Abstract

The climatic signal of Marine Isotope Stage (MIS) 11 iswell-documented in marine and ice-sheet isotopic records and is known tocomprise at least two major warm episodes with an intervening cool phase.Terrestrial records of MIS 11, though of high resolution, are often fragmentaryand their chronology is poorly constrained. However, some notable exceptionsinclude sequences from the maar lakes in France and Tenaghi Philippon in Greece.In the UK, the Hoxnian Interglacial has been considered to correlate with MIS11. New investigations at Hoxne (Suffolk) provide an opportunity to re-evaluatethe terrestrial record of MIS 11. At Hoxne, the type Hoxnian Interglacialsediments are overlain by a post-Hoxnian cold-temperate sequence. Theinterglacial sediments and the later temperate phase are separated by theso-called ‘Arctic Bed’ from which cold-climate macroscopic plant andbeetle remains have been recovered. The later temperate phase was depositedduring an episode of boreal woodland and is associated with the artefacts, adiverse vertebrate fauna and molluscs. New amino acid geochronological data andbiostratigraphical considerations suggest that the post-Hoxnian sequencecorrelates with late substages of MIS 11. The paper further investigates thecorrelation of the sequence at Hoxne with the palynological sequences foundelsewhere in Europe and adjacent offshore areas.

1. Introduction

In recent years, the complexity and structure of Marine Isotope Stage (MIS)11 has been a focus of research, in part driven by the similarity of orbitallyforced insolation changes during MIS 11 and the Holocene (Oppo et al., 1998;Droxler et al., 2003;Loutre andBerger, 2003;Ruddiman,2005;Wu et al.,2007). MIS 11 is therefore important as an analogue forcurrent and future climate scenarios. An important aspect of this work is howglobal temperature changes affect terrestrial biota, which can be addressedthrough the correlation of marine and terrestrial records (Tzedakis et al., 1997;Desprat et al., 2005;Wu et al., 2007). It has become increasinglyclear that there is a much more complex relationship between the oftenfragmented terrestrial record and the marine and ice records. The complexity ofMIS 11 has now been shown through marine and ice-sheet isotope records (e.g.Bassinot et al., 1994;EPICA Community Members, 2004)and long palynological records from marine cores (Desprat et al., 2005). These all indicate a sharp warming atca 425 ka with what appears to be a relatively stable climatethrough to ca 390 ka. Thereafter, the records arecharacterised by a series of warm–cold oscillations until ca 360 ka with the onset of more extreme cold.

Two conventions have been established for the naming of isotopic andtherefore climatic fluctuations within numbered isotope stages. MIS 11 has beendivided into substages 11c, 11b and 11a (e.g.Tzedakis et al., 2001). However, in other records (e.g.MD900963,Bassinot et al., 1994) amore complex pattern can be seen with additional warm–cold oscillation(Fig. 1). Therefore, an alternative system identifies negative andpositive isotopic events, which are numbered using a decimal system(Imbrie et al., 1984;Bassinot et al., 1994;Desprat et al., 2005). This hasthe advantage of allowing additional isotopic events to be incorporated. Thesetwo conventions are different because the first denotes periods of time, whereasthe second identifies specific isotopic events, and therefore the terminologyshould not be used interchangeably. An additional short-lived warm episode hasbeen recognised in some records (e.g.Prokopenko etal., 2001) and referred to as 11e, but this is not prominentin either SPECMAP orMD900963. The structure and terminology for MIS 11 is usedin this paper are shown inFig.1.

