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Geology of the Winchester district. Sheet description of the British Geological Survey 1:50 000 Series Sheet 299 Winchester (England and Wales)

By K A Booth, A R Farrant, P M Hopson, M A Woods, D J Evans and I Wilkinson

Bibliographical reference: Booth, K A, Farrant, A R, Hopson, P M, Woods, M A, Evans, D J, and Wilkinson, I. 2008. Geology of the Winchester district. Sheet description of the British Geological Survey, 1:50 000 Series Sheet 299 (England and Wales). 79 pp.

Geology of the Winchester district. Sheet description of the British Geological Survey 1:50 000 Series Sheet 299 Winchester (England and Wales)

Authors: K A Booth, A R Farrant, P M Hopson, M A Woods, D J Evans and I Wilkinson

Keyworth, Nottingham: British Geological Survey 2008. © NERC 2008. All rights reserved. ISBN 978 0 85272 616 7

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(Front cover) Winchester Cathedral, a dominant feature on the landscape of the district, was built in various stages beginning in 1079. The two dominant building stones used in its early construction were Quarr Stone, from Quarr Abbey on the Isle of Wight, and an oolitic limestone from the Bath area (Tatton-Brown in Crook, 1993). Quarr stone (now Bembridge Limestone Formation) used for all the Romanesque masonry visible in the crypt, is a calcified bioclastic limestone with abundant bioturbation. It was frequently used for carved work. The second type of stone from the Great Oolite Formation (now named the Blisworth Limestone Formation) was quarried near Bath.

The cathedral is well known for its subsidence problems at the beginning of the century. At the end of the south-east chapel, the worst effects of the subsidence can be seen. The gravel base, on which the cathedral is built, slopes down towards the river. The water table is close to the surface and the medieval foundations were inadequate. As a result, this end of the cathedral in particular began to collapse at the turn of the 20th century and a major restoration project had to be undertaken. Even today, the crypt floods in the winter months as the level of the water table increases.

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Acknowledgements

This Sheet Description was compiled by K A Booth, D J Evans contributed to the description of the concealed strata. The manuscript was edited by P M Hopson and A A Jackson. Cartography by R J Demaine; page setting by A Hill. The authors’ thanks are due to the many landowners, tenants and quarry companies for access to land, and the Dean and Chapter of Winchester Cathedral for the front cover photograph.

Notes

The word ‘district’ refers to the area of Sheet 299 Winchester. National grid references are given in square brackets; unless otherwise stated all lie within the 100 km square SU. Borehole records referred to in the text are prefixed by the code of the National Grid 25 km2 area upon which the site falls, for example SU42SW, followed by its registration number in the BGS National Geological Records Centre. Lithostratigraphical symbols shown in brackets in the text, for example (NCk) refer to those shown on the published 1:50 000 map. Numbers at the end of photograph descriptions refer to the official collection of the BGS.

Chapter 1 Introduction

This Sheet Description details the geology of north-east Hampshire around Winchester and Stockbridge (Sheet 299) (Figure 1a). The district covers an area from Winchester and the M3 motorway in the east to the Hampshire–Wiltshire border (10 km east of Salisbury) in the west. It stretches from near Andover (and the A303 trunk road) in the north, to near Romsey in the south. The district is founded for the greater part on the Chalk with Palaeogene strata preserved in the south. The broad shallow slopes, and short, steep scarps, characteristic of the strata of the area, are cross-cut by the north-south-oriented Itchen and Test valleys, which split the area into two major interfluves (Figure 1b).

Geological history

Structurally, the district falls within the Wessex Basin (Figure 2), which extends over much of southern England. This basin comprises a system of post-Variscan extensional sedimentary basins and ‘highs’ that covered central southern England (and extended offshore) south of the London Platform and Mendip Hills during Permian to Mesozoic times (Table 1). At greater depths are 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-oriented wrench faults, thought to have originated during the Variscan Orogeny, have been tentatively identified in the basement, principally from seismic reflection data. This deformation was followed by a long period of erosion and a major unconformity marks the base of the Permo-Triassic succession.

In Permian times, subsidence associated with periods of tectonic extension began to affect southern England, initiating the development of a number of smaller fault-bounded basins within the Wessex Basin. 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 succession 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–Wessex and Channel basins, separated by the Hampshire–Dieppe High (also known as the Cranborne- Fordingbridge High).

This district straddles the northern margin of the Hampshire–Dieppe High and part of the Weald Basin; the boundary between these two structural provinces lies along the Portsdown–Middleton Faults, which underlie associated anticlines (Hopson, 2000). The Hogs Back–Kingsclere–Pewsey structure to the north of this district marks the boundary between the Weald Basin and the London Platform in the Andover–Basingstoke area.

Syndepositional movement on major faults resulted in thicker Jurassic successions being laid down on the downthrown (hanging wall) sides, the beds commonly thinning 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, rates of sedimentation increased evenly towards the depocentre of the Weald Basin towards the east of this district.

The sea began to flood the Wessex Basin in Rhaetian (Late Triassic) times, depositing sediments of the Penarth Group. The area of deposition increased gradually throughout the Jurassic, although minor periods of erosion occurred, mainly at the basin margins. By Upper 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 due to a combination 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) through shallow marine (Portland Group), to brackish water and evaporate precipitation (Purbeck Group), and fluviatile (Wealden Group). The final period of extensional fault movement, marked by normal faulting, resulted in the accumulation of thick successions of Wealden Group sediments in the main fault-bounded troughs in the Wessex 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 Group, Gault Formation, Upper Greensand Formation, and eventually the Chalk Group 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-Cainozoic 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 former 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 299 Winchester. The major extensional faults that control the asymmetric fold structures such as the Dean Hill Anticline can be seen beneath West Dean (Section 1, Sheet 299). The location of the Winchester–East Meon Pericline and associated fault can be noted (Section 2, Sheet 299) and the dramatic thinning of the Wealden and Lower Greensand Formations to the west (Section 1) is thought to be caused by progressive onlap of younger strata. The major folds are also well picked out by the structure contours on the base of the Stockbridge Rock Member and Palaeogene deposits.

History of research

The district was first systematically surveyed at the ‘one-inch’ scale by H W Bristow and published on ‘Old Series’ One-inch Geological Sheets in 1856–60. Part of the area was described by H W Bristow and W Whitaker in their memoir covering parts of Berkshire and Hampshire (sheet 12) in 1862. A J Jukes-Browne and Hill recorded some observations on the Upper Cretaceous rocks of the area in their memoir on the Cretaceous rocks of Britain published in three volumes between 1900 and 1904.

The first new series ‘six-inch’ survey was completed by W Whitaker and C E Hawkins and published in the ‘one-inch’ series in 1896. The memoir of the Geology of the country around Winchester and Stockbridge by H J Osborne White (sheet 299) was published in 1912. The sheet was reprinted in 1949 without revision. The sheet was reconstituted from the one-inch scale without geological revision and reprinted onto 1st series 1:50 000 base in 1975, with a reprint in 1990. Elements of the stratigraphy for this area are discussed within the memoir for the Southampton Sheet 315 (Edwards and Freshney, 1987).

The 1:10 000 scale revision survey of this district was carried out by P M Hopson, A R Farrant, K A Booth and C R Bristow between 1997–2000.

Early publications by Mantell (1822), Fitton (1824) and Murchison (1826) created a framework for the succession in the Weald and this part of east Hampshire. In an important memoir devoted to western Sussex, Martin (1828) was one of the earliest workers to clearly recognise the major sub-divisions of the Lower Greensand and superposed strata and he introduced a nomenclature to cover the succession from the Hastings Beds to the Lower Chalk. Brydone (1912) produced biozonal maps for the Chalk of Hampshire.

Within the district several authors have described aspects of the sedimentology of the successions. The correlation of the Lower Chalk of southeast England was expounded by Kennedy (1969) and Robinson (1986); whilst the petrology, condition of deposition, and diagenesis of the Chalk Group was considered by Hancock (1975). The detailed stratigraphy for the traditionally named Middle and Upper Chalk of East Sussex was demonstrated in Mortimore’s papers of 1986 and 1987. His named members can be successfully traced into this district and form the basis of the description of the Chalk contained herein (Bristow, Mortimore and Wood, 1997; Rawson, Allen and Gale, 2001).

Chapter 2 Pre-Cretaceous

The stratigraphy of the rocks buried beneath the district is known from boreholes sunk primarily for hydrocarbon exploration. Those at Farley (SU22NW/2) [SU 2358 2852], Lockerley (SU32NW/15) [SU 4306 1259], Goodworth (SU34SE/14) [SU 3694 4195] and Furzedown (SU32NE/3) [SU 4368 1284], together with a number of boreholes around Winchester (falling into sheets SU42NE, SU53SW and SU52NW) and Stockbridge (falling into sheets SU43NW, SU43NE, SU43SW, and SU33NE) form the basis of this account. The thicknesses of strata within these boreholes are summarised in (Table 2). At depth, a thin Permo-Triassic succession of limestone, siltstone, sandstone and breccia overlies beds of siltstone and orthoquartzite tentatively assigned to the Devonian ‘basement’. The structural contours and subcrops of the sub-Permian surface for the southern half of the United Kingdom (Smith, 1985) show a broad band of Devonian rocks stretching from south of the Mendips south-eastwards, across this district, and into part of the English Channel.

Devonian to Triassic

The Devonian has only been penetrated in the Goodworth 1 (SU34SE/14) [SU 3694 4195] and Stockbridge 4 (SU33NE/3) [SU 3964 3765] boreholes in the north of this district. Up to 40 m of ‘Old Red Sandstone’ is preserved beneath a major unconformity that removes much of the Carboniferous strata beneath this district. These rocks are predominantly sandstones with subordinate siltstones and mudstones preserved in fining-upwards cycles of fluviatile origin.

These early Devonian continental successions were deposited on the Brabant Massif to the north of the Cornwall Basin (Ziegler, 1982), a part of the Variscan Foredeep Basin; both basins derived much of their sediment from the continent of Laurasia to the north. Carboniferous strata, above the post-Devonian unconformity, has been encountered within boreholes to the south. These successions are principally Carboniferous limestone and up to 280 m was preserved in Farley 1 (SU22NW/2) [SU 2358 2852] in the far west of the district.

A thick succession of Permo-Triassic (P-T) strata is preserved above the unconformity throughout the district, namely Sherwood Sandstone Group, Mercia Mudstone Group and the Penarth Group. These have a maximum proved thickness of 315 m in borehole Goodworth1 (SU34SE/14) [SU 3694 4195] in this district. The Sherwood Sandstone Group is of variable thickness ranging from 10 m in the south-west to 57 m in the north comprising, red, yellow and brown sandstones, pebbly in part with subordinate red mudstone and siltstone. The Mercia Mudstone Group consists of mottled reddish brown and greyish green calcareous siltstone and marl with some thin sandstone. The overlying Penarth Group comprises fissile, dark grey mudstone and white to pale brown limestone.

Jurassic

The whole of the Jurassic succession is represented in rocks at depth below the district (Table 3). They are mainly marine in origin and rest conformably on the Penarth Group having been deposited within the subsiding Wessex Basin. The relatively uniform, cyclical successions of the Jurassic provide evidence, regionally, for an eastward shift of the area of maximum subsidence in the Wessex Basin when the faults bounding the Hampshire–Dieppe High became active. The Weald and Channel Basin depocentres developed at this time. In general, the beds thicken northwards and eastwards into the Weald Basin against major faults.

Chapter 3 Lower Cretaceous

Lower Cretaceous strata in southern Britain comprise an important succession that shows considerable vertical and lateral variation in both thickness and facies: the succession generally being fullest and thickest towards the basin centres (Whittaker et al., 1985). The Cretaceous period began with a short-lived marine transgression. Despite renewed subsidence at this time, clastic deposition into the Weald Basin was maintained in a nonmarine facies by an abundant sediment supply from the uprising London–Brabant Ridge to the north, Armorica to the south, and other land masses to the west and south-west. These lower Cretaceous sedimentary rocks are formally called the Wealden Group.

Wealden Group (W)

The Wealden Group includes the Weald Clay Formation and Hastings ‘Beds’. The Wealden was deposited in predominantly freshwater conditions, comprising a large shallow lake or lagoon that occupied much of the present area of Hampshire and the Weald. Some of the major siltstone-sandstone bodies are thought to have formed by lateral accretion from migrating channels of braided streams, but the thickest sand units are attributed to accretion of sediment transported into the basin from 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. Thicknesses vary greatly across the district and parts of the succession are completely absent in some boreholes.

In the Winchester district, the Lower Cretaceous strata are completely buried and relatively poorly understood with little published regarding their distribution and development. This is particularly so of the lowermost Wealden, which are generally concealed at depth beneath the Lower Greensand (LGS), Gault, Upper Greensand (UGS) and Chalk. However, a series of deep hydrocarbon exploration wells drilled across the Winchester and surrounding district (Figure 3a) provide valuable information on the subsurface nature and distribution of the concealed Wealden Group and other Lower Cretaceous rocks. Geophysical logs were run over the Lower Cretaceous interval in a number of these boreholes and the strata show characteristic log signatures that can be widely correlated between boreholes and to lithostratigraphical units. The correlations of the Lower Cretaceous Wealden Group presented here are 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 west-east correlation diagrams of the Lower Cretaceous sequences (Figure 3a) and (Figure 3b), illustrate that considerable lateral variations exist in the individual units. This is seen not only in the thinning of units to the north and west, but also the gamma-ray and sonic log responses which reflect lithological variations. However, despite the considerable thinning of the Wealden Group, there appears to have been no northerly or westerly overstepping of the earlier Wealden Group successions by the succeeding rocks. 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 boreholes in the extremes and beyond the present district for example Egbury 1 [SU 4447 5236] to the north, and Farley South [SU 2358 2852] in the west, (Figure 3b). The Welford Park Station Borehole [SU 4066 7364] proved Kimmeridge Clay overlain by thin Lower Greensand Group (LGS), illustrating that between it and the Egbury Borehole the entire Wealden, Purbeck, Portland and uppermost Kimmeridge Clay successions are truncated beneath the LGS (Figure 3a).

The lateral change in log character is most clear in the mudstones of the Weald Clay Formation 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 fine and highly serrated character. To the north and west, the signal becomes more deeply serrated (‘ratty’), with increasingly thick units of lower gamma-ray value 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, reflecting proximity to basin margins to the north and west of the district. It also serves to make the distinction between the Upper Tunbridge Wells Sands and the sandier Weald Clay Formation increasingly difficult towards the basin margins.

The attenuation of the Wealden Group towards the basin margins may occur partly through onlap. However, the dramatic thinning of the Weald Clay Formation is strongly suggestive of the removal of the younger Weald Clay succession beneath the Lower Greensand. Evidence of this is seen in borehole logs. Between Winchester, Stockbridge and Goodworth boreholes (Figure 3a), and more obviously the Old Alresford and Stockbridge boreholes (Figure 3b), the formation thins dramatically. Farther westwards, the Weald Clay Formation is absent in the Lockerley Borehole (Figure 3b).

Lower Greensand Group (LGS)

Rising sea levels flooded the Wessex Basin leading to the re-establishment of marine conditions. The boundary between the lower nonmarine succession, the Wealden Group, and the upper, marine Lower Greensand Group (LGS) is marked by the Late Cimmerian unconformity. This represents a gap in the succession that is greatest at the margins of the Weald–Wessex Basin, where much of the lowest Cretaceous is missing. This gap diminishes towards the centre of the basin and the unconformity divides into a number of short periods of nondeposition. Tidally influenced shallow marine and shoreline sands and clays form the Lower Greensand succession. Thicker successions were deposited in the Wessex Basin which subsided faster than the London–Brabant Ridge. Deepening of the basin continued into Albian times when the Gault, a succession of deeper marine clays, was deposited. The concealed Cretaceous strata are summarised in (Table 4).

Deep boreholes also reveal notable changes in the Lower Greensand Group to the north and west of the district. The dramatic westerly thinning of the group, seen in the Alresford district (Sheet 300), continues across the Winchester district and the unit is either absent or much attenuated and below the resolution of the geophysical logs, in the Farley 1 Borehole (SU22NW/2) [SU 2358 2852]. However, there are differences to the relationships, for example in the Alresford district, the Strat B1 Borehole demonstrates the absence of the Lower Greensand Group whereas to the north of the present district, the Welford Park Station Borehole [SU 4066 7364] proved the northerly persistence of the group.

At present it is not clear as to the likely nature of the thinning of the Lower Greensand Group. It seems most reasonable to suggest that it becomes either extremely thin or is lost due mainly to progressive northerly and westerly onlap, rather than truncation beneath younger strata of Lower Cretaceous age.

Gault Formation (G)

The Gault consists mainly of pale to dark grey, fissured, soft, silty clay with scattered phosphatic nodules up to 15 mm across. Its proven thickness is relatively uniform across the district, thinning only slightly to the south-west. Its maximum thickness (up to 80 m) in this district was proved in Winchester 2 Borehole (SU52NW) [SU 4544 1276].

Upper Greensand Formation (UGS)

This formation consists of pale, yellow-brown, grey and greenish grey bioturbated siltstone and silty, very fine-grained sandstone, with variable amounts of mica and glauconite. Its proven thickness is relatively uniform, up to 56 m thick (proven in boreholes) over much of the district but thins rapidly south-eastwards.

Chapter 4 Upper Cretaceous

Up to about 400 m of Upper Cretaceous chalk underlies the district, forming the extensive dip slopes across the area. The stratigraphical nomenclature used in this district is based on that of Mortimore (1986a) modified in Bristow et al. (1995, 1997) and as revised by the Geological Society Stratigraphic Commission (Rawson et al., 2001). The Chalk Group is divided into the Grey Chalk Subgroup and the White Chalk Subgroup, subsequently divided into ten formations, which form the basis of lithological mapping (Bristow et al., 1997) (Table 5).

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

Grey Chalk Subgroup (GYCK)

This unit, between 85 and 90 m thick comprises two formations, namely the West Melbury Marly Chalk Formation which is overlain by the Zig Zag Chalk Formation. The lower formation is entirely concealed within this district but is known to be a repetitive sequence of hard limestone and softer marl couplets, each pair being between 0.5 and 2 m thick at most. The base of the 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 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 includes all the chalk of the Cenomanian M. mantelli, M. dixoni and 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. The West Melbury Marly Chalk generally forms an aquitard between the Upper Greensand and the Zig Zag Chalk due to its high clay content. This formation is estimated to be 25 to 30 m thick in total at depth in this district.

Details

A series of boreholes investigating the hydrocarbon potential of the periclinal structure around Chilcomb can be interpreted to give information on the level of the Glauconitic Marl and the Plenus Marls members. Borehole (SU52NW/1) [SU 5034 2849] proved the Glauconitic Marl Member at 56.08 m (6.4 m OD). This indicates that the top of the West Melbury Marly Chalk Formation is likely to be encountered at depth between 35 and 30 m OD in the vicinity of this borehole. A nearby borehole (SU52NW/19) [SU 5010 2795] on the Chilcomb Ranges shows the Glauconitic Marl at -7.1 m OD. Farther east, within this district, the Glauconitic Marl is proven at 41.5 m below OD in Borehole (SU42NE/9) [SU 4827 2876] and at 97.3 m below OD in Borehole (SU42NE/4) [SU 4708 2778]. This demonstrates a westward plunge to this east-west structure.

Zig Zag Chalk Formation (ZCk)

This formation is composed typically of medium hard, greyish white, blocky chalk but maintains in its lower part the limestone/marl couplet characteristics of the formation below. In this district the Zig Zag Chalk is between 55 and 60 m thick but only the uppermost 40 m is seen at outcrop. The base of the formation is the Cast Bed (Bristow et al., 1997), which outside this district is known to be a very fossiliferous, pale yellow-brown calcarenite. In basin marginal situations such as in the Chilterns this marks a period of Mid–Cenomanian erosion that has removed the upper part of the West Melbury Marly Chalk Formation in places. However, in basinal successions, like that developed in the Winchester district, the Cast Bed normally rests on the Tenuis Limestone, the highest unit of the West Melbury Marly Chalk Formation, without break.

Higher in the succession the formation becomes less marly and is pale cream or white in colour. This colour change is thought to occur at the level of ‘Jukes-Browne Bed 7’ (a calc-arenite bed with phosphatic nodules). The top of the formation is taken at the erosion surface below the lowest marl of the Plenus Marls Member.

Details

In this district the Zig Zag Chalk outcrops only in the east near Winchester. Surface brash consists mainly of off-white to pale grey firm chalk fragments in thin calcareous soils. There are no extensive exposures in this area at the time of survey. Much of the outcrop is beneath pasture/recreation grounds and has been heavily landscaped during the construction of the M3 motorway (Hopson, 2001).

Jukes-Browne and Hill (1903) mentioned a pit ‘recently opened at Bar End’ which exposed ‘firm, massive chalk, greyish when wet but drying white’ which they attributed to the ‘Holaster subglobosus’ Zone based on a fairly extensive fossil collection. They give no details on thickness exposed, nor on its exact location, however, Brydone (1912) shows the location as south of Chilcomb Lane and north of Bull Drove on the east side of Bar End Lane. This area has been heavily restructured by both the works carried out for the old Winchester bypass and the new M3 motorway and this site is thought to be at a location [SU 4890 2827] which is now occupied by a small industrial complex surrounded by made ground.

White Chalk Subgroup (WCK)

This unit comprises eight formations in Southern England, but in the Winchester district, the youngest part of the succession (= upper Portsdown Chalk and Studland Chalk formations) has been removed by pre-Palaeogene erosion. Generally the Subgroup is characterised by white chalk with numerous flint seams, and is up to 350 m thick.

Holywell Nodular Chalk Formation (HCk)

The Holywell Nodular Chalk Formation includes the Plenus Marls Member, a series of closely spaced, marl beds at its base. This member is usually 1 to 3 m thick and is rarely exposed although it can be identified in field brash at a number of localities. The marls are overlain by the hard nodular chalks of the Melbourn Rock Member (about 5 m thick), that generally lacks significant shell debris. Above the Melbourn Rock the Holywell Nodular Chalk is characterised by its nodular chalk lithology and by its shell debris (dominantly of Mytiloides), which is in rock-building proportions where the bivalve has its acmes. The higher part of the Holywell Nodular Chalk is conspicuously more shell-rich than the lower part. In hand specimen the rock has a grainy rough texture, a feature that, in the absence of significant shell debris, helps distinguish these beds from the chalks above and below. The succession also contains thin interbedded flaser marls but these are only readily apparent in sections. The upper limit of this formation is at the top of the highest shell-detrital nodular chalk.

The Holywell Nodular Chalk belongs to the Upper Cenomanian M. geslinianum and N. juddii zones and the lower Turonian Mytiloides spp. Zone, with the stage boundary near the top of the Melbourn Rock. The base of Gaster’s I. labiatus Zone coincides with base of the Melbourn Rock.

The Holywell Nodular Chalk Formation is between 25 and 30 m thick, based on field estimates. It is seen at outcrop around Winchester itself.

Details

South-eastern area

The Holywell Nodular Chalk forms the short steep lower slopes encircling the floor of the Chilcomb valley and the floor of Cheesefoot Head Coombe [SU 529 282].

During the recent survey a small degraded, partly infilled and heavily overgrown pit with the remains of a kiln (presumably for the production of ‘quick lime’) was noted [SU 4889 2817]. This is thought to be an extension of this Bar End pit complex. The locality identified as being ‘another small pit about 10 feet above the last (the Bar End locality) has yielded a specimen of Actinocamax plenus [Praeactinocamax plenus]’. This site is probably that shown as a quarry [SU 4893 2800] on the ‘six-inch’ scale Ordnance Survey maps adjacent to the old Morestead Road. The area is now completely restructured and for the most part buried by the M3 and sliproads at Junction 10.

Griffith and Brydone (1911) note that their zone of Actinocamax plenus extends for some 10 feet (about 3 m) below ‘a thick marl band at the base of the Melbourn Rock’. In modern usage this would imply that the Plenus Marls at this locality must be about 3 m thick, the maximum thickness for this member in the Winchester district.

Griffith and Brydone (1911) noted further occurrences of their ‘Zone’ at the ‘Great Western Railway Goods-yard’ and ‘a small section at Wharf Hill, just east of Blackbridge’. The former is probably Brydone’s (1912) locality 55 at approximately [SU 4865 2870] and is within the mapped extent of the Zig Zag Chalk, whilst the latter locality as described at [SU 4859 2882] is within the basal Plenus Marls Member part of the Holywell Nodular Chalk. Neither locality is visible today.

Two pits [SU 4836 2789] on the north-western side of St Catherine’s Hill probably constitute Brydone’s localities 80 and 117 (but see also locality 117 in the section on the New Pit Chalk). At present these sections are heavily overgrown and degraded and show only very poor exposures in rabbit and badger diggings. There are two discernible working sites here, the lower is probably locality 80 and still retains an arcuate steep though obliterated face; with the upper (117) being poorly defined and completely degraded. It was much the same when visited by Osborne White (1912) and his description is essentially that contained in Barrois (1876). He described ‘hard compact chalk in beds about 3 feet (0.91 m) thick, separated by seems of marl and very nodular at the base’. The nodular chalk (in part the top of the Melbourn Rock) is reported as flintless about 33 feet (10 m) thick and dips at 6° to the south. This lower of the two pits probably constitutes much of the Holywell Nodular Chalk Formation with the exception of the base of the Melbourn Rock and Plenus Marls members as the higher pit is reportedly in Terebratulina lata Zone chalk characteristic of the New Pit Formation.

A platform [SU 4987 2892] excavated for new buildings at Hampshire County Councils sport facility south of the Petersfield Road exposed hard nodular and grainy chalk incorporating conspicuous pink bivalve debris and some larger fragments of inoceramid including Mytiloides (Woods, 1998, WH/98/3R)

The hard grainy, nodular and often shelly nature of this formation is noted frequently as field brash through the Highcliffe district towards Wharf Hill on the northern crop within the Winchester anticline centred around Chilcomb. The heavily wooded railway cutting now converted to a relief road (Barfield Close and its extension northwards) and which passes underneath the Bar End Road/Chesil Street junction shows infrequent small exposures of hard grainy and shelly chalks. A less overgrown section [SU 4872 2899] shows moderately hard, large blocky white to off-white grainy chalk with an uneven fracture and with some pink shell debris. The apparent dip at this locality is about 20° to the north-north-west.

The southern crop of the Holywell Nodular Chalk is greatly obscured by the works for the Winchester Sewage Farm, either side of the M3 motorway, on the north-eastern flanks of St Catherine’s Hill. To the east however, hard nodular and occasionally shelly chalks are noted as field brash in the thin pasture soils on the steep ‘buttressed’ slope leading to the Chilcomb Rifle Range. The Melbourn Rock Member is noted on a prominent positive feature at the base of the slope immediately adjacent to the rifle range.

The Melbourn Rock has been used to determine the structure of the area as shown in (Figure 4).

