Age-estimate evidence for Middle-Late Pleistocene aggradation of RiverNene 1st Terrace deposits at Whittlesey, eastern England

H. E. Langford", M. D. Bateman", K. E. H. Penkman", S. Boreham",R. M. Briant", G. R. Coope" & D. H. Keen?"

LANGFORD, H. E., BATEMAN, M. D., PENKMAN, K. E. H., BOREHAM, S., BRIANT,R. M., COOPE, G. R. & KEEN, D. H. 2007. Age-estimate evidence for Middle-LatePleistocene aggradation of River Nene 1st Terrace deposits at Whittlesey, eastern England.Proceedings of the Geologists' Association, 118, 283-300. At Whittlesey, eastern England,Pleistocene interglacial sediments (unit G3) deposited in marine oxygen isotope stage (MIS) 7appear to be truncated by a sequence comprising: (i) a limestone-rich gravel containing organicmud beds (unit FI); (ii) vertically aggrading gravel beds with sand-clay-lined bases (unit F2);and (iii) interbedded sands and gravels (units F4-F6) with associated overbank deposits (unitG4). Preliminary investigations of the floral and faunal assemblages of the organic muds wereconsistent in providing evidence for deposition under cool conditions. This apparent singlecool/cold-phase sequence therefore could have been deposited in either MIS 6 or MIS 5d-2. Thepresence of sand beds in units F5, F6 and G4 and of molluscs in the organic mud beds of unitF I provided the opportunity for obtaining age estimates using optically stimulated lumi­nescence (OSL) and amino acid racemization (AAR). Rather than a single coolie old-phasesequence the age-estimate data revealed multiphase aggradation, with the AAR data indicatingthe possibility that the organic muds in unit F I were deposited earlier in MIS 7 than theinterglacial deposits of unit G3. Therefore, the succession could be: unit FI was truncatedinitially by unit G3, with unit F2 subsequently incising both unit FI and unit G3. The OSL ageestimates indicate that units F5, F6 and G4 are Early to Middle Devensian in age (MIS 5d-2),and therefore unit F2 was deposited sometime between late MIS 7 and MIS 5d. This paper hasdemonstrated the utility of using dual age-estimate techniques in dating complex fluvialsequences. Furthermore, the organic mud beds of unit FI could provide important newinformation on the complex character of the MIS 7 interglacial. In addition, the OSL data andthe fluvial style recorded by units F4-F6 and G4 allow comparisons to be made with recentinvestigations of nearby Devensian deposits.

Key words: amino acid racemization, optically stimulated luminescence, Pleistocene, marineoxygen isotope stages, Whittlesey

1/6 Magnolia A venue, Longthorpe, Peterhorough P£3 9QT. UK2Geography Department, University ofSheffield, Winter Street. Sheffield SJ() 2TN, UKJBioArch. Biology S Block, University of York, York YOlO 5YW, UK"Quaternary Palaeoenvironments Group, Godwin Institutefor Quaternary Research, Depart­ment of Geography, University of Cambridge. Downing Place, Cambridge CB23EN, UK5Department of Geography, Queen Mary, University ofLondon, Mile End Road, London E14NS, UK6Tigh na Cleirich, Foss, by Pitlochry. Perthshire PH16 5NQ, Scotland, UK71nstitute of Archaeology and Antiquity, University of Birmingham. Birmingham B15 2TT, UK

1. INTRODUCTION

This paper describes a late Middle and UpperPleistocene sequence of sands and gravels with organicmud beds at Funtharri's Lane East (Hanson's WestFace Quarry), Whittlesey, eastern England [NationalGrid Reference TL 238979). Whittlesey lies on the

'David Keen died as this paper was being revised. Hiscontribution to Quaternary science was immense and he willbe missed greatly. An obituary was published in the Proceed­ings volume 118 part 2 (Harrison, 2007).

Proceedings of the Geologists' Association, 118. 283-300.

western margin of the Fen Basin in eastern England(Fig. I), about 8 km to the east of Peterborough(Fig. 2), and is situated on a slightly elevated 'island'(up to 9 mOD; Fig. 3b) in the low-lying Fen Basin.The island is formed by a Pleistocene outlier sur­rounded by Holocene peat and alluvial deposits(Fig. 3a). Funtham's Lane East is situated at thewestern end of this outlier, and the geology is recordedby the British Geological Survey (BGS, 1984) asPleistocene River Nene 1st Terrace overlying JurassicOxford Clay (Fig. 3a). Preliminary accounts of the site

0016-7878/07 $15.00 (0 2007 Geologists' Association

284 H. E. LANGFORD ET AL.

NORTHSEA

~The waSh

o•

Approximate areaof the Fen Basin

Fig. 1. Location of Whittlesey in the Fen Basin, easternEngland.

appear in Langford (2002, 2005) and Langford et al.(2004a).

Previous research in the Nene Valley has concen­trated on mapping the dissected fluvial gravel spreads,both where they are confined by bedrock upstream ofPeterborough and as the river emerges from the lime­stone uplands downstream (Fig. 2; Horton et al., 1974;Castleden, 1976; Booth, 1982; Horton, 1989; Davey,1991). River Nene 1st Terrace deposits (Ecton Memberof Maddy, 1999) are usually interpreted as Devensianin age on the basis of radiocarbon determinations fromvarious sites in the upstream parts of the catchment,near Wellingborough and Thrapston (e.g. Shottonet aI., 1969, 1970). In contrast, until recently, littleinformation has been available on River Nene 1stTerrace deposits downstream of Peterborough, withthe exception of a brief report of Coelodonta antiqui­tatis skulls from Tanholt Farm, Eye (Chancellor& Langford, 1992). Recent work downstream ofPeterborough (Briant, 2002; Briant et al., 2004a, b,2005) also provides Devensian age estimates for RiverNene 1st Terrace deposits. Indeed, optically stimulatedluminescence (OSL) dating suggests that River Nene1st Terrace deposits started to accumulate from earlyDevensian times but ceased by the Last GlacialMaximum. Ipswichian (last interglacial) depositswithin the River Weiland lst Terrace at Maxey (Fig. 2;

4

4

. Market OeeplngeOeeplng st James

4

e Crowland

~Eye

N

i4 4

0 5, ! ! .5 kin

4

e Guyhlm

4 5

4

6

6

Altitude above 00 (m).>60 40-60 20-40 D 10-20 D 0-10 ~ Below 00 4-8 Spot height (m 00)

Fig. 2. Topographic details at the western edge of the Fen Basin in the area of Peterborough, eastern England. (© CrownCopyright Ordnance Survey. All rights reserved EOIOOOI8617.)

AG E E S T I M ATES F O R DEPOSITS AT W HITTLESEY . UK 285

o 250...............metres

........... _- .

C,D & E Channels

SF Sect ion F

SG Sect ion G

· 4 Spot height (m 00)

~ Funtham's Lane East

Illm Funtham 's Lane West

~ Bradley Fen

Fig. 4. Details of the Funtham's Lane East site, showing thelocat ion of section F and the sites of Funtham's Lane Westand Bradley Fen.

French , 1982; Davey et al., 1991) and at DeepingSt James (Keen et al., 1999), however, reveal thepotenti al for a more complex pattern of fluvial aggra­dation in such low-lying settings. This paper describessuch a complex sequence for the first time from RiverNene Ist Terrace deposits, and further complexity isseen in other sections not reported here (in Funtham'sLane East, the adjacent Bradley Fen and King's Dyke,Figs 3 & 4; Langford et al., 2004a--e).

