A review of the stratigraphic significance of the Wolvercote Terraceof the Upper Thames Valley

D. Maddy, S. G. Lewis* and C. P. Green

MADDY, D., S. G . LEWIS & C. P. GREEN. 1991. A review of the stratigraphic significanceof the Wolvercote Terrace of the Upper Thames Valley. Proc. Geol. Ass., 102(3), 217-25 .The significance of the Wolvercote Terrace deposits of the Upper Thames is reviewed withreference to their lithological content, and to the ir stratigraphic position in relation both to theolder terrace deposits and to the local glacigenic sediments. Examination of published data,and of new lithological evidence, shows that the convent ional stratigraphic interpretation ofthese deposits is without foundation. There is no secure lithological evidence to support thecorrelation of the Wolvercote Terrace deposits in the area around Oxford with glacial outwashdeposits in the upper reaches of the Evenlode valley as suggested in previous schemes , or tojustify the separation of the Wolvercote Terrace from older terraces on lithological grounds , ineither the Evenlode or Cherwell valleys. Furthermore, there is great confusion over theassignment of deposits to the various terrace levels, in both the Thames and Evenlode valleys,with key deposits being related to different terraces by different authors. The lack of a readilyidentifiable stratigraphic scheme for the Upper Thames excludes the possibility, at least for thepresent, of any correlation with the sequence in the Middle Thames and therefore precludesthe use of the Middle Thames stratigraphy to establish an age for the Midland glacial sequence,or vice versa.

Centre for Quaternary Research, Department of Geography, Royal Holloway and Bedford NewCollege, University of London, Egham, Surrey , TW200EX

1. INTRODUCTION

The sand and gravel deposits underlying theWolvercote Terrace of the Upper River Thames havebeen generally accepted as providing the keystratigraphic marker in the correl ation of thePleistocene sequence of the River Thames with that ofthe West Midlands , in particular with the glacialsequence represented in the Wolston Series (Toml­inson, 1929; Arkell , 1947; Mitchell , Penny , Shotton &West , 1973).

The recognition of such a relationship between theWolston glacial sequence, the Wolvercote Terrace andthe terrace sequence of the Middle Thames isdependent on a number of inter-related assumptionswhich are set out here.

(1) That the Wolvercote Terrace deposits aredistinguished from the older terraces of the UpperThames by a significant increase in the proportion offoreign material , in particular flint.

(2) That the increase of foreign material derivesfrom two closely related sources; (a) meltwaterdrainage from the glacier responsible for thedeposition of flint-rich tills (Moreton Drift) which liewithin the upper basin of the River Evenlode(Tomlinson , 1929), and (b) overflow from glacial'Lake Harrison' through the Fenny Compton gap into

• Present addre ss: Department of Geogr aphy and Geology ,Cheltenh am & Gloucester College of Higher Educat ion ,Shaftesbury Hall, Cheltenham, Gloucestershire , GL503PP

the upper valley of the River Cherwell (Shotton, 1953;Bishop , 1958).

(3) That upstream from the type-site near Oxford,the reconstruction of the Wolvercote Terrace in thevalleys of the Rivers Evenlode and Cherwell lendspositive support to a correlation based on flint contentbetween the glacigenic deposits and the WolvercoteTerrace deposits .

(4) That the Wolvercote Terrace in the UpperThames basin can be successfully correlated with anequivalent terrace in the Middle Thames valley, wherea more secure basis is thought to exist for thestratigraphic interpretation and relative dating ofPleistocene events.

(5) That the flint-rich deposits in the upper valleysof the Rivers Evenlode and Cherwell can becorrelated with flint-rich glacigenic sediments in thevalley of the River Stour, a tributary of theWarwickshire Avon , which in turn can be correlatedwith flint-rich sediments in the Wolston Series .

The bases upon which the first four of these fiveassumptions are founded is examined in this paper ,mainly through a critical review of the publishedliterature.