Only recently has it been possible to recognise these complex changes inthe terrestrial record, particularly in southern Europe where pollen sequenceshave enabled correlation with marine isotope substages (Reille and de Beaulieu, 1995;Tzedakis et al., 1997;de Beaulieu et al., 2001;Desprat et al., 2005;Tzedakis et al., 2006). In Britain, suchsequences have not been found, and most palynological records are of relativelyshort duration (cf.Thomas, 2001).Although there is now widespread agreement that the Anglian glaciationcorrelates with MIS 12 and the Hoxnian Interglacial broadly with MIS 11(Bridgland, 1994;Bowen, 1999;Rowe etal., 1999;Grün andSchwarcz, 2000;Preece andPenkman, 2005;Preece et al.,2007), individual substages of MIS 11 have not beenconvincingly identified (but seeSchreve(2001a, b)). The climatic record ofthe Hoxnian has been largely based on palynology (West, 1956;Turner,1970), but it is still not clear whether the Hoxnianencompasses the whole of MIS 11 or just one substage. One site that has thepotential to provide information of this kind is the site of Hoxne, Suffolk, UK(TM176767), where recent fieldwork has shown a more complex sequence of climatefluctuations that may be attributable to marine isotope substages.

The sequence at Hoxne forms the stratotype of the Hoxnian Interglacial(Mitchell et al., 1973) which,based on the analysis ofWest (1956)of the lacustrine sediments, spans pollen zones HoI-III. However, thestratigraphy also includes an important series of sediments that post-date thislacustrine sequence. These are of particular importance because they containabundant palaeoenvironmental evidence and also a rich Palaeolithicarchaeological record (Singer et al.,1993). Despite the long history of research at Hoxne, itremains unclear how the primary context human industries relate to theenvironmental record and the correlation of this part of the succession with themarine isotope sequence is uncertain (Bowen et al.,1989;Gladfelter et al.,1993;Turner and West1994;Ashton et al.,1995;West and Gibbard,1995; Grün and Schwarcz 2000;Schreve 2001a, b). Thecurrent research has focussed on these issues as part of a wider investigationof human presence during MIS 11 under the auspices of the Ancient HumanOccupation of Britain Project (Stringer and AHOBProject Members, 2003;Ashton etal., 2006).

Since the discovery at Hoxne of Lower Palaeolithic handaxes byFrere (1800), the site has beenthe subject of several investigations, providing often radicalre-interpretations of previous work. This work has focussed on two pits, eitherside of the Hoxne to Eye road (Figs. 2 and3). The Old Brick Pit to the east of the road was the subjectof the earliest investigations, and these were supplemented by work in theOakley Park Pit when this was first opened in the mid-19th century. The two pitswere opened for gravel and clay extraction from the infillings of a basin thatis now located on the interfluve between the Goldbrook stream and River Dove,which flow into the River Waveney. The current research has involvedinvestigation of archive material together with cutting and sampling of keysections (between 2000 and 2003;Ashton et al.,2003) and has enabled a re-evaluation of thepalaeoenvironmental and archaeological evidence from the site.

2. Previous interpretations

The basis for much of our understanding of the site comes from the work ofClement Reid (Evans et al., 1896). Heprovided detailed and clear descriptions from boreholes and open sections of allthe major sediment units and undertook the first palaeobotanical investigationsat the site. Reid's work demonstrated that a basin, formed in the surfaceof the ‘boulder clay’ (till), was infilled with interglaciallacustrine sediment (Bed E). Drying out of the lake was indicated by theformation of peat (Bed D), prior to the re-establishment of the lake under coldconditions (‘Arctic Bed’: Bed C). These lacustrine sediments wereoverlain by a fluvial, shelly, gravel (Bed B), and the artefact-bearing sedimentor ‘Palaeolithic Loam’ (Bed A). The latter extended beyond theconfines of the basin (Figs. 4 and5).

In the 1950s, detailed fieldwork was undertaken byWest (1956), who also examined the palynologyof the lake sediments. West argued for important modifications to thestratigraphy offered by Reid. Other than the addition of a cold lacustrinesediment (Stratum F) above the till (now Stratum G), he argued that the lowerpart of Reid's Bed A had been misinterpreted and was in fact decalcifiedBed (now Stratum) E. This implied that the human occupation of the site wasassociated with the lacustrine sediments of the newly defined HoxnianInterglacial, rather than in the later sediments at the site (Figs. 4 and 5). No archaeology wasdiscovered in Stratum E during West's work, other than two flakes fromsections 40 and 100 on the west of the Oakley Park Pit (West, 1956;Fig.3). However, it is clear from re-examination of the sectiondrawings and the heights of the objects in comparison to those found in the1970s and during the recent excavation that they were actually recovered fromsediments overlying Stratum D.West(1956) defined pollen zones at Hoxne, which were subsequentlymodified following work on the more complete sequence at Marks Tey, Essex. TheHoxne lake sediments (Strata E–D) were assigned to pollen zones HoIthrough to HoIIIa, with HoIIIb and HoIV being absent from the sequence(Turner, 1970).