Brydone (1912) locality 79 [SU 4885 2797] is now obliterated by the extensive made and worked ground of the Winchester Sewage Works, the old Winchester Bypass and M3 Motorway. From the descriptions in Osborne White (1912) and Jukes-Browne and Hill (1903) this Brydone locality is probably the same as that referred to as Great Western Lime Works (‘on the east side of the road from Winchester to Morestead’). Osborne White (1912, pp.12, 15) describes the ‘northern’ part of the quarry including the Plenus Marls Member within his Lower Chalk according to the traditional Chalk stratigraphy. The section description is transcribed below:

Beds 2 and 3 were attributed to the subzone of Praeactinocamax plenus and Bed 1 to the Lower Chalk. Thus, Bed 1 is the topmost Zig Zag Chalk Formation; Beds 2 and 3 the Plenus Marls Member of the Holywell Nodular Chalk Formation, with Bed 4 the Melbourn Rock Member of the same formation. The beds are noted as dipping south at 4° to 5°.

‘The lower beds of the zone (‘Rhynchonella cuvieri’) are exposed in the upper stage of the quarry at the Great Western Lime Works, north-east of St Catherine’s Hill. The group of nodular and fissile bands representing the Melbourn Rock passes up into lumpy chalk, succeeded by homogenous white chalk which, owing probably to its greater proximity to the surface of the ground, has a more closely jointed character than the corresponding chalk at Chilcomb. Examples of Inoceramus labiatus [Mytiloides spp.] and Rynchonella cuvieri [Orbirhynchia cuvieri] are plentiful especially in the lumpy beds in the middle of the section.’

Although no thicknesses are given the included fossils indicate that the ‘lumpy beds’, at least, are within the Holywell Nodular Chalk Formation with the possibility that the highest beds extend into the overlying New Pit Chalk Formation.

New Pit Chalk Formation (NPCk)

The New Pit Chalk comprises medium-hard, massive-bedded, pure white chalk with regularly spaced pairs or groups of marls, each up to 15 cm thick. In this district, flints are confined to the upper half of the succession although, elsewhere in Sussex, they are known to occur sparsely down to within a few metres of the base of the formation. It is locally fossiliferous, especially with brachiopods and inoceramid bivalves. Thin-shelled Mytiloides hercynicus/subhercynicus are present near the base; they tend to be flattened and typically lack any preserved shell. Higher in the succession, Terebratulina lata and Inoceramus cuvieri are characteristic.

The formation is between 40 and 45 m thick in this district and its upper part is clearly exposed with the overlying Lewes Nodular Chalk in the M3 Twyford Down Cutting  [SU 490 278] (Plate 1), where the strata are seen to dip towards the south (at about 4°).

Details

South-eastern area

The New Pit Chalk forms the arcuate outcrop around the Chilcomb valley and into south-west Winchester where the plunging Winchester Anticline closes. The formation forms the steep slopes beneath The Soke [SU 489 292], Magdalen Hill Down near Spitfire Bridge [SU 496 294], through Winchester from the West Hill [SU 475 292] to the St Cross [SU 475 277] districts, around St Catherine’s Hill [SU 484 277] and the northward facing scarp of Twyford Down [SU 49 27]. The base of the New Pit Chalk is taken at the base of the Gun Gardens Main Marl, this being marked by the disappearance of abundant inoceramid debris and nodular chalk. The base of the formation lies in the topmost part of the M. labiatus Zone of the traditional scheme. Biostratigraphically the New Pit Chalk covers the uppermost part of the Mytiloides spp. Zone and the greater part of the overlying Terebratulina lata Zone. Brydone uses the now obsolete terms Rhynchonella ‘cuvieri (in part) and Terebratulina ‘gracilis’ (in part) zones to cover a similar interval. In the standard sections in Sussex, the formation covers the interval between the Gun Gardens Main Marl up to the base of Glynde Marl4 (Mortimore, 1986).

Brydone (1912) identified chalks of his Terebratulina ‘gracilis’ (lata) zone thought to be attributable to this formation at localities 78 [SU 4868 2880], in the Great Western Railway cutting now occupied by the Barfield Close Road and its extension northwards; and in the nearby locality (113A) described as the Station Cutting [SU 4877 2923]. The Station Cutting is described as containing ‘some of the chalk shown in the St Giles’s Hill quarry’. Modern mapping indicates that this must be strata within the lower part of the St Giles’s Hill Quarry that is identified as locality 113 [SU 4893 2914] by Brydone (1912). This quarry, near The Soke on St Giles’s Hill, is regarded as the best exposure of these beds on the northern flank of the Winchester Anticline and descriptive sections are shown in Jukes-Browne and Hill (1903) and Osborne White (1912) both based on translations of the section in Barrois (1876). A transcription of this section is given below:

The section is considered to include the Terebratulina gracilis and Holaster planus zones of Brydone the boundary between which is placed at the base of Bed 9. Lithostratigraphically the section must span the boundary of the New Pit Chalk and Lewes Nodular Chalk formations that is conventionally placed at the lowest nodular horizon. This would suggest that this lithostratigraphical boundary should be placed at the base of Bed 6 as described. There is some discord between the Osborne White and Jukes-Browne and Hill accounts with the former giving the dip as ‘8º a little east of north’ and the latter as ‘dipping to the north at 5º’.

Additional sites associated with the Winchester Bypass are described in the next section as they include some part of the upper New Pit Chalk Formation but also contiguous and more extensive sections in the overlying Lewes Nodular Chalk Formation. The northern end of the Twyford Down Cutting between [SU 4895 2763] to [SU 4880 2731] exposes a complete section of the upper part of the New Pit Chalk formation. This is shown graphically in (Figure 5) within the Lewes Nodular Chalk Formation section.

Lewes Nodular Chalk Formation (LeCk)

The Lewes Chalk comprises interbedded, hard to very hard, nodular chalks, with soft to medium-hard chalks and marls. The first persistent seams of flint occur near the base. The flints are typically black or bluish black with a thick white cortex. The formation is generally between 50 and 65 m over much of its crop. The Lewes Chalk is divided into two informal units by the Lewes Marls and the Lewes Flints, the latter comprising a ramifying system of black cylindrical burrow-form flints. The lower unit consists of medium- to high-density chalk and conspicuous, iron-stained, hard, nodular chalks. The upper unit is mainly of low- to medium-density chalks with evenly spaced thin hard nodular beds. The entire Lewes Nodular Chalk Formation can be seen in the Twyford Down M3 motorway cutting (Hopson, 2001a). The upper Lewes Nodular Chalk is further distinguished by the occurrence of the bivalve Cremnoceramus (Mortimore, 1986). There are several levels of discordant sheet flints within an interval of 4 or 5 m in the lower part of the Upper Lewes Nodular Chalk. The higher beds of the cortestudinarium Zone contain carious, ‘rinded’ flints.

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 and Pomerol, 1996) adjusted to the Glynde Marl 4 in Bristow et al. (1997).

The Lewes Nodular Chalk includes the upper part of the Terebratulina lata Zone, and all of the Plesiocorys (S.) plana and Micraster cortestudinarium zones. The base of Gaster’s Holaster planus Zone occurs within the lower part of the Lewes Nodular Chalk, about 10 m above the base. The base of Gaster’s Micraster coranguinum Zone should occur in the upper part or at the top of the Lewes Nodular Chalk, but in practice the correspondence is only very approximate.

Details

South-eastern area

The Lewes Nodular Chalk forms the steepest slopes around the northern margins of the Chilcomb valley and the steep-sided dry valleys and interfluves within the Winchester urban area (particularly around West Hill [SU 475 292], Sleepers Hill [SU 468 290] and Stanmore [SU 46 28]). The formation underlies Teg Down [SU 458 297] and forms the summit of St Catherine’s Hill [SU 484 277] and all of Twyford Down [SU 48 27]. The notorious Twyford Down Cutting, the scene of much anti-road-building protests in the 1990s, exposes the whole of the Lewes Nodular Chalk Formation [SU 488 274] to [SU 481 269] (see below). Positive features locally occur at various levels within the formation and are presumed to mark the hardest horizons. The base of the Lewes Nodular Chalk was taken as the base of the Glynde Marl 1 in Sussex, but one of the higher Glynde Marls (most commonly 4, see Bristow et al., 1997) is used elsewhere although invariably in the interval Glynde Marls to Southerham Marls.

A sketch of the whole of the M3 motorway cutting at Twyford Down is shown in (Figure 5) and (Plate 2a); (Plate 2b). The cutting shows the topmost part of the New Pit Chalk Formation, the whole of the Lewes Nodular Chalk Formation (although the upper third is not accessible from the carriageway catch ditches) and, at the highest level near the southern end, the Bar End Hardgrounds at the junction with the Seaford Chalk Formation (between Shoreham Marl 1 and 2, with Shoreham Marl 2 being the base of the Seaford Chalk). The beds dip at 4° to the south-west. The greater part of the succession can be observed from the top of the east cutting where a footpath crosses the motorway [SU 4895 2770] and from the common ground to the south. Access to the section is severely restricted and permission to visit is strictly controlled by the agents acting on behalf of the Highways Agency.

In a written communication to Mr Hopson from Professor R Mortimore (1st June 1998) the following observations were given based on his observations of the cutting during construction and whilst the higher beds could be reached.

‘Twyford Down is by far the largest of the three cuttings (...Bar End, Twyford and Shawford...) with 4 million cubic metres of chalk excavated. At the northerly end (near Morestead Pumping Station) the upper beds of the New Pit Chalk are exposed. The whole central part of the cutting is in the Lewes Nodular Chalk and the southern end just brings in the Belle Tout Beds of the Seaford Chalk. From north to south the features in this cutting include:

In addition there is a very fine example of the conjugate fracture style characteristic of the New Pit Member [now formation] and the lower Lewes Chalk. Karst features include a partially sediment-filled palaeocave system in the centre of the cutting and calcreted karst at the southern end along the main fractures and along the surfaces of the Bar End Hardgrounds and the Belle Tout Marls.

Abundant fossils include typical inoceramids, Micraster, Echinocorys and brachiopods characteristic of each horizon.’ (end of communication Mortimore, 1998).

The road cutting adjacent to Spitfire Bridge [SU 4973 2942] and for 400 m north and 200 m south of that locality exposes strata from the topmost New Pit Chalk Formation, all of the Lewes Nodular Chalk Formation and a considerable part of the Seaford Chalk Formation. A detailed log for this section, identified as M3 Cuttings Bar End, appears in Mortimore and Pomerol (1987, fig. 3, p.102). In the southern part of the section the dip is between 10° and 12° to the north but slackens off to the north such that it does not exceed 4° at the farthest northward observable point. The section although apparently open and fresh when observed from the road, upon close inspection shows that the face has been extensively netted to prevent rockfalls onto the carriageway and the in situ strata is obscured behind a wall of debris. Woods (1998, WH/98/3R) reports fauna indicative of the Seaford Chalk Formation between 83 m and 412 m north of Spitfire Bridge. The fauna includes thick-shelled Platyceramus and Cladoceramus undulatoplicatus together with, at the most northerly part of the section, abundant Conulus sp. This indicates that the Seaford Chalk exposed is probably in the range of the Seven Sisters Flint (in the south) to Whitaker’s 3-inch Flint and higher in the Micraster coranguinum Zone in the north. South of Spitfire Bridge no fauna was collected but the nodular lithology indicates that the Lewes Nodular Chalk is present for some distance until smoother blocky chalks characteristic of the New Pit Chalk are encountered in the drainage ditches around the Petersfield Road roundabout. In a communication to Mr Hopson from Professor R Mortimore (1st June 1998) the following observations were given based on his observations of the cutting before it was netted.

Bar End Cutting (Spitfire Bridge). The most northerly cutting (of the M3) is adjacent to Spitfire Bridge and exposed Upper Lewes Chalk from the Lewes Marl to the Shoreham Marls and most of the Seaford Chalk up to Whitaker’s Three Inch Flint Band. The Chalk dips north 12° in this cutting.

Features in the Bar End Cutting/Spitfire Cutting include:

A two-metre section [SU 4827 2645] (Woods, 1998, WH/98/119R) adjacent to a covered reservoir on Twyford Down Golf Course shows coarse nodular chalk becoming up-sequence white firm chalk with three distinct nodular flint horizons. The included fauna including Micraster sp., Cremnoceramus sp., Terebratulina striatula and Mimachlamys cretosa suggests assignment to the Micraster cortestudinarium Zone and hence the upper part of the Lewes Nodular Chalk.

A small section HP35 [SU 4565 2955] at the Butts in the valley east of Teg Down on the Royal Winchester Golf Club shows 1.78 m of hard to very hard, off-white to yellow stained, nodular chalk in beds up to 0.32 m thick interbedded with moderately hard to soft marly white chalk (a single bed 0.40 m thick) and numerous grey marl partings and thin beds, the thickest of which is 8 cm.

The St Giles’s Hill Quarry is described in the previous section but includes the basal part of the Lewes Nodular Chalk Formation.

Brydone locality 139 [SU 4884 2928] on the scarp at the south-west edge of the St Giles’s Hill recreation ground is within his Holaster planus zone, as is the southern portal of the St Giles’s Railway Tunnel locality 140 [SU 4877 2929].

Within Stanmore, [SU 4690 2830] at the site of a public house, a degraded pit with no exposure is equated with Brydone locality 114. This site is considered to be within the Terebratulina ‘gracilis’ zone of Brydone but lithologically it falls within the lower part of the Lewes Nodular Chalk.

Similarly Brydone’s locality 115 [SU 4715 2792], and the adjacent 140A [SU 4714 2789], although heavily degraded, still shows intensely to very hard, nodular, off-white, uneven fractured chalk typical of the Lewes Nodular Chalk. The site is described as within Brydone’s Terebratulina ‘gracilis’ var. lata and Holaster planus zones by Osborne White (1912) who describes a poor exposure as yellowish grey lumpy chalk in the Hyphantoceras reussianum Subzone, thus identifying equivalent beds to the ‘Chalk Rock’.

A small pit, now no more than a shallow scrape, is Brydone’s locality160 [SU 4410 2978] near Crab Wood, west of Winchester. Field brash locally shows hard grainy chalks attributed by Brydone to his Micraster cortestudinarium Zone. The same zone is exposed at locality161 [SU 4727 2720] in the railway cutting east of the demolished Bushfield Camp.

The Old Winchester Bypass formerly exposed this formation in the deep cutting to the west of St Catherine’s Hill. This exposure, for which there is apparently no modern published description, is now completely infilled with the excess material dug from the Twyford Down M3 cutting. The top of the New Pit Chalk Formation was exposed in ‘ a large quarry (perhaps two closely spaced quarries referred to as north and south in Osborne White) on the western side of Twyford Down’ which was also incorporated into the bypass cutting. This quarry was reported upon in Jukes-Browne and Hill (1904) and in Osborne White (1912) and is probably Brydone’s (1912) locality 116. A section, based on that published by Barrois (1876), is given in Jukes-Browne and Hill (1904) as follows:

Bed 9 - Chalk with layers of flints, which are generally cavernous. Inocerami with thick shells 13 feet [3.96 m]

Bed 8 - Nodular chalk with numerous flints, partly covered by talus, Micraster cortestudinarium 33 feet [10.06 m]

Bed 7 - Nodular white chalk, with Holaster planus, Micraster breviporis, Rhynchonella cuvieri, Spondylus spinosus, etc 6.5 feet [1.98 m]

Bed 6 - Layer of grey clay 1.5 inches [45 mm]

Bed 5 - Very nodular chalk 13 feet [3.96 m]

Bed 4 - Layer of yellow nodules in white chalk 8 inches [203 mm]

Bed 3 - Compact white chalk, Terebratulina gracilis ?var. lata 8 inches [203 mm]

Bed 2 - Band of soft marl 6 inches [1.52 mm]

Bed 1 - Compact white chalk, with bands of marl, a few scattered black flints 13 feet [3.96 m]’

The beds dip at 8° to the south and Jukes-Browne places the base of the ‘Holaster planus Zone’ at the base of Bed 7. It is tempting to equate Bed 4 here with Bed 6 at the St Giles’s Hill Quarry to the north (see New Pit Chalk section). In modern lithostratigraphical terms the boundary between the New Pit Chalk and Lewes Nodular Chalk formation would be placed at the top of Bed 3, below the first upward sign of nodularity in the section. Osborne White (1912) describing a section in the south of the same, but even more obscured, quarry gives the following details:

Bed 4 - Nodular chalk: greyish, coarse, and massive; with many scattered small flints 6 feet [1.83 m]

Bed 3 - Yellowish grey marl 6 inches [152 mm]

Bed 2 - Subnodular white chalk, with hard yellow nodules and scattered flints. A well-marked course of flints at the base 4 feet [1.22 m]

Bed 1 - Nodular white and greyish chalk, with fine marly venules and thin bands of yellow nodules. Flints small and scarce, and confined to a band 1.5 feet [0.48 m] at the top 10 feet [3.05 m].

Osborne White gives a dip of 5° to the south and equates his Bed 3 with that of Bed 6 in the Barrois/Jukes-Browne section. The whole of this section however would equate lithostratigraphically with the Lewes Nodular Chalk Formation.

A further pit referred to by Barrois as ‘by the side of the road a little farther south’ is probably locality 141 [SU 4800 2680] of Brydone at the southern end of old Winchester Bypass Cutting. He describes the beds seen as ‘hard and nodular, containing brownish-black flints of irregular shapes’. He noted Micraster cortestudinarium amongst a number of fossils but this species was not found in the extensive Brydone collection for this locality held by BGS. Woods (1998, WH/98/64R) on re-examining this collection found a fauna indicative of the upper T. lata and lower Plesiocorys (S.) plana zones, particularly a large morphotype of Micraster leskei, which characterises a narrow interval spanning the Lewes Marl.

Central area

The Lewes Chalk is exposed in the Test valley around Stockbridge and farther eastwards in the Winchester–Sparsholt area where it outcrops in the valley bottoms. Although there are numerous small exposures on the steep valley sides south-east of Sparsholt around Lanham Down [SU 453 304], principally of very hard nodular or grainy chalk, there are very few large exposures. The best exposures occur on the east side of the River Test around Stockbridge. Several pits expose good sections; one is in a roadside quarry [SU 3588 3472], where about 10 m of hard nodular chalk with thin marls, hardgrounds, nodular flint bands and sheet flints is exposed (Figure 6). Woods, (1998c locality 9) records Micraster cortestudinarium and Cremnoceramus crassus, indicative of the higher part of the Lewes Chalk. The two indurated surfaces above flint three may equate with the Hope Gap Hardground. Two prominent sheet flints typical of the upper Lewes Chalk occur in the centre of the succession. The succession dips to the south and is cut by three minor faults with throws of about 1 m.

Some 500 m farther south is another small pit adjacent to a track [SU 3565 3414]. Here, 4.5 of moderately dipping hard nodular flinty chalk with regular marly horizons and a hardground at the base is exposed (Figure 6)a beneath a thin veneer of river gravels (second terrace). The fauna collected by Woods (1998c locality 21) suggests a level at the base of the M. cortestudinarium Zone or top P. (S). plana Zone, and thus lower in the sequence than the site detailed above.

There is a limited outcrop of the Lewes Nodular Chalk Formation between Tilebridge Farm [SU 344 334] and the outskirts of Stockbridge [SU 350 350]. The formation is identified on the basis of the hard nodular chalk brash in the fields on the flank of the Test valley and within the small tributary valley trending south-westward towards the Homestead [SU 343 342].

Brydone identified the Micraster cortestudinarium Zone in his locality 169, which is identified (at least in part) as the now heavily degraded pit [SU 3456 3416] on the crest of the spur and to the south of the road to the Homestead. This would place the quarry in the upper Lewes Nodular Chalk. Subsequent collecting by Woods (2000, IR/00/24) found considerable amounts of fragmentary Platyceramus and two specimens of Cremnoceramus sp. whose co-occurrence indicates the basal M. coranguinum Zone, lower Seaford Chalk Formation and probably the Belle Tout Beds of Mortimore (1986). It is evident that this pit was formerly more extensive in depth and to the north of the road, as the Brydone collection held at BGS includes Micraster normanniae and Tylocidaris clavigera spines in a nodular chalk matrix with carious flints all of which are indicative of the M. cortestudinarium Zone (Woods, 1998a, WH/98/64R). The present exposure is limited to 2 to 3 m of firm to moderately hard smooth white chalk with flints and a single thin grey marl plexus visible above a flint and brick wall. Westward down-slope along the road, and hence down succession, the chalk becomes very hard in places. To the north along the field boundary at right angles to the road, field brash, created during deep ploughing (and possibly within the confines of locality 169), includes carious flints and a mix of very hard nodular discoloured chalk and off-white grainy chalk with sponges, brachiopods as well as some Platyceramus debris. In practise the base of the Seaford Chalk has been placed above the highest nodular bed in the succession locally.

The Lewes Chalk outcrop is limited southward at Tilebridge Farm [SU 344 333] by a fault trending west-north-west and down-throwing to the south. Micropalaeontological evidence (PMH 3459 and 3460, Wilkinson, 2000, IR/00/31) demonstrates very basal Seaford Chalk up-slope from the farm and this together with a grainy and nodular chalk and carious flint surface brash are sufficient to justify the boundary shown on the map at about 48 m OD. The fault must have a throw of at least 18 m as the Lewes Nodular Chalk does not reappear to the south of the fault on the river bluff adjacent to the floodplain whose base is at 30 m OD.

North-eastern area

The only clear section of Lewes Chalk north of Stockbridge occurs on the east side of the River Test behind a private garden [SU 3606 3506] (Figure 7). Woods (WH/98/188R, locality 12) records Cremnoceramus, of the M. cortestudinarium Zone, indicative of the higher part of the Lewes Chalk. A band of very hard, iron stained chalk, and, at the base of the exposure, a sheet flint is visible in the 2 m section.

Two pits [SU 3620 3535] near Stockbridge and [SU 3690 3710] near Leckford have been noted by Brydone (1912). In the former pit the presence of M. normanniae and M. cortestudinarium infer Lewes Chalk. Within the second pit, no longer exposed, Brydone found M. normanniae, again indicating Lewes Chalk.

Seaford Chalk Formation (SCk)

The Seaford Chalk is composed mainly of soft white chalk with seams of large nodular and semi-tabular flint. 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. 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 flaggy bedded nature and pure whiteness of the soft chalk serve to distinguish it from the Lewes Chalk below.

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 horizon of intensely hard porcellanous silicified chalk, the Stockbridge Rock Member, is commonly developed. It contains abundant sponge spicules, mostly as moulds, together with some complete sponges and rare echinoids. This lithology is readily identifiable in the brash (forming equant, blocky fragments up to about 5 cm across) and forms a useful marker horizon. In many places it is associated with a positive topographic feature. It has not been observed in any exposed bedrock section during recent surveys except for a poor section in a silage pit at Beech Farm, Nether Wallop [SU 2845 3537] (Farrant, 2001). Its thickness is not known. Field evidence suggests that there might be several thin, hard bands between 5 and 10 m below the base of the Newhaven Chalk, each separated by short intervals of white chalk. In this district the Stockbridge Rock Member outcrops widely between Salisbury and Winchester but can be quite sporadic in occurrence. It dies out along the line of the King’s Somborne Syncline and becomes patchy farther east onto the Alresford district (Sheet 300) and east of the River Itchen. Its patchy distribution 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 about the level of 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 just above the Stockbridge Rock Member. Across this district the Seaford Chalk is estimated to range between 40 and 70 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, 1986). This boundary is also marked by the incoming of Cladoceramus. In the standard Sussex succession the formation covers the strata from Shoreham Marl 2 to the base of Buckle Marl 1. Foraminifera are common in the formation and foraminiferal zones BGS14 to 17 can be recognised (Table 5).

Much of the outcrop is controlled by the underlying structure. Across the central swathe of the district the top of the Seaford Chalk forms a distinct stratimorphic surface between the Wallops and Winchester. Outcrops are also found on the flanks of the Winchester anticline, and north of the Sutton Scotney syncline. The Seaford Chalk dips gently beneath the secondary escarpment in the south of the region.

Details

South-eastern area

In this area the Bar End Hardgrounds are strongly developed between the Shoreham Marl 1 and 2 in the topmost Lewes Nodular Chalk Formation with the Shoreham Marl 2 marking the base of the Seaford Chalk. The Seaford Chalk is estimated to be between 60 and 70 m thick in this area and occupies the long ‘dip slopes’ in the west and south of this district beneath the secondary escarpment that is generally degraded.

Typically, in brash, the lower part of the Seaford Chalk contains an abundance of fragments of the bivalves Volviceramus and Platyceramus, whilst the brash of the upper part contains Cladoceramus and Platyceramus (Mortimore, 1986). In the absence of these bivalves the flaggy nature and pure whiteness of the soft chalk serves to distinguish it from the Lewes Nodular Chalk below.

The exposures for Spitfire Bridge and the M3 cutting through Twyford Down are described in the previous section (see also Woods, 1998, WH/98/64R).

There are numerous exposures along Badger Farm Road, Winchester, from the cutting adjacent to the Sainsbury’s superstore [SU 462 275] south-eastwards past Bushfield Farm [SU 468 271] towards the roundabout [SU 472 268]; all are within the Seaford Chalk Formation. The cutting shows a 6 to 7 m-high face, degraded and overgrown for the most part, but with sufficient exposure to see a consistent succession of flaggy and blocky soft pure white smooth chalk with regularly spaced large nodular flint courses. The beds, except the uppermost 2 m in the cutting itself, are best exposed where the Whiteshute Lane path crosses Badger Hill Road [SU 4639 2740]. Biostratigraphically (Woods, 1998, WH/98/119R) the upper 2 m of this section is placed in the upper part of the Micraster coranguinum Zone on the basis of the co-occurrence of Conulus and Cordiceramus cordiformis, whilst the exposures at Whiteshute Lane crossing included specimens of Cladoceramus undulatoplicatus indicative of the basal Santonian and hence within the middle of the Seaford Chalk Formation. Along the road towards the south-east, numerous small exposures were visible at the time of survey within a partially backfilled trench. Small cuttings (including HP36) on the northern side of the carriageway were seen from the entrance to the former Bushfield Camp [SU 4692 2701] (at the time of survey being redeveloped) towards the roundabout. These all show soft smooth flaggy chalks with large nodular flint courses and common Platyceramus and Volviceramus involutus indicating a position within the lower part of the Seaford Chalk. A small pit [SU 2672 2708] at Bushfield Farm shows a poor section, 1.5 m high, of firm white smooth chalk.

A small section, HP34, [SU 4464 2873] north of Vale Farm, Pitt — see (Figure 8), exposes 3.25 m of soft to firm white smooth chalk with regular small nodular flint courses. Near the base a large tabular almost continuous course of flints above a poorly developed sponge bed was noted. The included fauna of the bivalve Platyceramus and the echinoids Echinocorys scutata and Micraster ex gr. coranguinum, indicate a level high within the Seaford Chalk Formation.

The M. coranguinum Zone (essentially the Seaford Chalk) is exposed in the cutting to the St Giles’s Hill Railway Tunnel northern portal [SU 4890 2965] and in a further cutting to the north-east. Jukes-Browne and Hill (1904 p.61) note ‘the base of the zone is exposed in a cutting beyond the northern end of the St Giles’s Hill tunnel, where the dip is about 6.5º north. Higher beds are seen in the next cutting to the north’ [SU 4908 2996].