The sequence of sands and gravels with organic mudbeds described in this paper occurs at section F inFuntham's Lane East (Fig. 4). Preliminary results frompalaeontological analyses were consistent in indicatingthat the organic mud beds were deposited under coolconditions (Langford et al., 2004a). Initial investiga­tions suggested a single-phase sequence (units 4-6 inLangford et al., 2004a) that cuts out earlier interglacialdeposits . Amino acid racemization (AAR) age esti­mates on molluscs from these interglacial depositsindicate a late marine oxygen isotope stage (MIS) 7 age(Penkman, 2005). Therefore, this apparent single cool!cold-phase sequence of sands and gravels with organicmud beds would appear to have been deposited ineither MIS 6 or MIS 5d-2. In order to determine theage of this sequence, OSL samples were collected fromsand beds in the upper part, and molluscs from theorganic mud beds in the lower part were used for AARanalyses.

Anal yses of samples from deposits at Funtharn'sLane East and the adjacent Funtham's Lane West andBradley Fen are ongoing. Preliminary results are pre­sented in Langford et a!. (2004a, b). Subunits G3a andb of the MIS 7 interglacial depos its are the subject of a

FLE Funlham's Lane East

TF Tanholl Farm

P Pode Hole

Key :

§:I No gravelsbeneath Holocene deposits

IIIIIIII GroundabovelsI Terrace level

c:J Baseof gravel·5 andbelow00 (m)

- • Location of mainchannel

~,;;t,l;'if,···,~~.~--..........

•, "~~: " lrlihi:'\: ";:;i'~'i':;:"

Fig. 3. (3) The geology and (b) topo graph y of the Whittlesey'island ', and the location of Funtham 's Lane East (FLE) andsections A-C at King' s Dyke (Langfo rd, 1999; Langfordet al., 2004c; redrawn from data in Booth , 1982). (c) Locationof the Funtharn's Lane East, Tanh olt Farm and Pode Holesites relat ive to the main channel s of the River Nene.Co ntours show the base of Pleistocene gravels (ada pted fromHort on , 1989).

286 H. E. LANGFORD ET AL.

Log3F

Log4F

Log5F

Log Log5AF 6F

Log7F

Log8F

Log2F

Log1F

-2.4 00

~'t:~i::=:::;:;::::::3fUnitG3

Unit F2

OSl Shfd030021 ~

Unit G4

Unit F6 ~

------------Unit FS------------------2mL10m

[jJ-~ Clast-lithology samplesC Sample for ColeopteraM Sample for molluscs & AAR

Organic-rich beds

Fig. 5. Sketch of section F at Funtham's Lane East showing the relationships between the different units and the locations ofsedimentary logs and clast-lithology and palaeontology samples. Units FI and F2 can be distinguished by their internaltwo-dimensional facies architecture, shown schematically by dashed lines. Note that the contact between units FI and F2 is notclear and could be distinguished in the field only where the upwardly concave lower contacts of beds in F2 truncate theeastwardly inclined bases of beds in unit Fl.

paper in preparation and further results will be pub­lished when they are available. This paper focusespurely on the age relationship of sedimentary units insection F. Brief details of the sediments and palaeon­tology are provided in the following two sections. Theage-estimate data obtained are presented in section 4and the local and regional implications are discussed insection 5.

2. SEDIMENT DESCRIPTION

The focus of this paper is on units FI, F2, F4, F5, G4and F6 at section F, Funtham's Lane East (Fig. 5).Units prefixed by F are either present only in section For are best developed in that section, whereas thoseprefixed by G are better developed to the west insection G (Langford et al., 2004a). Preliminary descrip­tions of units G I, G3 and F3 (Fig. 5) can be found inLangford et al. (2004a) and are not described in moredetail here. Briefly, unit G I is a flint-rich graveldeposited by a braided stream during a cold stagepre-dating MIS 7, whereas unit G3 is essentially afossiliferous, coarse- to fine-grained channel fill,with AAR data indicating deposition late in MIS 7(Penkrnan, 2005). Unit F3 comprises shelly, troughcross-bedded sands and gravels, with the shells appar­ently being reworked from the underlying unit G3(samples from this unit have still to be analysed).

Section F was graded by the operator of the quarryprior to the commencement of fieldwork (Fig. 6a).Therefore, vertical stepped logs (IF-8F) were exca­vated and discontinuities recorded in these were tracedlaterally in order to determine the upper and lowercontacts of the main sedimentary units (Fig. 6b).Although it is apparent from the field relationshipsdetermined that unit FI pre-dates unit F2, the exact

relationship between unit FI and units GI and G3 isunclear, leading to the initial assumption that units FIand F2 comprised a single unit (Langford et al.,2004a).

Unit Fl

Unit FI is dominated by pebbly, clast-supported,closed framework gravel with its base at approximately- 2 mOD. Discontinuities (shown schematically bydashed lines in Fig. 5) at the base of logs 6F-8Fsuggest gravel aggradation from west to east, withcontinuous to discontinuous ribbons of clayey silt,fossiliferous in places, and trails of Oxford Clay rip-upclasts at the base of individual aggradations. Thisgravel aggradation is interrupted at the top of the unitby accumulation of two laterally continuous beds oforganic mud between logs 6F and 8F, separated by athin bed of gravel (Fig. 7; this detail is impossible toshow at the scale of Fig. 5 and so the two beds oforganic muds and the intervening thin bed of gravelare shown schematically). At both the western andeastern ends of the organic mud beds, small-scale(SoI ill wide) gravel-filled channels occur containingrip-up clasts of organic mud and Oxford Clay. Thethin bed of gravel separating the organic mud beds canbe traced laterally to the earlier of these small-scalegravel-filled channels. This interrelationship of organicmud beds and adjoining gravel-filled channels suggestsabandonment by the main channel, periodic streamactivity at the margins of the mud beds and reacti­vation of the channel during a major flooding event.

The lower contact of unit FI is irregular and erosive,whereas the upper contact is planar erosive at the topof the latest mud bed, markedly irregular and erosivewestwards, where it is cut out by unit F2, and inclined

AGE E STIMAT E S FOR DEPOSITS AT WHITTL ES EY, UK

... G4

287

Fig. 6. (a) Photograph of the graded section F at the location of the organic mud beds in unit FI. Spade in left -hand foregroundis 900 mm long. Dashed lines mark the approximate boundaries of sedimentary units. (Photographed by H. E. Langford, July2001.) (b) Photograph of the continu ous to discont inuous ribbons and pockets of fossiliferous sandy silt/clay that mark thebases of individual beds (dashed lines) in unit F2. Note the house bricks in right-hand foreground for scale and position of log2F. Solid lines mark the app roximate boundaries of sedimenta ry unit s. (Photogra phed by H. E. Langford , 4 September 2001.)

288 H. E. LANGFORD ET AL.

Unit G1(j) O,, !, ,

~:~ ?~Units

G4, F4-F6

800 +- .--__-. ......... .-__--'(100

100 0

Fig. 8. Triangular plot of clast-lithology assemblages forsamples from units FI, F2, G4 and F4-F6 in section F,Funtham's Lane East and those from sections A, Band C inKing's Dyke (Figs 3a, b).

planar erosive to the east, where it is cut out by unitF4.

