 m east of West Meon Hut (Osborne White, 1910). At The Dean [SU 631 270], north-east of Brockwood, a loose, structureless gravel with many flint-pebbles and some bits of sarsen stone was dug to a depth of 1 to 2 m in a group of irregular workings. Some of these Sarsen stones have been left behind and are still visible today (Plate 14). Poorly bedded gravel, containing many small pebbles of brown iron ore and pellets of chalk was dug to a depth of 2 m in a field pit [SU 5982 2309] 500 m north-north-east of Hinton Ampner Church (Osborne White, 1910). A cutting [SU 6651 2681] behind a barn at Stock Farm reveals 3 m of red clay, with bedding defined by thin flint-rich layers, overlying chalk; the contact is uneven with 2 m relief.

To the east of the Chalk outcrop, a roadside exposure at Lindford [SU 8125 3575] revealed subrounded, glauconitic sandstone clasts in a sandy matrix.

Landslides

These are a ubiquitous feature of the Upper Greensand-Gault contact along much of the crop from Binstead in the north-eastern corner of the district south to Langrish, often forming deep rounded embayments in the escarpment known locally as ‘hangars’. They result from a combination of spring-head erosion and the physical properties of pore pressures and high moisture content. The resultant landforms are quite striking: for the most part they are composites of successional rotational slips and slab slides, with fault-like back scarps up to 30 m high with ponds trapped by slip slices, and hummocky ground commonly with a prominent toe separating the slips from the undisturbed Gault surface. The age of the slips is uncertain, almost certainly they were initiated under periglacial conditions, but the landforms are still remarkably fresh suggesting recent movement. Elsewhere in the district landslides are uncommon. Inevitably, much of the affected land is wooded, or under pasture.

Details

A landslide occurred on the night of March 8–9th, 1774 along the Upper Greensand escarpment to the west of Hawkley, following a period of very wet weather. The slip, just north of Scotland Farm at [SU 756 295] was graphically described by Gilbert White (1789) and affected about 20 hectares of land. This slip was part of a much larger feature which extends along the length of the escarpment. The Selborne area was also the site of a geotechnical slope stability experiment (Cooper et al., 1998).

Fluviatile and aeolian deposits

River terrace deposits

Four sets of river terrace deposits are present in the district, associated with the major river systems; the Godalming Wey, the Alton Wey, the Itchen and the Rother. In the north and west (Alton Wey and Itchen river systems) the terrace deposits are predominantly gravels and sandy gravels, principally of subangular to angular with some well-rounded and nodular flints; with subordinate quartz, ironstone, sarsen and other exotic clasts. In the south-east and east, associated with the rivers Rother and the Godalming Wey, the deposits are more sandy and many occurrences are graded as pebbly sands, reflecting the lithology of the source area. In places clayey and sandy silt and silty clay mask the underlying aggregate, perhaps indicating preservation of overbank or aeolian deposits at the top of each fluvial cycle. Flint again predominates, together with cherts, polished fine quartz and larger fragments of pebbly ‘carstone’ (sandstones with a ferruginous cement) derived from the Folkestone Formation. In general the terraces are up to 5 m thick.

There is little direct evidence of the age of the terraces, but most aggradations are probably periglacial in origin. Terrace deposits above the second show cryoturbation structures indicating that they have suffered at least one periglacial event, and thus suggesting they are all pre-Devensian.

Details

Godalming Wey

Three terraces of the Godalming Wey have been recognised in and around Bordon. The first terrace is the most extensive and lies up to 5 m above the floodplain. The second terrace occurs in small areas in Bordon and lies about 25 m above the present river. The third terrace, referred to as the 300’ terrace by Middlemiss, (1959), lies some 35 to 40 m above the modern flood plain and caps some of the low hills in the area. In the Bordon area the first terrace deposits consist mostly of sand, presumably derived from the Folkestone Formation.

Three sections in the first terrace occur in the Alresford district. A ditch section in Forkpond Inclosure [SU 8166 3184] revealed 1 m of flinty sand on 1 m of yellowish buff sand overlying 1 m of soft, glauconitic sandy clay with flints. Farther west, in Woolmer Forest, soft, wet glauconitic sand was proved to 1.6 m at [SU 8034 3180]. A small section in the first terrace near Lindford, seen by Middlemiss (1959), around [SU 805 364] exposed ferruginous gravel consisting of coarse-grained red sand full of small fragments of cherty sandstone and flint. He also reported 0.9 to 1.2 m of brown flint gravel belonging to the third terrace on Long Down, near Longmoor Camp [SU 810 325].

Two terraces are mapped in the vicinity of Brimstone Inclosure. These are extensions of larger spreads to the east associated with tributary streams of the River Wey. The deposits are thin (1 to 3 m) and composed largely of fine- to medium-grained quartz sand with varying proportions of silt and clay. They can be differentiated from the bedrock sand on which they rest, by their content of small, rounded, quartz and ironstone pebbles.

River Rother

Five river terraces of the River Rother have been identified in the Alresford district, principally in the area between Petersfield and Rogate. Deposits belonging to the highest (5th) terrace are only found on the north side of the river between Durford Wood [SU 776 247] and Rogate [SU 806 244], between 90 and 76 m OD, some 40 to 45 m above the present flood plain. The dominant lithology is angular, brown flint gravel. The fourth terrace occurs in roughly the same area at about 30 m above the river level. The lithology ranges from coarse-grained sand to angular to subangular gravel with flints, chert and siliceous sandstone.

The third terrace is more extensive and occurs mostly on the south side of the river at elevations between 65 and 60 m OD. It consists principally of coarse-grained sand with a relatively minor gravel component, although locally it has a gravelly base.

The second terrace is the most extensive, and is found on both sides of the river at heights of between 6 to 8 m above the river level as far west as Petersfield. Much of the second terrace is obscured by soliflucted dark brown clayey sand (head), but the base of the deposit is thought to be gravelly (Bristow, 1991). Springs are common, issuing from the basal gravel on both sides of the river. Augering at [SU 7947 2336] proved 0.7 m of brown sandy clay (head) over 0.5 m of medium- to coarse-grained sand, which in turn rested on coarse-grained flint gravel.

The first river terrace has a limited outcrop in the Alresford district, but is more extensive in the Haslemere district to the east. The terrace is typically 1 to 2 above the floodplain and consists of coarse-grained, locally gravelly sand with a gravelly base. A small remnant occurs at [SU 8110 2313] and consists of about 0.6 m of poorly sorted flint gravel.

Alton Wey

Within Alton two terraces of the River Wey are mapped. Both terraces are composed of fine- to coarse-grained flint clasts with quartz gravel in a medium- to coarse-grained pale yellow-brown sand matrix.

The second terrace is between 10 and 15 m above the floodplain around Holybourne and forms widespread, flat-topped feature overlooking both sides of the River Wey, separated from the first terrace by a steep bluff. The height difference between the two terraces decreases upstream, to around 4 to 5 m in Alton and to virtually nothing at the source of the river at [SU 7079 3936]. Good exposures of the second terrace deposit can be seen at Neatham Farm [SU 7462 4105] where over 3 m of coarse, unstratified angular to subangular flint gravel can be seen. It has been worked in many localities, especially from small ‘borrow pits’ adjacent to the railway line. Osborne White, (1910) noted that some bones and molar teeth of a mammoth (Elephas primaigenius) were discovered in the railway cutting west and north-west of Mill Court [SU 7547 4195]. The first terrace is separated from the alluvium by a small bluff between 1 and 3 m above the general level of the floodplain and forms a well-developed, wide, flat-topped feature either side of the river.

River Itchen

River terrace deposits are associated with the River Itchen, from the western boundary of the district as far upstream as Cheriton [SU 584 286], and the River Arle eastwards from its confluence with the Itchen [SU 572 324] to east of Bishops Sutton [SU 615 318]. Minor terrace spreads are also mapped [SU 545 340] on the margins of the Candover Stream south of Abbotstone.

Two terrace spreads have been identified. The higher second river terrace between 5 and 10 m above the floodplain, has been identified on the right (eastern) bank of the Itchen at a number of localities centred around Tichbourne [SU 574 305]. The first, and more extensive, river terrace is closely associated with the alluvium and usually separated from it by a low bluff between 0.5 and 2 m above the floodplain.