The majority of the Brydone localities noted in his 1912 paper have either been completely obliterated or are so degraded that they show no clear sections. They are listed for completeness only, and are: 521 [SU 44362941] a fauna here includes Volviceramus involutus indicative of the lower part of the Seaford Chalk Formation; 522 [SU 4365 2920]; 523 [SU 4525 2802]; 524 ?[SU 4443 2824]; 525 [SU 4326 2800]; 526 ? built over c. [SU 455 276]; 526A c. [SU 470 258]; and 529 c. [SU 4925 2480].

Western area

Brydone (1912) records several pits in the Middle Wallop area, which he assigns to M. coranguinum Zone. Very hard, locally pocellaneous, blocky chalk, commonly yellowish or creamy in colour occurs in the field brash at the level of the Stockbridge Rock Member in many places around the Wallops. It can be traced from Boughton contouring round the valleys north-westward to Over Wallop. In many places this brash is associated with a persistent small positive topographic feature. Given the limitations of exposure, this bed could be continuous throughout the district, although in areas to the west it is considered to be probably discontinuous (Farrant 2001). A small exposure of Seaford Chalk occurs in the Wallop valley just north of the A30 at ‘Garlogs’ [SU 3066 3536] (Figure 9). Here a large 0.7 m-thick nodular flint with vertical columns up to 0.35 m long occurs possibly equating with Bedwell’s Columnar Flint, which coincides with an acme of Cladocermus undulatoplicatus in the middle part of the Seaford Chalk. The Seven Sisters Flint probably outcrops in the valley floor between here and Boughton, 2 km farther south. Nearby [SU 3068 3275] foraminifera including Stensioeina polonica and Reussella szajnochae praecursor are biostratigraphically significant in foraminiferal subzone BGS17iii located at the top of the M.coranguinum Zone.

Central area

The Seaford Chalk has an extensive outcrop in this central area, covering most of sheets SU43SE and SU33SE and much of SU43SW. However, exposure is generally poor and restricted to field brash and isolated chalk pits. Many of these pits are degraded and only provide small often weathered or overgrown exposures. One of the best exposures is in a disused pit at Hoopers Farm, Kings Somborne [SU 3542 3298] overlooking the Test valley. Here, about 10 m of soft blocky weathered white chalk with thin marls, large nodular and semitabular flint bands with Volviceramus involutus is exposed (Figure 10). The association of Volviceramus involutus with thin wispy marls indicates a level below the Seven Sisters Flint, in the lower M. coranguinum Zone (Woods, 1998b locality 7). Brydone recorded a fauna indicative of the M. coranguinum Zone in this pit (Brydone, 1912 locality 553).

The Stockbridge Rock member is very well developed in this area and forms conspicuous spreads of blocky, hard brash where ploughed, especially on some of the interfluves between valleys, for example north-west of Little Somborne [SU 374 330].

Farther south, again adjacent to the River Test is a large disused quarry owned by Tarmac [SU 3510 3200]. The majority of the section (Figure 3a) and (Figure 3b) is in Newhaven Chalk, as is the adjacent coating plant, but the lower 5 or 6 m is in Seaford Chalk. The fauna (Woods 1998c locality 11) is indicative of the uppermost M. coranguinum Zone. A bed rich in Conulus on the lower bench compares with Rowe’s Echinoid bed of the North Downs. Just below this is Barrois’ Sponge Bed that in some places becomes a hardground (Stockbridge Rock Member). This level should occur at or just below the quarry floor and probably forms the indurated hardground seen in the Winchester district just below the Newhaven–Seaford boundary. This hardground may equate with the Whitway Rock of the Newbury area. Several other minor exposures occur in the vicinity along the disused railway line, but none provides a clear section. North of Winchester are several exposures in the disused railway cuttings around Springvale [SU 4830 3355] which provide limited exposures of soft slabby white smooth chalks with orange stained spongiferous chalk horizons and large flattened nodular flints. Faunas collected by both Brydone (1912 locality 499) and Woods (1998b locality 4) suggest a M. coranguinum Zone age. Farther south a disused quarry adjacent to the railway line near Headbourne Worthy [SU 4813 3196] displays an estimated 10 m of soft chalk with scattered nodular chalk and a sponge bed (Figure 4). The fauna here (Woods, 1998b locality 10) suggests the upper (Santonian) part of the M. coranguinum Zone.

Two pits [SU 3084 3444] 1 km north of Manor Farm Broughton [SU 3098 3350] show poor exposures of white, smooth, blocky, chalk with flint seams. Woods (2000, IR/00/24) collected inoceramid bivalves attributed to Platyceramus sp. and Volviceramus involutus with one specimen of the latter being preserved in a large tabular flint block. The association is indicative of the lower M. coranguinum Zone, specifically at the horizon of the Seven Sisters Flint.

The site identified as Brydone’s locality 551  [SU 3086 3389] and designated within the M. coranguinum Zone is 300 m north of Manor Farm, Broughton [SU 3098 3350], but is now backfilled. A more recent cut adjacent to the farm itself exposes 2.5 m of destructured chalk with broken flints presumably reflecting the weathering profile in the chalk on the flanks of the Wallop Brook valley.

A trench for a water pipe [SU 3220 3223] to [SU 3246 3210] north-east of Roake Farm, Broughton provided a temporary exposure of up to 10 m of the uppermost part of the Seaford Chalk as the excavation crossed a minor valley draining into the Wallop Brook. The section is noteworthy since is exposes two thin beds of spongiferous hard to intensely hard, in part porcellanous, off-white chalk within an otherwise firm, white chalk sequence with regular nodular flint seams. The spoil from the pit yielded a poor fauna including Platyceramus fragments and the echinoid spine Hirudocidaris hirudo (Woods, 2000, IR/00/24). The hard ‘bed’ is attributed to the Stockbridge Rock Member, as the exposure is just below the mapped base of the Newhaven Chalk, and this section is one of a limited number so far seen (other than field brash) in the Winchester district.

Brydone’s localities 552 [SU 3013 3343] (near Waterloo Farm, Broughton) and 554 [SU 3302 3255] at a pit on the bend in Steven’s Drive, Houghton no longer provide an exposure.

The presence of foraminiferal zonal index Gavelinella cristata at Broughton [SU 3145 3197] indicates a position stratigraphically no lower than the highest Seaford Chalk Formation.

The Seaford–Newhaven formational boundary occurs west of Houghton Farm [SU 3286 3196] to [SU 3202 3233], where the highest part of foraminiferal Zone BGS17 (characterised by Stensioeina polonica) through to subzone BGS18ii (with Gavelinella cristata and Stensioeina granulata perfecta) (uppermost M. coranguinum to mid U. socialis zones) can be recognised.

Brydone (1912) records several pits in the Danebury area (Brydone localities 536–539 and 550, which he assigns to his M. coranguinum Zone, although locality 538 probably occurs in the U. socialis Zone. Very hard, locally porcellanous, blocky chalk, commonly yellowish or creamy in colour, occurs in the field brash at the level of the Stockbridge Rock Member in many places around the Wallops, Danebury Hill. It can be traced from the Wallops contouring round the valleys north-west to Goodworth Clatford and Monxton. In parts of this district, the distribution of field brash suggests that a single hard bed occurs at this level.

A small pit just south of Westover Farm, Goodworth Clatford [SU 3668 4068] (Woods 2000b, WMD 8547–8548) exposes 6 m of soft flinty chalk with a persistent sheet flint horizon (Figure 11). Two small faults down-throwing to the east were noted in this pit. Woods (2000b) recorded Micraster coranguinum and a questionable specimen of Volviceramus involutus, which suggest the lower Seaford Chalk. However, given the elevation and location of this pit, mid-upper Seaford Chalk would seem more likely.

The Seaford Chalk has an extensive outcrop in the Leckford area, covering most of sheet SU33NE and much of SU43NE and SU43NW. However, exposure is generally poor and restricted to field brash and isolated chalk pits. Many of these pits are degraded and only provide small often weathered or overgrown exposures.

In the northernmost part of the area an old chalk pit at Cottonworth [SU 3804 3990] reveals about 5 m of soft white chalk with regularly developed nodular and semitabular flints (Figure 12). The fauna (Woods, WH/98/188R, locality 16) indicates M. coranguinum Zone within the Seaford Chalk. The general lack of inoceramid shell favours a position above the Seven Sisters Flint.

The largest exposures are found along the eastern banks of the Test River. Farther south, adjacent to the Test is a large disused quarry [SU 3655 3673]. The section is in Seaford Chalk (Figure 13). The fauna (Woods, WH/98/188R, locality 25) is indicative of the lower part of the M. coranguinum Zone. The section also exhibits regularly developed marl seams and laterally continuous horizons of thick-shelled Platyceramus. These marls almost certainly represent the ‘Belle Tout Marls’ of Mortimore (1986), and thus, a level below the Seven Sisters Flint may be inferred.

In a disused pit south of Chilbolton [SU 3818 3875] about 6 m of soft blocky weathered white chalk with large nodular and semi-tabular flints bands and Platyceramus and Micraster coranguinum is exposed (Figure 14). Brydone recorded a fauna indicative of the M. coranguinum Zone in this pit (Brydone, 1912 locality 542).

Seaford Chalk is also exposed in an old pit to the west of the Test valley, south of Longstock [SU 3529 3660]. Five metres of soft blocky white chalk with nodular flint bands are visible. The fauna here (Woods, WH/98/188R locality 18) was not definitive but assignment to the M. coranguinum Zone is the most likely.

A freshly excavated silage pit at Chilbolton Down Farm [SU 4064 3650] reveals cryoturbation patterns within the chalk and large tabular flints. The fauna is undiagnostic but field evidence suggests upper Seaford Chalk.

A small, poorly exposed section containing both Seaford and Newhaven chalk is located in the disused railway cuttings just east of South Wonston [SU 477 359].

North-eastern area

The Seaford Chalk has an extensive outcrop in the far north-east around Barton Stacey, covering most of the lower lying areas of sheets SU44SW and SU44SE mainly to the north of the River Dever. However, exposure is generally poor and restricted to field brash and isolated chalk pits. Many of these pits are degraded and only provide small often weathered or overgrown exposures. None in this area was found to expose Seaford Chalk at present. The majority of the chalk to the north-west of the River Test is obscured by gravelly terrace deposits.

Brydone (1912) recorded a locality (339) within this area, which he assigned to his Zone of Micraster coranguinum. This locality is a small pit at the base of the scarp by the River Dever [SU 4526 4120] near Bullington. Note that Brydone (1912, 1942) commonly assigned localities to the coranguinum Zone on the absence of crinoid debris, rather than the presence of any diagnostic fossils. Due to this fact and the identification of other fossil material during the present survey, it is thought that the stratigraphy in this pit is more likely to be in the basal Newhaven Chalk. The fauna from a 3.6 m section of soft, flinty chalk (Figure 15) includes calyx plates of the crinoid Uintacrinus socialis (Woods, 2000) inferring the basal Newhaven Chalk Formation.

An echinoid, Conulus albogalerus, was found near Lower Norton Farm [SU 4680 4114]. This fossil is most common in the higher part of the M. coranguinum Zone or younger (Woods, 2000), thereby confirming Seaford Chalk at this location.

Newhaven Chalk Formation (NCk)

This formation is composed of soft to medium-hard, smooth, white chalk with numerous marl seams and flint bands. 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).

In this district the Newhaven Chalk is estimated to be 40 to 70 m thick. The field brash is composed of 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 preserved in flint) and crinoid debris near the base of the formation serves as a useful marker for mapping the lower boundary. Individual thecal plates of the zonal index, Marsupites testudinarius, occur in numerous small pits, track exposures and occasionally, brash, but otherwise macrofossils are rare in the lower part. A large disused quarry revealing about 40 m of Newhaven Chalk is located just to the west of this district, south of East Grimstead [SU 4227 2710]. This quarry, also described by Mortimore (1986a) exposes good examples of the typical flint and marl bands within the soft Newhaven Chalk. Fossil evidence suggests Offaster pilula zone and the Hagenowia horizon (Woods, 1999). The uppermost part of the Newhaven Chalk is also exposed in the King’s Somborne Quarry (see below).

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 5). It crosses the Santonian–Campanian stage boundary, which is placed at the Friars Bay Marl in Sussex (Mortimore, 1986). In the standard Sussex succession the formation includes the strata from the base of Buckle Marl 1 to the base of the Castle Hill Marls but this has recently been reassessed in the most recent stratigraphic framework (Bristow et al., 1997) to a level at the top of the Offaster pilula Zone presumably around the Telscombe Marls.

Geomorphologically, the Newhaven Chalk Formation outcrops extensively across the Winchester district, occupying much of the sloping ground on and immediately below the secondary chalk escarpment. The base of the Newhaven Chalk usually corresponds with a small positive feature 5 to 10 m above the Stockbridge Rock Member. Many of the outliers of Newhaven Chalk form conspicuous hills rising above a flat stratimorphic surface at the top of the Seaford Chalk. This can be seen clearly when looking west across the district from highpoints on the A34 around Sutton Scotney. This outcrop pattern is generally controlled by the underlying structure. The Newhaven Chalk is preserved in the core of the synclines (e.g. between Sutton Scotney and Andover, and the King’s Somborne–Sparsholt syncline), and in the core of the Dean Hill anticline.

Details

South-eastern area

The Newhaven Chalk underlies sloping ground forming the front of the secondary chalk escarpment from Shawford [SU 472 252] westwards to Beacon Hill [SU 398 292] and gently sloping interfluves northwards from that scarp. The brash is composed of smooth, angular slabby fragments of white chalk very similar in appearance to that of the Seaford Chalk. In small exposures, chalks of this formation cannot be reliably distinguished on lithological grounds alone.

The Newhaven Chalk was exposed during the construction of the M3 Motorway at Shawford Cutting [SU 4712 2546] to [SU 4678 2490] but this was not accessible during the survey and is for the most part grassed over. A section, in part at least, for this cutting appears in Mortimore and Pomerol (1997); (Figure 16), and the following notes were given by Professor Mortimore (communication 1st June 1998).

‘Shawford is the most southerly exposure of chalk on the M3 around Winchester. This very badly weathered section from north to south included:

Belemnites in the highest beds exposed behind the retaining wall’ (end of communication Mortimore, 1998).

Excavations taking place at the time of the survey at the Yew Hill Reservoir [SU 4545 2645] exposed soft, low-density, smooth white chalk with very few flints. The spoil from the excavations included specimens of the echinoids Offaster pilula and O. pilula planata indicative of the highest Newhaven Chalk.

Brydone’s locality 721 around [SU 428 270] described as a ‘lane bank just north of Stanton Hursley’ is now degraded, his collection includes Uintacrinus socialis thus placing this locality within the lowest 10 m or so of the Newhaven Chalk. Locality 722 around [SU 443 275] in ‘a road bank at the turning to kennels south-west of Pitt’ is also within the same U. socialis Zone.

Brydone’s locality 873 [SU 4338 2684] is the site of a number of solution hollows exposing chalk and possibly also worked for lime in the past. It is described as ‘a pit on north slope of Nan Trodd’s Hill, Hursley’.

Brydone’s locality 874 [SU 4562 2616] is now degraded and shows no exposure, his collection includes plates of Marsupites testudinarius indicating beds within the lower part of the Newhaven Chalk Formation.

Brydone’s locality 1014 identified as ‘an old pit at south end of Compton Lane’ is estimated to be at around [SU 467 253] or [SU 4675 2521] There is no exposure nor sign of it on the ground at the first locality but a degraded pit is visible at the second, but with no exposure. He considered it to be within the ‘zone’ of abundant Offaster pilula and therefore at the top of the Newhaven Chalk.

Two pits show sections that cross the Newhaven–Culver Chalk boundary and were also both noted by Brydone. Locality 1040A [SU 4277 2606] is featured in Woods (1998, WH/98/119R and WH/98/64R). His fig. 4 is reproduced here as (Figure 17).

Brydone’s locality 1041 around [SU 4690 2505] has been incorporated for the most part into the M3 cutting near Shawford. An appraisal of the collection and description given suggests that the lower part of the section (about 3 m) up to the last significant marl is within the uppermost Newhaven Chalk containing abundant echinoids Offaster pilula, O. pilula planata and the bivalve Gryphaeostrea canaliculata indicating top Offaster pilula Zone. The upper part of the section contains the large morphotype of the echinoid Echinocorys scutata described by Gaster (1924), a large specimen of the brachiopod Isocrania egnabergensis and the belemnite Gonioteuthis indicating the Gonioteuthis quadrata Zone and therefore the lower part of the Culver Chalk Formation (Tarrant Chalk Member).

Western area

Various exposures on Whiteshoot Hill [SU 2888 3318] (WMD 8060- 8069; ARF 821–830; Woods, 2000, localities 16–19) provide faunas indicative of the middle Newhaven Chalk, ranging from the M. testudinarius Zone at the base of the hill to the upper O. pilula Zone (Subzone of abundant O. pilula) near the top. A fossiliferous bed [SU 2888 3318] was assigned to the basal O. pilula Zone, basal E. depressula Subzone. Farther west along the escarpment, the Khyber Pass [SU 276 337] also provides a series of 2 to 3 m sections through the middle/upper Newhaven Chalk. In the lower part [SU 2764 3382] to [SU 2752 3372], massive bedded chalk with small nodular flints and scattered marl seams yielded Echinocorys tectiformis, indicative of the U. anglicus and lower O. pilula Zone, (E. depressula Subzone). Near the top of the hill [SU 2786 3398], two exposures of blocky soft white chalk yielded O. pilula and Echinocorys depressula indicative of the Middle–Upper Newhaven Chalk.

A small 6 m exposure behind Dean Hill Barn Farm [SU 2814 2634] (Figure 18); Woods, 1999 locality 6) in soft white chalk with two 10 to 15 cm thick marl seams, scattered small flints and a strong sponge bed near the top yielded a fauna including Echinocorys depressula indicative of the middle Newhaven or basal Culver Chalk. The sponge bed may represent a level around the Arundel Sponge Bed of Mortimore (1986).

Much of the low ground in front of the secondary escarpment south of Broughton and around the West Dean–Lockerley area has yielded specimens of Uintacrinus socialis and M. testudinarius, but rarely are any clear exposures seen.

Central area

The Newhaven Chalk covers much of the central district, mainly along the secondary escarpment and the Winchester–Kings Somborne syncline or as outliers to the north. In places it is covered by a thin veneer of Quaternary deposits. Exposures are generally poor and restricted to a few pits. These are mainly concentrated around the Test valley adjacent to the disused railway line.

The largest exposure is in an old quarry north-west of King’s Somborne [SU 3510 3200]. The majority of the section is in Newhaven Chalk, as is the adjacent coating plant, but the contact between the Seaford and Newhaven Chalks is exposed near the base. A fauna indicative of the Uintacrinus socialis Zone was collected from two exposures within the upper part of the quarry. The coating plant nearby displays around 10 m of very weathered tar-coated soft white blocky chalk with abundant M. testudinarius plates. A thin veneer of river terrace gravel can be seen on the upper slopes in both sections. Several well developed dissolution pipes infilled with flint gravel have been exposed in both quarries extending up to 5 m below ground surface.

Farther to the south, adjacent to the old railway line at the level crossing [SU 3505 3055] 200 m west of How Park Farm are two disused chalk pits. The southerly pit exposes 13 m of soft blocky white chalk with a M. testudinarius Zone fauna, including a large Echinocorys elevata. Small smooth calyx plates of M. testudinarius occurred in the lower part of the succession, and ornamented forms in the middle and upper parts (Woods, 1998c locality 2). This is Brydone’s locality No718. The northerly pit displays 5 m of poorly exposed soft white chalk. A M. testudinarius plate was collected from the talus at the base of the exposure.

Two small exposures (1–3 m) in soft blocky white chalk occur 750 m south-west of Little Somborne. One behind some barns [SU 3796 3185], displays about 2 m of soft white chalk with abundant oysters (P. boucheroni) that are most common in the lower Newhaven. The second located in a deep slurry pit 50 m to the north had a poor section where M. testudinarius plates were found.

The Newhaven Chalk Formation is also exposed in the pit [SU 3320 3104] south of the junction of Beech Tree Walk and Horsebridge Road, 400 m west of Bossington House. This is also Brydone’s locality 1039. Two sections were measured (HP 46) and additional information was added at a later date (Woods, 2000, IR/00/24). In total over 10 m of beds were logged (Figure 19) in white, smooth, low density chalks with numerous marl, sponge and nodular flint seams. The extensive Brydone and recent collections (Woods, 1998a, WH/98/64R, 2000, IR/00/24) indicate the presence of the O. pilula Zone including the Echinocorys depressula Subzone and the Subzone of abundant O. pilula (belt of E. cincta). The beds exposed therefore cover the upper part of the Newhaven Chalk.

Details of the localities identified by Brydone are given below. His collection is registered with the BGS (at least in its greater part) and has been reassessed as part of this survey.

Brydone locality 717 [SU 328 319] one third of a mile (600 m) south-south-west of the bend in Stevens’s Drove Houghton is now entirely backfilled but yielded Uintacrinus socialis calyx plates and a solitary coral (Woods, 1998a, WH/98/64R).

The lower part of a pit three-quarters (1200 m) of a mile north of Horsebridge Station, at a level crossing and to the east of the railway embankment (all part of the disused railway line) is Brydone’s locality 718 [SU 350 315] (probably also Barrois’s ‘au nord de la ferme de Park House’). The site is now heavily degraded with no exposure. The fauna includes examples of the zonal index species U. socialis and the small, smooth form of Marsupites testudinarius indicating the lower part of the Newhaven Chalk (Woods, 1998a, WH/98/64R). The topographically higher contiguous second pit also contained M. testudinarius.

Brydone’s locality 870 [SU 334 312] in a gravel pit, now degraded, opposite Bossington House contains a limited fauna including the oyster Pseudoperna boucheroni and an indeterminate crinoid brachial. The co-occurrence would place the chalk here within the M. testudinarius or U. anglicus zones within the lower to middle Newhaven Chalk (Woods, 1998a, WH/98/64R).

South-west of Broughton on the southern flank of a deeply incised valley there is a degraded pit identified as Brydone’s locality 1002 [SU 304 320] (pit by road half mile, or 800 m, south-west of Cooler’s Farm, Broughton). The collection indicates assignment to the lower part of the Offaster pilula Zone with the inclusion of the oyster Acutostrea incurva and the echinoid Echinocorys depressula (Woods, 1998a, WH/98/64R) and thus the middle of the Newhaven Chalk sequence.

Brydone’s locality 1003 [SU 3132 3164] half mile (800 m) south of Broughton Mill was visited during the survey but is heavily overgrown and degraded. The pit was formerly up to about 8 to 10 m deep but only a limited 1.5 m exposure was visible which contained white, soft, blocky chalks with bryozoan and some small flints. The Brydone and recent collections contain Echinocorys depressula, Bourgueticrinus and the bivalves Acutostrea incurva and Spondylus sp. that indicate the middle of the Newhaven Chalk within the Offaster pilula Zone (Woods, 1998a, WH/98/64R; 2000, IR/00/24). Foraminifera present at [SU 3131 3166] include Stensioeina exsculpta exsculpta, which becomes extinct in the basal foraminiferal zone BGS19 (O.pilula Zone), and Rugoglobigerina pilula, which first appears in the subzone BGS18i (U. anglicus Zone) in the middle of the Newhaven Chalk Formation. However, the concurrent range of Stensioeina exsculpta exsculpta and Bolivinoides culverensis at Broughton Hill [SU 3064 3109] is indicative of basal foraminiferal zone BGS19 (basal O. pilula Zone).

The highest beds of the Newhaven Chalk Formation are identified in the quarries (Brydone’s localities 1064 to 1067) on the east flank of the Test valley around Brook where they also expose the Culver Chalk Formation. Discussion of these is contained in the Culver Chalk section below.

A number of exposures, mainly along the railway lines, also noted by Brydone (1912) occur on sheet SU42NE. All reveal fauna typical of the Newhaven Chalk. One such example is Waller’s Ash cutting [SU 491 357] (Brydone, 1912 locality 487).

Extreme western area

The Newhaven Chalk Formation covers much of the low-lying ground to the north of Pitton. In places the formation is covered by a thin veneer of Quaternary deposits. Newhaven Chalk is also exposed in the far south of the area, again on the low ground beneath the Dean Hill scarp. Exposures are generally poor and mainly restricted to a few old pits most of which are now overgrown with little exposure. However, a large, now disused quarry revealing about 40 m of dipping Newhaven Chalk is located just south of East Grimstead [SU 4227 2710]. This quarry has also been described by Mortimore (1986). A clear section can be traced in the quarry exhibiting good examples of the typical flint and marl bands within the soft, white Newhaven Chalk (Figure 20). Fossil evidence suggests O. pilula zone and Hagenowia horizon (Woods, WH/99/88R locality 1).

North-western area

There are no significant exposures of Newhaven Chalk in the north-west of the district although several fossil localities were identified. In particular, a site adjacent to the River Anton at Goodworth Clatford identified by Brydone as being of M. coranguinum Zone age (Brydone locality 538) yielded specimens of U. socialis (Woods, 2000b). Other specimens of U. socialis were noted at Kentsboro (Brydone locality 681) and Danebury (Brydone locality 682). Specimens of M. testudinarius were found at several localities around Goodworth Clatford, Danebury Hill and farther south between the River Anton and the A3057 towards Wherwell (Woods, 2000b). Specimens were found on top of the hill next to Barrow Hill Farm [SU 3525 4230] (ARF 909–913), the cutting to the Goodworth Clatford oil well site at [SU 3699 4202] (ARF 903–905), a pit adjacent to the sewage works [SU 3733 4129] (ARF 906–908) and brash adjacent to Brydone locality 815 [SU 3665 4188] (ARF 919–922).

North-eastern area

The Newhaven Chalk covers much of the north-eastern area. In places it is covered by a thin veneer of Quaternary deposits, and adjacent to the river, by a large expanse of terrace gravels. Exposures are generally poor and mainly restricted to a few pits.

An exposure in a large old pit near Bere Hill [SU 3712 4404] south-east of Andover is mostly degraded but fauna collected from just below the top of the pit included Echinocorys tectiformis, E. truncata and Offaster pilula (Woods, 2000) which confirms upper Newhaven Chalk.

A small exposure forming a wall by a private driveway on the steep slope above the village of Wherwell [SU 3880 4090] contained the crinoid Marsupites testudinarius (Woods, 2000) which indicates a level in the lower part of the Newhaven Chalk Formation.

A larger disused pit now forming the garden of a private house just north of Wherwell [SU 3968 4146] by the River Test was noted by Brydone (1912) locality No.818. He assigned this to his Uintacrinus Zone. During this recent survey Woods (2000) also noted a calyx plate of the crinoid Uintacrinus socialis found within an 8m section of soft chalk with widely spaced bands of medium nodular flints. There appears to be an increase in flint development towards the base of the Newhaven Chalk in this area.

A small gravel pit near Newton Stacey [SU 4118 4086] exhibits about 2 m of rounded flint gravel above soft white blocky chalk with oyster and Platyceramus fragments. This association is most common in the lower part of the Newhaven Chalk.