Clast-lithology data are presented in Table 1 (sample1). Unit FI has the most limestone-rich and flint-poorassemblage in the samples from Funtham's Lane East(Langford et al., 2004a) and therefore could be part of,or derived from, the lower gravel of sections A-C inKing's Dyke (Figs 3a, b, 8; Langford, 1999; Langfordet al., 2004a), to the east. An OSL age estimate of

77 ± 3.5 kyr

Unit F1

Unit F6

~~;;:,;;~.;O,,;S~L Shfd03018 89 ± 5.0 kyr

UnitG4

OmOOw~===

Log F8

5m 00 """"= """""""'""""""

-1.5m 00 F"l:J"'4= .:.a;.o:="'1i?

4,.{;'

Fig. 7. Sedimentary log 8F showing locations of opticallystimulated luminescence and clast-lithology samples.

Table 1. Clast-lithology data for the 11.2-16 mm fraction of units FI, F2, F4, F5, G4 and F6, Funtham's Lane East.

Sample Unit Lithology (%) Total count

Flint Limestone Sandstone" Ironstone Other

15 F6 31.1 44.6 13.0 6.8 4.5b 17714 F6 43.2 37.5 10.5 4.1 4.7b 29613 F6 37.5 45.6 7.7 5.2 4.0b 24812 F6 45.9 30.3 8.1 8.6 7.0b 18511 F6 45.9 37.5 10.1 2.4 4.1b 36810 F6 40.9 36.8 13.8 3.2 5.3b 2479 F6 45.6 34.4 12.0 2.5 5.4b 2418 G4 46.5 34.4 8.3 4.5 6.4b 1577 F5 58.0 27.6 9.9 1.8 2.8b .c 2836 F4 41.9 40.0 15.4 1.2 1.5 4085 F5 43.8 37.3 11.2 4.8 2.9d 4754 G4 32.6 43.0 17.4 5.6 1.4 1443 F2 32.1 36.5 12.0 12.9 6.4d 2492 F2 33.2 45.1 13.8 5.2 2.6d 572I FI 23.5 479 18.7 7.2 2.7d 583

"Includes quartz and quartzite.bIncludes nodular chalk."Includes secondary Ca concretions.dIncludes Fe-cemented aggregates.

AGE ESTIMATES f'OR DEPOSITS AT WHITTLESEY. UK 289

158± 14 ka (Shfd96 13I; here and elsewhere in thepaper uncertainty is given as ± one standard deviation(rr)) (Langford et al., 2004c) on sands overlying thelower gravel at section A in King's Dyke provides anupper age limit of MIS 6 for the influx of thislimestone-rich gravel into the area.

Unit F2

A later aggradation phase, recorded in the lower partof log 2F, comprises cut-and-fill gravel channels, withthe base of the earliest at approximately - 2 mOD.The base of several channels (shown schematically bydashed lines in Fig. 5) is marked by continuous todiscontinuous ribbons and pockets of fossiliferoussandy silt/clay. It is probable that these are troughcross-stratified gravels. Two-dimensional facies archi­tecture indicates deposition in north-south-trendingchannels, but it was not possible to determine thedirection of flow. When traced laterally to the east it isevident that these ribbons truncate the eastwardlyinclined bases of beds in unit Fl.

The lower contact of unit F2 comprises a planar,broad, upwardly concave, erosional surface where itoverlies Oxford Clay (Jurassic) at the base and to thewest, where it cuts out units Gland G3. To the east,where it cuts out unit Fl, the contact is more obscure.The upper contact of unit F2 comprises a series ofplanar, upwardly concave, erosional surfaces formedby the trough cross-bedded components of unit F3.

Unit F2 has incised into unit FI and units GI andG3, and therefore the clast-lithology data (Table I,samples 2 and 3) reflect derivation from these units(Figs 5, 8).

Units F4, F5 and G4

Units F4 and F5 infill a channel that truncates theeastern edge of unit FI and is incised into the under­lying Oxford Clay. The channel occupied by units F4and F5 could be traced on the cleared surface of theunderlying Oxford Clay to the north of section F,trending northeast to southwest and deepening to­wards the northeast. This, together with cross-beddingin sands in sections exposed to the northeast of sectionF (unpublished data), indicates flow towards thenortheast. Unit F4 (Fig. 5) comprises a pebbly, open­work, clast-supported gravel with its base at approxi­mately - 2 m Ol), passing gradationally upwards intopebbly, closed framework, clast-supported gravelsinterstratified with a number of medium to coarsesand beds (unit F5). The lower contact of unit F4 iserosional and upwardly concave.

Upwards the sands in unit F5 become more promi­nent and more laterally continuous, passing laterally(to the west) into structureless clay-silt with lenses ofrippled sands, interpreted as overbank deposits (unitG4; Langford et al., 2004a). Post-depositional cryo­genic deformation in the form of gravel involutions

affects both units G4 and F5, but is more marked atthe top of unit G4. The upper contact with unit F6 istherefore irregular. The lower contact with unit F4is transitional, but, above the organic muds of unit FI,is horizontal, planar erosional, becoming upwardlyconcave westward.

Clast-lithology data are presented in Table 1(samples 4-8). The dominance of flint over limestone isin contrast to unit FI, however, and this may indicatemainly reworking of unit G I deposits (Langford et al.,2004a), or diminution of the limestone clasts as a resultof comminution by stream processes. The presence ofnodular chalk in sample 7, however, may indicate freshinput of material from the valley sides. Samples 4 and8 (location not shown in Fig. 5) are from gravelinvolutions in unit G4, hence their small size.

Unit F6

Unit F6 is a widespread pebbly, closed framework,clast-supported gravel with occasional lenses ofmedium to coarse sand. The latter appear preferen­tially at the base of unit F6 and are often slightly tomarkedly reddish in colour. Cryogenic deformation,with tear-drop-shaped involutions being common, hasaffected much of the lower part of unit F6, includingsome of the lenses of reddened sand. Despite thecryogenic deformation, upwardly concave erosionallower contacts can be observed in components of unitF6, suggesting both upward and lateral aggradationand that - in contrast to units F4 and F5 - flow wasnot confined to a single main channel. Unit F6 reachesa maximum thickness of about 3 m in section F, withits base at about 2 m Of). The upper part of unit F6has been disturbed by soil formation and anthro­pogenic activity, whereas, owing to cryogenicdeformation, the lower contact is markedly irregular.

Samples 9-15 in Table I are from unit F6. They arefrom both cryogenically deformed and non-deformedgravels. Samples 13 and 15 (Fig. 5: from the top oflogs2F and 8F, respectively) have a higher content oflimestone, suggesting local reworking of earlierlimestone-rich gravels. Local flint enrichment, togetherwith the consistent presence of nodular chalk, whichdistinguishes it from the gravel of units F4, F5 and G4,suggests local erosion of slopes mantled by chalk-richdiamicton.

It should be noted, however, that for the most partunit F6 was obscured or had been partly removed, andattribution relies on the presence of nodular chalk andposition as the uppermost gravel facies present inthe various logs. Consequently, more than oneaggradational phase may be present.