In general in this district the terrace spreads are mapped on the basis of their geomorphological position and the gravelly nature of the surface brash. Presently, there are no working pits.

Ditch sections and excavations in association with the watercress industry of this district show that the deposits are generally fine- to coarse-grained angular flint gravel in a silty medium- to coarse-grained sandy matrix. Thin beds of fine- to medium-grained sand have been noted but they are not common. The surface levels of the deposits are generally illuviated presumably representing reworking of overbank finer deposits into these upper layers.

Undifferentiated terraces

Patches of high-level river terrace deposits are found principally near Langley around [SU 81 29] close to the watershed between the River Rother and the Godalming Wey, in Longmoor Inclosure [between 781 295] and [SU 796 299] and north of Rogate around [SU 802 256]. At Langley, they occur at heights of 115 to 120 m OD and consist of slightly clayey, coarse-grained sand with a variable pebble content, mostly of angular brown or white flints and scattered chert, and locally pebbles of ‘carstone’ from the Folkestone Formation. The gravel was worked in a number of old pits [SU 8062 2940] and [SU 8066 2942], but no section remains. Up to 3 m of pebbly coarse-grained sand was worked in a pit at [SU 8039 2874]. The deposits at Longmoor Inclosure consist of coarse-grained sand derived from the Folkestone Formation together with angular brown flints and range from 85 to 110 m OD.

Small patches of flinty gravel also occur around Tullecombe [SU 8046 2550], about 110 m above river level.

A small patch of undifferentiated river terrace gravels occurs around Neatham, near Alton [SU 742 406], which extends up to 115 m OD. This is probably part of the second terrace of the Alton Wey which has merged with a degraded higher terrace remanant.

Alluvium

In the Alresford district, alluvial deposits are confined to a narrow outcrop along the major river valleys. The alluvium generally comprises three distinct lithologies; well-sorted basal lag gravel, peat, and soft, organic, mottled silty and sandy clay. These are so interdigitated as to make their differentiation impractical.

The exact composition of the deposit varies according to the parent bedrock source; on the Chalk, fine-grained calcareous silt, clay and marls overlying coarse-grained flint gravels predominate, whilst in the area of the Lower Greensand, calcareous deposits are seldom seen, their place being taken by sandy or silty loams, often commonly with a coarse-grained sand texture. The basal lag gravel is composed of mostly small matrix-supported subangular/ to subrounded and rounded flints, probably derived from adjoining terrace or head deposits. Thin stringers of gravel may also occur elsewhere within the sequence, indicating channel migration or periodic increases in the flow regime of the river over time. The silty loam is normally pale grey and commonly contains fragments of flint and chalk. Small accumulations of peat and peaty material are associated with alluvium and the river terrace deposits throughout the area but appear to be more common in the streams draining the Lower Greensand strata. Peat deposits generally tend to accumulate in the backwater marshy areas away from the main stream. It occurs as a dark brown or black organic deposit with varying admixtures of marl and loam, and is typically fibrous and spongy. They are however generally too limited in extent to map. Several outcrops of dark, silty peat in excess of 1.5 m thick were noted east of Petersfield in the Rother valley [SU 772 226] in the extreme south-east of the district.

In general the alluvium in the Alresford district is thin, usually between 1 and 3 m in the upper reaches of rivers, and consisting mostly of gravel, but at major confluences and in the lower reaches of the rivers up to 8 m have been proved. A common characteristic of streams flowing over chalk bedrock is the presence of calcareous tufa associated with peat accumulations at springs. No occurrences of calcareous tufa were sufficiently large to be mapped in the district, but thin concretionary carbonate deposits coating stream bed gravels were noted in places in the Meon and Itchen river valleys.

Details

The Itchen and its tributaries

Much of the alluvium in the Old Alresford Pond [SU 590 331] has accumulated since, and as a result of, the damming of the valley there at the end of the 12th century (Osborne White, 1910). At Ovington and Avington the alluvium forms a peaty marsh, in many places rising only a few tens of centimetres above the stream, which traverses it in numerous shallow, braided channels. The alluvium here consists of a thin layer of peaty clay and chalky silt overlying loose, white gravel of chalk pebbles and tufa-coated flints. Boreholes where the old railway line crosses the valley [SU 5695 3234] prove up to 5 m of flinty gravel over Chalk. In the upper part of the Itchen Valley, above Itchen Stoke, many small exposures of brown loam and silty clay, capping a more or less chalky gravel, can be seen in the stream banks, drains, and watercress trenches at Cheriton and Hinton Marsh (Osborne White, 1910). At the source of the Itchen in New Cheriton, the sides of the stream channel show up to a metre of mottled brown, stiff, sandy marl in which fragments of Chalk fossils are plentiful. Here, up to 2 m of flinty gravel were proved in a borehole (SU52NE/20) [SU 58890 27430].

In the Candover Valley, dark loam overlying flint gravel was noted in the banks of the stream near Fob Down Farm, and other places below Abbotstone (Osborne White, 1910). A borehole (SU53SE/38) [SU 5693 3353] recorded 1.2 m of peat overlying a metre of gravel. Farther upstream, the alluvium at the surface in the valley south of ‘The Grange’ [SU 5637 3536], consists of a white marly flinty clay. Upstream of the artificial lake, the clay is replaced by flinty gravels which merge imperceptibly with the valley head further up-valley.

River Rother and its tributaries

The bulk of the alluvium here is a brown, ferruginous, silty sand, although nearer the outcrop of the Gault Clay, the alluvium is generally heavier and more clay rich. Below Sheet, the Rother has higher and more sharply defined banks than the other streams of the district. The alluvium and its narrow alluvial flats, lie up to 3 m or more above normal river level, and are frequently bordered by small bluffs, forming a succession of minor terraces. These features are well displayed at Durford, and to the south of Rogate, where the alluvium is notably sandy (Osborne White, 1910). The maximum thickness of alluvium in the Rother valley is 3.5 m near Petersfield [SU 7220 2348]. South of Wenham Manor Farm [SU 7891 2333], the alluvium consists of 1.4 m of greyish brown sandy clay with a gravelly base, resting on the Pulborough Sandrock Member. Nearby over 3.5 m of alluvium was proved, consisting of mottled yellow and grey, slightly silty clay, becoming yellowish brown and stiffer with depth.

Alton Wey and its tributaries

Brown silty clay, and paler, grey-brown marl (the latter composed largely of material derived from the Grey Chalk Subgroup) are seen in the banks of the Wey at Alton, and in those of the Caker Stream south-east of Wilsom. By Haw Bridge south-east of Cuckoo’s Corner [SU 7447 4117] the banks of the Wey show thin silt and clay over stratified, sandy, calcareous gravel containing malmstone in subangular blocks (Osborne White, 1910).

Borehole (SU73NW/29) [SU 7232 3955] in the alluvium just south of Alton station prove almost 4 m of firm compact greyish white to pale brown chalky silt, with intact fragments of grey chalk increasing in size and quantity with depth.

Meon valley

Above West Meon the alluvium consists mostly of brown silty clay, but farther downstream it assumes a dark tint, due to the presence of peat. Half a mile north-east of Warnford a channel in the water meadows shows grey and brown marl with modern mollusca, beneath a thin cover of black, peaty soil. Drains and stream banks, north of the bridges at Warnford, show up to 0.5 m of peat, resting partly on grey marl and chalky gravel. A borehole (SU62SW/12) [SU 6246 22340] proved about 3 m of flinty gravel over chalk (Osborne White, 1910).

Blown sand

East of West Heath Common there is a tract of hummocky ground [SU 794 227] composed of coarse-grained, brown sand, irregularly mantling the Folkestone Formation, Marehill Clay and Pulborough Sandrock. The Folkestone Formation probably provided the source material, although it is possible that the river terrace deposits may have contributed. It is thought to have accumulated under periglacial conditions when the lack of vegetation allowed wind erosion of the relatively uncemented sands of the Folkestone Formation. Here it is estimated to be only a few metres thick.

Artificial deposits

The more extensive areas of artificial deposits and worked ground are shown on the map but many minor occurrences have been omitted for clarity. The 1:10 000 scale maps of the district, listed in the information sources show a more detailed distribution. Artificial ground is common, especially within the urban areas and associated with the development of major routeways.