The Newhaven Chalk covers much of the district to the north-east, mainly in the Wonston–Sutton Scotney area. In places it is covered by a thin veneer of Quaternary deposits. Exposures are generally poor and mainly restricted to a few pits. A drainage ditch by the A34 [SU 4602 3520] near South Wonston revealed faunas indicating the Santonian, U. socialis Zone of the basal Newhaven chalk (Woods, WH/98/119R locality 25).

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. A particular concentration of large flints, the Castle Hill Flints, occurs at the base of the Culver Chalk Formation (Mortimore, 1986) that is approximately at, or just above, the same stratigraphical level as the Arundel Sponge Bed (Mortimore, 1986).

The Tarrant Chalk comprises soft, white chalk without significant marl seams, but with very strongly developed nodular and semitabular Castle Hill flints. The Spetisbury Chalk Member consists of firm, white chalk with large flints, including tabular, paramoudra and potstone forms, with Gonioteuthis and distinctive forms of Echinocorys. Some parts of the Culver Chalk (within the Applinocrinus cretaceus Subzone) are characterised by abundant bioclastic debris, especially bryozoan debris.

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, 1986; Bristow et al., 1997).

The outcrops are again controlled by structure. The Culver Chalk caps the secondary escarpment along the southern part of the district and is also preserved on the top of outliers around Sparsholt and Porton Down. The formation forms good dip slopes on the north side of the Mottisfort–Alderbury syncline and also along the southern side of the sheet.

Details

South-eastern area

The Culver Chalk caps the secondary chalk escarpment from Compton Down [SU 460 252], in the east, to Farley Down [SU 397 280] to the west and underlies much of the ‘dip slope’ behind. It is for the most part concealed beneath a cover of clay-with-flints on this ‘dip slope’ and is buried beneath the Palaeogene to the south.

Chalk brash from the Culver Chalk tends to be blockier than that derived from the Newhaven Chalk, but chalks of these units cannot be reliably distinguished on lithological grounds alone, even in small exposures. Some parts of the Culver Chalk (within the Applinocrinus cretaceus Subzone) are characterised by abundant bioclastic debris, especially bryozoan debris, but this was not found in this district.

During the recent survey a small pit, HP37 [SU 4476 2518], exposes 7.5 m of large blocky soft to firm white chalk with well-marked medium to large nodular flint seams (Figure 22). This is probably the same site as Brydone’s locality 1082, which contained several specimens of the annelid Conorca turbinella associated with average-size Offaster pilula. This association suggests the lower G. quadrata Zone, Hagenowia Horizon, and is therefore within the Tarrant Chalk Member.

A small pit, HP38 [SU 3903 2561] west-north-west of Shacksted Manor, Hursley, exposes 6.1 m of white blocky chalk with regular, generally small finger and ‘spiky’ flints. Large pipe flints are common at the top of the succession whilst a small ‘paramudra’ flint was noted within a spread of medium to large spiky flints at 4.3 to 4.5 m from the top. The fauna (Woods, 1998, WH/98/188R) includes Offaster pilula nana indicating an assignment to the top Hagenowia Horizon A. cretaceus Subzone of the G. quadrata Zone and therefore within the Tarrant Chalk Member.

In a pit 0.6 km south of Shawlands Farm [SU 4370 2480] the fauna collected indicates the Aplinocrinus cretaceus Subzone of the G. quadrata Zone and is therefore within the Tarrant Chalk Member.

The fauna collected from the now obscured Brydone locality 1077 [SU 4126 2549] is not distinctive, containing only long lived forms. Its field assignment is to the Tarrant Chalk Member of the Culver Chalk Formation.

Brydone’s locality 1078 [SU 4297 2552] ‘the Hursley Road Pit’ is now degraded and built in. His collection includes two annelids Conorca turbinella and Glomerula gordialis, and the echinoids Cidaris subvesiculosa and Offaster pilula nana indicative of the A. cretaceus Subzone of the G. quadrata Zone. The Tarrant Chalk Member is identified.

Brydone’s locality 1079 [SU 4360 2550] was visited during this survey and within a slightly degraded 10 m face several conspicuous semi-continuous flint bands were noted in soft white smooth chalk. The section is faulted and the bed correlation shown in (Figure 23) is tentative. (Woods, 1998, WH/98/119R Fig1). The Brydone collection for this site includes the echinoid Cidaris subvesiculosa, common Conorca turbinella and the brachiopod Isocrania egnabergensis, indicating the lower part of the G. quadrata Zone Hagenowia Horizon and therefore the Tarrant Chalk Member.

Brydone’s locality 1080 [SU 4489 2612] is essentially a solution feature within his G. quadrata Zone. There is no modern exposure at this site.

The pit south of Down Farm Hursley identified as Brydone’s locality 1081 [SU 4482 2566] is degraded and overgrown with only minimal exposure. The fauna (Woods, 1998, WH/98/64R) is characteristic of the G. quadrata Zone, A. cretaceus Subzone and therefore within the Tarrant Chalk Member.

A pit north of Upper Silkstead Farm identified, as Brydone’s locality 1083 around [SU 4457 2487], within his G. quadrata Zone, is no longer visible. The site is partially occupied by a modern barn and no exposure is visible.

The Brydone locality 1084 around [SU 4540 2504] off Shepherds Lane is heavily degraded with no modern exposure and is designated as within his G. quadrata Zone.

A pit in Sparrowgrove Copse around [SU 468 237] within the G. quadrata Zone is probably Brydone’s locality 1085. It was not visited during the present survey. It is just to the east of the next localities mentioned here.

Brydone’s locality 1086 [SU 4650 2355] is at the old Southampton Waterworks (see Osborne White, 1912 p.35) and comprises a large degraded and possibly backfilled pit and smaller adjacent pit (1086A). The extensive fauna (Woods, 1998, WH/98/64R) is not accurately located and the specimens could indicate an assignment to the uppermost Newhaven Chalk through to the top of the Culver Chalk formations. The ‘best fit’ is lower to middle G. quadrata Zone and the field assignment is to the Culver Chalk Formation.

Brydone’s locality 1087 [SU 4778 2290] was not visited during this survey.

A pit near Hensting Farm which is probably that of Brydone’s locality 1088 [SU 4990 2225] shows soft white chalk with regular flint courses. Two sections, divided by 8 to 9 m of unexposed ground, were seen during the visit. The thicker sequence, in the quarry face, shows up to 8 m of beds with a fauna indicative of the A.cretaceus Subzone and therefore attributable to the Tarrant Chalk Member. Whilst spoil from a 5 m-deep excavation in the base of the pit yielded the small form of Echinocorys scutata (sensu Gaster, 1924) indicating the same but lower part of the Tarrant Chalk Member.

Brydone’s locality 1067 is described as ‘the more southern of two large quarries three-quarters of a mile north of Mottisfont Station’. This is thought to be a very degraded and overgrown pit [SU 3388 2757], facing north, over a minor tributary valley. The poorly located fauna from the recent survey (Woods, 1998a) indicates the lower Culver Chalk Formation, Tarrant Chalk Member. Farther south and connected to the north-facing outcrop noted above is a much larger and working quarry (King’s Somborne Lime Quarry) [SU 3380 2740]. This was visited and comprehensively logged during the survey and up to 49 m of section was recorded (Plate 3). This is in all likelihood Brydone’s locality 1067 which has been somewhat expanded since his visits. The extensive Brydone collection (regrettably not related to horizons) and that collected during this survey (from marked beds) indicate that the lower part of the exposure, with regularly spaced marls, sponge beds and little flint, is representative of the upper ‘belt’ of Offaster pilula, and hence of uppermost Newhaven Chalk Formation. However, the greater part of the section, characterised by regularly spaced continuous nodular flint beds in soft blocky chalk, is representative of the lower G quadrata Zone, Hagenowia Horizon, A. cretaceus Subzone (Woods, 1998a, 1999; Hopson, 2001b).

Western area

The best exposure is in the extreme south-west of the district in a series of pits around Whiteparish. The largest of these pits (Whiteparish B, Woods 2000 locality 9) is located just north of the village [SU 2512 2416] and contains a fireworks factory (Figure 24). It is a large pit about 300 m long, 50 to 100 m wide and 15 to 20 m deep at the northern end. At least 20 m of chalk is exposed, dipping at 3° to the south and consists of soft, very blocky, massive white chalk with good seams of medium to large nodular flint and prominent bedding surfaces or sub-bedding joints. Some of these surfaces have well developed dissolution cavities infilled with red-orange sandy clay.

A good 19 m section was compiled (for details, see Woods; 1999) and faunas collected from several horizons in the main part of the pit. Specimens included Conorca turbinella, Offaster pilula nana and Echinocorys marginata indicative of an unequivocal A. cretaceus Subzone (lower Culver Chalk) fauna. However, a smaller section near the quarry entrance which cannot be stratigraphically much higher than the main exposure yielded an occurrence of Belemnitella and inoceramid shell-rich chalk, usually associated with the highest G. quadrata Zone at the top of the Spetisbury Chalk or basal Portsdown Chalk. If this interpretation is correct, this would imply a very thin Spetisbury Chalk Member. Belemnitella does occur at one other horizon, but this is below the A. cretaceus Subzone. This suggests that much of the upper part of the Culver Chalk is attenuated or cut out by channelling similar to that described by Evans and Hopson (2000) in the Bournemouth area. Alternatively, the range and distribution of Belemnitella is variable, and it may be that this is a rare occurrence between its known sub A. cretaceus and high quadrata Zone occurrences.

A nearby pit (Whiteparish ‘A’; Woods, 1999 locality 8) (Figure 25) 300 m to the south-east of the Whiteparish ‘B’ pit [SU 2538 2390] displays a 7 m section in massive soft white flinty chalk, with five continuous small to medium nodular flint beds. A horizon near the base in very soft weathered chalk yielded Offaster pilula nana and many indeterminate shell fragments. Other faunas from higher in the section provided a fauna indicative of the G. quadrata Zone, (A. cretaceus Subzone) or possibly post-Applinocrinus Beds, corresponding to a level at or around the Tarrant–Spetisbury Chalk boundary. This is similar to the section seen in Whiteparish ‘B’. However, it is not possible to trace the Tarrant–Spetisbury Chalk boundary with any certainty outside these pits, not least because of possible channelling within the Spetisbury Chalk, pre-Palaeogene erosion and extensive cover of clay-with-flints.

Farther east, a section near Rowden Farm [SU 2684 2432], (Woods, 2000 locality 10) provides a good exposure of the Chalk just below the Palaeogene erosion surface. Chalk, 5 to 10 m thick, is exposed on two benches.

Several other pits occur in the Whiteparish–Lockerley area but most are now overgrown or infilled. A good 3 to 4 m-thick section of air-weathered soft very blocky white chalk with nodular flint seams occurs at Home Farm [SU 2591 2454], (Woods, 2000 locality 14), but no diagnostic fauna was found. Offaster pilula nana (A. cretaceus Subzone) was collected from a small weathered section in an old pit at Clifford’s Copse [SU 2916 2563] (Woods, 2000 locality 13).

On the northern limb of the Dean Hill anticline, several good exposures occur. A shallow pit at Glebe Farm, West Dean [SU 2620 2740] (Woods, 1999, locality 5) provides a 2 to 3 m weathered face of soft white ‘gritty’ chalk. Gonioteuthis sp. found here is associated with an inoceramid shell-rich chalk and also other faunal elements that are characteristic of the A. cretaceus Subzone also seen in the upper parts of the Whiteparish Pit ‘B’. A few hundred metres farther west are a pair of pits; one is very large (over 10 m deep) but overgrown with no exposure. The second, on Rectory Hill, West Dean [SU 2592 2554] is a recently excavated 3 to 4 m-deep section in moderately hard very blocky manganese-stained white flinty chalk with two thin-skinned nodular flint bands and a marl seam. According to the farmer, very hard chalk occurs just below the base of the pit. The chalk here dips at 10° to the north, but contains no diagnostic faunas. A pit next to Frenchmoor Lane [SU 2675 2742] has a poor 2 m exposure with a micropalaeontological fauna suggesting Spetisbury Chalk.

To the north of the Alderbury–Mottisfont Syncline, Culver Chalk is exposed in several pits around East and West Tytherley. An overgrown pit at West Tytherley [SU 2766 2964] has a very weathered section of soft white flinty chalk with a fauna indicating G. quadrata Zone ( A. cretaceus Subzone) (Woods, 1999 locality 4). A pit with stables just east of West Tytherley  [SU 2770 3016] (Woods, 2000 locality 7) displays a good 6 to 8 m face of soft white flinty chalk but is mainly inaccessible. A fauna including Offaster pilula nana and Conorca turbinella, indicates Tarrant Chalk.

At Strides Row, a kilometre to the north-east of West Tytherley [SU 2824 3090] (Woods, 2000 locality 9) (Figure 26) a small 2 m section of soft white chalk with two nodular flint seams yielded common bryozoans, Conorca turbinella, Echinocorys depressula and Gonioteuthis. Echinocorys depressula is normally typical in the Newhaven Chalk, but similar morphotypes occur in the basal G. quadrata Zone. This would suggest that the section occurs at a level near the base of the A. cretaceus Subzone, within the Tarrant Chalk Member. Another pit a kilometre to the east across the valley has a 3 m section of soft white slabby chalk with nodular and Zoophycos-like flints and an echinoid horizon near the base. The occurrence of bryozoa and Echinocorys aff. marginata suggests it lies within the Tarrant Chalk (A. cretaceus Subzone). Just east of the district is another pit at Little Bentley Farm [SU 3050 2970] with 6 to 7 m of soft white flinty chalk and Echinocorys marginata. This is consistent with the Tarrant Chalk.

Central area

Good exposures of the Tarrant Chalk occur in several large active and disused quarries along the River Test. An actively worked pit at Ashley Glebe Farm [SU 3882 3084] exposed 7 m of soft white blocky chalk with two major flint bands. Several forms of Echinocorys were collected from here including an E. scutata (the small form of Gaster, 1924) and locally abundant bryozoa. This fauna (Woods, 1998c locality 8) suggests an interval in the lower G. quadrata Zone, possibly spanning the junction between the Hagenowia Horizon and the A. cretaceus Subzone.

Another recently excavated pit a kilometre south-east of King’s Somborne at Hoplands [SU 3693 3012] exposes 2 m of soft white chalk with good medium nodular flints and a locally spongiferous chalk horizon. Abundant bryozoa and a specimen of Applinocrinus cretaceus, the index fossil for the cretaceus Subzone of the G. quadrata Zone was found here. One of the adjacent old pits is Brydone’s Locality 1069, within his A. quadrata Zone.

Farther south, two pits show clear sections in the Tarrant Chalk. The first is an active pit on Michelmersh Manor Farm [SU 3608 2640]. Here, 8 m of gently dipping fossiliferous soft white chalk is exposed. A prominent flint seam cuts across the pit and is displaced by a small fault with a 0.3 m downthrow to the south-west. Overlying a marly weathering section 1.8 m above the floor of the pit the rock changes to a coarser grained lithology. The chalk contains an abundant bryozoan rich fauna (Woods, 1998c locality 28) indicative of the basal cretaceus Subzone or the underlying Hagenowia Horizon.

The second at Pitt Farm [SU 3783 2624] displays 4 to 5 m of soft blocky white chalk with several prominent bands of large flints near the top of the section. A couple of sponge beds and hardgrounds are also present, the former being richly fossiliferous. Locally abundant bryozoa and relatively common specimens of Conorca turbinella (a common species of annelid worm, Woods, 1998c locality 22) indicate a level within the cretaceus Subzone.

A small much overgrown pit just south of Fir Hill [SU 3256 3104] has a series of limited exposures of soft to firm white chalk with a conspicuous and indurated sponge bed evident in places. Large nodular flints are abundant in the brash but they were not seen in situ. The brash and small exposures have yielded (Woods, 2000, IR/00/24) abundant bryozoan and two specimens of the small echonoid Offaster pilula nana whose co-occurrence indicates the G. quadrata Zone, A. cretaceus Subzone and therefore the Tarrant Chalk Member at the base of the Culver Chalk Formation.

A large pit [SU 3049 2974], now mostly backfilled, retains a limited section at its northern end. This appears to be the same as Brydone’s locality 1059 (East Tytherley, East End Farm Pit) about 500 m north-west of Little Bentley Farm. About 5 m of white, soft powdery chalk with four well-marked large nodular flint seams and a horizon of echinoids is presently visible (HP47) (Figure 27). The fauna (Woods, 1998a, WH/98/64R; 2000, IR/00/24) in the recently collected material includes Echinocorys marginata indicating the G. quadrata Zone, A cretaceus Subzone and therefore the Tarrant Chalk Member. However the Brydone collection includes a single example of an echinoid spine attributed to Tylocidaris (Oedematocidaris) pleracantha and the zonal index Gonioteuthis, which would suggest beds slightly higher in the Culver Chalk Formation and within the Spetisbury Chalk Member. It may well be that beds formerly exposed in the southern part of the pit were higher in the succession.

At Queenwood Farm, Bucksholt [SU 3005 3080] the foraminiferal assemblage includes Gavelinella usakensis, Bolivinoides culverensis and Gavelinella cf. clementiana, characteristic of foraminiferal subzone BGS29iii (‘mid’ G. quadrata Zone).

A pit [SU 3173 2981] on the east side of the B3084 north-east of Great Bentley Farm is the most likely site for Brydone’s locality 1060 [SU 315 297] ‘one-sixth of a mile [300 m] north-east of Great Bentley Farm, East Tytherley’. The pit is heavily degraded and partially backfilled with no clear exposures but burrows show that the chalk here is white, firm, and blocky with many loose large flint nodules. There is a poor fauna in the Brydone collection that is long ranging within the crinoid to G. quadrata zones (Woods, 1998a, WH/98/64R) but its field assignment to the Culver Chalk Formation is sound based on lithology alone.

Brydone’s locality 1061 is described as a ‘pit by river opposite Pittleworth Farm, Bossington’. This is recognised in a degraded and mostly backfilled pit [SU 3313 2955] adjacent to the river. During the survey there was a 4 m section in destructured soft white chalk with many large nodular flints (some shattered) within which only crude bedding could be recognised. There was no fauna collected.

Brydone’s locality 1062 is described as a ‘pit at north end of Claygate Copse, Bossington’ and is assigned to the G.quadrata Zone. This locality [SU 3260 2863] to the north of Clapgate Copse was visited during the survey. The pit, about 6 to 8 m deep, is degraded and only a limited exposure of 1 to 1.5 m shows a clayey flinty wash overlying soft white chalk with pipes of orange-brown clay. The base of the pit shows two collapsed solution pipes whose top can be little above the base of the valley to the north.

A sketch of Yewtree Pit, Mottisfont is shown in (Figure 28). This is Brydone’s locality 1063.

Brydone identified four pits (1064 to 1067) on the eastern flank of the Test valley around Brook and Lower Brook, all of which are attributed to the G. quadratus Zone, but later also assigned to the zone of Offaster pilula (Brydone 1912, 1914, 1939; Griffith and Brydone, 1911). The three most southerly of these still show reasonable sections that have been collected. These collections and the lithologies encountered confirm that all three pits span the Newhaven–Culver chalk boundary.

Locality 1064 [SU 342 289] cannot be accurately located though it is suspected that it is the entirely degraded pit north of the track leading onto the Test floodplain immediately north of Brook Dairy Farm. This accords reasonably well with Brydone’s description of ‘Brook. Roadside pit about one-half mile [800 m] south-west of Compton House’. His fauna is sparse with only long ranging species including the belemnite Gonioteuthis sp. Field evidence suggests that this locality is within the higher part of the Newhaven Chalk Formation.

Locality 1065 [SU 3407 2856] ‘Roadside pit one and a half miles [2.4 km] north of Mottisfont Station’ is described as 270 m south-south-west of Brook Dairy Farm in this survey. The pit is mainly overgrown and degraded with an inaccessible exposure. The recent collection (a single specimen of O. pilula) and Brydone collections (see Geological Magazine, 1914 p.509) show that the upper Newhaven Chalk Formation and the overlying Tarrant Chalk Member are present in this pit. In the Brydone collection, held in BGS, the large Echinocorys morphotype of Gaster (1924) is present and this characterises the lower part of the G. quadrata Zone (Hagenowia Horizon) and hence the Tarrant Chalk Member of the Culver Chalk Formation. This is not inconsistent with the presence of Offaster pilula and Conorca turbinella in the same collection. However Brydone (1914, 1939) also noted later the occurrence of Echinocorys truncata which is indicative of the subzone of abundant Offaster pilula and therefore the upper part of the Newhaven Chalk Formation (Woods, 1998a, WH/98/ 64R; 1998b, WH/98/188R)

Locality 1066 [SU 3396 2796] is ‘the more northern of two large quarries three-quarters of a mile [1200 m] north of Mottisfont Station’ and identified as the Brook Chalk Pit (disused) on the present Ordnance Survey map. This pit is degraded and overgrown and the poor exposures available are only crudely related to each other. Between 30 and 40 m of beds outcrop in the pit with the lower and middle parts seemingly of poorly flinty chalk with regularly developed marls and the upper part of flinty chalk. The collections indicate that the lower and middle parts of the succession contain abundant Offaster pilula whilst the large Echinocorys morphotype of Gaster (1924) was present near the top of the section. Thus essentially the same part of the succession is exposed here as at locality 1065 (Woods, 1998a, b, WH/98/64R; WH/98/188R).

Locality 1067 is described by Brydone as ‘the more southern of two large quarries three-quarters of a mile [1200 m] north of Mottisfont Station’ and as such could be the very degraded and overgrown pit [SU 3388 2757], facing north, over a minor tributary valley, towards locality 1066. The poorly located fauna from the recent survey (Woods, 1998a, WH/98/188R) indicates the lower Culver Chalk Formation, Tarrant Chalk Member. Farther south and connected to the north-facing outcrop noted above is a much larger and working quarry (Somborne Lime Quarry) [SU 3380 2740]. This was visited and comprehensively logged (HP45) during the survey and up to 49 m of section was recorded (Figure 29); (Plate 3), (Plate 4), (Plate 5), (Plate 6); the uppermost 5 m was inaccessible for detailed description in the vertical southernmost part of the exposure. This is in all likelihood Brydone’s locality 1067 if somewhat expanded since his visits. The extensive Brydone collection (regrettably not related to horizons) and that collected during this survey (from marked beds) indicate that the lower part of the exposure, with regularly spaced marls, sponge beds and little flint, is representative of the upper ‘belt’ of Offaster pilula, and hence of uppermost Newhaven Chalk Formation; whilst the greater part of the section, characterised by regularly spaced continuous nodular flint beds in soft blocky chalk, is representative of the lower G. quadrata Zone, Hagenowia Horizon and lower (?) A. cretaceus Subzone (Woods, 1998a, WH/98/64R; 1999, WH/99/88R; Figure 8).

Western area

Tarrant Chalk in this area forms both the Pitton and Dean Hill secondary scarps with very gentle southward dipping dip slopes. Small exposures of soft white flinty chalk are revealed in track cuttings along the face of the scarps and in small disused pits.

The road cutting through the scarp leading into Pitton [SU 2130 3118], just outside this district, exposes 10 to 15 m of soft, smooth white chalk with regularly spaced large flint bands and many thin, marls (Figure 30). Fossil evidence suggests the G. quadrata Zone within Tarrant Chalk (Woods, WH/99/88R, locality 3).

Spetisbury Chalk occupies small parts of the higher ground in the far south and appears to coincide with a very weak positive feature. The upper part of the formation is exposed in a disused quarry [SU 2172 2648] (just outside the area of this map), south of West Grimstead (Figure 31). The base of this quarry reveals Spetisbury Chalk, whilst the top layers are identified as Portsdown Chalk, however, fossil evidence is not diagnostic and an exact division cannot be made. Echinocorys, belemnites and oysters were observed and it was first thought to expose only the Portsdown Chalk, but this is now thought questionable. A previously detailed fauna from this locality (Woods, 1998d) suggested the presence of possible Echinocorys hrydonei, which on the basis of its range in the Isle of Wight (Wood, 1995), tends to favour the basal Portsdown Chalk (see also discussion in Woods, WH/99/88R).

Portsdown Chalk Formation (PCk)

Across most of the district, the Portsdown Chalk has been removed by Palaeogene erosion. Where it is preserved, only the basal part remains. The base is taken at the Portsdown Marl. The top of the unit is delimited by the pre-Palaeogene erosion surface although this surface can cut down to at least the Newhaven Chalk elsewhere in this district The Portsdown Chalk consists of relatively soft white chalk with common marl seams and some flints; in its lower part there are several horizons rich in inoceramid shell debris.

The Portsdown Formation outcrops only close to the axis of the Dean Hill Anticline near West Grimstead in the extreme south-west of the district, Whiteparish and possibly near West Dean. There is an estimated 5 m of strata preserved.

Details

Western area

Mitchell (1956) records two localities with possible basal Portdown Chalk faunas at Glebe Farm, West Dean [SU 2620 2740] (locality5 of Woods, 1999) and at Rectory Hill, West Dean [SU 2592 2554]. However, the first of these pits was examined by Woods (1999) who found faunal elements that are characteristic of the A. cretaceus Subzone and therefore, given the lack of definitive evidence to the contrary, these pits were assigned to the Culver Chalk Formation.

Extreme western area

Only a thin succession is seen at outcrop (just outside the area of this map) and is exposed in a small, disused quarry near West Grimstead [SU 2172 2648]. The zonation of this exposure is not conclusive but the occurrence of Echinocorys, belemnites and oysters suggest that the uppermost layers are of Portsdown Chalk age (see previous discussion in the Culver Chalk).

Chapter 5 Palaeogene

The Palaeogene strata are preserved as a major elongate outcrop within the asymmetrical Alderbury–Mottisfont Syncline and on the dip slopes south of the Winchester Anticline forming the northern margin of the Hampshire Basin. The succession consists predominantly of clay, silt and sand. Much of the early and late Palaeocene is not represented by strata in this district because at that time the region formed part of a land area separating the Paris and North Sea basins.

In latest Thanetian times, deposition occurred in a warm, swampy lowland traversed by braided rivers in which sands, pebble beds and mottled clays of the Lambeth Group were deposited. After a short hiatus, a marine transgression spread from the north and the district then lay within a broad embayment which included the London, Hampshire, Belgium and Paris basins. The presence of nummulitids attests to a marine connection to the west into the Tethyan Province at this time. The London Clay and Wittering formations were deposited in this broad sea. A hiatus separates the late Ypresian Wittering Formation from the overlying formations of the Bracklesham Group of Lutetian age, reflecting a eustatic sea-level lowstand.

The Palaeogene succession consists of a number of sedimentary cycles each of which commenced with a marine transgression, the transgressive surface commonly being marked by a thin bed of flint pebbles. These pebbles are overlain by sediments that were deposited as the coastline advanced into the former marine areas (Edwards and Freshney, 1987). Each cycle probably lasted between one and two million years. The structure in this area is dominated by a low southward dip. This general pattern is occasionally complicated by folding such as that represented by the Alderbury–Mottisfont syncline that creates an inlier of London Clay to the south of this district.