Major archaeological excavations by the University of Chicago in the 1970s(Singer et al., 1993) in theOakley Park Pit and in the field to the west of this pit (Fig. 3), provided the first properly excavatedartefact assemblages from the site and led to further re-interpretation. It wasargued that there were two significant phases of human occupation. The first or‘Lower Industry’ consisted of primary context handaxes, cores andknapping debitage in association with a temperate faunal assemblage, andoccurred in a single horizon towards the base of Stratum C. A new bednomenclature was introduced for a sequence of fluvial, alluvial and solifluctionsediments (Beds 1–9) that lie above Stratum D (Gladfelter, 1993). These had formerly been attributed toStrata B and A. The key units were a chalky gravel (Bed 4), which was overlainby a fine-grained alluvial sediment (Bed 5) and a further gravel (Bed 6). The‘Upper Industry’, consisting of pointed handaxes, flake tools, coresand debitage in variable condition, was recovered from the top of Bed 5 and insecondary context in the lower part of Bed 6. The ‘Lower Industry’was associated with a temperate vertebrate fauna. However, this conflicts withthe palaeobotanical evidence of Reid (inEvans etal., 1896) andWest(1956) who attributed Stratum C (‘Arctic Bed’) toa cold stage.

The dating of the site and its correlation with the marine isotope recordwas also unclear from this work (Gladfelter et al.,1993;Turner and West,1994). Amino acid D/L ratios onValvata shells from Stratum E suggested a correlationof the lacustrine sequence with MIS 9 (Bowen et al.,1989), with the implication that either there is a majorhiatus between the Lowestoft Till (MIS 12) and the lake beds, or that theglacial sequence dates to MIS 10. Dating of the overlying Lower Industry(interpreted as lying in Stratum C) was assessed through thermoluminescencedating on two burnt flints, which yielded a mean date of 210±20 ka, suggesting an MIS 7 age. However, the dosimeter readings(taken several years after the excavation) were from different locations andalso demonstrated considerable variation across the site. This suggested thatthere were likely to be considerable errors in the TL age estimates(Bowman, 1993). Initial ESR dateson enamel from two horse (Equus ferus) teeth alsoassociated with the Lower Industry gave an average age of 319±38 ka, suggesting that Stratum C was attributable to MIS 9(Schwarcz and Grün, 1993).However, subsequent remodelling of the data has suggested an MIS 11 age withdates of 404±33/42 and 437±38 ka (Grün and Schwarcz, 2000). Finally,assessment of the mammalian fauna that is associated with the Lower Industry andfrom Bed 4 has been argued to show marked similarities with that from Swanscombe(Stuart et al., 1993), and bothfaunal assemblages have been attributed to the first post-Anglian warm stage andassigned to the Swanscombe Mammal Assemblage Zone (MAZ) bySchreve (2001a, b).

3. Stratigraphic re-interpretation

A revised stratigraphy is proposed, based on the curent re-investigation ofthe site that focussed on the relationship between Stratum C and the sedimentscontaining the Lower and Upper Industries (Fig.5;Table1). This has resolved theconfusion inSinger et al. (1993) intheir varied interpretations of the relationship between Stratum C and Bed 4(seeBridgland, 1994;Turner and West, 1994). The stratigraphicinterpretations and nomenclature ofSinger et al.(1993) can now be reconciled with that ofWest (1956). This paper uses the Reid/Westnomenclature, with some modifications based on the current research(Table 1).

Fig. 3 shows the location of therecently excavated sections (Areas I–VII) and boreholes. The mostsignificant information comes from Areas III and IV. The latter was a narrowtrench, previously excavated in 1978 that was re-opened and widened to allowdetailed investigation and sampling. The trench linked the locations of theLower and the Upper Industries in the field to the west of the Oakley Park Pit(Figs. 3 and 6). Thissection is critical to understanding the relationship of the Upper and LowerIndustries to Stratum C and Beds 4–6.