3. PALAEONTOLOGY

Coleoptera

A sample was collected from the organic mud beds ofunit FI (Fig. 5) for coleopteran analysis. In addition

290 II . E . L ANGFORD ET AI-.

specimens were supplied by David Keen from thesample collected for molluscan analysis. The coleop­teran sample of about 10 kg was specifically processedfor insect fossils. The richness of this sample whencompa red with the assemblage from the molluscansam ple is undoub tedly a result of this process, as canbe seen by, for instance , the ab unda nce of Oclithebiuslenensis, which is a small inconspicuous species andeasily overlooked. Tabl e 2 lists the species obtainedfrom both the coleopteran and mollusc samples. Thenomenclature follows that of Lucht (1987) and thenumbers opposite each taxon indicate the minimumnumbers of individuals in the sample. Altogether, 55taxa of Coleoptera were obt ained, of which 35 could beiden tified to the species level. Of these, seven are nolonger living in the British Isles.

The local environment indicated by the Coleopterais that of a pond, which was colon ized by such plantsas Potamoge ton or Myriophyllum. Marginal vegetationwas probably Carex or similar plant s, but dry groundwith ruderal plants must also have occurred nearby.The beetles provide no evidence for the presence of anytrees.

The temperature was mod erately cold at this time,though not of truly arctic severity. Mutual Clima ticRange (Atkinso n et al., 1987) estima tes based on thisbeetle assemblage gave Tm a x , the mean temperature ofthe warmest month (July), between 9°C and 14°C, andTmin' the mean temper ature of the coldest months(Ja nuary and Febru ary), between - 20 0 and ODe.

Stra tigrap hically, the assemblage from unit F l doesnot closely resemble any of the Middl e Devensianfaunas (Coope, 1968). In spi te of its indication of coldconditio ns, and the consequent similarity of faunasthat cold climates impose on the faunas by restr ictingthe numbers of species that can survive these harshco nditions, it does not include the exotic speciescharacteristic of the Middle Devensian faunas, such asoccur commonly at the neighbouring sites of TanholtFarm and Pode Hole (Briant, 2002; Briant et aI.,2004a, b, 2005). Thus, it is suggested tha t this deposit isnot of Middle Devensian age. However, the presence inthis assemblage of the eastern Fennoscandian andSiberian weevil Otiorhynchus politus is rather interest­ing. This species is unknown in any of the numerousMiddl e Devensian faunas , alth ough it is seen in theEarly Devensian at Pode Hole (Briant et al., 2004b,2005).

Mollusca

Analysis of the sample from the orga nic-rich bedsof unit Fl (Fig. 5) revealed a rather undiagnosticfreshwater assemblage (Ta ble 3). The considerablenum bers of Valvata piscinalis suggest relat ively deep,moving water, a habit at also indicated by Pis idiumam nicum and Pisidium henslowanum. Th e lack of anyPlanorbidae suggests that there was little aquatic veg­etation. Only one land snai l species was present (A zeca

goodallii , which is a sna il of scrub and rocks. lnpresent-day Europe this species has a southern andcon tinental distribution (Kerney & Camero n, 1979).The freshwater compo nent of the assemblage is similarto that recorded in facies FI-Sr at section A, King'sDyke (Langford et al., 2004c), except for the presencehere of Sphaerium corneum and P. casertanum and theabsence here of Lymnaea peregra, Gyraulus laevis,Planorb idae and P. milium . Facies F l- Sr pre-dates anOSL age estimate of 158 ± 14 ka (Shfd96 131; Langfordet al., 2004c).

Aside from the single specimen of A. goodalli, theassemblage is climat ically uninformative and cou ld befound in tempera te to subarctic conditions. The singleshell fragment of A. goo dalli may indicate summerwarmth , but a larger sample would be required toreach a more definite conclusion about the environ­ment. None of the species present is a biostrat igraphicindicator, and the assemblage lacks Pupilla m uscorum,the grassland snai l so often characteristic of Devensia nfauna s (Ho lyoak, 1982) and present at bot h TanholtFarm and Pode Hole (Briant, 2002; Briant et al. ,2004a, b. 2005). This absence could, again, be anartefact of the sma ll sample size.

Pollen

Pollen has been analysed from two beds at log 6F(Fig. 5). A sample taken from the organic-rich bedof unit FI yielded countable pollen (Tab le 4), butmateria l from the overlying silt-sand of unit G4 wasbarren. Pollen from unit Fl was dominated by grasspollen, with pine (31.8%) and a range of herbs. Thepollen concentration in the sample was relat ively high(78000 grains per gram) and the palynomorphs weremoderately well preserved. Th is pollen spectru mappears to represent pre-temperate cond itions (sens uTurner & West, 1968), interpreted as a grass landenvironm ent with sta nds of bore al woodla nd. There isan indication of tall-herb communities and emergentvegetation. Taken together, the pollen assemblagesuggests a cool, bu t perhaps not harsh, glacial enviro n­ment.

4. AGE ESTIMATES

Amino acid racemization

A new technique of amino acid ana lysis has beendeveloped (Penkman, 2005), combining a new Reverse­phase High Pressure Liquid Chro matography method(Ka ufman & Manley, 1998) with the isolation of an'intracrysta lline' frac tion of amino acids by bleachtreatm ent (Sykes et al., 1995). Th is combina tion oftechniques results in the anal ysis of the laevo- anddextro-rot atory optical isome rs (L and D) of multipleamino acids from the chemically protected organicmatt er within the biomin eral, enabling both decreasedsample sizes and increased reliab ility. Two specimens

AGE ESTIMATES FOR DEPOSITS AT WHITTLESEY, UK 291

Table 2. Coleopteran counts for samples from unit FI, sectionF, Funthams Lane East.

Sample

Table 2. Continued.

M

Sample

C

C, coleopteran sample; M, molluscan sample; *, no longer living inthe British Isles.

CarabidaeNotiophilus aquaticus (L.)*Dyschirius septentrionum Munst.Dyschirius sp.Bemhidion hipunctatwn (L.)Bembidion aeneum Germ.Bemhidion sp.Patrobus assimilis Chand.Pterostichus diligens (Sturm)

DytiscidaeHydroporus sp.Potamonectes depressus (F.)Agabus sp.Rhantus sp."Colymbetes dolabratus (Payk.)Colymhetes sp.

HydraenidaeOchthehius lenensis Popp.Helophorus aquaticus (L.)Helophorus mise small spp.

HydrophilidaeCercyon haemorrhoidalis (F.)Cercyon marinus Thoms.Cercyon tristis (Illiger)Hydrobius fuscipes (L.)Laccobius sp.

SilphidaeSilpha sp.

M C

2I1I5I1I

2517

12I1

GeorissidaeGeorissus crenulatus (Rossi.)

HeteroceridaeHeterocerus sp.

LathridiidaeCorticarina sp.

Coccinellidae*Scymnus bipunctalus Kug.*Hippodamia arctica Schneid.

AnthicidaeAnthicus sp

ScarabaeidaeAphodius sp.

ChrysomelidaeMacroplea appendiculta (Panz.)Plateumaris sericea (L.)

CurculionidaeApion sp."Otiorhynchus politus Gyll.Otiorhynchus Matus (L.)Strophosoma faber (Hbst.)Notaris aethiops (F.)