2. CORRELATION BETWEEN THE UPPERAND MIDDLE THAMES

The stratigraphic significance attached to the Wolver­cote Terrace is illustrated in the recent debate overthe age of the 'Wolstonian' glaciation. This debate hasinvolved arguments and counter-argument s concern-

217

218 D. MADDY, S. G. LEWIS AND C. P. GREEN

ing the age of the glacial deposits at Wolston(Sumbler, 1983; Shotton, 1983; Rose, 1987; Shotton,1989), in particular whether they are of Anglian orpost-Anglian age. One of the most persistentarguments for ascribing a post-Anglian age to theglacial event at Wolston has been the supposed linkbetween the flint-rich 'Wolstonian' glacial deposits ofthe West Midlands (Tomlinson, 1929; Shotton, 1953)and the reported accession of fresh flint into theUpper Thames catchment during the formation of theWolvercote Terrace.

Initially this correlation was used to date theWolvercote Terrace and its underlying sediments tothe (post-Anglian) Wolstonian Stage (Mitchell et al.,1973). Lately however the argument has beenreversed. A supposed post-Anglian age for theWolvercote Terrace is now being used to support apost-Anglian interpretation of the Wolstonian glacialsequence:

"This is a matter which was not stressed in the periodwhen no-one questioned the age of the Wolstonian,but which is very pertinent now that its status is beingquestioned" (Shotton, 1983, p. 269).

This changed line of reasoning takes for granted theupstream link between the Wolvercote Terrace andthe glacial deposits of the Midlands and reliesadditionally on a downstream link between theWolvercote Terrace and the terrace sequence of theMiddle Thames valley. Gibbard (1988), followingClayton (1977) suggests that the Wolvercote Terraceis the upstream equivalent of the Taplow Terrace ofthe Middle Thames. As the Taplow Terrace lieswithin the post-Anglian valley of the Thames, itfollows that the Wolvercote Terrace must also be ofpost-Anglian age and hence that the West Midlandglacial deposits are of post-Anglian age.

However, any correlation between the Upper andMiddle Thames can, at best, be tentative because ofthe general lack of terrace sediments or morphologicalevidence in the Thames valley in the vicinity of theGoring Gap. Thus, Bowen, Rose McCabe &Sutherland (1986) were able to propose an entirelydifferent correlation, suggesting the equivalence of theWolvercote Terrace to the Winter Hill Terrace of theMiddle Thames, which is Anglian in age. Clearlytherefore downstream correlation of the WolvercoteTerrace is speculative and subject to considerableuncertainty. Thus the fourth of the five assumptionsidentified above is seen to lack a secure basis of fieldevidence.

3. THE WOLVERCOTE TERRACE: FLINTINFLUX-REAL OR IMAGINARY?

The supposed key to upstream, and inter-catchment,correlation is the composition of the sedimentsunderlying the Wolvercote Terrace, generally de-

scribed in terms of the amount of flint present. Inorder for the amount of flint in the sediments of theWolvercote Terrace to be accepted as evidence of asignificant event within the catchment, two conditionsshould be fulfilled:

(a) The flint proportion in the sediments of theWolvercote Terrace should be greater than thatrecorded from older terraces.

(b) The flint found within the Wolvercote Terracesediments should include fresh material, in addition toweathered flint available from the much olderNorthern Drift (Hey, 1986).

In an assessment of the supposed increase in foreignmaterial, it is important to understand the location ofthe Wolvercote Terrace remnants. Fig. 1 shows theoccurrence of the Wolvercote Terrace around Oxford(after Briggs, Coope & Gilbertson, 1985). Themajority of the undisputed remnants of the Wolverc­ote Terrace lie either within the valley of the Cherwellor around the confluences of the Rivers Cherwell andEvenlode with the River Thames.

(a) The River Cherwell

The Wolvercote and Hanborough Terraces of theRiver Cherwell were mapped and described by Bishop(1958) who considered that they could be distingu­ished on both altitudinal (Fig. 2) and lithologicalgrounds. Bishop (1958) considered that the depositsunderlying the Wolvercote Terrace of the Cherwellwere enriched in far-travelled materials relative to thehigher, and largely locally derived deposits underlyingthe Hanborough Terrace. His position on this point ishowever somewhat ambivalent. In one place he statesthat:

"The greater abundance of foreign pebbles in theWolvercote Terrace... can be related to two possiblecauses: (a) Direct outwash from Chalky Boulder Clayice with its predominance of fresh flint; (b)Solifluction and downslope movement from theNorthern Drift. The evidence is insufficient to proveeither... " (Bishop, 1958, p. 288).

However, following the work of Shotton (1953),Bishop concluded that the increase in foreign materialwas a direct consequence of the input of foreignlithologies, principally flint, into the Cherwell basinvia overflow of 'Lake Harrison' through the FennyCompton Gap (Shotton, 1953).