Stratum E was exposed at the base, overlain by a near-continuous horizon ofStratum D, which reached a maximum thickness of 35 cm at thesouthern end, but thinned to <1 cm black stained clay atthe northern end (Fig.6). Overlying this was a thinhorizon of Stratum C, 50-cm thick over most of the exposure, but cut out at thesouthern end by fine sand and chalky gravel of Stratum B.

Above this, a concave-up erosional lower bounding surface is incised intoStrata C and B, forming a broad (>30 m), shallow (ca 2 m) channel feature, infilled with bedded sands, silts and clays.These are interpreted as a lateral accretion facies and indicate lateralmovement to the north. The orientation of bone long axes and their distributionwith that of the artefacts also suggest a fluvial deposit and indicate aNE–SW orientation of the channel. This channel feature was not recognisedby previous workers and the sediment was thought to be part of the lacustrinesequence. It is here assigned to Stratum B because it is a fluvial deposit andis referred to as Stratum B1. The underlying chalky gravel is therefore assignedto Stratum B2 (Fig. 5).

Stratum A was sub-divided into A1 and A2 byWest (1956). As a result of the current work, Stratum A2 isfurther sub-divided into A2(i–iii). Stratum A2(iii), a sandy clay unit, isinterpreted as alluvium. Above this, a coarse flint gravel with a sandy claymatrix (Stratum A2(ii)) and a series of laminated sands and silts (A2(i)) arecapped by gravely sands (Stratum A1). Post-depositional disturbance anddownslope movement have affected the uppermost part of the succession.

4. Palaeoenvironmental context for human occupation atHoxne

The sedimentary succession at the site contains palaeoenvironmental dataindicating a fluctuating climate. The depositional environment, vegetational andfaunal character, and thermal conditions can be considered for each stratum inturn.

5. Amino acid geochronology

Amino acid racemization (AAR) analyses were undertaken on 12Bithynia tentaculata opercula using the methodsoutlined inPenkman (2005) andPenkman et al. (2008). The methodis based on the extent of protein decomposition, which increases with time,although there is an increased rate of breakdown during warm stages and aslowing in cold stages.

The samples were from Stratum E (NEaar 0498–0500, 2446–2447)and Stratum B2 (NEaar 3143–3150). The results show levels of proteindecomposition higher than those from sites correlated with MIS 9, but lower thanthose from sites of pre-Anglian age (Fig.7;Table 3). Furthermore, thelevels of protein decomposition are similar to those from sites correlated withMIS 11, including Elveden (Ashton et al.,2005), Beeches Pit (Preece etal., 2007), Barnham (Preece andPenkman, 2005), Clacton (Penkmanet al., in press), Woodston and Swanscombe (Penkman, 2005). This indicates an age for Hoxnebetween the Anglian (MIS 12) and early MIS 9. The opercula samples from StratumE tend to have slightly greater protein decomposition than those from Stratum B2and less degraded protein than found in opercula from the Lower Freshwater Bedat Clacton, which was deposited early in MIS 11 (Bridgland et al., 1999).

The opercula from Stratum B2 have some of the lowest levels of proteindecomposition determined from MIS 11 sites. This therefore suggests an age forthe opercula between mid-MIS 11 and early MIS 9. While the values obtained fromthe opercula from Stratum B2 generally show higher levels of proteindecomposition than those obtained from the MIS 9 sites analysed, the separationbetween the Stratum B2 samples and those deposited early within MIS 9 is small.As so little decomposition occurs in the cold stages, and because of the extentof natural variability in biological samples, it can be difficult todiscriminate the end of one warm stage from the beginning of the next. Althoughan age late in MIS 11 is more likely, it is not possible to rule out an earlyMIS 9 age, given the level of resolution currently obtainable from thetechnique.