II2

2

2

2II

Table 3. Mollusca from unit F 1, section F, Funtham's LaneEast.Staphylinidae

Omalium excavatum Steph.Olophrumfuscum (Grav.)*Olophrum boreale Payk.Eucnecosum brachyplerum (Grav.)Geodromicus kunzei HeerTrogophloeus sp.Oxytelus nitidulus Grav.Platystethus cornutus (Grav.)Platystethus nodifrons Mannh.Bledius sp.Stenus juno (Payk.)Stenus sp.Euaesthetus laeviusculus Mannh.* Tachinus caelatus Ullrich,Aleocharinae Gen. et sp. indet.

ElateridaeHypnoidus riparius (F.)

4II

1012I8I

I2I215

Habitat

Freshwater

LandTotal

Taxa

Valvata piscinalis (Muller, 1774)Bithynia tentaculata (Linne, 1758)Bithynia operculaLymnaea lruncatula (Muller, 1774)Sphaerium corneum (Linne 1758)Pisidium amnicum (Milller, 1774)Pisidium casertanum (Poli, 1791)Pisidium subtruncatum (Maim, 1855)Pisidium henslowanum (Sheppard, 1823)Pisidium nitidum (Jenyns, 1832)Pisidium spp.Azeca goodalli (Ferussac, 1821)

Number

5025I43I9I6

43I

121

HelodidaeGen et sp. indet.

DryopidaeDryops sp.

of Va/vata piscinalis shell (NEaar 1245-6), one speci­men of Bithynia tentaculata shell (NEaar 1244) andtwo specimens of B. tentaculata opercula (NEaar2381-2) were analysed (supplied by David Keen) fromthe mollusc sample taken from an organic mud bed in

292 H. E . L A N G F O R D £ 7' A L.

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Trees and shrubsPinus 31.8

HerbsPoaceae 40.2Cyperaceae 4.5Apiaceae 0.9Brassicaceae I .8Helianthemum 1.8Plantago lanceolata 3.6

Lower plantsUndifferentia ted trilete Pterop sid spores 1.8Undifferentiated monolete Pteropsid spores 13.6

AquaticsSparg anium erectum 4.2Typha Iatifolia type 2.5

Total count (land pollen+spores+ aquatics) 110

Thu %

unit FI (Fig. 5). All specimens were prepared followingthe methods outlined in Penkman (2005). In brief, eachindividual specimen was powdered and bleached ,and two sub-samples taken. One fraction was directl ydemineralized and the free amino acids analysed(referred to as the 'free' fraction, 'F'), with the secondtreated with 7 M HCI unde r nitrogen at 110°C for 6(H6) or 24 hours (H*), referred to as the 'hydrolysed 'fraction.

The concentrations of the amino acid enant iomersfor each fraction are analysed separately, using highsensitivity chiral amino acid analysis with automatedderivitization, enablin g the measurement of the con­centrations and OIL values of aspartic acid/asparagine(Asx), glutamic acid/glutamine (Glx), serine (Ser),alanine (Ala) and valine (Val) (Kaufman & Manley,1998). These measurements were then comb ined toprovide an overall estima te of protein.

On the basis of the relati ve OIL values and concen­trations (Table 5), the amino acid data - when com­pared with unpublished values from MIS 5, 7 and 9sites - are consistent with a correlation with MIS 7(Penkrnan , 2005). The amin o acid dat a should betreated with caution, however, owing to the smallnumber of specimens analysed (one B. tentaculata shelland two opercula, two V. p iscinalis shells), comparedwith the number required to fulfil the criteria for thedefinition of an aminozone (Miller & Hare, 1980).Despite this, it is possible to place these samplestentatively within an aminostrat igraphic frameworkfor the UK . In a closed system, the amino acid ratiosof the free and the hydrolysed sub-samples should behighly correlated. When the amino acid ratios forthese sub-samples from the intracrystalline fract ion ofgastropod shells and opercula from UK interglacialdeposits are plotted for each substrate, the data fallinto discrete clusters. These clusters have been corre­lated with marine isotope warm stages (Penkman,

Table 4. Percent age pollen from un it Fl , section F (Log 6F ),Fu ntha m's Lane East.

AGE E S T I M AT E S FOR D EPOS I T S AT W H ITTLESEY, U K 293

2005) . (Note that the rat ios used for th is co rrela­tio n from the sites listed herein were determined byPenkm an and are not those pu blished in the or igina larticle s, i.e. the original refere nces cited are for back­gro und informatio n only.) Both the B. tentacu latashells and opercula and the V piscina lis shells haveamino acid ratios that a re higher than those of thesame specie s from sites such as Oeeping St Jam es(Fig. 2; Keen et al., 1999) and Trafalgar Square(Gi bb ard, 1985), which have been correlated with MI S5e. The ratios a re also lower than those obtained fromma terial from sites attri buted to MI S 9 (Penkma n,2005), such as Cudmore Grove (Roe , 1994) andHackney (Green et al., 2006) . This indicates thatdeposit ion of the sediments occurred between MIS 8and MI S 6. The amino acid data from bo th speciescluster with those obtained from sites correlated withMI S 7 (Penk man, 2005), such as Stanton Harcourt(Bucki ng ham et al., 1999), Aveley (Bridgland et al.,1995) and Lio n Pit (Schreve et al., 2006).

Amino acid dat a obtained from the intracrystallinefract ion of the calcitic Bithyn ia ope rcu la have beenfound to be a particularl y ro bust reposi tory for theoriginal protein. Th e low degree of nat ural varia bilityobserved in th is material a llows an increased level ofchronological reso lution . Th e amino acid dat a for theoperc ula from unit F I indica te tha t they are older thanthose fro m unit G3 , 4 Bithyn ia tenta culata operc ula(NEaa r 1300, 1302-3, 1306) (Figs 9 & 10; Penkman ,2005) .

Th e ope rcula dat a from unit F I can be compa redwith thos e from uni t G3 (F igs 9 & 10) using box plots.The OIL va lues (Fig. 9) for the free and the hydrolysedfrac tion are all higher in the unit F I samples tha n thosein the un it G3 samp les, except for those of Ser and Alain the free frac tio n. Th e spread of dat a in free Ser isquite la rge, al tho ugh this is not unusual in samples ofth is age du e to the rapid ra tes of race mizatio n anddecomposition of the free Ser. Therefore, the OILvalue of free Ser becomes less useful as an ageindica tor, but the concentra tion data from Ser areimp ort ant.

Serine is one of the most geochemically unstableamino acids (Bada et al., 1978), with one of itsdecomposition products being alanine. Th erefore, thera tio of the concentratio n of seri ne ([Ser]) and theconcentration of alanine ([Ala]) can be used as anindication of the extent of prot ein decomposition. The[Ser]/[Ala] value should decrease with increasingtime. The [Ser]/[Ala) value in the unit FI sam ples islower tha n those found in the unit G3 samples (Fig .10).

Th erefor e, a ll the measur es of protein decomposi­tion , except the OIL of Ala in the free fraction , indicat ethat the opercula samples fro m un it F I are slightlyolder than those from un it G3 . It mu st be noted,however, tha t the limited num ber of samples ana lysedonly a llows th is to be a tent ative conclusion at thi sstage .