Made ground

Extensive areas of made ground are associated with major routeways such as the A31 Alresford bypass, the A3 and M3, particularly where these routes have been upgraded over the last 30 to 40 years. The nature of the fill it not known in detail but is generally engineered to take the weight of traffic.

Many other smaller areas of made ground occur in the Alresford district, most notably the considerable embankment dating from the 12th century holding back the Old Alresford Pond [SU 5884 3312]. Made ground is also associated with developments such as sewage works [SU 590 306], construction projects such as new schools, farm buildings and housing estates. Many of these are too small to be shown on the map. Many urban areas are underlain by a variable amount of made ground resulting from previous development.

Worked ground

Worked ground is shown where natural materials are known to have been removed, for example in quarries and pits, road and rail cuttings and general landscaping. There are a number of disused pits and quarries in this district associated with the extraction of chalk, river terrace and head gravels, the Gault Clay Formation and the Folkestone Formation. Only major areas of worked ground, generally associated with mineral extraction, are shown on the published maps.

Kingsley Sand Quarry comprises two sites either side of the B3004 to the west of the village of Kingsley where sequences (2 to 8 m in thickness) of sand and partially indurated sandstone towards the top of the Folkestone Formation can be seen. The northern site (Lode Farm) [SU 779 379] totals an area of 10.1 hectares and contains the quarry plant and an unrestored quarry void used for the supply of water and silt settlement and disposal. The southern site at Rookery Farm [SU 774 371], about 1 km south-west of Kingsley covers about 12.6 hectares and contains the current sand working and reserves. This part of the quarry was not in existence at the time of survey and is not shown on the Alresford sheet. Extraction in this area has been continuous from at least the turn of the century and pits were noted in the Alresford Memoir (Osborne White, 1910). Abandoned quarries are being restored to agricultural production, principally by domestic landfill, and new, greenfield sites (Rookery Farm) were being developed at the time of the survey. The Folkestone Formation has also been worked for sand in pits around Sleaford [SU 800 384]; [SU 805 384]; [SU 809 385].

The Gault clay has been worked from several old pits along the outcrop [SU 812 391], the largest of which is the Selborne Brickworks [SU 767 343], where it is dug for the manufacture of bricks and some specialised brick mouldings.

Infilled ground

Several areas of infilled ground are shown, most are backfilled old railway cuttings or mineral workings. In most cases the nature of the fill is unknown. Smaller areas of infilled are not shown on the 1:50 000 maps but are shown on the larger scale geological maps held in BGS archives.

Several of the disused railway cuttings on the line between Warnford and Alton have been infilled, particularly north of Privett [SU 6734 2836] and [SU 6745 2796] and near Meon Hut [SU 6513 2558]. A sand quarry just west of Sleaford [SU 799 384] has now been infilled.

Chapter 8 Applied Geology

Hydrogeology

The Chalk is the major aquifer in the district and has the largest storage capacity and catchment area. It is a dual porosity aquifer with both matrix and fracture porosity. The overall porosity of the Chalk varies between about 5 per cent and 45 per cent and depends on stratigraphy (Price, 1987; Bloomfield et al., 1995). For example, the upper part of the White Chalk Subgroup of southern England has an average porosity of 39 per cent, the lower part has an average porosity of 28 per cent and the Grey Chalk Subgroup a porosity of 23 per cent (Bloomfield et al., 1995). Generally more clay-rich chalks, often found lower in the sequence, are associated with lower matrix porosities and, in addition, low porosity is also associated with nodular and hardground bands such as the Melbourn Rock and the Stockbridge Rock Member. Chalk pore-throat sizes have been described by (Price et al., 1976) and average pore-throat sizes are typically in the range 0.1 to 1 microns. Consequently, because of the small matrix pore-throat size matrix hydraulic conductivity is very low, of the order of 6 x 10⁻⁴ m/d (Allen et al., 1997), and most of the flow takes place through the fracture network. The fracture style is affected by the stratigraphy (Mortimore, 1993), which influences local and sometimes regional groundwater flow.

Each Chalk formation has differing aquifer properties resulting from the lithological control on fracture style and spacing, the presence or absence of marl seams, and the frequency and style of flint bands, hardgrounds and other stratigraphical discontinuities. Marl seams, bedding planes, sheet flints and tabular flints are all horizons where downward percolation of water may be impeded. Dissolution often occurs where flow is concentrated along these horizons, creating small-bore anastomotic conduits. The strength of the chalk is also important. Fractures in very soft chalk are often commonly sealed by remoulded chalk putty, and thus form aquitards or even aquicludes. Joints in harder, nodular chalks often may remain open and thus solution cavities can develop more readily.

Certain thicker, persistent hardgrounds, such as occur in the Lewes Nodular Chalk and Holywell Nodular Chalk, and persistent marl horizons consistently provide stratigraphical controls on groundwater movement. Commonly the more competent hard bands are highly fractured relative to the surrounding softer chalk and can act to channel flow. Marly horizons may provide a barrier to vertical flow, with a zone of increased dissolution forming above. A study by Headworth et al. (1982) using seasonal groundwater abstraction in connection with the Candover river augmentation scheme showed that the Seaford Chalk around Alresford has a particularly thin and well-developed 6 m-thick zone possessing both high transmissivity and storativity.

Some of the water issuing from springs at the Gault/Upper Greensand contact in the Alton Wey valley is probably derived in part from the Chalk which is in hydraulic continuity with the Upper Greensand. With the exception of the Itchen, the Alton Wey and Meon rivers and the lower reaches of minor tributary streams in the district, valleys are normally devoid of surface water over the Chalk.

Water is also obtained from the Upper Greensand, which is in hydraulic continuity with the Chalk, and from the Lower Greensand. The latter is a separate aquifer beneath the aquiclude of the Gault. Water is also obtained in small quantities from the superficial deposits, but supplies are variable in both quantity and quality. The Upper and Lower Greensand sands are porous, essentially non-fissured aquifers, although the Upper Greensand is loosely indurated with some fissuring. Wells in the Chalk are generally unlined whilst those in the sands require screening.

Details

Numerous small springs issue from the Atherfield Clay and Beds and lower Hythe Formation on the sides of Harting Combe [SU 810 258], but much of the groundwater flow in this area is downdip away from the anticlinal axis, resurging at strong springs on the north or east side of the River Rother between Mangers (east of Liss) and Rogate.

The Upper Greensand is generally quite porous, and there is generally little surface drainage. Small springs occur along the front of the escarpment, but the largest springs occur in the deep valleys which indent the Upper Greensand escarpment and extend back to the Chalk scarp. Most of the springs occur at or near the base of the Upper Greensand, close to the contact with the Gault clay.

The largest springs issue from the Chalk. Yields from the Chalk Group of the Alresford district (Flett and Hearsum, 1976) vary between the formations with values of the order of 67 l/s in the White Chalk Subgroup. The highest yields, up to 150 l/s, are obtained from large diameter shafts, boreholes and headings in the upper part of the Chalk sequence. Wells in the lower more marly Chalk generally provide lower yields. Many small springs, for example the Well Head spring (Plate 15) at Selborne [SU 7433 3273] mentioned by Gilbert White (1789) and Gaswell’s spring, Holybourne [SU 7324 4120] rise at the base of the Chalk escarpment at or close to the base of the West Melbury Marly Chalk, or at the base of the Zig Zag Chalk. Typically these springs produce fairly small yields (around 2 to 4 l/s). The aquifer also contributes to the base flow of the rivers draining across the Chalk outcrop.

Very few springs occur in the Holywell Nodular Chalk or the New Pit Chalk, with the exception of the head of the Alton Wey at [SU 7076 3937] and along the River Meon around Warnford where the chalk is quite steeply dipping. The largest springs occur round Alresford, and form the headwaters of the River Itchen. These rise from the upper part of the Seaford Chalk and, around Cheriton, the lower Newhaven Chalk. Many of these have been adapted for use in the watercress industry. The location of the springs may be controlled in part by the well-developed flint seams in the Seaford Chalk. Many other small springs probably occur along the length of the Itchen valley, but any discrete input from the Chalk generally enters the gravelly alluvium beneath the valley floor. These gravels form a highly porous aquifer in direct hydrological contact with the river. Thus any discrete point inputs from the chalk become diluted into this aquifer before entering the river as a diffuse outflow.