As can be seen in Figs 1 & 2, this hypothesis oweslittle or nothing to field evidence for the lateralcontinuity of the stratigraphic units involved. Thegradient of the Wolvercote Terrace proposed byBishop (1958) shows a marked but unexplainedsteepening 5-km downstream of Kirtlington nearBletchington, while upstream of this locality, there isonly one other site attributed to the WolvercoteTerrace, with an intervening gap of 20 km. Moreover,

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WOLVERCOTE TERRACE, UPPER THAM ES VALLEY 221

the lithological distinction between the terraces is notsupported even by the evidence presented by Bishophimself from the Cherwell valley. Table 1 shows thatthe overall lithological properties of the Wolvercoteand Hanborough Terraces , based upon an admittedlylimited number of samples , are similar.

It might be argued that the use of gross percentagesin Table 1 disguises significant changes in theincidence of far-travelled material. It will be seen thatthe terrace gravels are dominated by local componentswhich can be expected to vary greatly from site to site ,dependent upon degrees of decalcification and uponvariations of input from the valley side , Thus the realaccession of 'new' flint should be looked for in termsof an increase relative to the other far-travelled,durable lithologies. However, the highest flint value,i.e. the lowest A ratio ('Bunter' + sandstone: flint), isrecorded from the Hanborough Terrace gravels. Thusthe published data do not signal a significant change inthe supply of flint between the deposition of the twoterraces.

Ratio B, the ratio of non-local ('Bunter' +sandstone + flint) to local (limestone + ironstone)material , demonstrates that the high values of flintwithin the Wolvercote Terrace gravels at Somertonresult from the relatively low content of locallyderived sediment, and not from an increase inavailable flint. This is confirmed by ratio A , whichdisplays values similar to those recorded from otherterraces sites , while values for ratio B are larger thanelsewhere.

A similar interpretation can be offered for thelargely decalcified solifluction gravels. The high flintcontent of the solifluction gravels lying on theHanborough Terrace (Table 1, solifluction gravels 2and 3) is the result of a smaller local component, notan increase in the occurrence of flint. Ratio A againdisplays values similar to those from other terracesamples .

The composition of the Wolvercote Terrace gravelsis confirmed by a recent reinvestigation at Wolvercoteitself. As part of an archaeological reconnaissance

TABLE 1. Clast lithological data for the Wolnrcote and Hanborough Terraces and associated solifluction gravels, in theCherweU VaUey, from Bishop (1958). Intercomponent ratios :

Ratio A, 'Bunter' + Sandstone: Flint,Ratio B, 'Bunter' + Sandstone + Flint: Limestone + Ironstone

TERRACE GRA VELSHanborough Terrace Wolvercote Terrace

Location 1 2 3 4 5 6 7 8 9 10 11'Bunter' 1.9 11.6 4.5 5.3 10.7 6.0 3.4 13.6 7.6 7.0Sandstone 1.0 3.8 1.8 2.0 3.5 12.2 5.0Flint 10.6 10.4 10.6 19.7 9.1 14.0 7.2 35.0 35.0 39.0Ironstone 29.5 37.0 9.0 9.0 8.0 29.0 27.0 37.0 22.0 19.8 20.0Limestone 51.0 55.0 57.0 61.0 53.0 37.5 53.0 42.2 21.0 18.4 26.0Gryphaea 4.9 7.7 7.1 15.0 10.7 9.4 5.3 6.1 3.0Other 0.5 1.3 1.8 2.3 0.7

Ratio A 0.27 1.48 0.42 0.36 1.39 0.42 0.47 0.48 0.56 0.31Ratio B 0.17 0.39 0.21 0.43 0.32 0.25 0.13 1.21 1.43 1.10Locations : 1-2, Kirtlington; 3-6, Wolvercote : 7-8, Gibraltar; 9-11, Somerton .