Optically stimulated luminescence

The samples were ana lysed a t the Sheffield Ce ntrefor Int ernational O rylands Re search where they wereprepared under subd ued red lighting following stan­dard procedures to extract and clean coarse grained(90- 125Ilm) qua rtz (Bateman & Ca tt, 1996). Th epurity of the pre pared quartz extract was checkedusing infra-red stimula ted luminescence. Initially, feld­spar contamination was found but, after a fur ther20 min etch in H F and re-sieving, no further feldsparcontami nation was seen. All OSL measurement s werecarried out using an upgraded OA- 12 Rise lumi­nescence read er fitted with a lSO W filtered (GG-420)halogen lam p and with OSL measured thr ough aHoya-340 filter. Palaeodoses (De) were derived usingthe single aliquot regenerative (SAR) ap proach(Murray & Wintle, 2000), with the last irradiat ion dosereplicating the first to check if sensitivity cha ngescau sed by repea ted measurement of the same aliquo thad been monitored correctly and cor rected for by theSAR pro tocol. All aliquo ts where the ratio of first andlast do se point fell outside the range 0.9-1.1 wereexcluded from further ana lysis. A preheat plateau testde termi ned that a pre hea t of 240 °C for 10s prio r toOSL measurement was most appropriate for thesesamp les. All sam ples respo nded well to the SA Rprot ocol , with a goo d signa l to noise ratio, goo dincrease in OSL signa l, with addi tio nal artificiallaborato ry do se indica ting that they were not in satu­ra tion, and recycling values within the range 0.9- 1.1.

Sample dose ra tes were determined both in the fieldusing a portab le gamma spectrometer (EG&G M icro ­no mad) and in the lab orat or y using induct ivelyco upled plasma mas s spectromet ry (lCP-MS) a t theXRA L laborat ories Ontari o , Canada . Conversionfrom elemental concen trations to effective dose ratesmade use of the coefficients given by Aitken (1985),incorporating atten ua tio n factor s relating to sedimentgrai n sizes, density and palaeomoisture (based onpresent-day mois ture values with a ± 5% error to tryand incorporate any past fluctuations). As the unitssampled for Shfd03017 and Shfd0 3018 were thin(30 em and 12 em, respectively), contributions to thesamples' gamma dose rate from over- and unde rlyinguni ts were also determined ba sed on ICP- MS dat afrom these uni ts and gamma dose gradient data pro­vided by Aitken (1985). The cont ribution to dose ra tesfrom cosmic sources was calc ulated using the equationpublished in Prescott & Hutton (1994, p. 500).

Between 12 an d 19 replicate measurements weremad e per sample in orde r to provide an indica tio n ofthe reprod ucibility (Shfd03 0 17 n=12, Shfd03018 n= 14,Shfd03019 n=1 9, Shfd0 3020 n=1 8 and Shfd0302 1n=17). For each sample, indi vidu al replicate De values(and associa ted uncertainties) were com bined to for mprobability density fun ction plot s (F ig. II ). With theexception of sample Shfd03017, all samples display ata il of high De values or a very broad distri butionindicative of samples which contain a percentage of

294 H. E. LANGFORD ET AL.

0.30 1.10.76

0.29 F---j ,...---

0.741.0

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~0.28

0.90.72 r---

.J 0.27- 0.8C 0.260.70

B 0.25 0.7

0.88

El0.24 0.6 L.--

Asx bF Glx bF SerbF0.88 0.23

UnitF1 UnitG3 UnitF1 UnitG30.5

Unit F1 UnitG3

0.35 0.20

0.34 0.19 EJB 0.190.33

.J0.18-0.32

C 0 0.18

0.310.17

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0.62 0.210.76

0.20 B0.74

0.50

D 0.72

00.19 0.70

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EJ0.88

C 0.18

0.56 0.66

00.17

~0.64

0.54 0.620.16

Asx bH* Glx bH* 0.50 Ser bH*0.52 0.15 0.58

Unit F1 UnitG3 Unit F1 UnitG3 Unit F1 UnitG3

0.27 0.16

0.28

D 0.15

B0.26

0.25 0.14

0.25

.J-024 0.13

C0.24 0 E10.12

0.23Ala bH* ValbH*

0.23 0.11

(b) Unit F1 UnitG 3 Unit F1 UnitG3

Fig. 9. Box plots of D/L values of Asx, Glx, Ser, Ala and Val for (a) the free and (b) the total protein (hydrolysed) fraction ofbleached opercula from units Fl and G3. In each case, the results from both of the duplicate analyses for each sample arepresented (i.e. there are four data points for the samples from unit Fl and eight data points for the samples from unit G3). Theboundary of the box closest to zero indicates the 25th percentile, the solid line within the box marks the median, the dashed linewithin the box marks the mean and the boundary of the box furthest from zero indicates the 75th percentile.

AG E E STI MATES FOR DEPOSITS AT WHI T T L E S EY. U K

0.65 0.50

0.60[Ser]/[Ala] bF 0.48 [Ser]/[Ala] bH* F---I

0.460.55 E---I 0.440.50

0.42

0.45

B 0.40

0.400.38

0.35 0.36

295

0.30 0.34 J..----_-r .- ....J

(a) Unit F1 Unit G3 (b) Unit F1 Unit G3

Fig. 10. Box plots of [Ser]/[Ala] values for (a) the free and (b) the hydrolysed protein fraction of bleachedopercula from unitsFl and G3. In each case, the results from both of the duplicate analysesfor each sample are presented (i.e. there are four datapoints for the samples from unit FI and eight data points for the samples from unit G3). The boundary of the box closest tozero indicates the 25th percentile, the solid line within the box marks the median, the dashed linewithin the box marks the meanand the boundary of the box furthest from zero indicates the 75th percentile.

sand grai ns tha t were inco mpletely reset prior toburial. The Dc from sampl e Shfd030 17 is highly repro­du cible and thought to be the most reliable of the fivesamples. In o rde r to try and overco me any co ntamina­tio n from aliquots containing significant numbers ofunbl eached grains, replicat e aliquot s from a samplewere used in subsequent calculat ions of age only if theyfell within two standard deviat ion s of the mean . Thela tter stra tegy proved necessary only for samplesShfd030lS and Shfd030 19, where five and six aliquots ,respectively, were excluded . All aliqu ot replicate da tawere used for the other samples when ca lculating finalages . In order to calculate an age for each sample, theweighted mean value of De was calculated usingweights inversely pr oportional to th e varia nce of eachdeterminati on . Ages are qu oted in years fro m whenmeasured (2003), with one standard deviat ion uncer­tainty intervals. Results are presented in Table 6 andare discussed below.

Owing to the high reproducibil ity of sampleShfd 030I 7 (unit F6), it is inferred th at its OSL age of77 ± 3.5 ka is the most reliable. Because of stratigraphi­cal age reversals, possibly due to incorp orat ion of somemater ial not fully reset prior to bu rial , other OSL agesare used cautious ly as they may be overestima tions oftrue buria l age. Th e lack of sample OSL resetting maybe a function of the deposit ion al co ntext of samplesfrom units G4 and F5 at log SF, reflect ing tran sport a­tion in a mid-channel setting und er cloudy waterconditions . All OSL ages fall between 103± 5.4 ka and73 ± 4.2 ka, thu s post-dating the last interglacial (MIS5e). Ages from un its F5 and G4 range fro m 91 ± 5.3 kato 73 ± 4.2 ka and possibly co uld be co rrelated with therapid clima tic oscillations asso ciated with MIS 5b-5a.The maximum age range difference between samplesShfd030 17 and Shfd03020 is 27 ka, ind icatin g rapid

sediment emplacement of un its F5, G4 and F6 dur ingthe Ea rly to Midd le Devensian . The OSL date of103 ± 5.4 ka (Shfd0302 1) from unit F6 almos t certainlyreflects da ting of reworked wea thered products fromthe last interglacial , as ind icated by lenses of reddenedsand. Its depositional context within a braided riverchannel sequence increases the probability that fullOSL resetting of sand prior to bur ial has not tak enplace.

