Late Middle Pleistocene temperate and associated events in lowland England

Journal Pre-proof Late Middle Pleistocene temperate and associated events in lowland England P.L. Gibbard, R.G. West PII:

S1040-6182(19)30942-5

DOI:

https://doi.org/10.1016/j.quaint.2019.12.017

Reference:

JQI 8097

To appear in:

Quaternary International

Received Date: 18 October 2019 Revised Date:

18 December 2019

Accepted Date: 21 December 2019

Please cite this article as: Gibbard, P.L., West, R.G., Late Middle Pleistocene temperate and associated events in lowland England, Quaternary International, https://doi.org/10.1016/j.quaint.2019.12.017. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Ltd and INQUA. All rights reserved.

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Late Middle Pleistocene temperate and associated events in lowland England P.L. Gibbard1,*, R.G. West2 1Scott

Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, England. 23A Woollards Lane, Great Shelford, Cambridge CB22 5LZ, England. *Corresponding author: P.L. Gibbard. Scott Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, England. E-mail: [email protected] (P.L. Gibbard ) Abstract This article examines the interpretation and implications of certain coniferdominated pollen assemblages recorded in lowland England, at sites glaciated during the Middle Pleistocene Wolstonian Stage. Such assemblages indicate the absence of severely cold-climate during a predominantly cold period and the presence of northern temperate boreal-type forest. The unambiguous stratigraphical position of the sequences provides evidence of climatic change during the late Middle Pleistocene. Nine sequences are considered, six in the English West Midlands, and three in eastern England. Evidence for temperate climate, and at some, subsequent coldclimate (periglacial) conditions is present within deposits pre-dating Wolstonian-age glacial deposits. In the Midlands, Wolston Formation glacial sediments overlie deposits of a pre-existing river system, the Baginton Formation. The latter accumulated during the transition from boreal to subarctic conditions. Evidence is based on sequences at Mathon, Waverley Wood, Brandon, Brooksby, Witham-onthe-Hill, High Lodge and Barnham. Since the Wolstonian glaciation occurred during the Late Wolstonian Substage (= Late Saalian, Marine Isotope Stage [MIS] 6), the Baginton Formation must span the MIS 7/6 boundary. Reinterpretation of the sequences indicates that the temperate continental climate interval, termed here the Waverley Wood temperate event, potentially represents the latter part of MIS 7 (Substages 7a-c, or 7e). This correlation is supported by comparison with sites on the near Continent. The implications of these conclusions are presented. Keywords: Wolstonian, MIS 7/6, Baginton Formation, glaciation, interglacial, Picea, cold-climate

1. Introduction

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The Middle Pleistocene geology of lowland eastern England has been the subject of research for over two centuries, and much is now known about the detailed evolution of the region. Yet knowledge of events during certain intervals have remained obscure. The major interval about which only fragmentary information has been available until relatively recently has been that during the late Middle Pleistocene Wolstonian (= Saalian) Stage. However, detailed recent research has cast new light on this critical period. The purpose of this article is to consider the interpretation and implications of certain conifer (Pinus-Picea) pollen assemblages which have been recorded in a number of Quaternary sites in parts of lowland England associated with glaciation during the Wolstonian Stage. Such assemblages may be significant in indicating the absence of severely cold-climatic conditions during predominantly cold stages and the presence at a particular time of a northern temperate type of forest or woodland. Sometimes they are related to a clear vegetational history, as for example where they occur towards the end of an interglacial (temperate) stage (as in the Hoxnian-age sequence at Quinton, Birmingham: cf. West, 1980); at other times they occur in sediments not so related, for example in fluvial sequences, interbedded with sands or gravels. In the former examples, the stratigraphical position of the assemblages may be clear; in the latter, there is uncertainty. It is the latter occurrence of assemblages which concern us here, in order to support a discussion of times of presence of coniferous vegetation in the late Middle Pleistocene, and of any relation these may have to times of climatic amelioration on the Continent. The stratigraphical nomenclature follows Mitchell et al. (1973), modified as noted above. Eight sequences are considered in this article, five of which are located in the West Midlands, the remaining three in eastern England (Figs 1, 2).