The hydrology of the Candover area in the north-west of the district was the subject of a major investigation by Southern Water in the late 1970s as part of a project to use pumped boreholes to augment the flow of the River Itchen. This involved the construction of six boreholes, three of which were used for production at Axford (SU64SW/45) [SU 611 430]; Bradley (SU64SW/2) and (SU64SW/3) [SU 626 419] and Wield (SU64SW/51) [SU 615 405] linked via a pipeline to the outflow at Swarraton [SU 5685 3673]. The mean flow at the outlet was 148 l/s. The detailed hydrological observations and data are recorded in a report by the Southern Water Authority (1979).

There are no well-defined stream sinks in the region although it is said that more water escapes from Old Alresford Pond by leakage to underground sinks than by normal overflow at the dam and ‘sometimes the water drains away so rapidly that the fish have no time to escape, and are left behind on the mud which forms the bed of the pond’ (Osborne White, 1910). However, some bourne holes have been recorded in the upper reaches of the Itchen catchment around Bramdean, and on the River Meon between East and West Meon, which may act as sinks under certain flow conditions.

Bulk minerals

Sand and gravel

Sand and gravel has been won from the Folkestone Formation, river terrace deposits and from the gravelly head in the major valleys. Fine- to medium-grained sands are extracted from the Folkestone Formation at West Heath [SU 785 228] in the south of the district and for building sand around Kingsley. Several disused sand pits occur around Sleaford [SU 800 384]; [SU 805 384]; [SU 809 385]. Flint gravel has been extracted from numerous small shallow pits in the gravelly head deposits in the west of the district around Brown Candover [SU 586 399], the valley between Lasham and Alton (for example at [SU 6777 4130]) and from many sites along the upper reaches of the Bramdean valley between Cheriton and Privett.

Clay

In the past, the Gault, Weald Clay, Reading Formations and the ‘brickearth’ were used in the manufacture of bricks and tiles. There is one working pit at Selborne where the Gault is worked to produce bricks and specialised brick mouldings. The Gault was usually used for manufacturing bricks and rough earthenware. Many other small disused brick pits are known along the Gault outcrop, and also in Harting Combe where the Weald Clay was used. Brick clays have been worked from the Reading Formation around East Stratton and from many sites scattered across the clay-with-flints outcrop, for example at West Park near Preston Candover [SU 5990 4213]. Some of these sites may be working degraded Palaeogene outliers or clay infilling dissolution pipes.

Chalk

There are many pits in the district attesting to the great historical use of the material for the liming of fields. Many of these are scattered around the clay-with-flints outcrop and may represent former sinkholes. Most are abandoned and degraded but agricultural lime is still produced from Dudman’s Quarry [SU 658 305] near Ropley Dean and from several small pits near Preston Candover. Many small pits have been ploughed over, infilled or degraded.

Building stone

Building stone is not produced commercially in this district, but in the past locally derived materials have been used in construction. Only the Upper Greensand ‘malmstone’ or ‘bluestone’ was extensively worked. The best quality building stone comes from indurated calcareous siltstones (‘bluestone’) found as discrete beds within the malmstone. Excellent examples of houses built of this stone can be seen in all of the villages along the foot of the escarpment. This stone used to be in great demand as a hearth stone.

Limited use has been made of the harder beds within the Chalk sequence (Melbourn Rock, nodular beds within the Lewes Chalk). Flint nodules were extensively used for building, both as dressed squared-flint and single-faced trimmed nodules, particularly in churches and larger houses. Flint, as a ‘waste’ product of chalk extraction and from ‘field picking’, has also been used to maintain farm tracks. Blocks of Cenozoic sarsen stones have been used together with flint in churches, stone walls and some buildings. Some of the Lower Cretaceous sandstones such as the ‘Bargate Stone’ and the harder cherty sandstones of the Hythe Formation have been used around Liss.

Iron ore

Iron ore has been worked in the past from a thin sideritic mudstone in the Weald Clay near Petersfield. The workings are mainly shallow bell pits and are now disused.

Fuller’s earth

The Hollygate Borehole at [SU 8085 3404] proved two thin beds of fuller’s earth towards the top of the Sandgate Formation, at 15.90 to 16.58 m and 22.7 to 23.3 m. Characteristically, the fuller’s earth beds show a high smectite content (>90 per cent) towards the base of the bed, with increasing quartz towards the top. The fuller’s earth deposits are too thin to be of economic interest (Moorlock and Highley, 1991).

Hydrocarbons

The Alresford area lies within the western part of the oil-prone Weald Basin. This covers a large area of southern England, south and south-west of London, and contains several small oil fields (Figure 54). The Weald area was first explored in the 1930s and, more successfully, in the 1980s with the discovery of eleven oil and gas fields including the Humbley Grove, Stockbridge, Horndean, Singleton and Storrington fields. The producing oil fields are located in the western half of the Weald basin, as the quality of the reservoir decreases to the east due to facies variation and less favourable diagenetic history (McLimans and Videtich, 1987; Scott and Colter, 1987). The oil is derived from a mature oil ‘kitchen’ in the central part of the Weald basin, from where oil migrated up into the oil reservoirs around the basin margin.

Two of these fields are located in and around the Alresford district; at Humbly Grove [SU 692 443] just to the north of the district, 5 km north-west of Alton, and a recently discovered oil field at Matterley Farm, [SU 550 300] near Avington which is still undergoing evaluation. Oil was also found in an exploratory well at Lomer [SU 595 235], on the southern margin of the sheet.

The main reservoir in the Alresford district is the Middle Jurassic (Bathonian) Great Oolite Group, and particularly the Great Oolite Limestone (Butler and Pullen, 1990). The process of hydrocarbon formation, migration and entrapment is controlled by east-west, pre-Albian extensional faults. The Humbly Grove Oilfield is developed on a clearly defined tilted horst block bounded by two such (now reversed) extensional faults. In the basins to the south of the major faults, and particularly in the centre of the Weald Basin, the Lower Lias source rocks (mostly mudstones), and possibly the Kimmeridge Clay were buried sufficiently deep to generate hydrocarbons. The hydrocarbons migrated south from the centre of the Weald Basin into the Great Oolite rocks of the palaeohighs, where antithetic faults provide traps. Migration probably began in Early Cretaceous times and may have continued until uplift in mid Cenozoic times (Penn et al., 1987; Hawkes et al., 1998). Although Cenozoic compression caused inversion of the Weald Basin, it did not destroy all the traps. Many anticlines in the both the Weald and Wessex Basins, for example the Portsdown and Littlehampton anticlines, do not contain oil and gas, suggesting that primary oil migration ceased before they were formed.

Details

The Humbly Grove Oilfield is located on the northern margin of the Weald Basin, just north of the Alresford district. The geology and development of the oilfield have been summarised by Sellwood et al., (1985) and Hancock and Mithern (1987). Two other small satellite fields occur near by at Herriard and Hesters Copse. Seismic reflection survey in the late 1970s, revealed the existence of a clearly defined, tilted, east-west-orientated horst block covering 50 hectares, bounded by two (now reversed) extensional faults, and closed to the east and west by the dip.

The initial discovery was made in May 1980, when the discovery well, Humbly Grove 1 (HG1-X1), was drilled. It encountered 41 m of oil-bearing Great Oolite limestone. Further wells were drilled into the Great Oolite reservoir in the early 1980s following further seismic surveys. One of these wells (HG2-A1) encountered a gas cap. Further appraisal identified two permeability zones within the reservoir; an upper zone of relatively high permeability and an underlying low permeability zone. Smaller amounts of oil and gas were also proved in the uppermost Triassic strata. Proven and probable reserves in the Great Oolite limestones were estimated at 13 million barrels of 39º API oil, with a gas cap of 3 billion cubic feet (Department of Trade and Industry, 2003). Geochemical analysis of the oil suggests the source rock is probably the Lower Lias clays and mudstones. Structural inversion of the basin in late Cenozoic times had little effect on the oil field except to terminate hydrocarbon production from the source rocks. To 2007, the Humbly Grove field has produced 734 000 tonnes of crude oil with another 34 000 tonnes at Herriard (Department of Trade and Industry, 2008). The Humbly Grove Oilfield is now becoming depleted and is being developed for underground gas storage.