6. Biostratigraphy

The mammalian fauna from Strata B1 and B2 also provides an indication ofage. Three species are of possible biostratigraphic significance. The mostimportant of these isMicrotus (Terricola) cf.subterraneus. Although it is widespread in Europetoday, it appears to have been absent in Britain after MIS 11 (Parfitt, 1998). Of particular significance isits absence from the very rich faunal assemblages from Cudmore Grove, Grays andPurfleet, all of which have been attributed to MIS 9 and from any younger sites(Bridgland, 1994;Schreve et al., 2002).

Of lesser significance is the presence ofTrongontheriumcuvieri andTalpa minor. Although theyare thought to have become extinct after the Hoxnian in Britain, and possiblythe Holsteinian in Europe, their remains are so rare that any apparent absencein sites attributed to MIS 9 or later might be due to insufficientsampling.

7. Discussion

Both the amino acid geochronology and the biostratigraphy, together withthe reassessment of the ESR dates (Grün andSchwarcz, 2000; see above), suggest that Strata B1 and B2 aremost likely to be attributable to MIS 11. This therefore implies that theunderlying Strata E and D (Hoxnian) date to the first prolonged temperatesubstage in MIS 11, and that Strata C and B are later cold and warm substages,respectively, within MIS 11.

This correlation of the sequence at Hoxne with substages of MIS 11 haswider implications for its correlation with other terrestrial sites in the UKand further afield. Although the full Hoxnian Interglacial sequence is not foundat Hoxne, a complete succession is found at Marks Tey (Fig. 2), where pollen zones HoI-IV arerepresented (Turner, 1970).Furthermore, the palynology suggests that there is no evidence for a hiatusbetween the Anglian till and the lacustrine sediments at either Hoxne or MarksTey. The Hoxnian record at Marks Tey is an overlapping composite sequence fromtwo main cores. The interpretation of these cores is of a continuous temperatesequence through the Hoxnian without any indication of a cold event. Togetherwith the evidence from Hoxne of a later MIS 11 cold substage, this suggests thatthe Hoxnian Interglacial can be equated with the first major temperate substagewithin MIS 11.

Palynology has also been used to correlate the lacustrine deposits at Hoxneand Marks Tey with the organic channel-fills at Clacton and Tillingham, whichform part of the Thames/Medway sequence (Fig.2). At Clacton, the Freshwater Beds and Estuarine Bed(Pike and Godwin, 1953) have beencorrelated with HoIIb–HoIIIb (Kerney,1971;Bridgland et al.,1999), while at Tillingham, the silty sands and organic siltsare attributed to HoIII (Roe, 2001)(Fig. 8). On the basis of their lithology, terrace stratigraphy andmolluscan assemblages (Bridgland,1994;Roe, 2001;Preece et al., 2007), both thesesites are argued to be part of the same terrace aggradation as the Lower Gravel,Lower Loam and Middle Gravels at Swanscombe (Fig.2). All three sites record the immigration of the‘Rhenish’ fauna, probably in late HoII (indicating a confluence ofthe Thames with the Rhine). Furthermore, the presence of estuarine molluscsindicates a high sea-level stand, argued from the evidence at Clacton andTillingham to occur during HoIIIb (Fig.8).

These correlations therefore suggest that the sequences at Clacton,Tillingham and the Lower Gravel to Middle Gravels at Swanscombe can also beattributed to the first temperate substage of MIS 11. This is at variance withthe interpretation of Swanscombe proposed bySchreve (2001a, b) who attributed theMiddle Gravels to a later temperate substage within MIS 11.

The interglacial sequence at Quinton in the West Midlands has beeninterpreted as spanning the entire Hoxnian Interglacial on the basis of itspalynology (Horton, 1989). However,evidence from the Coleoptera indicates a more complex climatic picture with a‘cold interlude’ occurring during the latter part of theinterglacial (Coope and Kenward,2007). The beetle fauna from this ‘cold interlude’ isvery similar to that of the ‘Arctic Bed’ at Hoxne and suggests apossible correlation. Alternatively, since the uppermost samples of the Quintonsequence, attributed to the onset of the succeeding glacial, also yielded asimilar suite of cold-adapted beetle species, correlation of the Hoxne ArcticBed with these uppermost samples at Quinton is a possibility. The beetleevidence for the ‘cold interlude’ at Quinton is at odds with thepalynological evidence which “does not appear to show any response to thiscold episode” (p. 3284). A similar discrepancy in the evidence fromStratum C at Hoxne has been accounted for by reworking of temperate pollen intoStratum C (see above andTurner,1970). A comparable situation may have occurred at Quinton wherepollen of temperate character is reworked from the underlying deposits and foundin conjunction with an autochthonous coleopteran assemblage indicative of coolerclimatic conditions. A re-evaluation of the palynology of the Quinton successionmay help to resolve these problems associated with correlation of the Hoxne andQuinton sequences.