In the central part of this district the Palaeogene strata comprise the Reading, London Clay and Wittering formations. They outcrop in the south within the degraded ‘Tertiary’ escarpment that forms low hills from Ampfield [SU 40 23] in the east, through Michelmersh [SU 34 25], Carter’s Clay and Lockerley [SU 30 26] to the west and Farley beyond. This is the northern extremity of the ‘Tertiary’ Hampshire Basin described fully in the Southampton Memoir (Edwards and Freshney, 1987).

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 rests unconformably on the eroded surface of the Chalk, and is between 20 and 25 m thick. 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 sand or interbedded sand and clay with abundant rounded to well-rounded, 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. Marked lateral variations in lithology occur along outcrop towards the River Test where sands predominate (Farrant, 1999, Hopson, 2001b).

Details

Central area

Lenticular bodies of well-sorted, fine to medium-grained sand occur locally at various levels, particularly at the top and base. Examples of these sands can be clearly seen in Kimbridge Sand and Gravel Pit [SU 323 253] (Plate 7) where finely bedded cross-sets of quartz sand are interbedded with thin silt and clay beds.

Locally around Braishfield and Mottisfont, the formation forms the steep face of the escarpment and thin northward extensions and outliers from it. The basal bed is present throughout the area (as it can be augured whenever ground conditions permit) although it is rarely exposed at present and frequently buried beneath Quaternary deposits at the foot of the escarpment. It is also intimately involved with the development of the clay-with-flints (see Quaternary Chapter). In the east of the district the formation above the basal bed comprises principally red-mottled clay, including variable proportions of silt, and thick successions of sand and well-rounded flint gravel, examples of which are shown in (Plate 8). The colour mottling in shades of red, reddish brown, greyish purple, olive-brown and greenish grey is the result of the oxidation of iron-minerals. Where non-oxidised the strata are predominantly grey.

Around Timsbury, Michelmersh and Awbridge the strata comprise thick cross-bedded sand units with lenticular bodies of well-rounded ‘chatter-marked’ flints and only thin mottled clays. Perhaps representing a broad distributary fluviatile environment.

The red mottled clays in this district give rise to heavy wet clays soils and are mainly under pasture and hence there are few natural exposures. The Reading Formation is worked for sand and to a lesser extent gravel in the Michelmersh and Braishfield areas. There are no details for the mostly degraded pits in the Michelmersh area. The formation was exposed during the survey in one working sand and gravel pit at Kimbridge, at two disused quarries and at a large gas transfer development site around Carter’s Clay and Kimbridge (see below).

In a large partially landscaped and flooded pit near Carter’s Clay [SU 3043 2470], a section exposed fine to medium-grained cross-bedded quartz sands with some coarse quartz and angular flint sand, with rip-up clasts, balls and thin lenses of pale grey waxy clay. The sands are bleached white in their upper part (exhibiting a ‘pepper and salt’ texture in places) becoming yellow-brown with depth and are crosscut by iron-stained (and poorly cemented) oxidation fronts running parallel with the overlying drift deposits. These sands are preserved beneath a variable thickness of head comprising earthy textured silty, clayey sand with pebbles and an uneven base.

To the north of the exposure described above a large site was being developed as a gas transfer station. In the extensive exposures a variety of facies within the Reading Formation were visible, principally on a cleared inclined surface with minor small ‘cuts’, amounting to some 6 m of beds. The section, HP40 [SU 3033 2507], shown in (Figure 32) is a composite from these temporary, overlapping exposures. Elsewhere in the site clay containing well-rounded flints, grades up into a soil. This is stratigraphically above the in situ gravel facies at the top of the measured section.

To the east of the last exposure there is an extensive area of old and current workings between Dunbridge Hill and Kimbridge where extraction of sand and gravel has taken place from the second to third terrace sequence of the Test and the underlying Reading Formation. The older sites are, for the most part, degraded and heavily wooded and exhibit only limited exposures of yellow sand or clayey gravel (or both) in rabbit burrows and more extensive badger sets. More recent activity has been landscaped and returned to agriculture but there are two sites examined during this survey and worthy of inclusion here. To the west of Dunbridge Lane a complex of exposures known as Kimbridge Quarry [SU 3215 2550] provides the composite section HP41 shown in (Figure 33), see also (Plate 8) and (Plate 9). To the north-east a smaller section HP44 in Barley Hill Wood [SU 3239 2578] shows terrace gravels resting on a very wet excavated platform which when augered revealed the underlying Reading Formation (Figure 34).

Michelmersh Brickworks [SU 343 258] still produces bricks for the specialist market from the Reading Formation. There are a number of pits in the area but it is not known whether they all still deliver clay to the main works. One pit at [SU 346 256] is overgrown and degraded and partially filled with chalk debris. White (1971) claims that the brickworks utilises clay from the London Clay and Reading formations but all of the local pits within the Michelmersh area are founded on the Reading Formation. White (1971) gives the following account of the working method and the bricks are still mixed by hand in this way: ‘The clay is brought to the pit by a Crawler tractor to the feeder and then the pug mill. Here breeze is added by hand before being mixed and passed on to the brickmakers’ benches’. ‘The green bricks are set on pallets and transferred to the drying sheds which utilise the excess heat from the kilns. They are left for a week before being set in a kiln for burning. The pair of kilns are dome shaped, circular down draught kilns, hold between 35 and 38 thousand bricks and are 20 feet [6 m] in diameter. They are oil fired and reach a temperature of 1050º Centigrade and it is this heat which produces the yellow, brown, deep red, purple and blue colours for which Michelmersh bricks are known’.

The memoir (Osborne White, 1912) gives the following description of the Michelmersh and adjacent areas demonstrating the variability of the Reading Formation locally. The grid references and metric conversions have been added, in parenthesis, for clarity.

‘At Michelmersh sand is dug in several places. About three furlongs [about 600 m] north [SU 3485 2610] of the Water Works [SU 346 255] a pit some 20 feet [6.1 m] in depth shows grey silty clays confusedly interbedded with yellow and brown sands. Here the sands contain many galls of clay, together with a few green-coated subangular and rounded flints. Concretionary ironstone is abundant. Homogenous grey sand is worked in a smaller pit a little to the southeast of the above (not now identifiable), and brown sand, with much ironstone, appears in the banks of the lane to the northwest, near the crossroads by the church [SU 346 266]. The lower beds around Michelmersh consist of brown loam and mottled clay, which are shown in small pits at the brickyard about half a mile [about 800 m] south [SU 344 259] of the church.’

‘The Bottom-bed was formerly well displayed in the short railway cutting [SU 324 259] to [SU 327 256] west-north-west of Kimbridge Mill. Sir Joseph Prestwich’s account of the section (Prestwich, 1847) here, with accompanying diagram [(Figure 35) in this report] are reproduced below.

  1. Ochreous flint gravel
  2. Red clays mottled with grey, dark plum-colour, and yellow at its base. No fossils. 15 feet [4.57 m]
  3. Clayey yellow and greenish sand, with the usual layer of slightly-rolled, large green-coated flints at the bottom; mixed also with a few small rounded flint pebbles and imbedded in an impure ochreous and argillaceous green-sand. Above the flints, and partly intermingled with them, there is at the point ‘y’ a layer about 2 feet [0.61 m] thick of large Ostrea bellovacina. Towards the south end of the cutting it gradually thins out, and disappears altogether about midway in the section, The shells of these oysters are mostly very thick and large, and much corroded. 4 feet [1.22 m]
  4. Chalk with flints. Its upper surface is rather uneven and irregularly bored into from the greensand layer above, the substance of which now fills the tubular holes.’

‘Yellow current-bedded sands are exposed at the bottom of a gravel pit (?[SU 3270 2515]) a quarter of a mile (400 m) south-west of Kimbridge Mill ([SU 3296 2556]) and in another ([SU 324 256]?, Barley Hill area) half a mile (800 m) southeast of Dunbridge Station ([SU 3186 2616]). In the latter working the sand is overlain by a lenticular bed of mottled grey clay, which appeared to the present writer to be part of the Reading Beds, and in situ, though the latter point has recently be called into question (by W Dale in the Proceedings of the Geological Society, No 913, 1911, p.3).’

‘About Lockerley, (just to the west of this district) there are indications of a thickening in the mottled clays, which are more strongly developed in the area north of Dean Brook (presumably the River Dun). South of Lockerley, however, the sands retain their preponderance. Between Critchell Green ([SU 293 259]) and Brooke’s Copse ([SU 284 246]) they contain much compact ironstone, which can be seen in position in a small pit (? [SU 2976 2518]) 400 yards [365 m] north of Hole Farm (now Chapel Farm [SU 2988 2468]) and occurs freely, in small flat pieces, in the soil over the chalk hereabouts.’ Similar ‘ferruginous cemented sand doggers’ were noted during this survey in the Michelmersh area.

‘A well (299/11 [SU 306 248]) bored at Carter’s Clay ([SU 306 247]) proved the following descending succession in the Reading Beds:

Sharp white sand 5 feet [1.5 m]
Black Clay 10 feet [3.0 m]
Mixed sand and clay 27 feet [8.2 m]
Mottled clay 15 feet [4.6 m]
Dark Green Sand 2 feet [0.6 m]
Soft Chalk’

‘South and west of Carter’s Clay, flint pebble beds are well developed, apparently at more than one horizon, but mainly in the upper part of the formation. The principal bed north of Newton [SU 309 237] seems immediately to underlie the London Clay. It is noteworthy that Mr. Whitaker observed mottled clay above part of this pebble bed in a roadside pit (? one of two pits on Tote Hill [SU 301 243]) half a mile [800 m] north-west of Newton. At this spot the pebbles occur mostly in seams amid current-bedded sands, exposed to a depth of 7 feet [2.1 m]. The mottled clay is no longer visible.’

‘The Bottom Bed can be distinguished on the western side of the little inlier of Chalk (around Doctor’s Hill Road [SU 303 233], possibly in the overgrown Chalk pit at [SU 3028 2345]) south-west of Newton,… (oyster shells are also noted at this locality)’.

‘Along the outcrop immediately north of the Dean Valley (River Dun) between Hawks Grove, to the west of this district at [SU 238 283] and Mottisfont [SU 325 268], sections are rare, but indications of mottled and brown clays are to be seen in many places.’

‘In the record of a well-boring made at Holbury Mill [SU 291 270], north of Lockerley Green, the Reading Beds are entered simply as ‘clay’, with a note that ‘oyster-shells were found at the base’. The thickness (from the base of the London Clay to the Chalk) is given as 77 feet [23.5 m], which is approximately 20 feet [6.1 m] less than that found at Carter’s Clay and Braishfield.’ [Implying a total thickness of about 29.6 m for the formation hereabouts.]

‘No sections worthy of mention were observed in the Test valley north of Mottisfont, nor along the northern outcrop, between Pittleworth Farm ([SU 328 296]) and West Tytherley ([SU 275 299]). So far as can be judged from the character of the soil, and from the poor exposures offered in the banks of lanes, the formation hereabouts is almost entirely argillaceous.’

A number of small, degraded, pits are present in the area to the north of Pucknall. Here the poor exposures and localised surface brash contain medium to coarse sand with many well-rounded flint pebbles. One of these bodies of flint pebbles, around Fern Hill Cottages [SU 3824 2569], is sufficiently large to be delimited.

To the south of Braishfield Primary School [SU 3758 2478] the surface brash demonstrates the existence of another larger body of medium to coarse sand packed with fine to coarse-grained well rounded flint gravel.

The basal bed was identified in a recently ploughed field just to the north-east of Fernhill Farm [SU 3840 2628] where greenish brown clay fragments were brought to the surface.

A large sand pit is being actively worked at Hunts Farm, Michelmersh [SU 3530 2550]. Temporary exposures showed about 10 m of coarse-grained pebbly red ferruginous cross-bedded sand. Some clay horizons were interbedded within the sands, which also contain horizons with clay rip-up clasts up to 5 cm across. In places the sands have been cemented into concretions by a ferruginous cement. The sands became more clay rich towards the base of the section. Most of the land to the south has been worked in the past and several 2 to 3 m sections through red-yellow ferruginous medium to coarse-grained sands can be seen, but the majority of the exposures have now been largely obliterated by landfill.

Western area

A small area of very coarse pebbly gravel was noted at the top of the escarpment south of Lopcomber Corner [SU 2590 3485]. Abundant small very well rounded pebbles derived from the Reading Formation occur in the superficial deposits in this area.

Extreme western area

The basement bed (≅Upnor Formation) of the Reading Formation unconformably overlies the Portsdown, Spetisbury and Tarrant Chalks and comprises a reddish brown sandy clay with abundant rounded to well-rounded, stained flints with locally glauconitic sandy clays. This basal pebble bed can be seen in the small road cutting [SU 2157 2650] near West Grimstead.

Thames Group

London Clay Formation (LC)

The London Clay Formation, within the Thames Group, consists mainly of grey, pyritic, bioturbated, silty and fine-grained sandy clay with interbedded seams of calcareous cementstone and rounded flint pebble beds; a glauconitic sandy bed occurs at the base (‘Basement Bed’). The succession contains sheet-like and lenticular bodies of fine-grained sand which generally mark the top of coarsening-upward sedimentary rhythms (King, 1981). Each rhythm, when complete, has a basal pebble bed of a richly glauconitic horizon that passes up into silty clay, which becomes progressively more silty and sandy upwards. The rhythm is completed by cross-bedded sand or interbedded channel-fills. Some of these sands may be very shelly such as the informally named ‘Lingula Sands’ (Meyer, 1871). The lithological changes in each rhythm reflect an early marine transgression, followed by low-energy marine sedimentation and a final progradation of coarse sediment from the margins of the depositional basin. The thickness of the formation varies greatly; between 30 and 85 m, with the greatest thickness in this district beneath the axis of the Alderbury–Mottisfont Syncline. The London Clay Formation was formerly worked for brick clay near East Tytherley [SU 2910 2870] and West Dean [SU 2600 2830] where there are several poor sections of silty pebbly micaceous orange-brown clay (Farrant, 2001).

There are no natural exposures of this formation in the district although drainage ditches show up to 1.5 m of pale yellow brown silty, fine-sandy clay grading down into pale and dark grey mottled silty clay in the deeper or freshly cleaned ditches.

Details

Central area

Good sections are rare, although the clay was formerly worked for brick clay near East Tytherley [SU 2910 2870] and at West Dean [SU 2600 2830] where there are several poor sections of silty pebbly micaceous orange-brown clay.

Drainage ditches show up to 1.5 m of pale yellow-brown silty, fine-sandy clay grading down into pale and dark grey mottled silty clay in the deeper or freshly cleaned ditches. There are a number of old pits in the Spearywell area (grid squares [SU 31 27] and [SU 31 28]) but they are all completely degraded and show no exposure. They are all small borrow pits with the exception of the two flooded pits adjacent to Spearywell Chapel [SU 3159 2742]. Whether these pits are part of the East Tytherley Pottery Works identified farther west [SU 290 300] is unknown, but White (1971) states that there is ‘little trace of this works which probably produced flower pots and garden objects’.

In the memoir (Osborne White, 1912) the following account appears of the Spearywell locality and another farther west:

‘In the disused brick-yard at Spearywell (presumably the site near the Chapel and marked on Hampshire Sheet 48 as Mottisfont Brickworks) stiff, silty clay near the middle of the formation has been worked; and at Buzzard Brick Works ([SU 304 287]), half a mile [800m] north-east of Lockerley Hall, the Basement-bed, with green grains and a thin layer of pebbles, is poorly exposed, in the south-eastern part of the yard, mottled clay of the Reading Beds appearing just beneath it.’

South-eastern area

In the vicinity of Brook Copse [SU 432 242] and Windmill Copse [SU 433 241] north-east of Ladwell [SU 428 239], and in Fremantles Copse [SU 449 239] south of Silkstead [SU 446 245] a sandy unit is mapped at the base of the London Clay Formation. Local minor exposures demonstrate micaceous, yellow, very fine-grained sandy silt and silty fine sand without flint pebbles.

The Whitecliff Sand Member at the top of the London Clay Formation is mapped on the highest hills north of Ampfield [SU 405 235]. Surface brash over Little Fir Hill [SU 412 246] consists of silty sand soils with a few well-rounded flint pebbles and grey fine to medium ‘soft’ sand is augered and is the favourite medium for badger and fox holes. In the past this unit has been utilised extensively for building and numerous small hollows can be seen throughout its outcrop. On Hawker’s Fir Hill [SU 408 242] the highest levels within the member are represented by pebble beds, which are manifest in the sandy clay surface brash packed with black ‘chatter marked’, well-rounded flint pebbles.

Bracklesham Group

This group contains a varied succession of interbedded clay, silty and sandy clay, silt and sand. Shell, lignite and pebble-bed horizons throughout the succession reflect deposition in transgressive-regressive sedimentary cycles. The group is divided into four formations, of which only the lower Wittering Formation is preserved in this district.

Wittering Formation (Wtt)

The Wittering Formation occurs as small outliers around Awbridge [SU 320 243] in the extreme south of the district. There are three main lithologies thought to be deposited on intertidal mud and sand flats, and in the subtidal zone. The first and most widespread in this district is clay-dominated comprising olive-grey clay and sandy clayey silt with lenses of very fine sand. The second comprises sand and silty sand with lignite and pyritised bivalves interbedded with clay. The third consists of fineto medium-grained, sparsely glauconitic sand with silty clay laminae. The three main lithologies interfinger both laterally and vertically, their relationship is so complex and there is so little exposure in this district that it was not possible to map them individually.

The base of the Wittering Formation is taken at the base of thinly bedded to laminated clays or sands that rest on a variety of London Clay lithologies, most noticeably the fineto medium-grained sands of the Whitecliffe Sand Member in this area. Overall the formation is up to 35 m thick in this district. Few exposures are present and the numerous pits described by Reid (1903) are no longer visible. There are no natural exposures of these soft easily degraded deposits and the outcrop is delimited by augering.

Details

South-western area

The Wittering Formation consists of ferruginous sands, pipe clays and thin beds of ironstone. It occurs as a small outlier near Holbury Farm, north of Lockerley [SU 2850 2740] where it was worked for sand. It is no more than about 5 to 7 m thick.

Central area

The outlier [SU 311 283] of the ‘lower Bagshot Sands (Beds)’ (presumably the Wittering Formation equivalent) marked on the Winchester Sheet within Spearywell Wood was not identified in this survey. The area is very sandy but the grain size is medium to coarse and there are copious quantities of well-rounded, multicoloured and angular, bleached white, flints both on the surface and in auger holes. In places there are wet patches developed on clayey gravel. On balance the evidence suggests that this area is one of the higher level terrace accumulations associated with the development of the Test River. Although the possibility that these gravels are mixed periglacially with a Palaeogene sand body cannot be discounted, such a scenario would, in this case, suggest the sand body must be within the middle part of the London Clay locally, since the Reading Formation crops out 30 to 35 m lower topographically only a short distance to the north.

Chapter 6 Quaternary

About 60 million years is estimated to have elapsed between the deposition of the youngest preserved Palaeogene and the oldest Quaternary deposits in this district. During this time younger Palaeogene and Neogene strata were deposited across much 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 significant break in deposition occurred after the initial accumulation of the clay-with-flints and before the deposition of the younger Pleistocene drift.

During the Pleistocene, sea levels rose and fell according 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 both by solifluction and by an extensive river system flowing to much lower base levels (up to 100 m below present sea level in the most extreme glacial episodes).

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

Residual deposits

Clay-with-flints

Clay-with-flints is typically composed of orange-brown or reddish brown clays and sandy clays containing abundant flint nodules and rounded pebbles. At the base of the deposit the matrix is stiff, waxy and fissured (slickensided), and dark brown in colour. Relatively fresh nodular flints are stained black and/or dark green possibly 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 about 5 to 6 m as a 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 is diffuse on the chalk dip slope. This down-slope feather edge is obscured by a lateral passage into a late-stage solifluction deposit or head gravel, distinguished with the prefix ‘G’ on the map. These deposits have a more sandy matrix and a surface brash composed principally of gravel-sized broken angular flints.

Details

Extensive spreads of clay-with-flints occurs on the gentle dip slopes behind the secondary escarpment. These deposits become more extensive and increasingly gravelly or pebbly towards the Paleogene outcrop, especially around East Tytherley. Little or no clay-with-flints occurs on the Seaford Chalk outcrop, although there are spreads of flint clay wash in places. There are very few good sections in the clay-with-flints except in some of the chalk pits where thin deposits of weathered reddish flinty clay are occasionally exposed. A new road cutting to Norman Court School [SU 2720 3079] exposes about 2 m of dark orange-red pebbly clay-with-flints over very soft white chalk. The rockhead here was very irregular with many small pipes up to several metres deep.

Large tracts of this area are covered by clay-with-flints; the two main areas are between Furzedown [SU 3670 2920] and Braishfield [SU 3750 2550] where it covers much of the Tarrant Chalk dip slope, and on the hilltops around Littleton, Sparsholt and the Sombornes. Chalk pits often display clay-with-flint material preserved in solution pipes and karstic cavities (commonly developed along sheet flint horizons and bedding planes), penetrating several metres into the chalk. The clearest section is probably in a pit near Braishfield [SU 3807 2581], which exposes about 1m of rounded stained flint pebbles in a waxy orange clay.

To the south the clay-with-flints becomes co-extensive with the Reading Formation. Here, the contact between the clay-with-flints and the underlying Reading Formation becomes very diffuse; indeed much of the clay-with-flints in this area may simply be cryoturbated and weathered Reading Formation. The abundant rounded flint pebbles are reworked from the underlying Reading Formation. Again the deposit is relatively thin, maybe no more than a few metres thick.

Several minor spreads of clay-with-flints occur on the gentle plateau around Great Wood [SU 315 430], Danebury Hill and Red Rice [SU 338 418]. Many of these deposits merge imperceptibly into older head deposits.

Large areas in the north-east are covered by clay-with-flints. The main spread on the hilltops west of the River Test to the north of Wherwell covers much of the Newhaven Chalk. The main spread on the hilltops adjacent to the River Test around Leckford (Sheet SU33NE) covers much of the Seaford Chalk.

Deposits also occur on the hilltops around Freefolk Wood [SU 4900 4450], south of Bullington [SU 4500 4050], around Dumper’s Oak [SU 405 352] and Stockbridge Down [SU 382 353]. However, none of these localities provides a clear section through the clay-with-flints.

Thin flinty clays can be seen at the top of a small chalk pit at Merdon Manor Farm [SU 4125 2671] and [SU 4140 2648] and in a pit south-west of Nan Trodd’s Hill [SU 4328 2643]. In general the clay-with-flints is poorly drained and the frequent ditches carrying away mole and land drainage expose the upper metre or so of this deposit. These ditches tend to degrade quickly and only recently cut or cleaned ditches show a friable red-brown flinty soil, usually 20 to 30 cms thick resting on stiff waxy, reddish brown unctuous clay with orange-brown stained nodular flints.

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 this district, head is ultimately 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. Clast composition varies depending on source materials; those deposits derived mainly from the chalk were formerly mapped as ‘dry valley deposits’ or ‘coombe deposits’ In comparison with the clay-with-flints, head generally includes a greater proportion of frost-shattered flints. A small proportion of the very well-rounded flint pebbles derived from the Palaeogene is commonly also present but this tends to be less than in the clay-with-flints.

Head is 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 suggest that the head is mostly less than 2 m in thickness, but could locally attain 5 m or more.

The most important difference between head and clay-with-flints is that the former has undergone gradual down-slope movement. The Chalk bedrock on which head lies is thus less likely to be part of an ancient landscape surface that 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 karstic 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 karstic topography.

Head occurs both in valley bottoms and on interfluves, but in the present area most occurrences of head, other than those on the valley floors, are considered too thin and too irregular to record on the map in any useful way. Head in the 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 the gravelly head or (in some areas) alluvium. The term ‘head’ here includes the chalky, flinty materials which floor many of the valleys in Chalk downlands, and which were formerly mapped as ‘dry valley deposits’. Head is in part shown on the older geological maps of the area 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.

Many parts of the Seaford Chalk and lower Newhaven Chalk outcrop have a heavy clayey flinty soil, especially on very gently sloping ground on ridges around the Wallops, but also on some valley sides. Traces of red-brown clay and local concentrations of flinty gravel occur in these soils. However, the head deposit is generally much less than 1m in thickness.

These observations show that the flinty clay deposits on the Seaford Chalk should be treated as head rather than as clay-with-flints, although much of the constituent material is presumed to be ultimately derived from a previous cover of clay-with-flints or Palaeogene deposits. Its position on interfluves suggests that it could be regarded as ‘older head’, but it was evidently largely remobilised during the formation of the head deposits seen in the valley bottoms. The distribution of head on valley sides and on interfluves is irregular and there is no topographic expression of its limits.

Gravelly Head

These broad, sheet-like deposits are composed mainly of angular flint gravel set in a stiff, sandy clay matrix. In some exposures the matrix contains chalk, but elsewhere this has been lost by decalcification. The head gravel is generally regarded as the result of solifluction of chalk, Palaeogene deposits and clay-with-flints down the dip slope of the Chalk during cold phases of the Quaternary.

The valleys of the River Dun around West Dean is underlain by very coarse to cobbly, poorly to moderately sorted, clast-supported flint gravel, here classified as ‘gravelly head’. The near-surface part of the deposit is seen to have been decalcified or winnowed, presumably by running water. While most of the flint clasts resemble those found in head, and are predominantly angular, some are subangular or subrounded and have evidently undergone transport by water. This gravelly head seems generally to be between 1 and 5 m in thickness, but there is very little information to demonstrate this.

This valley-bottom gravel is interpreted as the product of both solifluction and fluvial transport in a periglacial environment. Within the present project area the formation of these valley-floor gravels is thought to have been dominated by mass-movement processes, and so they have been named as a form of head. This gravelly head is in part shown on the older geological maps as ‘alluvium’. It differs from the deposits here recognised as alluvium in being predominantly very coarse and very weakly bedded. Other parts are shown on the older geological maps as ‘River and Valley Gravel’ or ‘Valley Gravel’. Moreover, some areas previously shown as ‘Valley Gravel’ are now shown partly as gravelly head and partly as head.

Solifluction deposits emplaced in the valley floor may be reworked by subsequent surface run-off, either during later periglacial periods or by more recent wet weather flow. This surface run-off has left a coarse gravel lag, having preferentially removed fines and promoted dissolution of the carbonate fraction of the existing deposits from its line of flow. The presence of a central channel is taken as a simple criterion to separate head from gravelly head where these occur in the bottom of otherwise similar dry valleys.

Another patch of gravelly head occurs near Tytherley common [SU 2640 2890] where a dry valley draining the chalk dip-slopes crosses onto the Palaeogene outcrop. Here, surface drainage from the Palaeogene sands and clays has probably contributed to the winnowing and decalcification of the head occupying the valley floor. The deposit dies out southwards away from the chalk outcrop, reflecting the limits of initial soliflucted flinty material.

A third occurrence occurs in a tributary valley to the Wallop Brook near Nether Wallop. The valley deposits here are very coarse to cobbly, poorly to moderately sorted, clast-supported flint gravels. Although not seen in section, the field brash is very gravelly. In wet weather, a small stream flows in the valley downstream of Spring Pond [SU 2785 3610].