1.1. The Wolstonian Stage: dating and its Marine Isotope Stage equivalents The term Wolstonian was originally proposed for the 'glacial' (cold) stage intermediate between the Hoxnian (=Holsteinian) and Ipswichian (=Eemian) 'interglacial' temperate stages (Shotton and West, 1969; Mitchell et al., 1973). The definition of the Wolstonian Stage was based on the glacial sequence (Wolston Formation) of the English Midlands by Shotton (1953), the unit-stratotype sited close to Wolston, Warwickshire. However, Shotton's views were subsequently questioned, particularly by Sumbler (1983 b) and Rose (1987), who suggested that the Wolston glacial sequence might belong to the Anglian Stage. These authors implied that in this case the term Wolstonian would be a synonym for Anglian and therefore it should be dropped. Shotton (1976; 1983 a, b, 1989) noted two interglacial localities in the Birmingham area, Nechells and Quinton which include fossiliferous sediments firmly correlated to the Hoxnian Stage, overlain by glacigenic deposits. These post-Hoxnian glacigenic deposits must also pre-date the Ipswichian Stage since they lie outside the maximum limit of the Devensian (= Weichselian) glaciation in the English Midlands. The details of these sites are not questioned. Regarding the definition of the term Wolstonian, Gibbard and Turner (1988) discussed the retention of the name of the chronostratigraphical stage, i.e. a time

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period, not solely a glaciation, and they formally-defined an unambiguous boundary parastratotype for the base of the Wolstonian Stage in East Anglia (Gibbard and Turner, 1990, p. 40), as follows: at Marks Tey brickpit, in Essex (Turner, 1970) the Hoxnian-Wolstonian Stage boundary, being recognised on palynological evidence (Marks Tey III, but see also Marks Tey II). The end of the Wolstonian Stage is the base of the Ipswichian Stage as defined at the Ipswichian boundary and unit stratotype at Ipswich, Suffolk (at 5.90 m in borehole 3 by West, 1957). Whilst there have been a number of studies of intervals that fall broadly into the Wolstonian time period, few have been related to the chronostratigraphical timescale for the stage in a precise fashion, apart from being correlated, or rather compared, to the marine isotope stage (MIS) record in general terms (cf. Jones and Keen, 1993, ch. 7). On the basis of the numerical dating and correlations currently available, the Wolstonian Stage lasted approximately 260 ka overall (Gibbard et al., 2018). Division of the Wolstonian Stage (Table 1) into Early, Middle/Mid- and Late substages, based broadly on the equivalent MIS-cycle divisions; MIS 11b–10, MIS 9– 8 and MIS 7–6, respectively, was proposed by Head and Gibbard (2015). Events within the substages are identified using the same climatostratigraphical approach as that for the Devensian / Weichselian Stage. This terminology is applied herein. Most recently the reinvestigation of the Fenland (Gibbard et al., 2009, 2012, 2013, 2018) has reinforced Shotton’s conclusions regarding the age of the Wolston and underlying Baginton formations in the Midlands and equivalent deposits in eastern England (Table 1). This research has demonstrated that the Fenland was glaciated during the Wolstonian Stage. Indeed the age of the Tottenhill glaciation advance to the maximum glacial limit Skertchly Line complex in Fenland has been shown to have occurred during the Late Wolstonian Substage (i.e. Late Saalian Substage, ~MIS 6). This conclusion is based on geomorphology, litho- and morphostratigraphical relationships in the region, optically stimulated luminescence (OSL) ages from individual localities (c. 160 ka) and pedostratigraphic evidence (Gibbard et al., 2009, 2012, 2013, 2018; S.M. Pawley and E. Rhodes, personal communication) and elsewhere. Suggestions that the glaciation occurred in the Middle Wolstonian (c. MIS 8) have been based on terrace deposits of the East Midlands’ River Trent, which in places overlie the Wragby Till (glacial diamicton) attributed to this event. This interpretation relies principally on amino-acid racemisation chronology (AA) determinations and OSL ages (Straw, 2000, 2011, 2015; White et al., 2010, 2017), described as ‘inaccurately determined’ (Schenninger et al., 2007). In the light of this and the multiple age-determinations arising from the Fenland region studies noted above (e.g. Gibbard et al., 2018), correlation of the East Midlands’ glacial sequences with MIS 8 has been rejected. The results of these investigations confirm the stratigraphical evidence that there is no reliable basis for identifying glaciation of the region intermediate between the Anglian (=Elsterian) Stage and Late Wolstonian Substage (= MIS 6) (sensu Head and Gibbard, 2015) Tottenhill advance events in eastern England (cf. Hughes and Gibbard, 2019). Notwithstanding the reliability or otherwise of the numerical ages which have been determined for some of the deposits discussed herein, using techniques including amino-acid racemisation chronology (AA), U-series, and most recently optically