In Europe, significant advances have been made over the last decade inrelating the vegetational record from long, continuous sequences from sites insouthern Europe to the marine isotope record. Key to this success has been coreMD01–2447, near the northwest coast of the Iberian Peninsular(Fig. 2), where the marine isotoperecord can be directly compared to pollen that reflects vegetational changesinland (Desprat et al., 2005). Thiscore is argued to span the last 426 ka and has been comparedto other continuous or composite palynological sequences from Tenaghi Philipponin Greece, and Velay maar sites (Praclaux, Le Bouchet and Ribains;Fig. 2) in France (Reille and de Beaulieu, 1995;Tzedakis et al., 1997, 2001,2006). All these sequences show a similar pattern of vegetationand climate change with successive interglacial/glacial cycles. These can berelated to records of global climate change from deep-sea cores (Oppo et al., 1998;McManus et al., 1999), ice cores (Petit et al., 1999;EPICA Community Members, 2004) and the changes in thebiogenic silica content in the sequence from Lake Baikal (Prokopenko et al., 2001) (Fig. 9). Absolutedates from the terrestrial sites support these correlations with⁴⁰Ar/³⁹Ar dates on trachytictephra in deposits of the third interglacial at Velay (Le Bouchet Interglacial)suggesting an MIS 7 age (de Beaulieu et al.,2001), and palaeomagnetic analyses and U-series dates on thesequence at Tenaghi Philippon providing further tie-points to the marine isotoperecord (Tzedakis et al., 1997,2006).

For core MD01–2447, the first part of MIS 11 has been characterisedas showing a long, marked warm period from 426 to 394 kacalled the Vigo Interglacial, which has been correlated with the PraclauxInterglacial at the Velay sites. The Praclaux Interglacial has also been arguedto be similar to the Holsteinian palynological records of northern Europe(Reille and de Beaulieu, 1995;Turner, 1998;de Beaulieu et al., 2001;Desprat et al., 2005; though also seeGeyh and Müller, 2005;Geyh and Müller, 2006;Scourse, 2006) and to the HoxnianInterglacial (Turner, 1998). Theevidence from Hoxne would support this interpretation. Key features of theHoxnian pollen records are the early occurrence ofPicea,the development of mixed oak forest followed by a marked phase ofAbies, and the occurrence ofPterocarya in the later part of the interglacial. Wetherefore conclude that the Hoxnian, Holsteinian, Vigo and Praclauxinterglacials all correlate with the first part of MIS 11.

In the later part of MIS 11, three cold/warm cycles have been recognised incore MD01–2447. These cycles are similar to a series of short-livedcold/warm phases in the Velay sites, which occur after the Praclaux Interglacialand prior to the Bargette cold episode of MIS 10. At Velay, twostadial/interstadial cycles have been named (Chaconac stadial/Jagonas 1interstadial and Coucouron stadial/Jagonas 2 interstadial).

During the stadials, the pollen from core MD01–2447 indicates thateither heath or dry grassland dominated the local vegetation, while at Praclauxthe environment was open with an abundance of steppe taxa. The interstadialsindicate the re-emergence of forest cover with some deciduous woodland. In coreMD01–2447,Pinus andQuercusare prominent, with lesser quantities ofCarpinus andAbies. Pine, however, was argued to beover-represented due to better dispersal ability and buoyancy. The upland siteof Praclaux is characterised during these interstadials by the dominance ofPicea, but also by the presence ofCarpinus,Quercus,Buxus,Fraxinus andTilia. It is suggested that the presence ofCarpinus (up to 10%) may indicate that there was agreater abundance of this taxon at lower altitudes (Reille and de Beaulieu, 1995).