Slope Head

Slope Head (‘Older Head’) 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 in the clay-with-flints. 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, 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.

Derivation by solifluction from the clay-with-flints can be demonstrated where the two deposits are contiguous but there are ‘outliers’ of older head isolated on spur tops underlain by chalk in the Houghton district e.g. centred around [SU 334 329] and [SU 332 347]. These are considered to be equivalent to the older head purely on their orange-brown very flinty clay soils but there is still the possibility that they may be remnants of ‘high level’ river terrace aggradations. Indeed there is probably a continuum of development from older head to terrace over much of the Chalk downlands in this part of southern England.

Fluviatile and organic deposits

River Terrace Deposits

River terrace deposits are associated with the major river systems of the Test and the Itchen. The River Test flows north to south across the centre of this district and its entire catchment covers the greater part of the Winchester Sheet. Terrace aggradations are found throughout the district but are best-developed in terms of lateral extent and vertical height range near to the confluences with the rivers Dever and Anton in the north, near Wherwell, and in the south with the River Dun near Mottisfont. Up to eight aggradations have been mapped.

The terrace deposits are generally gravels and sandy gravels, principally of subangular to angular with some well-rounded and nodular flints, and with subordinate quartz, ironstone, sarson and other exotic material (Hopson, 2001b). Some clasts are rubified, probably derived from the clay-with-flints. Gravels are both matrix and clast supported and planar to cross-bedded. The sand matrix is predominantly medium with fine and some coarse quartz, the coarser fraction containing ironstone and flint shards. The lower terrace aggradations are generally ‘clean’ with little silt and clay content whereas higher terraces become progressively more ‘clayey’. In places iron cementation has occurred (Hopson, 2001b).

The River Itchen flows across the south-east of the district, through the city of Winchester and southwards past Twyford. There are three terrace aggradations, with the deposits being predominantly clayey sandy gravels. They are mapped principally on the western side of the valley indicating that the stream migrated eastwards, however, this is contradictory to the south-westward dip of the strata and may indicate a structure (e.g. fault) buried beneath the broad alluvial tract (Hopson, 2001a). 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, again, some clasts are rubified. In general the terrace deposits are up to 5m 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 terrace show cryoturbation structures indicating that they have suffered at least one periglacial event, and thus suggesting they are all pre-Devensian.

Details

River Test valley

The Test has eight mappable terraces within the district. In the north of the district the River Test has up to four terraces, the first and second of which can be distinguished, but above these the deposits are very degraded and any features are difficult to identify.

In this northern area the first terrace of the Test has been mapped almost continuously along both banks around Newton Stacey [SU 4120 4060], Bransbury [SU 4220 4240] and Longparish [SU 4320 4450] forming a hummocky terrace about 2 to 5m above river level. The second terrace gravels around Longparish and southwards sit some 8 to 10 m above the floodplain.

The gently rising ground above second terrace level carries a covering of granular terrace material but individual terrace units could not be distinguished on geomorphological grounds. By comparison with areas outside this district, two further terrace aggradations (third and fourth) are suspected within this 10 to 15 m rise. Above this, the level interfluve areas are generally capped with remnants of clay-with-flints.

These terraces have been worked in a series of small pits along the north-western side of the Test but these are now overgrown and degraded. An extensive working, north-west of Forton [SU 4120 4390] was identified on aerial photographs taken in 1993. This site has subsequently been infilled and so carefully landscaped that there was no evidence for this pit on the ground at the time of this survey.

Moving southwards, the lowest terrace occurs again around Stockbridge and Marsh Court [SU 354 332] forming a hummocky terrace about 2 to 5 m above river level. To the south-west these gravels merge and interdigitate with tufa deposits. This terrace has been extensively worked in a series of pits just south of Stockbridge [SU 357 345], one of which now contains the sewage works. The second terrace occupies a small flattish spur (a fragment of former valley floor) south of the sewage works [SU 3570 3415] about 15 m above river level. Only a small remnant remains. A pit here exposes about 1 to 2 m of flint gravel with no discernible bedding, resting on pitted and karstified chalk. The rockhead is very irregular.

A third terrace occupies a large area north-west of King’s Somborne between 20 and 25 m above the river. Exposures are limited to disused pits, but extensive sections can be seen at the Tarmac quarry north of How Park Farm [SU 3505 3200], which displays about 1 to 2 m of flint gravel overlying chalk, with abundant flint-filled pipes that may extend over 5 m below the surface. Another clear section can be seen in a disused gravel pit just west of the district on Sheet SU33SW [SU 3485 3086]. A formerly extensive area of terrace gravel has been worked, together with the underlying sands of the Reading Formation around Casbrook Common (grid square [SU 35 25]), but very few exposures now remain.

Moving further southwards again, the broad valley of the River Test (Plate 10) around Mottisfont supports terrace successions principally on its western bank indicating that it has migrated eastwards during each subsequent downcutting event.

There are six sites with reasonable exposures noted during this survey. Sections HP41 [SU 3215 2550] and HP44 [SU 3239 2578] are shown in (Figure 33) and (Figure 34) (see Reading Formation; (Plate 11); (Plate 12)). These two exposures show sections in the second to third terrace aggradation at the Kimbridge Quarry and the Barley Hill Wood site, respectively.

The same terrace aggradation, resting on the Culver Chalk Formation, is noted at HP 42 [SU 3215 2743] and HP 43 [SU 3255 2796] (Figure 36) and (Figure 28), respectively. The first is probably the site referred to as Hatt Hill in the Southern River Palaeolithic Project publication.

The lowest, first terrace is exposed in a small pit [SU 3271 2573] north-west of Manor Farm, Kimbridge (Plate 13). Here up to 2 m of clayey sandy clast-supported fine to coarse-grained gravel with some cobbles was seen in a limited exposure dug to maintain the farm tracks over the alluvial floodplain.

A small exposure in third terrace, of clayey sandy gravel preserved as a thin surface layer and within broad solution pipes into the chalk is seen behind the tarmac coating plant at Yew Tree Hill [SU 3485 3085] chalk quarry. Osborne White considered this outcrop to be within his ‘high-level’ gravels but since it is only 20 to 25 m above the floodplain it is here considered to be representative of the third terrace and therefore his ‘Belbins Stage’.

In the memoir (Osborne White, 1912) four groupings of ‘gravels’ are described. Those at a high level, 100 feet [30.5 m] or more above the floodplain, and principally founded upon Palaeogene strata, are equivalent from the modern mapping to the fifth and higher terraces. There are two ‘stages’ within the confines of the present valley that contain Palaeolithic implements. These are described by Osborne White as the ‘Belbins Stage’ (70 feet or 21.3 m above the floodplain), named after the farm of that name, at [SU 359 233] to the east of this district but represented here by the aggradations covering Dunbridge Hill [SU 318 259] and equivalent to the second to (?)fourth terraces as mapped, and the ‘Mottisfont Stage’ (40 feet or 12.2 m above the floodplain) which appears, in part, to be equivalent to the same group of terraces. The ‘low-level’ terrace as described is adjacent and underlies the alluvium, and is equivalent to the first terrace a little above (1 to 2 m) the floodplain.

However, placing the locations mentioned in the memoir onto modern maps suggests that the Belbins and Mottisfont stage concept is flawed. For example the lower site identified at Belbins, being only 15 m above the floodplain, would accord more accurately to their description of the Mottisfont stage, whilst the terrace on which Mottisfont stands ranges over 5 to 20 m above the floodplain and indeed one site on that spread (Hatt Hill) is considered to be representative of the Belbins Stage. It is evident from the most modern mapping, as demonstrated by the grouped terrace numbering, that spreads of gravel are likely to represent more than one aggradation cycle and that subsequent down-slope movement of surface material has disguised terrace feature breaks. More detailed studies are required to elicit the correct relationships between height, geomorphology, lithology and palaeolithic implement content in the middle reaches of the Test valley north of Romsey.

John Wymer led a team that reported upon the Palaeolithic finds in the rivers of southern England (The Southern Rivers Palaeolithic Project, Trust for Wessex Archaeology Limited and English Heritage, 1993). This review identified numerous sites from Romsey northwards where worked flint implements were found. The ‘Belbins Pit’ (attributed to Terrace 4) from which a large collection, principally hand axes, was obtained, is identified at [SU 364 236] but this is some distance (600 m) to the north-east and 10 m higher topographically, at about 45 m OD, than ‘Belbins Farm’ identified by Osborne White (1912) for his higher ‘Belbins Stage’. Large collections were also identified from Kimbridge [SU 327 251] (east of Dunbridge Lane) at about 40 m OD, Dunbridge Hill [SU 318 258] at about 45 m OD and at Ready Mix Concrete Gravel Pit Dunbridge Hill [SU 320 257] at 45 to 50 m OD. These were attributed to third to fourth terrace in the case of Kimbridge and Terrace 5 to 6 for the other two. Modern mapping places these three sites in the second to third terrace. Elsewhere only limited finds are reported, often only a single or small group of worked flints. There seems little doubt therefore that the terrace ‘staircase’ in this area is not well understood. The grouping shown on the present maps is based entirely on the surface brash and topographic range of the deposits. There is little evidence on thickness or basal topography on which to divide the larger and topographically extensive spreads into individual terrace aggradations. Under the present scheme herein, the major implement-bearing gravels are all within the second to third terrace undivided.

There are numerous references to the terrace sequence within the Test valley in the memoir (Osborne White, 1912, p.69 to 73) most give little detail other than the presence of a terrace at a given locality but some useful abstracts are given below.

‘On the west side of the valley the Belbins Stage is represented by the gravel-flat at the top of Dunbridge Hill ([SU 318 258])… a good section is shown in a pit half a mile [800 m] south-east of the station (?Dunbridge Pines [SU 320 257]). The gravel, about 7 feet [2.1 m] thick, is ochreous and strongly current-bedded, and contains bands of brown loam. Pebbles are abundant, and small rounded blocks of sarsen and ironstone not uncommon. The gravel rests on an uneven surface of Reading sand… The pit has yielded many palaeoliths, which occur in all horizons in the gravel. Mr W Dale (Proceedings of the Geological Society, 1911) states that the tools near the middle are often water-worn, whereas those in the upper and lower parts of the deposit are fresh and unrolled. From the same authority the writer gathers that the implements in the upper layer differ little from those of the lower, except in their colouring, though a form arrived at by trimming a pebble to a point at one end appears to be characteristic of the latter (i.e. the lower part); also, that while finely-pointed tools seem somewhat commoner here than in the pits at Belbins, there is ‘not any real difference’ in the facies of the implements from the two localities.’

Despite what is said in the memoir there is sufficient evidence in the text to suggest that these early workers were looking at a complex of more than one gravel aggradation and it is certainly true that the deposits described do range over a considerable topographic range both at Dunbridge and Belbins. Indeed the Belbins site is described as... ‘represented... by the well-marked terrace (120 to 130 feet [36.6 to 39.6 m])... and the adjacent plateau... (130 to 138 feet [39.6 to 42.1 m]).’

Further references to the deposits referable to the ‘Belbins Stage’ are given. ‘North of Dunbridge the up-valley succession of deposits referable to this stage is continued in a small gravel patch, at 150 feet [45.7 m], on Hatt Hill ([SU 318 266] and in second to third terrace); in two other little patches at about the same level to the east of Spearywell (actually at 55 to 60 m OD and mapped as fourth terrace), and in two larger spreads with terrace features (at and above 150 feet [45.7 m]) north and south of Pittleworth Farm ([SU 328 296]).’ The latter being also mapped as second to third terrace.

Deposits attributable to the ‘Belbins Stage’ are not identified for a further seven miles [11.3 km] north in the Test valley in the memoir.

The ‘Mottisfont Stage’ is also identified at a number of places within this district. In the south-east of The White House [SU 331 238] (Awbridge Farm in the memoir but not the present building of that name which is some distance to the north) a small patch of gravel is shown on the old county sheet [Hampshire 48]. This is shown as third terrace but being only some 10 to 15 m above the floodplain may well incorporate elements of the second terrace.

Farther north the following description appears in the memoir. ‘Between a quarter and half a mile [400 to 800 m] south-west of Kimbridge Mill [SU 3295 2559] there is a marked terrace (112 to 115 feet [34.1 to 35.1 m]) in which gravel and sand are worked in large pits from 10 to 15 feet [3.0 to 4.6 m] deep. One of these excavations, on the south side of the road to Kimbridge Mill, displays well-bedded ochreous gravel, mostly of coarse texture, and containing little-worn flints up to 18 inches [46 cm] in diameter. Beneath the gravel is yellow Reading sand, of which the upper parts, with intercalated gravelly seams, have clearly been rearranged. Mr Dale writes ... ‘A large number of implements have been found in this pit, almost always at the base of the gravel. They are nearly all of rough workmanship, deeply stained on the upper side, and so far as can be ascertained, no pointed ones have been found, but only forms roughly ovate and much water-worn.’ Associated with these tools are some ‘large flakes, carefully trimmed on one side only and little water-worn.’ The gravel of this terrace appears to be joined to that on the higher flat at the top of Dunbridge Hill by a spread covering the intervening slope.’

‘The terrace that supports the village of Mottisfont (112 to 119 feet [34.1 to 36.3 m])’... and now part of the more extensive spread of second to third terrace... ‘is particularly distinct, but no sections were seen in it, nor in the two patches of gravel (120 to 124 feet [36.6 to 37.8 m])’... also amalgamated into a larger spread of second to third terrace... ‘along the road to the north of the village. The larger spread [see section HP43 shown in (Figure 28)] between half a mile and a mile north (800 to 1600 m) of Mottisfont appears to belong to this stage; also the little mass on the edge of the low bluff east of Pittleworth Farm [SU 328 296]. A pit in the latter shows 8 feet [2.4 m] of iron-stained gravel mostly unstratified.’

The low-level gravel, essentially the first or ‘floodplain’ terrace, forms only low terrace features with a slightly undulating surface adjacent to the alluvium.

Terraces five to eight have been mapped in the far south-west of the district, on the western side of the River Test. Two areas of terrace five/six sit on the London Clay in Spearwell Wood [SU 312 275] and [SU 312 283] north-east of Lockerley. Terraces seven to eight sit on the hilltop near Upper Ratley [SU 323 237].

River Dun valley

The River Dun is a tributary of the River Test in the south of the district. Two terraces have been identified in the River Dun valley. The lower terrace, mapped around Lockerley and in places farther west around West Dean is around 2 to 5 m above river level, while the second higher terrace to the south-east of Lockerley sits some 5 to 10 m higher. Neither terrace is exposed, but field brash consists of abundant well-rounded and broken flint gravel, with clasts of varying sizes, set in silty sandy clay. Some are stained and rubified, and are probably derived from the clay with flints or Palaeogene deposits. Boreholes adjacent to the railway line near Lockerley [SU 2985 2645] prove 1.95 to 2.45 m of silty clays and gravel overlying the Reading Formation.

Wallop Brook valley

No terrace deposits associated with the Wallop Brook, a tributary of the River Test, were identified in the district.

River Dever valley

Gravelly terrace deposits are also associated with the River Dever, a tributary of the River Test, in the north of this district. Here, one terrace, 2 to 5 m above river level is mapped within the Dever Valley. A second terrace is mapped some 5 to 10 m above river level around Stoke Charity [SU 495 395].

River Itchen valley

The first terrace has been worked [SU 470 232] and [SU 470 228] to the east of Otterbourne but these pits were not visited during this survey as they are just to the south of the district described herein.

There are some scant details of exposures around Winchester and to the south within the old memoir (Osborne White, 1912, p.73). He noted three levels of ‘gravels’ in the Itchen valley that seem to accord with the first to third terrace as mapped recently. He equated his highest level about 70 feet [27.4 m] above the floodplain as equivalent to similar deposits at ‘Belbins’ (‘Belbins Stage’) near Timsbury in the Test valley; and deposits, like those south-west of St Cross, at 40 to 50 feet [17.2 to 21.3 m] above the floodplain with his ‘Mottisfont Stage’. Both deposits in the Test valley yielded Palaeolithic tools of various forms. His ‘low level’ gravels equate to the first (and presumably the ‘sub-alluvial gravels’) terrace as mapped principally in the southern part of Winchester. These are reported as containing ‘elephant remains and palaeoliths’ in excavations at the Cathedral beneath 25 feet [7.6 m] of ‘soil, peat and marl’, and the gravel below the water table is reported to be ‘contain much chalk’.

Alluvium

The alluvium comprises soft, organic, mottled silty and sandy clay, which generally overlies a basal lag gravel. Thin stringers of gravel may occur within the succession, indicating channel migration or periodic increases in the flow regime of the rivers over time. In general the deposit is thin, usually between 1 and 3 m in the upper reaches of rivers, 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 association of calcareous tufa and peat accumulations with the overbank alluvium. Major occurrences of these deposits are discussed below. (Plate 14) shows a typical bankside exposure of the floodplain of the River Test near Kimbridge [SU 3320 2630]. Grey silty clay overbank deposits are closely associated with variably silty and clayey calcareous tufa both resting on a basal bed of dark fibrous peat.

The alluvium found in parts of the River Dun and Wallop Brook valleys generally comprises three distinct lithologies: well-sorted gravel, peat and silty fine-grained sandy clay. These are so interdigitated as to make their differentiation impractical. The gravel is composed of mostly small loose subangular to subrounded and rounded flints, probably derived from adjoining terrace or head deposits. Peat occurs as a dark brown or black organic deposit with varying admixtures of marl and loam, and is typically fibrous and spongy. The silty loam is normally pale grey and commonly contains fragments of flint and chalk. The more peaty soils tend to be in the backwater marshy areas away from the main stream.

In the Dun valley, alluvium occurs throughout the valley except for a small section around West Dean. A small patch occurs near East Tytherley in the valley floor. Alluvium occurs in much of the Wallop Brook, up as far as the headwaters at Over Wallop, and part way up some of the tributary valleys.

Alluvium, and related deposits, are best seen during low flow periods. Examples of the sections seen are given in (Plate 14) and (Plate 15) and a reasonably full account of the deposit and associated peat and calcareous tufa are given in the memoir (Osborne White, 1912).

Because of the intricate inter-relationship between the ‘end-member’ lithologies (alluvium, peat, calcareous tufa) of the floodplain, the maps give a broad indication of the lithology at surface. It can be expected that any excavation through the floodplain it likely to encounter a very variable profile with representatives of each ‘end-member’ lithology and deposits of an intermediate nature. Examples of descriptive logs from boreholes penetrating the ‘alluvial sequence’ in each of the major valleys (Test, Dun and Wallop Brook) are given below.

The following are three examples of the ‘alluvial sequence’ from north to south in the Test valley.

Borehole (SU33SW/28) [SU 3421 3095] Depth m
Made Ground 0.20
Flint gravel, medium dense, white mottled black brown, sandy fine to coarse-grained, angular to subrounded with scattered cobbles 8.50
Chalk, structureless composed of very soft to firm, white clay matrix material with many fine to coarse gravel sized chalk fragments and occasional fine to coarse angular to subrounded flint clay 13.00
Chalk, structureless composed of coarse subangular gravel-sized fragments with some matrix material of very soft gravelly chalk 15.00
Borehole (SU32NW/6) [SU 3272 2632] Depth m
‘Chalky’ topsoil 0.50
Clay, firm grey ‘chalky’ 0.70
Peat, soft black 1.10
Peat, soft, brown-black silty 2.00
Peaty clay, soft black, with gravel 3.20
Gravel, dense, angular fine and medium-grained flint, with some coarse sand 8.50
Chalk, white rubbly >10.00
Borehole (SU32SW/6) [SU 3465 2374] Depth m
Topsoil 0.85
Peat, soft black 3.25
Gravel, loose to medium dense, fine and medium-grained with thin layer of soft grey silty clay at 9.10 m 11.00
Clay, brown silty with claystones (London Clay) >15.00

The following two examples are from the tributary Wallop Brook and River Dun demonstrating that there are similar but thinner deposits associated with these streams

Borehole (SU33SW/18) [SU 3210 3186] Depth m
Topsoil 0.10
Clay, soft to firm, light brown, chalky silty, with much fine chalk gravel and fine to medium-grained angular to subangular flint gravel 2.20
Flint gravel, very dense becoming dense, black, slightly clayey sandy fine to coarse-grained, subangular to subrounded with scattered cobbles 4.20
Chalk, structureless, composed of stiff cream clay matrix with scattered fine gravel-sized chalk fragments >5.00
Borehole (SU32NW/13) [SU 3130 2607] Depth m
Topsoil 0.15
Clay, soft grey 0.80
Peat, soft, dark brown, clayey 1.30
Gravel, loose, grey, silty, sandy 2.50
Gravel, dense, fine, medium and coarse, with some large flints and some sand 4.90
Chalk, cream/white rubbly >6.50

Within the Itchen valley boreholes where the M3 crosses the floodplain show 1 to 1.5 m of peaty silts and clays resting on dense gravels to a depth of 4.5 to 5.5 m below ground level. Within the floodplain areas of Winchester around the Guildhall [SU 484 294] and commercial centre up to 9.5 m of alluvium resting on dense gravel have been found.

In the Dever valley, most of the alluvium is of a loamy peaty character. North and south of the confluence of the Dever with the Test, around Bransbury Common [SU 4120 4180] the alluvium is usually peaty, but with much disseminated fine chalk pellets and forms extensive areas of marshy ground. In the Wherwell area [SU 3900 4100] the alluvium deposits merge and interdigitate with tufa.

Tufa

Extensive patches of tufa occur in the Test and Itchen valleys. The tufa commonly forms raised (1 to 2 m) hummocky spreads, superficially very similar to river terraces on the valley floor and for the most part, the distribution shown on the map reflects the occurrence of this characteristic morphology. The deposit usually consists of small amorphous grains or nodules of calcium carbonate, commmonly coating flint pebbles or other nuclei. Mollusc and shell fragments are locally common. The level of the raised hummocks probably represents the winter flood level of the water or marsh before the river channels were straightened and the marshes drained.

Details

River Test valley

In general the most extensive areas of tufa are marginal to the alluvial tract on the east side of the Test valley (particularly north of Mottisfont and near Cotttonworth) and associated with the larger spreads of peat. Elsewhere, small patches of calcareous tufa-rich soils have been noted within the overbank silty clay alluvium particularly where the flood meadows have been ploughed. A small area of tufa also occurs in the Anton valley close to the confluence with the Test valley. Tufa deposits in this area may be related to calcareous springs, the ‘Whirly Wells’, from which Wherwell got its name.

River Itchen valley

Calcareous nodules are a common occurrence within the alluvium but mapped concentrations associated with discrete hummocky terrain areas are noted south of the M3 crossing of the Itchen floodplain around Compton Lock [SU 476 255]. Farther south from Shawford House [SU 475 249] to the confluence [SU 468 225] of the Otterbourne stream (outside the district described herein) with the River Itchen the floodplain is almost entirely covered by calcareous tufa. Frequent bankside exposures are commonly seen in this area during low water conditions and on the outside of meander cuts.

Peat

Small accumulations of peat and peaty material are associated with alluvium and the river terrace deposits but these are generally too limited in extent to map. More extensive spreads of peat were mapped in the Kimbridge to Timsbury area where it consists principally of fibrous wood and sedge material. Peat was also mapped north of Oakley Copse [SU 334 286] and east [SU 344 313] of Bossington. In each case the peat is seen to pass under, or grade into, alluvium and calcareous tufa.

Elsewhere peat is noted beneath overbank silty clay deposits along many of the drainage channels. In all occurrences there is an intimate association with calcareous tufa and there is a continuum between fibrous pure peats and silty clays with a large humic content (both finely disseminated and as lenses of limited thickness and extent).

Worked and made ground

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 1:10000 scale maps of the district, listed in the Information sources show a more detailed distribution. Artificial ground is common, especially within the urban conurbation and associated with the development of major routeways.

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, terrace gravels, the London Clay Formation and the Reading Formation. Most lie along, or close to, the tracks of the major rivers.

Details

Near Mottisfont on the River Test is a large working quarry (Somborne Lime Quarry) [SU 3380 2740] where the Newhaven and Culver Chalk Formations are extracted. Another large partially landscaped and flooded pit is situated near Carter’s Clay [SU 3043 2470]. An extensive area of old and current workings occurs between Dunbridge Hill and Kimbridge where extraction of sand and gravel has taken place from the second to third terrace sequence of the Test and the underlying Reading Formation. Kimbridge Quarry [SU 3215 2550] is presently worked (Reading Formation) as mentioned above, and Michelmersh Brickwork’s [SU 343 258] still produces bricks for the specialist market from the Reading Formation.

The most extensive areas of Worked Ground are engineered cuttings carrying the main A30 and A343 roads, the mainline railway between Southampton and Salisbury, or their associated underpasses.

Smaller cuttings occur locally on other roads in the area, or have been made to accommodate farm buildings, slurry pits, dew ponds, recreation grounds and the disused canal running along the Dun valley. Pits up to about 100 m in diameter occur widely in the area, being especially numerous in the south-west, associated with the clay-with-flint outcrop. Most were for the extraction of chalk, flint or gravel, but clay was formerly worked near East Tytherley [SU 2910 2870] and at West Dean [SU 2600 2830] at Fox Farm. All these pits are now disused, most are completely degraded and some have been partly or wholly backfilled, either as waste tips or to restore the land. Sand has been worked from the Reading Formation to the south and east of the district.

Some small circular depressions marked as Worked Ground may instead be dolines and some of the pits (in particular any used for brick clay) could mark the site of former dolines.

Extensive tunnels in the Culver Chalk occur beneath Dean Hill as part of the Royal Navy depot at West Dean.

Made ground

Made ground is shown in areas where material was deposited by man upon the natural ground surface. There are two main categories:

Details

Most areas of Made Ground are engineered embankments carrying the main A34, M3, A30 and A343 roads, the mainline railway between Southampton and Salisbury, or their associated bridgeworks. Major landscaping and dumps of inert fill (not shown on the map), which in some cases have been used to form screening embankments, occur around the military installations at West Dean, Grid square [SU 26 26], Porton Down and Middle Wallop.

Several large landfill sites occur in the area around Casbrook Common [SU 3600 2500], mainly containing domestic waste.

Major landscaping and dumps of inert fill (not shown on the map), which in some cases have been used to form screening embankments, occur around the military installations at Middle Wallop and the Andover sewage works near Goodworth Clatford.

Infilled ground

Infilled ground comprises areas where the natural ground has been removed and the void, wholly or partly backfilled with man-made deposits which may be either natural or waste material, or a combination of both. Where quarries and pits have been filled, the ground restored and landscaped, built on or returned to agricultural use, there may be no surface indication of the extent of the backfilled area. In such cases the boundaries of these sites is taken from archival sources such as earlier aerial photographs, local authority records and old topographical and geological maps.

Details

In this district the cuttings associated with the old course of the A3 Winchester bypass which swings around the west side of St Catherine’s Hill have been infilled with chalk waste derived from the development of the M3 motorway.

Landscaped ground

Consists of areas that have been extensively remodelled or landscaped, with complex patterns of cut and fill, too small to be identified separately. Such areas commonly include parkland, golf courses and major construction sites.