SOLIFLUCTION GRAVELSHanborougli Terrace Wolvercote Terrace

Location 1 2 3 4 5 6 7 8 9 10'Bunter' 15.4 19.0 12.4 19.0 25.5 6.8 6.0 20.0 3.6 17.3Sandstone 2.5 4.5 7.0 6.0 1.4 1.8 0.5 8.4 7.0Chert 1.1 5.0 0.15 3.8Flint 27.0 55.0 55.4 40.0 40.0 13.6 12.0 42.0 4.2 48.0Ironstone 54.5 21.5 24.5 33.0 27.0 no 79.0 29.0 92.0 22.5Limestone ,. 0.5 2.75 0.3Other 0.5 2.0 0.7 1.2

Ratio A 0.66 0.42 0.35 0.63 0.67 0.63 0.54 0.48 0.85 0.51Ratio B 0.82 3.65 3.05 1.96 2.47 0.28 0.22 2.42 0.08 3.21

Locations : 1-3, Kirtlington ; 4-5, Wolvercote; 6-9, Gibraltar; 10, Somerton.

222 D . MADDY . S. G. LEWIS AND C. P . GREEN

survey to locate the Wolvercote Channel , severalauger holes were sunk upon the Wolvercote Terraceat Wolvercote (Fig. Ib). The lithostratigraphic logs ofthese auger holes are shown in Fig. 1c.

Four gravel samples were collected and the11.2-16.0 mm size fraction was separated andsubjected to clast lithological analysis . The results ofthis analysis, together with two additional analysesfrom published sources are shown in Table 2.

These counts tend to confirm the lithologicalcontent of the Wolvercote Terrace gravels asdescribed by Bishop (1958). However, a furtherimportant observation concerns the nature of the flintin the gravels. All of the flint recovered in thesesamples was weathered. It is not possible therefore,from the evidence of these samples, to confirm theoccurrence of 'new' flint in the Wolvercote Terracedeposits.

The composition of river gravels in the terracesediments of the River Cherwell fails to support theargument for an accession of 'new' flint into theCherwell valley during the formation of theWolvercote Terrace, nor is there any possibility ofreconstructing the terrace surface. Hence , a lithologi­cal distinction between the Wolvercote and Han­borough Terrace sediments cannot be justified in theCherwell valley on the basis of the published evidenceand assumptions 1,2 and 3 set out in the Introductionto this account are without support in the Cherwellvalley.

(b) The River Evenlode

The argument for an increase of flint in theWolvercote Terrace deposits has seemingly ignored

TABLE 2. Clast lithological data for the WolvercoteTerrace, including data coUected during this study and datafrom published sources, Intercomponent ratio calculation as

in Table 1.

Location 1 2 3 4 5 6Quartz 3.3 3.5 3.8 3.7 4.2 TQuartzite 8.8 8.8 12.3 12.1 3.4 5.2Sandstone 0.2 l. l.

Chert 2.1 1.8 0.8 1.1Flint 7.9 10.9 9.8 to.7 8.1 8.2Ironstone 2.9 2.8 2.5 2.9 T 8.5Limestone 72.6 69.7 68.1 66.0 83.5 78.0Shell 1.7 2.1 2.7 2.2 l. l.

Other 0.5 0.4 0.0 1.3 0.7 0.0

Ratio A 1.55 1.13 1.64 1.47 0.94 0.63Ratio B 0.26 0.32 0.36 0.38 0.18 0.151-4, Wolvercote, (Present Study);5, Oxford, (Goudie , 1976);6, Abingdon Area (Corser, 1978)

the flint present in the Hanborough Terrace of theRiver Cherwell , discussed in the foregoing para­graphs , and has centred on the apparent lack of flintin the Hanborough Terrace of the River Evenlode.

However, the evidence available to substantiate alithological distinction between the Wolvercote andHanborough Terraces in the Evenlode valley isequivocal, partly because there are few publishedstone counts from the critical sites, and partly becauseof the difficulty of separating terrace levels in theuppermost reaches of the valley. According to Arkell(1947) the Wolvercote Terrace in the Evenlode valleyis 'insignificant relative to the others' (p . 215), butTomlinson believed that it could be linked, viadeposits at Chadlington and Milton under Wychwood,directly to the flinty outwash gravels of the MoretonDrift around Daylesford (correlated with the easterlyderived members of the Wolston Series by Bishop,1958).

Tomlinson (1929, pp. 187-88) states that:

"No undoubted outcrops of the Moreton drift occurbetween Daylesford and the 'Wolvercote Terrace' ofDr. Sandford at Chadlington , but a bench of gravelscontaining flints near Milton may belong to theMoreton Drift suite . However, flints are much lessnumerous on the surface here than in the typicalMoreton Drift , and by the time we reach Chadlingtonthere are comparatively few in the Wolvercot eTerrace gravels".