The Avington prospect is located around Matterly Farm [SU 550 300], 5 km south-west of Alresford. Drilling by Carless in the 1987 (Avington-1 borehole) proved oil within the Great Oolite limestone both here and at the Lomer Borehole. Here the Great Oolite here was deposited in a high-energy shelf, with up to 13 per cent porosity. Further drilling and a revaluation of the seismic data demonstrated that the oil is contained within a composite structure comprising a footwall fault block and a hanging-wall inversion anticline. Small amounts of oil were also encountered in the overlying Cornbrash Formation and the younger Corallian sequence. The field is currently undergoing further development.

Geotechnical considerations

There are four principal hazards inherent in the strata of this district. These are documented in (Table 9) which gives potential ground constraints and the deposits with which they are commonly associated. The following statements should be taken only as a guide to likely or possible problems and should not replace site-specific studies.

The relatively loose sand of the Folkestone Formation provides unreliable foundations on steep slopes. Freshly ploughed fields or exposed ground can become gullied during heavy rainfall. The Gault contains highly shrinkable clays with high smectite content. Consequently they may move and crack during extreme drought conditions. Suitable precautions should be taken during construction. Peat, and other alluvial deposits which contain thin beds of peat, may be liable to compression and differential compaction when the ground is subject to loading.

Landslides and foundering of strata along the spring line between the Upper Greensand and the Gault is a known hazard along stretches of the crop. Most other natural slopes are thought to be stable in the district but this can be strongly influenced by human activity, particularly where oversteepened slopes are created during construction work.

The chalk may be affected by solution phenomena which result in small surface depressions (sinkholes) that range in size up to 50 m across and up to 6 m deep. These are common features of chalk outcrop in southern Britain, but distinguishing them from small, old chalk pits can sometimes be difficult. As a consequence of dissolution, fractures naturally occurring in the chalk are enlarged. The resultant pipes that may be filled with clay-with-flints, continue to provide sumps for excess surface water, and may be liable to further subsidence and differential settlement. Solution features are likely to be common on the outcrop of the higher chalk formations, particularly where a thin clay-with-flints or Palaeogene cover occurs nearby. Chalk adjacent to solution features or close to rockhead may often be highly weathered, and rubbly in texture indicating preferential dissolution along fractures and joints. Many borehole logs record a comparable upper rubbly top to the Chalk, particularly beneath the clay-with-flints or alluvium where the chalk is commonly in contact with flowing groundwater.

Chalk also has a number of unique engineering properties, which may create potential problems for ground engineering projects. The rock mass properties of each chalk unit are different and this affects their engineering and hydrological properties. Each formation has a particular fracture style and fracture spacing which varies depending on the type of chalk. This can affect the stability of excavations in the chalk which is largely controlled by the frequency and direction of natural cavities and joints. Some chalks, particularly the softer chalks in the White Chalk Subgroup have high natural water content and that may lead to slurrying if over compacted. These soft chalks are prone to puttying when weathered, which can seal fractures and significantly weaken the rock strength and integrity. Some units are extremely flinty, in particular the Seaford Chalk and Lewes Nodular Chalk formations. This can affect rock mass strength and cause problems for ploughing, earth moving and tunnelling.

In addition to the naturally occurring hazards, man has had considerable influence on the landscape. Many of the abandoned sand and gravel, chalk and clay pits in the area have been used as landfill sites particularly adjacent to the urban areas. Records are held by the local authorities but old areas of fill are commonly poorly documented. Cuttings and embankments for major road and rail links are commonplace in the district. Most natural slopes are thought to be stable in the district but this can be strongly influenced by human activity, particularly where over-steepened slopes on Palaeogene or superficial deposits are created during construction work.

Information sources

Further geological information held by the British Geological Survey relevant to the Alresford district is listed below. Enquiries concerning geological data for the district should be addressed to the Manager, National Geological Records Centre, BGS, Keyworth. Geological advice for this area should be sought from the Chief Geologist, England, BGS, Keyworth.

BGS books

British Regional Geology

• The Hampshire Basin and adjoining areas, 4th edition, 1982
• The Wealden district, 4th edition, (1965) 4th impression 1992

Memoirs

• Geology of the country around Andover, Sheet 283, 1908*
• Geology of the country around Basingstoke, Sheet 284, 1909*
• Geology of the country around Aldershot, Sheet 285, 1929*
• Geology of the country around Winchester and Stockbridge Sheet 299, 1912*
• Geology of the country around Alresford, Sheet 300, 1910*
• Geology of the country around Haslemere, Sheet 301, 1968
• Geology of the country around Southampton, Sheet 315, 1987
• Geology of the country around Fareham, Sheet 316, 1913*
• Geology of the country around Chichester, Sheet 317, 1903*
• Geology of the country around Bognor, Sheet 332, 1897*
• *out of print

Sheet explanations

• Geology of the Fareham and Portsmouth district, Sheet 316, 2000
• Geology of the Alresford district, Sheet 300, 2002.
• Geology of the Winchester district, Sheet 299, 2002.
• Geology of the Chichester and Bognor district, Sheet 317/332, 2003.

Sheet descriptions

• Geology of the Chichester and Bognor district, Sheet 317 and 332, 2002.
• Geology of the Fareham and Portsmouth district, Sheet 316 and 331, 2000.
• Geology of the Winchester district, Sheet 317 and 332, 2009.

Technical reports

• Technical reports relevant to the district are described below. Most are not widely available but may be purchased from BGS or consulted at BGS and other libraries

Geology

• Reference numbers for the technical reports covering the geology of individual or combined 1:10 000 scale geological sheets are given with the list of 1:10 000 series maps.

Biostratigraphy

• There are 17 biostratigraphical reports covering the Alresford district. Readers are recommended to contact the BGS, Keyworth (www.bgs.ac.uk) for access to these reports and to the Palaeontological collections.

Maps

Geology maps

• 1:1 500 000
• Tectonic map of Britain, Ireland and adjacent areas, 1996
• 1:1 000 000
• Pre-Permian geology of the United Kingdom, 1985
• Geology of the United Kingdom, Ireland and the adjacent continental shelf 1:1 000 000 South sheet, 1991.
• 1:625 000
• Bedrock geology of the United Kingdom (south sheet) 2007.
• Quaternary map of the United Kingdom (south sheet) 1977.
• 1:250 000
• Sheet 51N 02W Chilterns, Solid geology 1991.
• 1:50 000
• Solid and drift
• 283 Andover 1975* (new map in preparation 2008/2009)
• 284 Basingstoke 1974*
• 285 Aldershot 1976
• 299 Winchester 2002
• 300 Alresford 1999
• 301 Haslemere 1981
• 315 Southampton 1987
• 316 Fareham 1997
• 317/332 Chichester and Bognor 1996
• remapping recently completed or in progress.
• 1:10 000/1:10 560
• Details of the original geological surveys are listed on editions of the 1:50 000 geological sheets. Copies of the fair-drawn maps of the earlier surveys may be consulted at the BGS library Keyworth.

The maps covering the 1:50 000 Series Sheet 300 Alresford are listed below together with the surveryors’ initials and the date of survey. The surveyors were P M Hopson, A R Farrant, C R Bristow, R K Westhead, and A Pedley.

The maps are not published but are available for public reference in the libraries of the British Geological Survey at Keyworth and Edinburgh and the BGS London Office in the Natural History Museum, South Kensington, London. Uncoloured sheets are available for purchase at the BGS Sales Desk. Some sheet areas may be available as digital copies.

Geochemical maps

• 1:625 000
• Methane, carbon dioxide and oil susceptibility, Great Britain - south sheet, 1995.
• Radon potential based on solid geology, Great Britain - south sheet, 1995.
• Distribution of areas with above national average background concentrations of potentially harmful elements (As, Cd, Cu, Pb and Zn), Great Britain - south sheet, 1995.