5. DlSCUSSION

Aggrada tion of units FI , F2, F4 and F5 appears toha ve been confined to a single cha nnel, with depositionof uni t Fl being associated with local erosion of softbed rock clays (Jurassic Oxford Clay) and the con tem­poraneous land sur face. The organic mud beds of unitF I po ssibly represent two periods of channel inac tivityinterrupted on at least one occasion by renewed chan­nel activity. Alte rnati vely, the small- scale gravel-filledchann els at the edges of the two organ ic mud beds,which contain rip-up clasts of organic mud and bed­rock clay, could indicate a bar-top setting with occa­siona l channel activity at the edges of the bar. Th eoverban k deposits of unit G4 are associated with un itF5 and ind icate a period of cha nnel sta bility. For un itsF4 and F5 the direction of flow was to the northeast,and it is likely that this was also the case for units F Iand Fl. Un it F6. however, is laterally more wide­spread, suggesting flow expan sion within a braid edstream environment.

Palaeont ological dat a (molluscs, insects and pollen)ind icat e that the organic mud beds in unit Fl accumu­lated und er coo l rather than temperate conditions,with minimum temp eratures between - 20° and O°C

296 H" E. LANGFORD ET AL.

...-. De from individual aliquot

f{]-; Weighted mean of all aliquots

0.35 Shfd03019

025

0.20

11.

0.15

0.10

0.05

0.000 100 200 300

Palaeodose(Gy)

0.25

0.20

11.

0.15

0.10

005

000400 0 100 200 300

Palaeodose (Gy)400

0.35Shfd03020

0.35Shfd03021

0.30 0.30

0.25

Y0.25

0.20 0.20

11. 0...

0.15 0.15

0.10 0.10

0.05 0.05

0.00 0.00+---'-o 100 200 300 400 0 100 200 300 400

Palaeodose(Gy) Palaeodose (Gy)

Fig. 11. Combined probability (P) density functions for palaeodoses (Dc) derived from replicate optically stimulatedluminescence aliquots (solid) showing degree of interaliquot scatter. Also plotted (on arbitary y axis) are the ranked individualaliquot D; values (solid diamonds) and the overall weighted mean (open square). Numbers of determinations: Shfd03017, 12;03018, 14; 03019, 19; 03020, 18; 03021, 17.

indicated by the coleopteran assemblage. Preliminaryresults of ostracod analysis indicate a cool fluvialassemblage (1. Whittaker, pers. comm., 2006). The

consistently cool nature of the faunal and floralassemblages indicated by the palaeontological data isunlikely to result by chance from the reworking of

AG E E S T I M ATES F O R DEPOSITS AT WHITTLESEY. UK 297

Table 6. Optically stimulated luminescence data and ages (with ± I o uncertaint y intervals) for samples from units F5, G4 andF6, section F, Funtharn's Lane East.

Samp le details Radioactivity data" Dosimetry data

Sample Depth Unit U Th K D cosm ic Total dose rate" Palaeodose" Age(m) (ppm) (ppm) ('X,) lI.lGy ka- J

) (~Gy ka- 1) (Gy) (ka)

Shfd030021 1.80 F6 1.5 6.6 1.1 165± 8 1876± 77 194 ± 6.0 103 ± 5.4Shfd030017 2.10 F6 0.8 3.7 0.6 159 ± 8 1211 ± 48 94 ± 2.1 77± 3.5Shfd030018 2.75 G4 1.2 4.8 l.l 146±7 0801 ±76 152±5.3 89 ± 5.0Shfd030019 3-85 G4 1.4 5.7 1.3 127±6 1962±90 142±5.0 73±4.2Shfd030020 5.60 F5 1.3 5.2 l.l 103 ±5 1726±78 157 ± 5.7 91±5.3

"Radioactivity data based on ill situ measurement by port able gamma spectro meter."Tota l dose rate incorp orate s modelled gamma contributions from sediments over- and underlying sand lenses sampled."Palueodose derived from weighted (by inverse var iance) mean of replicate aliqu ots, excluding those falling outside two standard deviations of

the unweighted mean.

previous temperate depo sits, or by the rruxmg ofprevious cold and temperate deposit s. There fore, thecool-phase assemblage can be regarded as being in situ,indicat ing that the shells analysed for AAR were notreworked from unit 3G deposits. This would appear tobe corroborated by the AAR data for B. tentaculataopercula, which suggest the possibility that unit FI isolder within MIS 7 than unit G3 . Within the gastropodshell data, the unit FI sample s have some of thehighest ratios within the MIS 7 cluster. The lack ofamino acid ratios for B. tentaculata shells from manyother sites of comparable age does not enable furtherdiscrimination for this species. Compared with theratio s obtained by Penkman (2005) for V. piscinalisfrom unit G3, and those obtained from Latton (Lewiset al., 2006), those obtained for specimens from unit F Ialso appear to suggest an older age, i.e. deposit ionwithin an earlier part of MIS 7.

The curve for MIS 7 has two temperate peaks(Bowen, 1999) and Schreve (200 I) has suggested thatdifferences in the mammalian assemblages at Aveleycould correspond to these. Result s from ongoinganalysis of samples from un it FI will provide a morecomplete record of the fossil assemblages for this coolphase , which may allow corr elation with other sites inthe region and recognition of the limb of the MIS 7interglacial peaks to which the cool phase possiblybelong s.

Figure 8 plots the percentages of flint, limestone and'other' lithologies recorded in samples from sectionsA-C, as well as in samples from units FI , F2, F4, F5,G4 and F6. The clast-lithology data indicate that unitF I is either part of, or is derived from, the limestone­rich gravel at the base of sections A-C, King's Dyke(Figs 3a, 3b, 8), to the south and east of section F. Thelimestone-rich gravel is interpreted to be no youngerthan early MIS 6 (based on an OSL age estimate of158± 14 ka (Shfd 9613I) on overlying sand s in sectionA) and probably no older than MIS 8 (based onD-alloisoleucine/L-isoleucine (All) data obtained byion-exchange chromatograph y from a Littorina shellfound in the limestone-rich gravel at section A and

presumed to be reworked from MIS 9 deposits)(Langford, 1999; Langford et al., 2004c). If thelimestone-rich gravel represents a cold-stage, braidedfluvial deposit (Langford , 1999; Langford et al., 2004c)rather than the channelized sediments deposited undercool conditions indicated for unit Fl , then it is olderthan FI and the AAR data for unit FI would constrainthe age of the lower, limestone-rich gra vel at sectionsA- C in King's Dyke to MIS 8. Furthermore, if thelimestone-rich gravel correlates with the Nar, Weltonand Welton Beck Members, i.e. other cold-stagedepo sits of the region , then an age of MIS 8 couldapply to these rather than the tentative MIS 6 ageassigned by Lewis (1999).