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stimulated luminescence (OSL), etc., it is important to question the results of these methods which are often contradictory and therefore must be regarded with caution. In particular, the mismatch of regional stratigraphy and relative age determined by the AA method appears to be an increasingly frequent phenomenon, and implies an inherent, unresolved problem with the latter. In all such cases stratigraphy should take priority in sequence interpretation and correlation. Figs 1 and 2 2. Sequence descriptions 2.1. Mathon, The Brays The sediments exposed at The Brays pit, Mathon, Herefordshire [NGR SO 7290 4411] (Fig. 1) were described by Coope et al. (2002). Here, west of the Malvern Hills, the Mathon Formation (Maddy, 1999; Richards, 1998, 1999) fluvial sand and gravel sequence infill a palaeovalley of a southward-flowing river (Barclay et al., 1992). The area was subsequently overridden by an ice sheet that deposited till originally correlated to the Anglian-Stage glaciation (Risbury Formation). Here a lenticular bed of grey silt and sand sediment up to 44 cm thick occurred (Brays Bed) interstratified in the gravel and sands, resting, in turn, in a depression in the underlying SiluroDevonian Raglan Mudstone bedrock infilled by a thin gravel and sand band (up to 20 cm thick) resting directly on the bedrock (Fig. 2). Overall the sequence represents deposition in a river channel complex, form of which could not be determined from the limited exposure that was available at this site during the investigations. The form, situation and sedimentary sequence of the silt bed indicated predominantly fine-sediment deposition with occasional influxes of flowing water that washed in abundant plant and other fossil remains. The Brays Bed yielded a diverse and consistent palaeontological record. The wellpreserved pollen spectra represent a single Picea-Pinus-Abies-Larix pollen assemblage biozone, the tree pollen representing at least 70 % of the total land pollen recovered. The conifers Picea and Pinus dominate the assemblage throughout, although Larix is a significant minor component, together with low numbers of broad-leaved taxa including Carpinus, Quercus, Ulmus and Fraxinus. Only low frequencies of non-tree pollen occurred, the pollen of the ericaceous shrubs Empetrum and Bruckenthalia also being recorded. The herb pollen and plant macrofossils, represent a variety of plants of local habitats. These records are confirmed by the plant macrofossils, the remains including cones of Pinus sylvestris, Picea abies and Larix. Altogether the palaeobotanical evidence indicated that coniferous woodland dominated the drier areas, with an understorey of ericaceous shrubs. Dry, partially disturbed grassland occurred on the floodplain with marsh and aquatic vegetation fringing the channel. Reworked pre-Pleistocene palynomorphs were also inwashed into the deposit. This interpretation was confirmed by the diverse insect assemblage, indicating a range of local environments. Nine coleopteran species in this assemblage are nonnative to the British Isles today. Four characteristic Coleoptera recorded included Dupophilus brevis Mulsant & Rey, 1872, which has only been recovered in similar