Geophysical maps

• 1:1 500 000
• Colour shaded relief gravity anomaly map of Britain, Ireland and adjacent areas, 1997.
• Colour shaded relief magnetic anomaly map of Britain, Ireland and adjacent areas, 1998.
• 1:625 000
• Gravity Anomaly, UK South, 2007
• Magnetic Anomaly, UK South, 2007
• 1:250 000
• Sheet 51N 02W, Chilterns, 1980, aeromagnetic anomaly
• Sheet 51N 02W, Chilterns, 1983, Bouguer gravity anomaly
• 1:50 000
• A geophysical information map (GIM) at a scale of 1:50 000 is available for this district. This shows information held in BGS digital databases, including Bouguer gravity and aeromagnetic anomalies and locations of data points, selected boreholes and detailed geophysical surveys

Hydrogeological maps

• 1:625 000
• Sheet 1, England and Wales, 1997
• 1:100 000
• South Downs and part of the Weald 1978
• Hampshire and Isle of Wight, 1979
• Groundwater vulnerability of north-west Hampshire, Sheet 44, 1995
• Groundwater vulnerability of south Hampshire and Isle of Wight, Sheet 52 1996

Minerals maps

• 1:1 000 000
• Industrial minerals resources map of Britain 1996

Documentary collections

Boreholes

Borehole data for the district are catalogued in the BGS archives (National Geological Records Centre) at Keyworth on individual 1:10 000 sheets. For further information contact: The Manager, National Geological Records Centre, BGS Keyworth.

BGS Lexicon of named rock unit definitions

Definitions of the named rock units shown on BGS maps, including those shown on the 1:50 000 Series, Sheet 300, Alresford are held in the Lexicon database. This is available on website www.bgs.ac.uk. Further information on the database can be obtained from the Lexicon Manager at BGS Keyworth.

Material collections

Palaeontological collections

Macrofossils and micropalaeontological samples collected from the district are held at BGS Keyworth. Enquiries concerning all fossil material should be directed to the Curator, Biostratigraphy Collections, BGS Keyworth.

Petrological collections

Hand specimens and thin sections of rocks from the district are held in the England and Wales Sliced Rocks collection at BGS Keyworth. Enquiries concerning all petrological material should be directed to The Manager, Petrological Collections, BGS Keyworth. Charges and conditions of access are available on request from BGS, Keyworth

Borehole core collection

Samples and entire core from a small number of boreholes in the Alresford district are held by the National Geosciences Records Centre BGS, Keyworth.

BGS photographs

Copies of these photographs used in this report are deposited for reference in the BGS Library, Keyworth, and are accessible via the BGS website http://geoscenic.bgs.ac.uk.

Other relevant collections

Groundwater licensed abstractions, catchment management plans and landfill sites

Information on licensed abstraction sites, for groundwater, springs and reservoirs, catchment Management Plans with surface water quality maps, details of aquifer protection policy and extent of washlands and licensed landfill sites are held by the Environment Agency.

Earth Science conservation sites

Information on Sites of Special Scientific Interest present within the Alresford district is held by English Nature, Headquarters and Eastern Region, Northminster House, Peterborough PE1 1UA .

References

Most of the references listed below are held in the Library of the British Geological Survey at keyworth, Nottingham. Copies of the references can be purchased, subject to current copyright legislation. BGS Library catalogue can be searched online at http://geolib.bgs.ac.uk

Aldiss, D T, Marks, R J, Newell, A J, Royse, K R, Hopson, P M, Farrant, A R, Aspden, J A, Napier, B, Wilkinson, I P, And Woods, M A. 2002. The geology of the Pang-Lambourn catchment, Berkshire. British Geological Survey Commissioned Report, CR/02/298N.

Allen, D J, Brewerton, L J, Coleby, L M, Gibbs, B R, Lewis, M A, Macdonald, A M, Wagstaff, S J, and Williams, A T. 1997. The physical properties of major aquifers in England and Wales. British Geological Survey Technical Report, WD/97/34. Environment Agency R&D Publication 8.

Allen, J R L, and Narayan, J. 1964. Cross-stratified units, some with silt bands, in the Folkestone Beds (Lower Greensand) of south-east England. Geologie en Mijnbouw, Vol. 43, 451–461.

Allen, P. 1975. Wealden of the Weald: a new model. Proceedings of the Geologists’ Association, Vol. 86, 389–437.

Allen, P. 1981. Pursuit of Wealden models. Quarterly Journal of the Geological Society of London, Vol. 138, 375–405.

Allen, P. 1989. Wealden research: ways ahead. Proceedings of the Geologists’ Association, Vol. 100, 529–564.

Bloomfield, J P, Brewerton, L J, and Allen, D J. 1995. Regional trends in matrix porosity and dry density of the Chalk of England. Quarterly Journal of Engineering Geology, Vol. 28, S131-S142.

Booth, K A. 2002. Geology of the Winchester district. Sheet Explanation of the British Geological Survery, Sheet 299, (England and Wales).

Bristow, C R. 1991. Geology of the Petersfield district, Hampshire. Explanation of 1:10 000 Geological Sheets SU72NW, SU72NE, SU72SW, SU72SE, SU82NW and SU82SW. British Geological Survey Technical Report, WA/91/24.

Bristow, C R. 1998. Geology of the Rowledge-Headley-Liphook area (Hampshire and Surrey). British Geological Survey Technical Report, WA/98/64.

Bristow, C R, and Wyatt, R S. 1983. Geological notes and local details fro 1:10 000 sheets TP 01 NW, SW and SE, Pulorough and Storrington: part of 1:50 000 Sheet 317 (Chichester). Institute of Geological Sciences Technical Report, WA/83/003.

Bristow, C R, Morter, A A, and Wilkinson, I P. 1987. The stratigraphy and palaeontology of the Lower Greensand of the Hoes Farm Borehole, near Petworth, Sussex. Proceedings of the Geologists’ Association, Vol. 98, 217–227.

Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales).

Bristow, C R, Mortimore, R N, and Wood, C J. 1997. Lithostratigraphy for mapping the Chalk of southern England. Proceedings of the Geologists’ Association, Vol. 108, 293–315.

Bristow H W, and Whitaker, W. 1862. The geology of parts of Berkshire and Hampshire. Memoir of the Geological Survey of Great Britain.

Brydone, R M. 1912. The stratigraphy of the Chalk of Hants. (London: Dulau and Co. Ltd.)

Brydone, R M. 1942. Some zonal notes on the Chalk of Hants. (London: Jarrold and Sons.)

Butler, M, and Pullen, C P. 1990. Tertiary structures and hydrocarbon entrapment in the Weald Basin of Southern England. 371–391 in Tectonic events responsible for Britain’s oil and gas reserves. Hardman, R F P, and Brooks, S J (editors). Geological Society of London Special Publication, No. 55.

Buurman, P. 1980. Palaeosols in the Reading Beds (Paleocene) of Alum Bay, Isle of Wight, UK. Sedimentology, Vol. 27, 593–606.

Carter, D J, and Hart, M B. 1977. Aspects of mid Cretaceous stratigraphical micropalaeontology. Bulletin of the British Museum (Natural History)(Geology), Vol. 29, 1–135.

Casey, R. 1961. The stratigraphical palaeontology of the Lower Greensand. Palaeontology, Vol. 3, 487–621.

Chadwick, R A. 1986. Extension tectonics in the Wessex Basin, southern England. Journal of the Geological Society of London, Vol. 143, 465–488.

Cooper, M R, Bromhead, E N, Petley, D J, and Grant, D I. 1998. The Selborne cutting experiment. Géotechnique, Vol. 48, 83–101.

Department of Trade and Industry. 2003. The hydrocarbon prospectivity of Britain’s onshore basins. Department of Trade and Industry.

Department of Trade and Industry. 2008. UKCS oil production. Available from http://www.og.dti.gov.uk/information/bb_updates/appendices/Appendix9.htm

Dines, H G, and Edmunds, F H. 1929. The geology of the country around Aldershot and Guildford. Memoir of the Geological Survey of Great Britain, Sheet 285 (England and Wales).

Dines, H G, and Edmunds, F H. 1933. The Geology of the Country around Reigate and Dorking. Memoir Geological Survey Great Britain, Sheet 286 (England and Wales).

Dines, H G, Buchan, S, Holmes, S C A, and Bristow, C R. 1969. Geology of the country around Sevenoaks and Tonbridge. Second edition. Memoir of the Institute of Geological Sciences, Sheet 287 (England and Wales).