In units F4, F5. G4 and F6 the amounts oflimestonedecline and the flint component increases. This isespecially the case in unit F6, in which there is apersistent presence of nodular chalk and lenses ofreworked, reddened , medium to coarse sand, someof which are cryogenically deformed . In section A,King 's Dyke (facies assemblage AS; Langford, 1999;Langford et al., 2004c), lenses of reworked reddenedsand and gravel are younger than an OSL da te of158 ± 14 ka (Shfd 96I3I) and are associated with asynformational cryogenic horizon. The reddening isthought to result from temperate-climate weatheringprobably during MIS 5e, and therefore the associatedsynform ation al cryogenic horizon must post-date theIpswichian, i.e. it is Devensian . This is in concordancewith the previously published OSL date of l16± 16 ka(Shfd 96130) on sand s that pre-date the cryogenicdeformation at section C, King 's Dyke (Langfordet al., 2004c). The minimum age limit for units F4, F5,G4 and F6, therefore , is Devensian. The AAR data forunit G3 (Penkman, 2005) places a maximum age limitof late MIS 7 for units F4, F5 and G4. The OSL datafrom this study further constrain the ages of units F5,G4 and F6 to Early to Middle Devensian. Althoughit has not been possible to provide an age estimatefor unit F4, the transitional upper cont act with unitF5 suggests that these units were part of the sameerosional and aggradational sequence.

298 Ii 10. LANGFORD ET AL.

Units FI, F2 and F4 cut down to about -2 mOD.In addition, units G I, G 3, F2 and channel C (inBradley Fen, Fig. 4) also cut down to about - 2 mOD,indicating that at this location downcutting to thislevel is a feature common to the past three cold stagesand two interglacials. This downcutting to a commonlevel is in contrast to the terrace stratigraphy adoptedby the British Geological Survey (Horton et aI., 1974;Booth, 1982; BGS, 1984; Horton, 1989) and thatoutlined by Bridgland et al. (1991), but is in keepingwith the situation found by West et al. (1999) atSomers ham on the southern margin of the Fen Basinand by Smith (1999) in the upper Nene valley - see alsoLangford & Briant (2004).

Although this downcutting may not be related to afall in sea-level, there is evidence for Pleistocene marineconditions this far inland. The Woodston Beds(Horton et al., 1992) record an earlier marine trans­gression (MIS 9 or II) that penetrated further inlandthan Whittlesey, and the later (MIS 7 or 5e) MarchGravel (e.g. Keen et al., 1990), containing marinemacro- and microfauna, crops out nearby (Fig. 3a). Inaddition, marine macro- and microfauna have beenrecorded at sections A and C. King's Dyke (Langfordet al., 2004c). and estuarine ostracods have beenrecorded in unit G3 (J. Whittaker. pers. comm .• 2005).Therefore, the downcutting associated with unit F2may be related to a fall in sea-level. As it has beensuggested that high sea-levels persisted through theMIS 7-6 transition (Lefebvre, 1993; Bates et aI., 2000),unit F2 could have been deposited late in MIS 6.

The OSL dates reported here, although problematic,place units F5, G4 and F6 within the Devensian Stage.In addition to the comparison of unit F6 with facies ASat King's Dyke (Langford, 1999; Langford et al.,2004c), which is interpreted as being deposited underan arctic nival regime (cf. Bryant, 1983), the switchfrom seemingly channelized to a more laterally exten­sive mode of deposition from unit F5 to unit F6 invitescomparison with the better exposed sequences atTanholt Farm and Pode Hole (Chancellor &Langford, 1992; Briant, 2002; Briant et al., 2004a, b.2005). These have a comparable situation at somedistance from the main channel (Fig. 3c). At both thesesites, intercutting channel forms and overbank depositssimilar to units F5 and G4 pass upwards into domi­nantly horizontally bedded gravels (Chancellor &Langford, 1992; Briant, 2002; Briant et al., 2004a, b,2005). At Pode Hole, organic material associated withthese two distinctive facies associations suggests aclimatic control on this shift in sedimentology (Briantet al., 2004b, 2005). The channelized deposits areattributed to very early glacial conditions, before cli­mates reached their full harshness, possibly related to aless peaked hydrological regime. In contrast, the hori­zontal bedding is attributed to a river with a full arcticnival discharge regime (cf. Church, 1974), dominatedby a single snow-melt flood. It is possible that a similarchange was experienced at this site, but this is difficultto prove without palaeontology from units F5, G4 and

F6, and without more reliable OSL dating, using, forexample, recently developed single-grain measurementtechnology (e.g. Duller, 2004).

6. CONCLUSION

Age estimates for a late Middle and Upper Pleistocenesequence of sands and gravels with organic mud bedsat Funtham's Lane East, Whittlesey, eastern Englandhave been obtained. Initial impressions were that asingle cool/cold-phase sequence (units F l , F2, F4 andF5) truncated Pleistocene interglacial sediments (unitG3) deposited late in MIS 7. The AAR data suggest,however, that the organic muds in unit FI possiblywere deposited earlier in MIS 7 than the interglacialdeposits of unit G3. Therefore, the sequence of eventscould be: unit G3 truncated unit FI and unit F2 incisedboth units Fl and G3. As the OSL age estimatesindicate that units F5, F6 and G4 are Early to MiddleDevensian in age (MIS 5d-3), unit F2 must have beendeposited sometime between late MIS 7 and MIS 5d.

The floral and faunal assemblages of the organicmuds in unit Fl provide a consistent picture ofdeposition under cool conditions and therefore theassemblages can be regarded as in situ. Together withthe results of ongoing analyses of samples from theorganic mud beds, these assemblages could provideimportant new palaeoenvironmental information forthe early to middle part of the MIS 7 interglacial.

The Early to Middle Devensian age of units F5, G4and F6 indicated by the OSL dates allows the switch influvial style (from channelized to laterally more exten­sive) recorded by these units to be compared withsimilar sequences in River Nene 1st Terrace deposits atthe nearby sites of Tanholt Farm and Pode Hole(Briant, 2002; Briant et al., 2004a, b, 2005).

This paper demonstrates the importance of datingtechniques in distinguishing between cold-stage fluvialaggradations that are otherwise indistinguishablebased on alluvial architecture or sedimentological evi­dence. There have been recent and rapid advances withAAR dating (Penkman, 2005). Advances and refine­ment in the OSL measurement and the understandingof sediment bleaching within fluvial sediments (e.g.Olley et al., 2004) also have been made. Therefore, bypairing both techniques and sampling intensively,future research should be able to obtain good, absoluteand high-resolution chronological control spanning anumber of glacial-interglacial cycles. With such datingcontrol much more can be learned about how sedi­ment recycling, aggradation and erosion have operatedduring cold c1imates in lowland fluvial regimes.

ACKNOWLEDGEMENTS

The authors are grateful to Hanson Bricks plc,especially Chris Boyles and Rob Donnelly, for allow­ing continuing access to the site and induding aRIGS in the remediation of the site. The Geologists'

AGE ESTIMATES FOR DEPOSITS AT WHITTLESEY, UK 299

Association (Curry Fund), the Quaternary ResearchAssociation, NERC and English Heritage (ASLF) areacknowledged gratefully for providing funding forsome of the age estimates. Matthew Collins and thetwo reviewers are thanked for their comments on an

earlier draft, and the constructive comments of theEditor, Professor Richard J. Howarth, are acknowl­edged gratefully. Paul Coles is also thanked for hiscartographic skills in producing the figures associatedwith this work.

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Manuscript received 18 October 2005; revised typescript accepted 18 May 2006