Archaeological earthworks are sporadically distributed across the area, the largest of which is the ‘iron-age’ hill fort on Danebury Hill. Many include ditches (mostly infilled) as well as embankments. Those earthworks are indicated on the topographical base-map and have not been recorded during this survey.

In this district some golf courses rely entirely on the natural contours (e.g. Royal Winchester [SU 45 29] and Twyford Down [SU 48 26] golf courses) and little landscaping has occurred, others are heavily re-contoured with significant unnatural features being present (e.g. South Winchester Golf Course [SU 45 27]).

Chapter 7 Structure

The district lies within the Wessex Basin, a broad extensional basin developed during the Jurassic and inverted during the Miocene (Alpine) compressional event. 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 between the east-west-trending Wealden Anticline (Weald Basin) in the east and the remainder of the Wessex Basin to the west. The Pewsey–Kingsclere hogsback structure lies to the north and the Wardour–Portsdown Inversion, to the south (which is expressed farther west as the Mere Fault running east-west through the Vale of Wardour, then south of Salisbury across to Portsdown) (Chadwick, 1986, 1993).

Faults (developed during the extensional phase) within the Jurassic strata at depth control the location of most of these fold structures seen within the district. The main structures affecting the Weald are thought to have been formed during the Miocene. The resultant structure in the western Weald is a broad, gentle anticline with shallow dips (less than 4°) to the south, variable dips (up to 20°) to the west or north-west, and a gentle plunge west-south-westwards. Periclinal structures associated with east-west faulting at depth are known to be associated with the Wealden anticline. Within this broad structure are a number of smaller, lower amplitude synclines and anticlines. In general, the small anticlinal structures have steeper dips on their northern limbs, probably reflecting the reactivation of deep-seated Jurassic fault blocks.

One such fold pair, the Winchester–Meon structure (pericline) seen in the adjacent Alresford area (1:50000 Sheet 300) that also fades westwards into this district as the Winchester Anticline and its associated Winchester- King’s Somborne Syncline to the north (Figure 37). This structure gently plunges to the west, mirroring the axis of the Wealden anticline. The axis of a similar but broader anticline (the Stockbridge Anticline) runs through the centre of the district but gradually dies westwards. To the north, around the Wallops and Stockbridge, the dip is less than 0.5° to the south-west; to the south of the axis, the dip increases to 1° to 2° and is more southerly. Its counterpart, the Micheldever Syncline farther north, trends east-west before turning northwards towards Andover.

Another major structure in this district is the Dean Hill Anticline and corresponding Alderbury–Mottisfont Syncline. The Dean Hill Anticline is the partner to the Winchester Anticline east of the Test valley and is similarly an east-west-trending periclinal structure with its axis running through the Dun valley parallel to the River Dun. It is an asymmetric pericline with a shallow 1° to 2° dip to the south and a much steeper 8° to 12° dip on its northern limb. It plunges eastwards at around 1° to 2°. The core of the anticline brings the lower Newhaven Chalk to surface around West Dean (Farrant, 2001); to the north, the core of the corresponding Alderbury–Mottisfont Syncline is occupied by the London Clay Formation. The northern limb of the syncline has a gentle southerly dip around 1° to 2°. Structure contours created on the base of the Stockbridge Rock Member and the base of the Palaeogene highlight the folding and regional structure of the district (see Sheet 299 Winchester).

The periclinal structure centred on Cheesefoot Head (Winchester Anticline) was intensely investigated for hydrocarbons. The information from a few deep wells into the Jurassic was enhanced by additional shallower borings proving the Melbourn Rock and Glauconitic Marl. This structure is known to have dips of 10° to the north of Spitfire Bridge [SU 497 294] section on its northern limb but as little as 3° to 4° to the south-west (Twyford Cutting) on its southern limb.

There is growing evidence that the Late Cretaceous was not a tectonically quiescent period, but that continued tectonic and eustatic movement occurred in phases throughout (Mortimore et al., 1998). Four major tectonic phases (demonstrated in Germany and the eastern Anglo–Paris Basin) generated channelling, slumping hardground and various flint development, phosphatic chalks as well as variations in the occurrence of marl throughout southern England. Some chalk characteristics in this district may be a result of these continued movements. Examples include the very hard silicified horizon, the Stockbridge Rock Member, near the top of the Seaford Chalk Formation and the thin marl seams in the Newhaven Chalk Formation.

There are few recognisable faults at surface, although smaller faults with throws of less than 1 m can often be seen in pits and quarries but cannot be traced farther. However, seismic surveys often indicate faulting at depth (in the Jurassic strata), which coincides with fold axes at surface. Instead of discrete faults, the strata may be displaced up to 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. The faults become attenuated within the softer chalk succession, and are expressed at surface as broad folds.

The notable exception is the Over Wallop Fault. This extends from just west of Castle Farm [SU 2700 3930] and runs east-north-east through Kentsboro [SU 3050 4035] and on towards Red Rice [SU 3350 4150] where it appears to die out (Farrant, 2001). It cannot be traced westwards because of lack of exposure across the military area of Porton Down. Total displacement of the fault is estimated to be approximately 15 to 20 m, downthrowing to the south. It displaces the Stockbridge Rock Member (Figure 38) and the Newhaven–Seaford Chalk boundary. A second, similar but much smaller fault was identified near Stockbridge [SU 3850 3590] along the line of the A30. This also displaces the Stockbridge Rock Member and Newhaven–Seaford Chalk boundary and downthrows to the south by approximately 5 to 10 m.

The Lewes Chalk outcrop is limited southward at Tilebridge Farm [SU 344 333] by a fault trending west-north-west and downthrowing to the south. This fault is confirmed by micropalaeontological evidence (Wilkinson, 2000).

Chapter 8 Applied geology

Geological factors have a bearing on the location and nature of future urban and industrial developments. By giving consideration to geological conditions at an early stage in the planning process, it may be possible to mitigate some of the problems commonly encountered during construction work. The diverse local geology gives rise to variable ground conditions and some significant aspects are discussed below. Other important factors are water resources, mineral workings and the risk of flooding.

Hydrogeology

The Chalk is the major aquifer in the district and has the largest storage capacity and catchment area, providing the major supply of potable water. The chalk aquifer is confined in the south of the district by the Palaeogene cover. In the unconfined aquifer, the water table broadly follows the surface topography in subdued form, with subsurface flows away from recharge areas on high ground. Natural annual fluctuations in the unconfined aquifer can exceed several tens of metres under the high parts of the Downs. In the confined aquifer, natural fluctuations of the potentiometric surface decrease away from the outcrop. The aquifer also contributes to the baseflow of the rivers draining southwards across the district.

Water is also stored at depth in the greensand formations. The Lower Greensand Group is a separate aquifer beneath the aquiclude of the Gault Formation whilst the Upper Greensand Formation is frequently in hydraulic continuity with the Chalk. Water is also obtained in small quantities from the Palaeogene and to a lesser extent, the drift, but supplies are variable in both quantity and quality.

Yields from the Chalk Group of the Winchester district (Hargreaves, 1981) vary between the formations typically producing 10.5 l/s (litres per second) from boreholes in the traditionally named ‘Upper Chalk’ (Lewes to Portsdown formations), to 2.3 l/s in the lower, marly chalks (West Melbury Chalk Formation). The highest yields, recorded elsewhere, such as the Fareham area, show up to 270 l/s are obtained from large diameter shafts, boreholes and headings in the White Chalk Subgroup.

The hydraulic properties of the Chalk aquifer are complex and result from a combination of matrix and fracture properties. The Chalk is microporous with low intrinsic permeability. The intergranular porosity of the Chalk is high, commonly around 35 per cent for the White Chalk Subgroup, falling to around 25 per cent for the Grey Chalk Subgroup (Bloomfield et al., 1995). However, the pore sizes are so small that the permeability of the rock is minimal. The high transmissivity of the aquifer is provided by fractures, which are commonly enlarged by dissolution.

Rapid groundwater flows are sometimes found in the unconfined Chalk aquifer where karstic-type development has taken place. This is commonly associated with the proximity of thin cover, such as the Palaeogene deposits or clay-with-flints. For example tracer studies on the floodplain of the River Pang in Berkshire have revealed rapid flows (velocities of over 6 km/d) between swallow holes and a spring known as the Blue Pool (Banks et al., 1995). Karstic groundwater flow may occur around the margin of the Palaeogene outcrop in this district.

Chalk water is usually of very good chemical quality. At outcrop it is hard to very hard, with carbonate hardness predominating. However, at depth in the confined aquifer, the water changes to a soft sodium bicarbonate type as a result of ion exchange. At the same time chloride ion and total dissolved solids increase (though not beyond potable limits), fluoride increases and anaerobic conditions set in, where nitrate is replaced by ammonia (Institute of Geological Sciences, 1978).

The Upper and Lower Greensand and the Palaeogene sands are porous, essentially, non-fissured aquifers, although the Upper Greensand is loosely indurated with some fissuring.

Wells in the chalk are generally unlined, while those in the sands require screening. Perennial springs occur in the Palaeogene and sink at the junction with the underlying Chalk. A number of these are recorded around the West Dean area. Valleys on chalk bedrock are normally devoid of surface water, although during extreme weather conditions, such as during heavy rainfall after hard frosts or torrential rain over successive days, can result in surface flow and groundwater flooding.

Details

Perennial springs occur at the base of the Chalk and within the valleys where the water table intersects the surface. The largest of these in the district is the spring [SU 3264 2688] in the grounds of Mottisfont Priory, which yields two million gallons daily (Whitaker, 1910) (equivalent to about 100 l/s) (Plate 16). However, this is known to dry up during prolonged dry periods. The spring was observed to be dry in September 2005. To the north and east of this district springs yield up to 3.79 l/s, but yields of up to 151.6 l/s have been recorded from such springs elsewhere in the nearby South Downs (Hargreaves and Parker, 1980). There are numerous short stream sections on the Palaeogene strata, some of which commence at springs, emanating from sand horizons in the succession [e.g. [SU 3241 2913]; [SU 3136 2857]; [SU 3147 2742]; [SU 3108 2724]; [SU 3086 2748]] and others supported by surface/field run-off. Most of these short surface streams sink into the Chalk at the margins of the Reading Formation.

Many small springs probably occur along the length of the Test valley, but any discrete inputs 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 areas of calcareous tufa may mark areas where groundwater springs were located before the river system was altered for water meadows and fishing. One such set of springs may have occurred around the village of Wherwell, which may derive its name from bubbling or turbulent springs or wells. The Somborne Brook rises at a series of bourne holes around Kings Somborne depending on prevailing season.

Much of the recharge into the River Itchen is similarly diffused through the alluvial gravels, but some springs occur in tributary valleys. A notable concentration of small springs feed a series of watercress beds at Headbourne Worthy [SU 485 323].

Karst features

Karst features, notably stream sinks, springs and sinkholes, are locally prevalent in the Winchester district, particularly around the margins of the Palaeogene outcrop preserved in the core of the Alderbury–Mottisfont Syncline and along the foot of the Chalk dip slopes in the south of the district.

Forty-six discrete sinks were identified, nearly all at or close to the margin of the Palaeogene outcrop. The largest of these occur along the Reading Beds–Chalk boundary between East Grimstead and Lockerley, and the Mottisfont area. Between East Grimstead and West Dean, six sinks occur, including one taking drainage from a sewage works [SU 2307 2762]. The River Dun appears to loose its distinct meandering channel between West Grimstead [SU 235 273] and West Dean. According to a local farmer in West Dean, the River Dun has been known to dry up along this stretch. It is possible that the river gradually sinks into its gravelly bed and thence into the underlying chalk. Five stream sinks occur between West Dean and Lockerly, including the ‘Devils Hole’ [SU 2735 2757], which used to be 3 m deep but is now infilled with sediment. A sink near Holbury Farm takes the drainage from a pig farm which sinks into an old chalk pit [SU 2815 2710]. To the east, another five stream sinks occur around Spearywell [SU 3138 2674], east and north of Mottisfont [SU 3190 2714]; [SU 3195 2750]; [SU 3205 2807]; [SU 3245 2882] and south of Crown Farm [SU 3196 2990]; [SU 3182 3018].

The drainage from the sinks around the Alderbury- Mottisfont Syncline is thought to resurge at three springs. In addition to the large spring at Mottisfont Priory (mentioned above), two other major springs are known. The first is a large spring in a pond at West Dean [SU 253 272]. Water wells-up in the floor of a large pond and over-spills into the adjacent River Dun. Interestingly, this spring is several metres above the general valley floor, and is probably fed by groundwater draining the Dean Hill area to the south and west. Farther downstream, near Holbury Farm, is an enigmatic 2 m deep hole in the river bed [SU 2837 2691], very close to the Chalk–Palaeogene boundary. This is almost certainly a significant spring in the river bed and is probably the outlet for a conduit system draining the stream sinks farther west. Water sinking underground probably flows east along strike in solutionally enlarged conduits at or close to the water table to emerge at the lowest point in the Chalk outcrop where the River Dun crosses onto the Reading Formation. However, a tracing program would be needed to confirm this. This spring is only 300 m away from a stream sink [SU 2815 2710] draining a local pig farm, and there is almost certainly a direct hydrological connection between the two. A couple of small stream sinks occur along the Palaeogene margin in the extreme south of the district near Whiteparish e.g. at [SU 2638 2402], which almost certainly drain to local springs.

On the north side of the syncline, several small stream sinks are known between East and West Tytherly, with a further six between West Tytherly and Bentley Wood. Most of these are small ephemeral streams that sink in small depressions up to 4 m deep. The largest is a flooded depression near Lye Farm [SU 2768 2925]. These are thought to flow to Mottisfont.

There are no stream sinks in the Wallops area, but the Wallop Brook rises from a deep pool just north of Over Wallop [SU 278 387], which dries up in dry summers. A second deep ‘bourne hole’ occurs at Spring Pond [SU 2785 3610], which is a seasonal spring. Water rises here at the base of a pool more than 3 m deep and in marshy ground nearby. Both these springs occur at the same stratigraphical horizon near the top of the Seaford Chalk just below the Stockbridge Rock Member. They may be associated with conduits developed on major flint horizons. Numerous other small springs and seepages occur along the Wallop Brook.

To the east of the River Test, several small stream sinks are known in the Michelmersh–Braishfield area e.g. [SU 3480 2649] and [SU 3422 2604]. Most are small seepages, but two larger sinks occur around Paynes Hay Farm. In the north-east [SU 3686 2546], a small stream sinks at the base of a 4 m deep depression, while 300 m farther to the north-east a second larger stream sinks at the base of an 8 m-deep depression. Both sinks probably feed a series of springs around Sharpes Farm [SU 3658 2520]. Several other small stream sinks may occur between Bunstead and the M3 motorway, but it is unclear whether these are land drains or true stream sinks.

Numerous dolines punctuate the clay-with-flint outcrop, although many have been worked as marl pits. Some of these were observed to take water during heavy rainfall events, especially after recent ploughing of adjacent fields. These are most numerous on the Culver Chalk dip slope, just below the sub-Palaeogene erosion surface, especially around Hursley, Michelmersh, and particularly around East and West Tytherly. Other concentrations occur on the clay-with-flints capping the hills around Sparsholt. Here, dissolution pipes up to 10 m wide infilled with Palaeogene material were noted in ploughed fields. To the south, a suite of large closed depressions [SU 3723 2842] near Furzedown may be old clay workings. No caves are known in the region, but several small sediment-filled karstic voids were noted during the construction of the M3 Twyford Down cutting.

Bulk minerals

Chalk

There are many pits in the district attesting to the great historical use of chalk. The widespread digging of chalk for marling adjacent to loamy land and acidic soils, for burning to produce lime mortar and as a source of flints for building goes back at least to Roman times. Most of these are abandoned and degraded, some have been utilised for disposal of inert domestic and industrial waste, but agricultural lime may still be produced from some of the smaller privately owned pits for use on individual farms. The only large quarrying operation at the time of survey, the Somborne Lime Works [SU 339 274], produces agricultural lime and, as a by-product, flints for building restoration. This is the last active site, amongst a number, on the steep eastern bluff of the River Test. A description of the site is given in the Newhaven and Culver Chalk sections. The memoir reports that the soft friable chalk of the Quadratus Zone was ‘held in especial esteem as dressing’ and that the quarries at Brook ‘supplied much of the country to the south of this district by barge, before the canals fell into disuse’.

Sand and gravel

Throughout the district sand and gravel has been worked from the river terrace deposits that occupy the interfluves, valley sides and floors. Sand has also been excavated sporadically from the Palaeogene Reading Beds and Wittering Formations. Large volumes have been taken from the Reading Formation at the Kimbridge Sand and Gravel Pit [SU 323 253] just south of Mottisfont on the western bank of the River Test. This quarry is still in operation to date.

Sand and gravel is commercially worked in this area around Timsbury (principally first terrace workings at present) and Kimbridge (second to third terrace) based on the terrace aggradations. In the case of Kimbridge, sands and pebble beds in the Reading Formation are also taken during extraction. Sand and gravel has also been won in the past from Yew Tree Quarry [SU 3485 3085] north of Horsebridge. Reading Formation sands and smaller deposits of gravel both as small lenses and from mapped expanses of pebble beds has been worked in the past to the east of Carter’s Clay [SU 307 247] and Newton [SU 309 236], and east of the Test around Michelmersh [SU 348 260]. Elsewhere there is only small farm-based extraction for the purposes of maintaining tracks or the development of fisheries. Descriptions of the deposits and representative sections are given in the relevant sections.

Clay

Local sources of brick clay include the London Clay, ‘plastic clays’ within the Bracklesham Group and the mottled clays of the Reading Formation. Brick manufacture has been an important industry in the past with clays, mainly from the Reading Formation being extracted. Today, Michelmersh Brickworks [SU 343 258] still produces bricks for the specialist market. There are a number of pits in the area but it is not known whether they all still deliver clay to the main works.

Several pits once operated at East Tytherley [SU 291 287] and [SU 291 282], and also at West Dean [SU 260 283]. Clay-with-flints and clay-rich head may also have been for brick-making. It is not clear, however, if local deep pockets (as might be found in pipes) were exploited for this purpose, or if the clay was taken from broad shallow excavations.

Building stone

Building stone is not produced commercially in this district but in the past locally derived materials have been used in construction. Limited use has been made of the harder beds within the Chalk succession (Melbourn Rock Member, Lewes Nodular Chalk Formation). Flint, as a ‘waste’ product of chalk extraction and from ‘field picking’, has also been used to maintain farm tracks and as a source of decorative ‘dressed’ flints for buildings.

Chalk blocks from the Brook quarries were used in the construction of Marsh Court [SU 357 336] in the early part of the 20th century. Chalk rubble (‘clunch’) has been extensively used in building construction in the Test and Wallop valleys. Osborne White (1912) gives the following insight into the construction of these walls that need considerable maintenance to prevent them collapsing. ‘The broken chalk, mixed with earth and straw or rushes, is worked into a stiff mud with water, and laid down in courses, from 1 to 2 feet thick [0.3 to 0.6 m], with a fork; a uniform width being secured by the aid of a two-legged gauge, set astride the wall, which is usually finished-off with a facing of plaster and a roof of thatch or tiles’

Extensive use is made of the flint nodules within the Chalk sequence for building, both as dressed and squared-flint (of which the western end of Broughton Church [SU 309 329] is a good local example), and single-faced trimmed nodules are used particularly in churches, vicarages and the larger estate houses and farms.

Hydrocarbons

The Weald Basin covers a large area of southern England, south and south-west of London. The first hydrocarbon discovery onshore in the UK was made at Heathfield in 1893. The Winchester district was first explored for hydrocarbons in the 1930s and, more successfully, in the 1980s with the discovery of the Humbly Grove Oil Field just to the north-east of the district. Eleven oil and gas fields were discovered in the Weald basin in the 1980s (including Horndean, Singleton and Storrington). The largest discovery was made at Stockbridge in 1984. The equivalent of 2500 bpd of oil was produced from four onshore wells at Stockbridge. Recoverable reserves originally present were estimated at 1.7 million tonnes (Pentex Oil UK, 2003). The reservoir rocks are in the Jurassic Great Oolite Formation.

The process of hydrocarbon formation, migration and entrapment is controlled by east-west, pre-Albian extensional faults. The Humbly Grove oilfield, as an example, 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 Lias Group source rocks, 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 palaeo-highs, where antithetic faults provide traps. Migration probably began in Early Cretaceous times and may have continued until uplift in mid-Tertiary times (Penn et al., 1987). Although Cainozoic compression caused inversion of the Weald Basin, it did not destroy all the traps. Many anticlines in 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.

Geotechnical considerations

There is a range of potential problems relevant to ground stability in the district. (Table 6) tabulates 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 sands of some of the units within the Palaeogene strata provide unreliable foundations on steep slopes. Freshly ploughed fields or exposed ground can become gullied during heavy rainfall.

The London Clay Formation contains highly shrinkable clays with a high smectite content. Consequently they may swell on wetting or crack during extreme drought conditions. Suitable precautions should be taken during construction.

Peat and other alluvial deposits that contain thin beds of peat may be liable to compression and differential compaction when the ground is subject to loading.

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 deposits are created during construction work.

Chalk is prone to dissolution because of the action of acidic rainwater and groundwater, especially in the near surface vadose zone. This process was more enhanced during prolonged periods of periglacial conditions in the Pleistocene. The resultant swallow or sink holes, which can measure up to 50 m in diameter and 6m deep, 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, which may be filled with clay-with-flints, continue to provide sumps for excess surface water, making them liable to further subsidence and differential settlement (see also discussion in the Karst features section of this report). 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. The chalk adjacent to the feature is 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 lower river terrace deposits where the Chalk is commonly in contact with flowing groundwater.

Chalk has a high natural water content and this may lead to slurrying if over compacted. The stability of excavations in chalk is largely controlled by the frequency and direction of natural cavities and joints.

Chalk also has a number of unique engineering properties, which may create potential problems for ground engineering projects. Properties to take into account may include the number, type and frequency of flints: at some levels flints can be very densely packed reinforcing the chalk; the variable rock mass fracture properties of each chalk formation: some chalks are heavily fractured to great depths whilst others are unfractured even at surface; the occurrence of putty chalk or loose debris along faults and/ or fractures causing variability in strength of the rock mass and also affecting water flow.

In addition to the naturally occurring hazards, man has had considerable influence on the landscape. Many of the abandoned aggregate, chalk and clay pits in the area have been filled, particularly adjacent to urban areas. Records are held by the local authorities, but old areas of fill are often poorly documented. Cuttings and embankments for major road and rail links are commonplace in the district.

Information sources

Further geological information held by the British Geological Survey relevant to the Winchester district is listed below. It includes published maps, memoirs and reports. Enquiries concerning geological data for the district should be addressed to the Manager, National Geological Records Centre, BGS, Keyworth.

Other information sources include borehole records, fossils, rock samples, thin sections, hydrological data and photographs. Searches of indexes to some of the collections can be made on the Geoscience Index system in BGS libraries. The indexes are:

Books

British Regional Geology

Memoirs

Sheet Explanations

Technical reports

Biostratigraphy

There are nine biostratigraphical reports by the authors M A Woods and I Wilkinson, covering the Winchester district. These are held as internal open file reports by the Biostratigraphy Group of BGS. Readers are recommended to contact the Group Manager, Biostratigraphy, BGS, Keyworth for access to these reports and Palaeontological collections.

Maps

Geological maps

Map Name Author Date
SU22NW Farley KAB 1999
SU22NE Dean ARF 1999
SU22SW Redlynch CMB 1997–98
SU22SE Sherfield English RAE/ARF 1978–1999
SU23NW Boscombe Down PMH 1999
SU23NE Over Wallop PMH/ARF 1999–2000
SU23SW Pitton KAB 1999–2000
SU23SE Buckholt ARF 1999–2000
SU24SW Cholderton DTA/ARF/PMH 2000
SU24SE* Grateley KAB/ARF/DTA 2000
SU32NW Mottisfont PMH 1999
SU32NE Braishfield PMH 1998
SU32SW Awbridge RAE/PMH 1977–80; 99
SU32SE Romsey RAE/ARF 1978–79; 99
SU33NW Danebury KAB 1999–2000
SU33NE Leckford & Stockbridge KAB 1998
SU33SW Broughton ARF 2000
SU33SE King’s Somborne ARF 1998
SU34SW* Abbots Anne KAB/ARF 2000
SU34SE* Wherwell KAB/ARF 2000
SU42NW Hursley PMH 1998
SU42NE Winchester South PMH 1998
SU42SW Chandler’s Ford RAE/PMH 1979–80; 98
SU42SE Twyford MTH/PMH 1979–1998
SU43NW Chilbolton KAB 1998
SU43NE South Wonston KAB 1998
SU43SW Sparsholt ARF 1998
SU43SE King’s Worthy ARF 1998
SU44SW Barton Stacey KAB 2000
SU44SE Bullington KAB 2000
SU52NW Chilcomb PMH 1997
SU52SW Owslebury RS/NGB/AP/ ARF 1979; 84; 95; 1998
SU53NW Micheldever CRB 1997
SU53SW Itchen Abbas PMH 1997
SU54SW Micheldever Station CRB 1997

* indicates sheet partly surveyed

Surveyors: K A Booth (KAB), P M Hopson (PMH), A R Farrant (ARF), C M Barton (CMB), Winchestersht C R Bristow (CRB), R A Edwards (RAE), D T Aldiss (DTA), R Scrivener (RS), N Fig 9 1st proof G Berridge (NGB), M T Holder (MTH), A Pedley (AP). Copies of these maps are available for public reference in the libraries of the British Geological Survey in Keyworth and Edinburgh. Copies are available for purchase from the BGS Sales Desk.

Geophysical maps

Geochemistry maps

Hydrologeological maps

1:100 000

Minerals maps

Hydrogeology

Documentary collections

Boreholes

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

Geophysics

Gravity and aeromagnetic data are held digitally in the National Gravity Databank and the National Gravity Aeromagnetic Databank at BGS Keyworth.

Hydrogeology

BGS hydrogeology enquiry service; wells and springs and water borehole records are held at the British Geological Survey, Hydrogeology Group, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX0 8BB. Telephone 01491 838800. Fax 01491 692345.

BGS Lexicon of named rock unit definitions

Definitions of the named rock units shown on the 1:50 000 series Sheet 299 Winchester are held in the Lexicon database. This is available on the BGS website www.bgs.ac.uk Further information on the database can be obtained from the Lexicon Manager at BGS, Keyworth.

Material collections

Palaeontological collection

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

Petrological collections

Hand specimens and thin sections are held in England and Wales Sliced rocks collection at BGS Keyworth. The Mineralogy and Petrology Group maintain a collection database at BGS Keyworth. The Group Manager should be contacted for further information, including methods of accessing the database. Charges and conditions of access to the collection are available on request from BGS Keyworth.

Bore core collection

The National Geosciences Records Centre, BGS Keyworth, holds samples and entire core from a small number of boreholes in the Winchester district.

BGS Photographs

Copies of these photographs are deposited for reference in the BGS Library, Keyworth. Colour or black and white prints and transparencies can be supplied at a fixed tariff.