This tentative statement by Tomlinson appears to bethe original basis of the widely accepted lithologicalrelationship between the Moreton Drift and theWolvercote Terrace. It is surprising therefore to findthat this relationship between the Daylesford andChadlington deposits has not been advocated by otherworkers in the Evenlode valley, and furthermore isnot supported unambiguously by the availablelithological evidence.

The deposits at Chadlington (underlying theSpelsbury Terrace) identified by Sandford (1924) andTomlinson (1929) as Wolvercote Terrace equivalent,appear (Fig. 2) to be too high to permit thiscorrelation, and subsequent workers (Arkell, 1947;Kellaway, Morton & Poole, 1973) have associated theSpelsbury Terrace at Chadlington and upstream toMilton with the higher Hanborough Terrace. Thiscorrelation is also suggested on lithological grounds byBriggs and Gilbertson (1973) who found that theSpelsbury Terrace deposits at East and West DeanGrove were dominated by limestone gravels with few,if any, flints. They considered this lithologicalcomposition to preclude a correlation with theWolvercote Terrace. Further upstream, the Bledin­gton Terrace was also correlated with the HanboroughTerrace, by Arkell (1947), again on lithologicalgrounds.

WOLVERCOTE TERRACE, UPPER THAMES VALLEY 223

The attribution of terrace remnants at Milton andBledington to the Hanborough Terrace is at variancewith the lithological details recorded by Tomlinson(1929). She describes an exposure in a pit at the southwest end of the village of Milton consisting oforange-red sands which, in places , are underlain byoolitic gravels and she comments that 'There weremany flints, some still white-coated and fresh , in thesand near the junction of the two deposits'.(Tomlinson, 1929, pp . 175-76). At Bledington,Tomlinson 's interpretation is based on the observationof Gray (1911) who records the presence of 'Somelarge fresh flints' (p. 263) from the lowest part of theexcavation at Bledington. Accordingly Tomlinsonconsidered the Bledington Terrace to be younger thanthe Moreton Drift and approximately equivalent tothe Wolvercote Terrace.

Thus, in the upper reaches of the Evenlode valley,the evidence cited by Tomlinson points to thepresence of fresh flint in the terrace deposits. But interms of elevation, only one terrace level has beenidentified in the area , and interpretation of terracegradients suggests that this is the Hanborough Terraceand not the Wolvercote Terrace. If this latterinterpretation is correct, fresh flint was present in theEvenlode valley prior to the formation not only of theWolvercote Terrace but also of the HanboroughTerrace.

Downstream of Chadlington, where separateHanborough and Wolvercote Terrace levels are morereadily identified, Arkell (1947) has recorded theassociation of flint with the Wolvercote Terrace atWhitehill Wood railway cutting, Blenheim Park gravelpits and Peartree Hill. Flints occur at Whitehill Wood ,along with quartzites, in 'brown loam' overlying anoolite gravel, those from Blenheim Park occur in'debris', and those from Peartree Hill occur in 'loamwith abundant flint'. Flints recorded from 'loam' areperhaps similar to those recorded in the decalcifiedsolifluction deposits forming the surface of theWolvercote Terrace of the Cherwell. The flints foundin 'debris' at Blenheim Park lack a reliablestratigraphic context. None of this evidence appears tohave impressed Arkell. He writes:

" . . . it does not follow from this that the WolvercoteTerrace is contemporaneous with the Moreton Driftand repre sents outwash from the eastern ice. .. I haveconcluded (Arkell, 1946) that the Moreton Drift isolder than the Wolvercote Terrace . . ." (Arkell, 1947,p. 109).

Thus in the Evenlode valley, as in the Cherwell valley,a lithological distinction between the deposits of theWolvercote Terrace and those of the older terraces(assumption 1) cannot be substantiated, and re­construction of terrace gradients (assumption 3)appears unhelpful in the differentiation of terrace

remnants in the upper reaches of the valley. Theredoes appear to be evidence for the accession of 'new'flint into the terrace deposits of the Evenlode valley(assumption 2) , but as the age of the terrace depositsin which it is found remains uncertain and lateralcontinuity of the stratigraphic units, either upstreamor downstream, has not been demonstrated, the flintcannot at present be employed as a lithostratigraphicmarker.