Drummond, P. 1983. The Micraster biostratigraphy of the Senonian White Chalk of Sussex, southern England. Géologie Mediterraneene, Vol. 10, 177–182.

Ellison, R A, Knox, R W O’B, Jolley, D W, and King, C. 1994. A revision of the lithostratigraphical classification of the early Palaeogene strata of the London Basin and East Anglia. Proceedings of the Geologists’ Association, Vol. 105, 187–197.

Evans, D J, and Hopson, P M. 2000. The seismic expression of synsedimentary channel features within the Chalk of Southern England. Proceedings of the Geologists’ Association, Vol. 111, 219–230.

Evans, D J, Hopson, P M, Kirby, G A, and Bristow, C R. 2003. The development and seismic expression of synsedimentary features in the Chalk of southern England. Journal of the Geological Society of London, Vol. 160, 797–814.

Farrant, A R. 1997. Geology of the area between Golden Pot and Bentley, Alton, Hampshire. British Geological Survey Technical Report, WA/97/68.

Fitton, W H. 1824. Inquiries respecting the geological relations of the beds between the Chalk and the Purbeck Limestone in the south-east of England. Annals of Philosophy, Vol. 24, 365.

Fitton, W H. 1836. Observations on some of the strata between the Chalk and the Oxford Oozite in the south-east of England. Transactions of the Geological Society of London, Vol. 4, 103–389.

Flett, A G, and Hearsum, P G. 1976. Records of wells in the area around Alresford. Metric well inventory of the Institute of Geological Sciences. (Keyworth, Nottingham: British Geological Survey.)

Gale, A S. 1989. Field meeting at Folkestone Warren, 29th November, 1987. Proceedings of the Geologists’ Association, Vol. 100, 73–82.

Gale, A S. 1995. Cyclostratigraphy and correlation of the Cenomanian of western Europe. 177–197 in Orbital forcing timescales and cyclostratigraphy. House, M R, and Gale, A S (editors). Geological Society of London Special Publication, No. 85.

Gossling, F. 1929. The Geology of the country around Reigate. Proceedings of the Geologists’ Association, Vol. 40, 197–259.

Hamblin, R J O, Crosby, A, Balson, P S, Chadwick, R A, Penn, I E, and Arthur, M J. 1992. United Kingdom offshore regional report: the geology of the English Channel. (London: HMSO for the British Geological Survey.)

Hancock, F R P, and Mithern, D P. 1987. The geology of the Humbly Grove Oilfield, Hampshire, UK. 161–170 in Petroleum geology of north west Europe. Brooks, J, and Glennie, K (editors). (London: Graham & Trotman.)

Hancock, J M. 1975. The petrology of the Chalk. Proceedings of the Geologists’ Association, Vol. 86, 499–535.

Hawkes, P W, Fraser, A J, and Einchcomb, C C G. 1998. The tectono-stratigraphic development and exploration history of the Weald and Wessex Basins, Southern England. 39–66 in Development, evolution and petroleum geology of the Wessex Basin. Underhill, J R (editor). Geological Society of London Special Publication, No. 133.

Headworth, H G, Keating, T, and Packman, M J. 1982. Evidence for a shallow highly permeable zone in the Chalk of Hampshire, UK. Journal of Hydrology, Vol. 55, 93–112.

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Hopson, P M. 1994. Geology of the Treyford, Cocking and Chilgrove district, West Sussex. British Geological Survey Technical Report, WA/94/48.

Hopson, P M. 1996. Geology of the Warnford and Droxford district, Hampshire. British Geological Survey Technical Report, WA/96/70.

Hopson, P M. 1998. Geology of the area around Alton and Selborne, Hampshire. British Geological Survey Technical Report, WA/98/49.

Hopson, P M. 2000. Geology of the Fareham and Portsmouth district. Sheet Explanation of the British Geological Survey, Sheet 316 and part of 331 (England and Wales.)

Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaecous Chalk of England and Scotland with statements on the Chalk of Northern Ireland and the UK offshore sector. British Geological Survey Research Report, RR/05/01.

Hopson, P M, Farrant, A R, and Booth, K A. 2001. Lithostratigraphy and regional correlation of the basal Chalk, Upper Greensand, Gault and uppermost Folkestone formations (mid Cretaceous) from cored boreholes near Selborne, Hampshire. Proceedings of the Geologists’ Association, Vol. 112, 193–210.

Humphries, D W. 1956. Chert: its age and origin in the Hythe Beds of the western Weald. Proceedings of the Geologists’ Association, Vol. 67, 215–238.

Humphries, D W. 1964. The stratigraphy of the Lower Greensand of the south-west Weald. Proceedings of the Geologists’ Association, Vol. 75, 39–59.

Jarvis, I. 2006. The Santonian-Campanian phosphatic chalks of England and France. Proceedings of the Geologists’ Association, Vol. 117, 219–237.

Jefferies, R P S. 1963. The stratigraphy of the Actinocamax plenus Subzone (Turonian) in the Anglo-Paris Basin. Proceedings of the Geologists’ Association, Vol. 74, 1–33.

Juignet, P, Rioult, M, and Destombes, J P. 1973. Boreal influences in the Upper Aptian-Lower Albian beds of Normandy, north-west France. 303–326 in The Boreal Lower Cretaceous. Casey, R, and Rawson, P F (editors). Geological Journal Special Issue, No. 5.

Jukes-Browne, A J, and Hill, W. 1900. The Cretaceous rocks of Britain. Vol. I.The Gault and Upper Greensand of England. Memoir of the Geological Survey of Great Britain.

Jukes-Browne, A J, and Hill, W. 1903. The Cretaceous rocks of Britain. Vol. II. The Lower and Middle Chalk of England. Memoir of the Geological Survey of Great Britain.

Jukes-Browne, A J, and Hill, W. 1904. The Cretaceous rocks of Britain. Vol. III. The Upper Chalk of England. Memoir of the Geological Survey of Great Britain.

Kennedy, W J. 1969. The correlation of the Lower Chalk of south-east England. Proceedings of the Geologists’ Association, Vol. 80, 459–560.

Kirkaldy, J F. 1932. The geology of the country around Hascombe, Surrey. Proceedings of the Geologists’ Association, Vol. 43, 127–151.

Kirkaldy, J F. 1933. The Sandgate Beds of the western Weald. Proceedings of the Geologists’ Association, Vol. 44, 270–310.

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Middlemiss, F A. 1959. Field Meeting in the Hindhead area. Proceedings of the Geologists’ Association, Vol. 69, 239–243.

Middlemiss, F A. 1962. A fauna from the Puttenham Beds (Lower Greensand) of Hampshire. Proceedings of the Geologists’ Association, Vol. 72 (for 1961), 455–459.

Moorlock, B S P, and Highley, D E. 1991. An appraisal of fuller’s earth resources in England and Wales. British Geological Survey Technical Report, WA/91/75.

Morter, A A, and Wood, C J. 1983. The biostratigraphy of Upper Albian-Lower Cenomanian Aucellina in Europe. Zitteliana, Vol. 10, 515–529.

Mortimore, R N. 1979. The relationship of stratigraphy and tectonofacies to the physical properties of the White Chalk of Sussex. Unpublished PhD thesis, Brighton Polytechnic.

Mortimore, R N. 1983. The stratigraphy and sedimentation of the Turonian-Campanian in the southern province of England. Zitteliana, Vol. 10, 27–41.

Mortimore, R N. 1986a. Stratigraphy of the Upper Cretaceous White Chalk of Sussex. Proceedings of the Geologists’ Association, Vol. 97, 97–139.

Mortimore, R N. 1986b. Controls on Upper Cretaceous sedimentation in the South Downs with particular reference to flint distribution. 21–42 in The scientific study of flint and chert. Sieveking, G de G, and Hart, M B (editors). Proceedings of the Fourth International Flint Symposium held at Brighton Polytechnic, 10–15 April 1983. (Cambridge: Cambridge University Press.)

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Appendix

Locations of major Chalk sections by formation

The table below shows the location of all the major sections seen in the district.

Figures, plates and tables

Figures

(Figure 1) Location of the Alresford district.

(Figure 2) Shaded relief topographical map of the Alresford district.

(Figure 3) The main geomorphic features of the Alresford district.

(Figure 4) Areas mapped by each geologist.