How far north this deciduous woodland stretched is difficult to gauge, dueto the paucity of sites that clearly correlate with these phases. Although thereis no unequivocal palaeobotanical information on the vegetation at Hoxne fromStratum B, the mammalian fauna includes obligate woodland species (e.g. beaver,fallow deer and macaque) providing strong evidence that there must have beensome forest cover.

The evidence from Hoxne, therefore, suggests that the ‘ArcticBed’ of Stratum C and the temperate phase of Stratum B correlate with oneof the cold/warm cycles in the later part of MIS 11, although because of thehiatus between Stratum D and C, it is not clear to which cycle they should beattributed. The problem of recycled pollen in both Strata C and B also makes itdifficult to reconstruct their vegetation histories, other than the survival ofleaves of dwarf birch and dwarf willow, in Stratum C. However, coreMD01–2447 and Praclaux provide clues about the vegetation that might havebeen present at Hoxne, despite differences in latitude, and in the case ofPraclaux in altitude (1100 m, compared to Hoxne at 30 m) between the sites.

Elsewhere in northern Europe, there is little agreement on the correlationof post-Holsteinian temperate events. Most authorities would now agree that theHolsteinian is attributable to MIS 11. If the interpretation favoured here iscorrect, that the Hoxnian and Holsteinian both correlate with the firsttemperate event of MIS 11, then this still leaves the question of whether laterMIS 11 interstadials can be recognised in northern Europe.

One of the best Holsteinian pollen records comes from the lacustrinesequence at Ossowka in eastern Poland (Nitychoruk etal., 2005;Fig. 2).This sequence has been constrained by TL dates of ca 430 ka atthe MIS 12/11 boundary, and the estimation of the duration of the sequence iscalculated from annual laminations in the interglacial part of the record. Likethe pollen sequences in southern Europe, after a stable temperate climate of anestimated 35–39 ka (the Holsteinian), there follows aseries of climatic oscillations with open, cold vegetation alternating with aboreal environment dominated by pine. If the estimated timescale ofNitychoruk et al. (2005) iscorrect, this would imply that the later temperate events in MIS 11 arecharacterised by boreal pine forest in central, northern Europe.

Correlation with other north European sites (e.g. Bilzingsleben andSchöningen) is as yet uncertain due to the varying interpretations that arecurrently put forward (cf.Mania,1995;Urban, 1995,2007;Turner,1998;Bridgland et al.,2006). However, it is worth noting some of the similaritiesbetween the Channel II, Level 4b deposits at Schöningen to Stratum B atHoxne. Level 4b, which includes most of the spears, is assigned to the ReinsdorfB Interstadial (Kolfschoten, 1993).The fauna is dominated by horse and the pollen indicates boreal forestpredominantly of pine, but with some spruce, birch and larch (Urban, 2007).

The differences in the vegetational records from southern to northernEurope would suggest quite a marked climatic gradient between 40° and50° latitude during the later interstadials of MIS 11. A similar pattern hasalso been identified for MIS 5, where the vegetational records for substages 5cand 5a at Grande Pile (France;Woillard,1978) show deciduous woodland, whereas those further north inthe Netherlands, Germany, Denmark and, to a lesser extent, the UK show that thevegetation was dominated by boreal forest (Behre,1989;Turner,1998). Turner suggests that either the phases were too short toallow for the immigration of thermophilous trees, or that there was a realclimatic barrier to the spread of deciduous woodland to the north. This may berelated to circulation patterns in the North Atlantic Ocean, with a southerlyshift in the Gulf Stream, leading to even cooler temperatures in northernEurope. There was also likely to have been a west–east gradient inclimate;Zagwijn (1990) has suggestedthat summer temperatures during substage 5c showed a marked decrease from thesouthwest to the northeast in Europe, unlike substage 5e, where the gradient wasfrom southeast to northwest. Although during substage 5c there seem to be fewvegetational differences between sites in Britain and those further east, whereforests of pine, birch and occasionally spruce were dominant (Behre, 1989), it has been suggested that Britainhad a more continental climate with cold winters, but warm summers(Coope, 1977). If this can beused as an analogue for the late MIS 11 interstadials, then Hoxne might have hadvegetation of boreal forest, but with warm summer temperatures. This conclusionis supported by the faunal evidence from Stratum B at Hoxne.