4. SOURCES OF FLINT

It is suggested in this review that the value of flint as akey guide to lithostratigraphic separation in the UpperThames has been greatly overestimated. However, theoccurrence of flint, particularly fresh flint, needsexplanation. Four possible sources have beensuggested.

Two hypotheses suggest a secondary source for theflint:(1) easterly derived glacigenic sediments of theMoreton Drift (Tomlinson, 1929).(2) older fluvial sediments of the Northern Drift(Bishop , 1958).

The further hypotheses suggest a primary source:(3) tributaries draining directly into this area from thechalk outcrop to the south .(4) a former chalk outcrop in this area , as suggestedby Gray (1911), which has now been completelyremoved.

There is no doubt that the first three of thesesuggestions could provide the flint recorded from thegravels. Table 3 shows recorded stone counts fromMoreton Drift outwash at Daylesford (Bishop , 1958;Briggs, 1973) and clearly demonstrates an adequatesource. Table 3 also shows several flint-rich stonecounts from the Northern Drift recorded by Hey(1986), once again demonstrating the Northern Driftto be a possible source. Hey (1986) explained thesehigh flint contents in the Northern Drift gravelsaround Witney as being the result of tributary streamsdraining northward from the chalk outcrop to thesouth. This is effectively the same as hypothesis threeand could equally well explain fresh flint in the lowerterraces. There is no evidence to substantiate the finalhypothesis. Indeed the patchy occurrence of fresh flintwould seem to preclude a local bedrock origin .

5. CONCLUSION

Assessment of the available evidence within thevalleys of the Rivers Evenlode and Cherwell indicatesthat there is little unequivocal support for thelithological separation of the Wolvercote Terrace fromthe higher Hanborough Terrace. Furthermore , thereis no morphological evidence to relate the MoretonDrifts to the Wolvercote Terrace around Oxford .

224 D . MADDY. S. G . LEWIS AND C. P . GREEN

TABLE 3. Clast Iitbologic:al data for non-terrace flint bearing gravels in the Oxford area, from publishedsources. (Location of sites, Fig. 1).

MORETON DRIFT(After Bishop, 1958) 'Bunter' Flint OtherDaylesford (SP244255) 22.0 53.0 25.0

22.0 59.0 22.0(After Briggs, 1973) Quartz Mudstone Sandstone Flint OtherDaylesford (SP243257) 30.0 23.0 9.0 36.0 2.0Blackpit (SP219265) 20.0 15.0 17.0 48.0 0.0Gravels Barn (SP247328) 16.0 22.0 7.0 27.0 28.0Oddington House (SP234259) 30.0 8.0 9.0 52.0 1.0

NORTHERN DRIFT(After Briggs, 1973) Quartz Mudstone Sandstone Flint OtherCumnor Hill (SP482047) 32.0 41.0 11.0 14.0 2.0Picketts Heath Farm (SP484030) 31.0 20.0 5.0 43.0 1.0

(After Hey, 1986) Quartz Quartzite Chert Flint OtherDeily End (SP356131) 52.6 29.8 0.0 17.6 0.0Hill Houses (SP382103) 37.9 13.1 1.0 47.6 0.5Cogges Wood (SP383117) 21.6 5.9 0.0 72.2 0.3Tangley (SP241172) 57.1 3.8 0.0 9.1 0.0

Although it may be possible to link some of thedeposits in the upper reaches of the Evcnlode valleyto the Moreton Drift it is not certain how thesedeposits relate to the Hanborough and WolvercoteTerraces in the area around Oxford. Given thissituation it would seem unwise to extend anycorrelation further downstream into the MiddleThames valley in order to determine the age of theMoreton Drift glacial sequence.

The deposits of the Upper Thames are still poorlyunderstood and the database of available informationis very small. Until this stratigraphy is re-investigated

in detail its wider implications cannot be accuratelydetermined.

ACKNOWLEDGEMENTS

OM and SL would like to acknowledge NERC fortheir support via studentships during which thisresearch was undertaken. Thanks also go to R. J.MacRae, Dr. D. Bridgland and the Nature Conser­vancy Council for support during the investigation atWolvercote .

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BRIGGS, D. J. 1973. Quaternary deposits of the Euenlodevalley and adjacent areas. Unpubl. Ph.D . thesis,University of Bristol.

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