(Figure 5) Stratigraphical nomenclature for the Lower Greensand of the western Weald.

(Figure 6) Structure of the Wessex - Weald Basin and cross-section across the Weald Basin.

(Figure 7) Structure contours on the base of the Lower Greensand Group. Scale 1:250 000. Contour values in metres below mean sea level.

(Figure 8) Fold and fault trends at surface as demonstrated by structural contours on selected horizons.

(Figure 9) Structural contours on the base of the (a) Glauconitic Marl and (b) the Melbourn Rock (basal Holywell Chalk) in the Chilcomb area.

(Figure 10) Depth to the Variscan basement.

(Figure 11) Lithological units subcropping beneath the basal Permo-Triassic.

(Figure 12) Map of the Lower Cretaceous strata in the Petersfield district.

(Figure 13) Correlation of boreholes along an east-west transect.

(Figure 14) Correlation of boreholes along a south-north transect.

(Figure 15) Schematic correlation of part of the Lower Greensand Group.

(Figure 16) The Folkestone Formation cored in Selborne 2 Borehole (SE73SE/39) [SU 7540 3435].

(Figure 17) Isopachyte plot of the Gault Clay (a), the Upper Greensand (b) and the combined Gault and Upper Greensand succession (c).

(Figure 18) Lithological logs of the Gault Formation and the Upper Greensand (‘Selbornian’) from the Selborne boreholes.

(Figure 19) A correlation of the Gault Formation based on published data.

(Figure 20) The Selborne Brickworks and adjacent ditch section.

(Figure 21) The principal features of the Gault Formation in the Selborne boreholes 1 to 3.

(Figure 22) Correlation of the lithological and geophysical logs across all three Selborne boreholes.

(Figure 23) Map showing the outcrop of the Upper Greensand.

(Figure 24) Upper Greensand Formation in the Selborne 1 Borehole (SU73SW/22) [SU 7320 3494].

(Figure 25) Correlation of the Upper Greensand based on published data.

(Figure 26) Contact between the Glauconitic Marl and the Upper Greensand, Water Lane, Alton [SU 7315 3810] to [SU 7330 3800].

(Figure 27) The basal Chalk Group from the Selborne 1 Borehole (SU73SW/22) [SU 7320 34940].

(Figure 28) Holywell Chalk sequence exposed near Charity Farm [SU 7391 3195].

(Figure 29) New Pit Chalk in a pit near Cadnam Farm [SU 7205 4139].

(Figure 30) New Pit Chalk sections in the Warnford - West Meon area.

(Figure 31) Lewes Chalk exposure at Becksteddle Farmhouse [SU 6980 3018] and Plain Farm [SU 6920 3018].

(Figure 32) Lewes Chalk succession at Crossing Cottage, near Bentworth Lodge [SU 6786 4133].

(Figure 33) Lewes Chalk seen in the north face of a pit near Bordean House [SU 6938 2418].

(Figure 34) Seaford Chalk exposures around Bentworth.

(Figure 35) Seaford Chalk sections on Sheet SU63NE.

(Figure 36) Sections near Hall Farm, Bentworth [SU 6641 3981] and Gaston Grange [SU 6530 3877].

(Figure 37) Sections in the railway cutting east of Four Marks and Medstead Station.

(Figure 38) Sections in the railway cutting south-west of Four Marks and Medstead Station.

(Figure 39) Seaford Chalk section in a pit near Kitwood Farm [SU 6735 3299].

(Figure 40) Section seen at Dudman’s agricultural lime quarry, Soames Lane, West Tisted [SU 6570 3050].

(Figure 41) Exposure of Seaford Chalk at the Grange, Swarraton.

(Figure 42) The Seaford Chalk section at Park Farm, Alresford [SU 5454 3253].

(Figure 43) Seaford Chalk sections in and around Alresford.

(Figure 44) Section in the disused railway cutting near Privett.

(Figure 45) Sections in the Newhaven Chalk around Bentworth, Medstead and Upper Wield.

(Figure 46) Newhaven Chalk exposures around Preston Candover.

(Figure 47) New Alresford railway cutting section [SU 5938 3238].

(Figure 48) Newhaven Chalk sections in the New Alresford - Cheriton area.

(Figure 49) Lithological log for the pit at Garrett’s Farm, West Meon. [SU 6457 2445]

(Figure 50) Lithological logs for the south and north portals of the Meon Valley railway tunnel [SU 6457 2483] and [SU 6485 2534].

(Figure 51) Junction of the Reading Formation and the Newhaven Chalk at East Stratton, after Osborne White, 1910.

(Figure 52) Principal Quaternary deposits and events in the Hampshire area.

(Figure 53) Generalised structural contours on the base of the clay-with-flints.

(Figure 54) Location of oil and gas fields in the Wessex-Weald Basin.

Plates

(Front cover) The River Itchen at Alresford, a typical chalk stream with a flint gravel bed. (Photograph A R Farrant) (P669600).

(Plate 1) Hythe Formation section on the Rogate to Rake road. (P212988).

(Plate 2) The now disused West Heath Sand Pit in 1981, 4 km east of Petersfield. (P212983). The pit is excavated in the Folkestone Formation. On the south side of the pit thinly-bedded sands with the bedding picked out by thin grey, buff or pink clay seams, up to 6 m thick, rest on medium- to coarse-grained, cross-bedded (not evident in this view which is at right angles to the dip of the foresets), friable sandstone. Fragments of ferruginous wood occur close to the junction of the two units.

(Plate 3) Representative core photograph from the Upper Greensand in the Selborne 1 Borehole; Ai at 15.70 m. (P741916).

(Plate 4) Representative core photograph from the Upper Greensand in the Selborne 1 Borehole; Aii at 23.60 m. (P741920).

(Plate 5) Representative core photograph from the Upper Greensand in the Selborne 1 Borehole; B at 28.85 m. (P741922).

(Plate 6) Representative core photograph from the Upper Greensand in the Selborne 1 Borehole; C at 39.40 m. (P741924).

(Plate 7) Representative core photograph from the Upper Greensand in the Selborne 1 Borehole; D at 63.15 m. (P741938).

(Plate 8) Road section through the Upper Greensand escarpment near West Worldham. (GS961). (P732271).

(Plate 9) This section micrograph of the Glauconitic Marl from the Selborne 1 Borehole. (P741930).

(Plate 10) The railway cutting to the east of Four Marks station in Seaford Chalk. (P741942).

(Plate 11) Contact of the clay-with-flints and the Newhaven Chalk near Medstead. (P741943).

(Plate 12) Structureless, fine- to coarse-grained flint gravel (older head) exposed in a pit at Chawton. (GS 964). (P732274).

(Plate 13) Bedales Sandpit, Steep. Older head overlying Folkestone Beds. (P212994).

(Plate 14) Sarsen stones excavated from old gravel pits in the valley bottom head deposits, Bramdean. (GS 958). (P732268).

(Plate 15) The Well Head water spout at Selborne. (P732275).

(Back cover)

Tables

(Table 1) Geological succession. Timescale from Ogg et al, 2008

(Table 2) Stratigraphical nomenclature and correlation of zonal schemes for the Chalk of southern England. #Traditional Chalk subdivision after Jukes-Browne and Hill (1903, 1904, for example). UGS = Upper Greensand; s.l. = sensu lato. *Foraminiferal zones after Carter and Hart, 1977; Swiecicki, 1980; Hart et al., 1989 (UKB zones) and Wilkinson, 2000 (BGS zones). Note to scale.

(Table 3) Deep oil exploration boreholes in and around the Alresford district.

(Table 4) The major subdivisons of the concealed pre-Jurassic strata of the district.

(Table 5) Major subdivisions of the concealed Jurassic strata of the district.

(Table 6) The principal elements of the concealed Lower Cretaceous strata of the district.

(Table 7) The lithological subdivisions of the Upper Greensand Formation.

(Table 8) Late Cretaceous foraminiferal and macrofaunal schemes in Southern England and their relationship to Chalk lithostratigraphy.

(Table 9) Potential ground constraints.

Tables

(Table 4) The major subdivisons of the concealed pre-Jurassic strata of the district

(Table 5) Major subdivisions of the concealed Jurassic strata of the district

(Table 9) Potential ground constraints