8. Conclusions

Hoxne is a key site for understanding the Middle Pleistocene sequence ofnorthern Europe and understanding how this correlates with sequences fromsouthern Europe. The site provides a stratigraphic sequence that includes twopost-Anglian temperate phases. The first of these (the Hoxnian) is argued tocorrelate with the first sustained temperate phase in MIS 11 between ca425–395 ka. The second, as represented by Stratum B,is correlated with a later interstadial in MIS 11. These two temperate phasesmay be tentatively correlated with substages 11c and 11a, respectively, whichare evident in the SPECMAP stack (Imbrie et al.,1984;Tzedakis et al.,2001). Alternatively, the acme of the Hoxnian may becorrelated with isotopic event 11.3 and Stratum B with either event 11.23 or11.1 ofBassinot et al. (1994). Theintervening cold episode, represented by Stratum C is correlated with marineisotope substage 11b and may equate to either event 11.24 or 11.22 in the LowLatitude Stack (Bassinot et al.,1994).

Lithostratigraphy, palynology and molluscan data suggest that the sequencesat Clacton, Tillingham and the Lower Gravels to Middle Gravels at Swanscombe canbe attributed to the first temperate event (the Hoxnian). Comparison with thecontinuous palynological records from southern Europe suggests that the Hoxniancorrelates with the Vigo Interglacial of northwest Iberia, the PraclauxInterglacial of the Velay maars sites and to the Holsteinian Interglacial ofnorthern Europe. Stratum B is argued to correlate with either the Jagonas 1 or 2Interstadial from the Velay sites. Reconstruction of the vegetation during theseinterstadials suggests that in northern Europe they were dominated by apine-birch boreal forest, which supported a diverse large mammalfauna.

Traditionally, these faunas have been interpreted as indicating fullyinterglacial conditions. The evidence from Hoxne, therefore, clearly indicatesthat similar faunal assemblages can also occur in environments of interstadialcharacter. This has implications for the biostratigraphical subdivision oftemperate episodes in the Middle Pleistocene based on mammalian evidence (cf.Schreve, 2001a, b).

Hoxne is also an important site for understanding the Lower Palaeolithicoccupation of northern Europe. The archaeological assemblages at Hoxne can nowbe shown to date to an interstadial that has not been previously recognised inBritain. Although there are several MIS 11 sites where fine-grained, organicsediments allow detailed environmental reconstruction, they have all suggestedthat human occupation was associated with deciduous woodland in fully temperateclimate (cf.Ashton et al., 2006). AtHoxne, however, humans can be demonstrated to have lived in a boreal forestenvironment and probably with distinctly cooler winters. This prompts questionsabout the technologies required (clothing, shelters, control of fire) orphysical adaptations needed in order to survive these cooler environments. Therange of environments that humans inhabited during the Middle Pleistocene haslong been the subject of debate (Gamble,1987, 1992;Roebroeks et al.,1992). Hoxne now adds to the small list of sites from theLower Palaeolithic where the human habitat can be reconstructed in more detailand indicates human adaptability to a range of different habitats.

Acknowledgements

We would like to thank the British Museum, the British Academy and the Societyof Antiquaries for funding the fieldwork, and NERC, English Heritage and theWellcome Trust for funding the AAR analyses. Thanks are also due to Andrew andMelanie Banham, Peter Whatling and Suffolk County Council for access to the sites.We are grateful to Robert Symmons and Silvia Bello for producing the illustrationsand to Richard Preece, Roger Jacobi, Charles Turner and Matthew Collins for helpfuldiscussions. The constructive comments of the referees is also acknowledged. Thispaper is a contribution to the Ancient Human Occupation of Britain project, fundedby the Leverhulme Trust.

References