Other relevant collections

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

References

British Geological Survey holds most of the references listed below, and copies may be obtained via the library service subject to copyright legislation (contact libuser@bgs.ac.uk for details). The library catalogue is available at: http://geolib.bgs.ac.uk

Banks, D, Davies, C, and Davies, W. 1995. The Chalk as a karstic aquifer: evidence from a tracer test at Stanford Dingley, Berkshire, UK. Quarterly Journal of Engineering Geology, Vol. 28, S31–38.

Barrois, C. 1876. Reserches sur le terrain Crétacé Supérieur de l’Angleterre et du l’Irelande. Mémoir Soc. Géol. Nord.,1. Lille.

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, S131–142.

Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H I, and Taylor, R T. 1995. Geology of the Country around Shaftsbury. 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 [Sheet 12]. Memoir of the British Geological Survey, Sheet 313, (England and Wales).

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

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

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

Chadwick, R A.  1993. Aspects of basin inversion in southern Britain. Journal of the Geological Society of London, Vol. 150, 311–322.

Edwards, R A, and Freshney, E C. 1987. Geology of the country around Southampton. Memoir of the British Geological Survey, Sheet 315 (England and Wales).

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(3), 219–230.

Farrant, A R. 1999. Geology of the King’s Somborne–Winchester district, Hampshire. British Geological Survey Technical Report, WA/99/06.

Farrant, A R. 2001. Geology of the Dean and Wallops area, Hampshire and Wiltshire. British Geological Survey, Technical Report, WA/00/11.

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. N.S. 8, 365–458. (Reprinted in 4 to in 1833).

Griffith,C, and Brydone, R M. 1911. The zones of the Chalk in Hants. (London: Dalau and Co.)

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

Hargreaves, R, and Parker, J. 1980. Records of wells in the area around Chichester. Metric Well Inventory of the Institute of Geological Sciences, Sheet 317.

Hargreaves, R, Parker, J, and Taskis, D M. 1981. Records of wells in the Winchester area. Metric well inventory of the Institiute of Geological Sciences, Sheet 299.

Hodgson, J M, Catt, J A, and Weir, A H. 1967. The origin and development of clay-with-flints and associated soil horizons on the South Downs. Journal of Soil Science, Vol. 18, 85–102.

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

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

Hopson, P M. 1998. Geology of the area around Alresford and Cheriton, Hampshire. British Geological Survey Technical Report, WA/98/50.

Hopson, P M. 2000. Geology of the Fareham and Portsmouth district—a brief explanation of the geological map Sheet 316 Fareham and part of Sheet 331 Portsmouth. Sheet Explanation of the British Geological Survey.

Hopson, P M.  2001a. Geology of the area around South Winchester, Hursley and Braishfield, Hampshire. British Geological Survey Internal Report, IR/01/126.

Hopson, P M. 2001b. Geology of the area around Kimbridge, Mottisfont, Houghton and Broughton, Hampshire. British Geological Survey Internal Report, IR/01/127.

Institute of Geological Sciences, and Thames Water Authority. 1978. Hydrogeological map of the south-west Chilterns and the Berkshire and Marlborough Downs including parts of hydrometric areas 39, 42, 43, and 53 (1:100 000). (Dunstable: Waterlow Ltd for IGS.)

Jukes-Browne, a J, and hill, W. 1900. The Cretaceous rocks of Britain. Vol. 1. The Gault and Upper Greensand of England. Memoir of the Geological Survey of the United Kingdom.

Jukes-Browne, A J, and Hill, W. 1903. The Cretaceous rocks of Britain. Vol. 2. The Lower and Middle Chalk of England. Memoir of the Geological Survey of the United Kingdom.

Jukes-Browne, A J, and Hill, W. 1904. The Cretaceous rocks of Britain. Vol. 3. The Upper Chalk of England. Memoir of the Geological Survey of the United Kingdom.

King, C. 1981. The stratigraphy of the London Clay and associated deposits. Tertiary Research Special Paper, No. 6, 1–158.

King, C, and Kemp, D J. 1982. Stratigraphy of the Bracklesham Group in recent exposures near Gosport, Hants. Tertiary Research, Vol. 3, 171–187.

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

Mantell, G A. 1822. The fossils of the South Downs, or illustrations of the Geology of Sussex, London.

Martin, P J. 1828. A Geological Memoir on a part of West Sussex. (London.)

Melville, R V, and Freshney, E C. 1982. British regional geology: the Hampshire Basin and adjoining areas. Fourth edition. (London: HMSO for Institute of Geological Sciences.)

Meyer, C J A. 1871. On the Lower Tertiary deposits recently exposed at Portsmouth. Quarterly Journal of the Geological Society of London, Vol. 27, 74–89.

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. 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.

Mortimore, R N. 1987. Upper Cretaceous Chalk in the North and South Downs, England: a correlation. Proceedings of the Geologists’ Association, Vol. 98, 77–86.

Mortimore, R N, and Pomerol, B. 1987. Correlation of the Upper Cretaceous White Chalk (Turonian to Campanian) in the Anglo-Paris Basin. Proceedings of the Geologists’ Association, Vol. 98, 97–143.

Mortimore, R N, and Pomerol, B. 1997. Upper Cretaceous tectonic phases and end Cretaceous inversion in the Chalk of the Anglo-Paris Basin. Proceedings of the Geologists’ Association, Vol. 108, 231–255.

Mortimore, R N, Wood, C J, Pomerol, B, and Ernst, G. 1998. Dating the phases of the sub-Hercynian tectonic epoch: Later Cretaceous tectonics and eustatics in the Cretaceous basins of northern Germany compared with the Anglo-Paris Basin. Zbl. Geol. Palaont. Tiel I, 1996 (11/12): 1349–1401; Stuttgart.

Mortimore, R N. 1998. Notes on the three cuttings on the M3 Motorway near Winchester. Personal Communication.

Murchison, R I. 1826. Geological sketch of the north-western extremity of Sussex. Transactions of the Geological Society of London, Series 2, Vol. 2, 97.

Osborne White, H J. 1912. The geology of the country around Winchester and Stockbridge. Memoir of the Geological Survey of Great Britain, Sheet 299 (England and Wales).

Penn, I E, Chadwick, R A, Holloway, S, Roberts, G, Pharaoh, T C, Allsop, J M, Hulbert, A G, and Burnsim. 1987. Principal features of the hydrocarbon prospectivity of the Wessex–Channel Basin, UK. 109–118 in Petroleum geology of north-west Europe, Brooks, J, and Glennie, k (editors). (London: Graham Trotman.)

Pentex Oil Uk. 2003. Source: http://www.egdon-resources. com/html/uk/south.htm

Prestwich, J. 1847. On the probable age of the London Clay, and its relation to the Hampshire and Paris Basin Tertiary systems. Quarterly Journal of the Geological Society of London, Vol. 3, 354–377.

Rawson, P F, Allen, Pm, and Gale, A. 2001. The Chalk Group - a revised lithostratigraphy. Geoscientist, Vol. 11, No. 1, 21.

Reid, C. 1902. The Geology of the country around Ringwood. Memoir of the Geological Survey of Great Britain, Sheet 314 (England and Wales).

Reid, C. 1903. Geology of the country around Salisbury. Memoir of the Geological Survey of Great Britain, Sheet 298 (England and Wales).

Robinson, N D. 1986. Lithostratigraphy of the Chalk Group of the North Downs, southeast England. Proceedings of the Geologists’ Association, Vol. 97, 141–170.

Simpson, I R, Gravestock, M, Ham, D, Leach, H, and Thompson, H D. 1989. Notes and cross-sections illustrating inversion tectonics in the Wessex Basin. in Inversion tectonics. Cooper, M A, and Williams, G D (editors) 123–129. Geological Society of London Special Publication, No. 44.

Smith, N. 1985. Structure contours and subcrops of the pre-Permian surface of the United Kingdom (South). British Geological Survey 150th Anniversary Publication.

Sumbler, M G. 1996. British regional geology: London and the Thames valley. Fourth edition. (London: HMSO for the British Geological Survey.)

Tatton-Brown, T, and Crook, J (editors). 1993. Winchester Cathedral: Nine Hundred Years, 1093–1993. (Phillimore: Chichester).

Trust for Wessex Archaeology Limited and English Heritage. 1993. The Southern Rivers Palaeolithic Project, Report No. 1, 1991–1992, The Upper Thames Valley, The Kennet Valley and the Solent Drainage System.

WHITE, W C F. 1971. A gazetteer of brick and tile works in Hampshire. Papers and Proceedings of the Hampshire Field Club, Vol. 28, 81–97.

Whittaker, a (editor). 1985. Atlas of onshore sedimentary basins in England and Wales. Post Carboniferous tectonics and stratigraphy. (Glasgow: Blackie.)

Whittaker, A, Holliday, D W H, and Penn, I E P. 1985. Geophysical logs in British Stratigraphy. Special Report of the Geological Society of London, Vol. 18.

Whittaker, W. 1910. The water supply of Hampshire. Memoir of Geological Survey of England and Wales. (London: HMSO.)

Wilkinson, I P. 2000. Chalk foraminifera from the Broughton Houghton area of the Winchester Sheet (299). British Geological Survey Internal Report, IR/00/31R.

Wood, C J. 1995. Notes on the macrofossil and macrofossil biostratigraphy of the traditional Upper Chalk macrofossil zones of southern England with particular reference to the zonal concepts of Rowe, Brydone and Gaster. British Geological Survey Technical Report, WH/95/31R.

Woods, M A. 1998a. Review of Upper Cretaceous Chalk (Chalk Group) macrofaunas from the Winchester Sheet (299), Hampshire. British Geological Survey Technical Report, WH/98/64R.

Woods, M A. 1998b. Chalk macrofossils from the Winchester (299) and Southampton (315) sheets: 1:10 000 quarter sheets: SU42 SE, SW, NE, NW, SU43SE, SW, NE and SU53NW. British Geological Survey Technical Report, WH/98/119R.

Woods, M A. 1998c. Chalk macrofossils from the Winchester Sheet (299): 1:10 000 quarter sheets: SU32NW, NE, SU33SE, NE, SU42NW, SU43SW, NW. British Geological Survey Technical Report, WH/98/188R.

Woods, M A. 1998d. Chalk macrofossils from the Dean Hill Anticline. British Geological Survey Technical Report, WH/98/145R

Woods, M A. 1999. Preliminary report on Chalk macrofossils from the Salisbury (298) and Winchester (299) districts. British Geological Survey Technical Report, WH/99/88R.

Woods, M A. 2000a. Macrofaunas from the chalk of the Andover (283) Salisbury (298) and Winchester (299) districts: 1:10 000 quarter sheets SU23SE, SW, NE, SU32SW, NE, NW, SU44NW. British Geological Survey Internal Report, IR/00/24.

Woods, M A. 2000b. Chalk group macrofossils from the Basingstoke District (Sheet 284) and adjacent areas. Technical Report of the British Geological Survey, IR/00/74

Ziegler, P A. 1982. Geological atlas of western and central Europe. (Amsterdam: Shell Internationale Petroleum Maatschappij BV.)

Figures, plates and tables

Figures

(Figure 1a) Geological map of the Winchester district.

(Figure 1b) Shaded relief topographical map of the Winchester district.

(Figure 2) Structures of the Wessex–Weald Basin.

(Figure 3a) Correlation of deep boreholes; north-south.

(Figure 3b) Correlation of deep boreholes; west-east.

(Figure 4) Structure contours on the base of the Melbourn Rock Member.

(Figure 5) Generalised log of the Twyford Down M3 Cutting (based on information from R N Mortimore, 1998).

(Figure 6) Sections in the Lewes Chalk Formation. For the detailed biostratigraphy see Woods (1998c).

(Figure 7) Lewes Chalk Formation section in a private garden, Stockbridge [SU 3606 3506].

(Figure 8) Small exposure of the Seaford Chalk Formation, HP34, north of Vale Farm, Pitt [SU 4464 2873].

(Figure 9) Seaford Chalk Formation section at ‘Garlogs’, Nether Wallop [SU 3066 3536] (Woods, 2000).

(Figure 10) Sections in the Seaford Chalk Formation and lower Newhaven Chalk Formation. Detailed biostratigraphy in Woods (1998b, c). a. Hooper’s Farm, King’s Somborne. b. King’s Somborne (Tarmac) Quarry, main face [SU 3510 3202].

(Figure 11) sections in the Seaford Chalk Formation at Westover Farm, Goodworth Clatford [SU 3668 4068].

(Figure 12) Chalk succession at disused quarry, Cottonworth [SU 3804 3990].

(Figure 13) Seaford Chalk succession, Leckford Golf course Quarry [SU 3655 3673].

(Figure 14) Chalk succession at disused quarry, Chilbolton [SU 3818 3875].

(Figure 15) Chalk succession at Lower Bullington showing details of key horizons [SU 4526 4120], (locality 35 of woods, 2000).

(Figure 16) Cutting on the M3 Motorway at Shawford (after Mortimore and Pomerol, 1997).

(Figure 17) Newhaven–Culver Chalk boundary. Brydone’s locality 1040A [SU 4277 2606] featured as Figure 4 in Woods (1998, WH/98/119R).

(Figure 18) Chalk succession, Dean Hill Barn Farm [SU 2814 2634], Woods 1999.

(Figure 19) Chalk succession, Bossington Chalk pit [SU 3320 3104].

(Figure 20) Chalk succession, East Grimstead Chalk Quarry [SU 4227 2710].

(Figure 21) Disused pit near New Farm, Leckford [SU 3914 3635].

(Figure 22) Chalk section at locality HP37 [SU 4476 2518].

(Figure 23) Brydone’s Locality 1079 [SU 4360 2552] near Hursley featured in 1 of Woods (1998, WH/98/119R).

(Figure 24) Disused Chalk pit, Culver Chalk, Whiteparish [SU 2512 2416].

(Figure 25) Whiteparish Pit A [SU 2538 2390].

(Figure 27) Brydone’s locality 1059 (East Tytherley, East End Farm Pit) (HP47) [SU 3049 2974].

(Figure 26) Chalk succession near Strides Row, West Tytherley [SU 2824 3090].

(Figure 28) Sketch of Yew Tree Chalk Pit, HP43 [SU 3255 2796] (Brydone’s locality 1063).

(Figure 29) Somborne Lime Quarry [SU 3380 2740].

(Figure 30) Chalk succession at Pitton logged along the road cutting [SU 2130 3118] to [SU 2128 3098].

(Figure 31) Chalk succession at West Grimstead chalk quarry [SU 2172 2648].

(Figure 32) Reading Formation section at the Gas Transfer Station north of Carter’s Clay, BP40 [SU 3033 2507].

(Figure 33) Reading Formation and river terrace deposits at the Kimbridge Quarry, BP41 [SU 3215 2550].

(Figure 34) Reading Formation and river terrace deposits at Barley Hill Wood, HP44 [SU 3239 2578].

(Figure 35) Section exposed in the Kimbridge railway cutting south-east of Dunbridge station [SU 324 259] to [SU 327 356].

(Figure 36) River terrace deposits and Culver Chalk Formation, Hatt Hill section, HP42 [SU 3215 2743].

(Figure 37) Sketch map of the district showing the main fold axes.

(Figure 38) Structure contours on the base of the Palaeogene Deposits (red) and base Stockbridge Rock Member (blue) showing the main structures and faults.

Un-numbered figure 1 Bouguer gravity in milligals (mGal) calculated against the Geodetic Reference System 1967, referred to the National Gravity Reference Net 1973. A variable reduction density has been used. Contour interval 1 mGal (1 mGal = 1 x 10–5 m/s2). Ticks on contours are on the side of the lower values. Based on data in the BGS National Gravity Databank. Station distribution approximately 1 per 1.3 km2.

Un-numbered figure 2 Total field magnetic anomalies in nanotesla (nT) relative to a local variant of IGRF90. Contour interval 5 nT. Ticks on contours are on the side of the lower values. Based on data in the BGS National Aeromagnetic Databank Survey flown at a constant barometric height of 549 m on N–S flight lines 2 km apart and E–W tie lines 10 km apart.

Plates

(Front cover) Antony Gormley’s statue in the flooded crypt of Winchester Cathedral (Photograph: David Fox, reproduced with kind permission of the Dean and the Chapter of Winchester Cathedral).

(Plate 1) Twyford M4 cutting, Winchester [SU 4895 2763]. New Pit Chalk and Lewes Nodular Chalk Formations, dipping about 4° south, exposed in this northern section of the cutting (GS1160).

(Plate 2a) Photograph of the west side of the Twyford Down cutting. Marls within the lower part of the Lewes Nodular Chalk north end of cutting (P526313).

(Plate 2b) Photograph of the west side of the Twyford Down cutting. Higher Lewes Nodular Chalk, Bar End Hardgrounds (below bright line at top of section, possibly the Shoreham Marls) and basal Seaford Chalk (P526327).

(Plate 3) King’s Somborne Lime Quarry. View looking south over working quarry. Newhaven and Culver Chalk formations [SU 3380 2740] (P526271).

(Plate 4) Anastomosing marl seam within Newhaven Chalk Formation. The marl and the bed below are associated with sponges causing the yellow-brown coloration. King’s Somborne Lime Quarry [SU 3380 2740] (P526260).

(Plate 5) King’s Somborne Lime Quarry [SU 3380 2740]. Typical view illustrating the blocky nature of the Newhaven Chalk Formation, marl seam (base of hammer) and sponge-rich bed (above hammer) (hammer 30 cm); (P526267).

(Plate 6) King’s Somborne Lime Quarry [SU 3380 2740]. Variably soft to firm blocky chalk with regularly spaced large nodular flint seams typical of the Culver Chalk Formation (P526270).

(Plate 7) Kimbridge Sand and Gravel Pit [SU 3230 2530]. Reading Formation sands: finely bedded cross-sets of fine to medium-grained quartz sand with thinner intervening silt and clay beds. Face is about 2 m high with Sandmartin burrows (P526255).

(Plate 8) Kimbridge Sand and Gravel Pit [SU 3230 2530]. Exposure of the Reading Formation showing mottled clay resting on a well-rounded flint pebble bed (hammer 30 cm); (P526247).

(Plate 9) Kimbridge Sand and Gravel Pit [SU 323 253]. Reading Formation sands overlying indurated (iron-bound) well-rounded flint pebble bed (face about 4 to 5 m high); (P526256).

(Plate 10) View from the Somborne Lime Quarry [SU 338 274] south-westward over the River Test floodplain. The horizon to left and centre is the chalk scarp of Dean Hill, the woodland to the right horizon is founded on Palaeogene strata preserved in the Alderbury- Mottisfont syncline (P526274).

(Plate 11) Kimbridge Sand and Gravel Pit [SU 323 253]. Typical face in second to third river terrace deposits showing pebbly head wash overlying sandy clay overbank deposits resting on clast-supported angular flint gravel in a clayey sand matrix. (map case is 30 cm high); (P526248).

(Plate 12) Kimbridge Sand and Gravel Pit [SU 323 253]. Close-up of clayey sandy, angular flint-rich gravel of the second to third river terrace deposits (map case is 30 cm high); (P526249).

(Plate 13) Manor Farm Pit, Kimbridge [SU 3270 2568]. Variably clast and matrix supported angular flint gravel in clayey sand matrix of the first terrace (auger 1.3 m); (P526295).

(Plate 14) Typical bankside exposure on the floodplain of the River Test near Kimbridge [SU 3320 2630]. Layers of humic silty sandy clays overlying granular calcareous tufa and a basal fibrous dark peat (auger 1.3 m); (P526290).

(Plate 15) View looking north-eastward over the River Test floodplain [SU 3304 2596] and fishing lodge north of Kimbridge Manor Farm, showing typical rough pasture, alder and willow vegetation and ploughed ground in preparation for maize planting. Dark brown peaty soils give way to dark (silty/clayey, overbank) and pale grey (calcareous tufa) deposits (P526294).

(Plate 16) Spring at Mottisfont Priory [SU 326 369]. The natural spring that feeds the River Test has been artificially formed into a well, cut down into the Culver Chalk Formation (P526278).

(Back cover)

Tables

(Table 1) Geological succession of the Winchester district. CK - Chalk, FM - Formation, Mbr - Member.

(Table 2) Summary of the principal deep boreholes in the Winchester district. Values are thicknesses of the deposit, given in metres.

(Table 3) The major subdivisions of the concealed Jurassic strata.

(Table 4) Concealed Cretaceous strata.

(Table 5) Correlation of zonal schemes for the Chalk of southern England. *Foraminiferal zones after Carter and Hart, 1977; Swiecicki, 1980; Hart et al., 1989 (UKB zones) and Wilkinson, 2000 (BGS zones). Not to scale.

(Table 6) Potential ground constraints and ground stability factors of the principal geological units in the district.

Tables

(Table 2) Summary of the principal deep boreholes in the Winchester district

Values are thicknesses of the deposit, given in metres.

Borehole Farley 1 Goodworth 1 Stockbridge 1 Stockbridge 4

Stockbridge 2

 Stockbridge 7 Stockbridge 5 Stockbridge 6
Quarter Sheet (SU22NW/2) (SU34SE/14) (SU43NE/5) (SU33NE/3)

(SU43NE/8)

 (SU43SW/4) (SU43NW/7) (SU43NW/8)
Grid Reference [SU 4235 1285] [SU 4369 1419] [SU 4451 1355] [SU 4396 1376]

[SU 4450 1355]

 [SU 4423 1338] [SU 4406 1357] [SU 4434 1364]
Upper Greensand Fm 44.4 45.6 47.4 47

50

 46 56 55
Gault Fm 51 58.9 64 59

68

 62 54.4 61
Lower Greensand Fm 17.7 12.5 8.6 14.3

10

 20 11.8 14
Wealden ‘group’ absent 183 237.4 219

252

 224 235.3 368
Purbeck Group 28.3 62 51 96

75

 88 106 123
Portland Group 50 55 61 86

73

 83 90 102
Kimmeridge Clay 184 218 234 384

438

 348 434 472
Formation

Corallian Group

 48 47.5 38 65

61

 54 69 66
Oxford clay formation 151 141.5 135.5 201

221

 168 215 211
Kellaways Formation 11 11 10 18

16

 16 17 15
Great Oolite Group 118 122 118 157

352(?)

 151+ 159+ 177+
Inferior oolite group 41.5 85 77 105

73+
Lias Group 256.5 487 433 528.5
Permo-Triassic 254 315 89 312
Devonian- Carboniferous 287+ 28+ 50+ 40+
Borehole Furzedown Winchester 1 Winchester 2 Winchester 3

Winchester 4

 Winchester 5 Lockerley
Quarter Sheet (SU32NE/3) (SU52NW/1) (SU52NW/2) (SU42NE/4)

(SU53SW/1)

 (SU52NW/3) (SU32NW/15)
Grid Reference [SU 4368 1284] [SU 4503 1284] [SU 4544 1276] [SU 4470 1277]

[SU 4510 1301]

 [SU 4502 1270] [SU 4306 1259]
Upper Greensand Fm 47 40.5 39 43

33

 41 41
Gault Fm 47 77 80 65

78

 70 49
Lower Greensand Fm 8 25 26+ 20

31

 20 35
Wealden ‘group’ 151 341 290

254

 290+ not recorded
Purbeck Group 60 77 24+

18+

 39
Portland Group 54 80 55
Kimmeridge Clay 222 275 186
Formation

Corallian Group

 49 109 51
Oxford clay formation 147 146 148
Kellaways Formation 15 11 12
Great Oolite Group 118 131 122
Inferioroolite group 86 128 65
Lias Group 518 287+ 421
Permo-Triassic 66+ 412+
Devonian- Carboniferous

(Table 3) The major subdivisions of the concealed Jurassic strata

Lithostratigraphical Division Thickness in metres Map code Subdivision Principal lithologies Subsidiary lithologies Notes
Purbeck Group 28–123 Pb Durlston and Lulworth formations Evaporites pass up to marl and shelly limestone Cherty, ooidal, shaly in parts Erosional contact at base in places
Portland Group 50–102 Pl Portland Stone and Portland Sand formations Sandstone and argillaceous sandstone pass up into shelly limestone Thin siltstones, mudstones, glauconitic
Kimmeridge Clay Formation 184–472 KC Upper, Middle and Lower Cycles of mudstone, shale, oil-shale and limestone Fissile and calcareous in part
Corallian Group 38–109 Cr Upper and Lower Limestone, sandstone Siltstone, mud-stone
Oxford Clay Formation 135–221 OxC Weymouth, Stewartby and Peterborough Sandy, silty mudstones, locally calcareous Silty, calcareous, carbonaceous
Kellaways Formation 11–18 Kys Kellaways Sand and Clay Members Silty mudstone passes up into fine-grained sandstone Micaceous, calcareous Single, coarsening up sequence
Great Oolite Group 118–177+ GtO Cornbrash, Forest Marble, Great Oolite and Fuller’s Earth formations Pyritic siltstone and mudstone passes up into limestone Fissile, calcareous, passes up into ooidal, shelly packstone Principal oil reservoir of Weald Basin
Inferior Oolite Group 41–128 InO Upper, Middle and Lower Limestone and calcareous siltstone Sandy, ferruginous, becoming ooidal
256–572 Li Upper, Middle and Lower Interbedded mudstone and limestone Thickness varies greatly across district

(Table 4) Concealed Cretaceous strata

Lithostratigraphical division Thickness in metres Map code Subdivisions Principal lithology Subsidiary lithologies
West Melbury Chalk Formation 25–30 WMCk West Melbury Chalk and Glauconitic Marl Highly glauconitic sand overlain by grey, marly chalk Thin hard, grey limestones
Upper Greensand 33–56 UGS Highly glauconitic calcareous silt and sandstone Clay lenses and siltstones
Gault Formation 47–80 G Fissured silty clay Scattered phosphatic nodules
Lower Greensand Group 8–35 LGS Folkestone, Sandgate, Hythe and Atherfield Clay Fossiliferous mud- stone overlain by glauconitic medium-grained sandstone Common siliceous sandstone and chert beds in Hythe Formation
Wealden Group 150–341 W Upper and Lower Non-calcareous car- bonaceous mudstone Thin sandstones and rare limestones

(Table 6) Potential ground constraints and ground stability factors of the principal geological units in the district

Geological unit Potential ground constraints

Worked ground

 Variable foundation conditions
Unstable sides on old workings

Made ground

 Variable foundation conditions
Leachate and methane production from waste
Infilled ground As above

Disturbed ground

 Slope instability
Variable foundation conditions

Head

 Variable foundation conditions
Ground heave

Peat

 Compressible strata
Risk of flooding

Alluvium

 Compressible strata
Risk of flooding
Variable foundation conditions

River terrace deposits

 High water table
Possibility of undocumented and filled former pits

Wittering Formation

 Local perched water tables
Ground heave in clay members
Loose sand prone to erosion and gullying

London Clay Formation

 Ground heave/shrink-swell in clays
Landslip and subsidence in clays
High sulphate content groundwater
Perched water table and springs in sand layers

Reading Formation

 Variable foundation conditions
Ground heave
Potential shrink-swell in clay horizons
Sink holes close to contact with Chalk
Perched water tables and springs in sand layers

Chalk Group

 Slightly elevated natural radon emissions
Groundwater protection requirement
Possibility of undocumented and infilled former pits
Dissolution cavities and sinkholes
Potential for high frequency of flint