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frequencies at Pools Farm, Brandon (cf. below: Maddy et al., 1994); Micropeplus hoogendorni Matthews 1970, a taxon that has been equated with the living Siberian species Micropeplus dokuchaevi Rjabukhin, 1991 (Coope et al., 2002). This species is also found in the silt deposits at Pools Farm, Brandon (Maddy et al., 1994), and at Waverley Wood (Shotton et al., 1993; cf. below); and a distinctive, unidentified species of Aphodius. Finally, Phthorophloeus spinulosus Rey, 1883 was found at both Mathon and Pools Farm, but at no other British Quaternary site. Today this species is widespread in continental Europe and is common whenever its preferred host plant, Picea, is present. Overall, the palaeontological assemblages indicate a temperate climate. Although no vertebrate material was found in the Brays Bed, abraded molar teeth of Mammuthus primigenius (Blumenbach, 1799) and Palaeoloxodon antiquus (Falconer & Cutley, 1847) were obtained from the Mathon Member at the nearby Clencher’s Mill Pit (Barclay et al., 1992). Evidence of disturbed ground recorded in both the plant and insect assemblages from the Brays deposit suggest the presence of large herbivorous mammals in the area at the time (Coope et al., 2002). 2.2. Waverley Wood At Waverley Wood quarry, west of Coventry [NGR SP 326713] (Fig. 1) organic, siltdominated fossiliferous fluvial sediments fill channels incised into the Triassic bedrock and underlie both the Wolston and Baginton Formations (Shotton, 1953, 1971, 1983 a, b, 1989; Rice and Douglas, 1991; Shotton et al., 1993; Keen et al., 2006), the latter truncating the channel sediments (Fig. 2). A similar sequence was found in the nearby Wood Farm pit (Keen et al., 2006). Correlation of the channel sediments with the late ‘Cromerian Complex’ Stage was based on biostratigraphical, principally molluscan evidence, while amino-acid racemisation determinations suggest an age equivalent to Marine Isotope Stage (MIS) 15 or 13 (Bowen et al., 1989; Penkman et al., 2010). In addition to the palaeontology, a series of Palaeolithic artefacts have also been recovered from 'lag' gravels immediately overlying the three channels at Waverley Wood and the nearby Wood Farm quarries (Shotton et al., 1993; Keen et al., 2006). The stratigraphical relationships at these sites unequivocally demonstrate that the organic deposits underlie the mass of the Baginton Formation gravels, although as Shotton (1989, p.33) emphasises 'the nature of the unconformities that they rest upon does not determine their date'. Nevertheless the organic channel-fills were included in the Baginton Formation by Maddy (1999). At Waverley Wood two pollen diagrams through partly laminated organic silt and fine sand in channel 2 (site MS 0.3 m thick, site WAII 1.4 m thick) show tree pollen represents c. 50 % of the pollen present. Pinus is best represented, with significant percentages of Picea and lower percentages of Alnus and Salix. High frequencies of Poaceae and Cyperaceae occur throughout both diagrams, with low frequencies of a considerable number of herb taxa. Ericales pollen taxa show low frequencies in the upper part of both diagrams. Towards the top of both diagrams pre-Quaternary microfossil percentages increase markedly. The MS diagram compares with the upper part of the WAII diagram, which is the longer sequence and appears to span most of the depth of the channel. Plant macrofossil analysis through the WAII

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sequence shows the presence of a number of reedswamp and aquatic taxa in a lower part of the channel (below 160 cm), above which they largely disappear and are replaced by very few macrofossils of dry land/open vegetation and of trees (leaves of Pinus sylvestris Linnaeus, 1753, Picea abies (Linnaeus) H. Karsten, 1881). The pollen diagrams and plant macrofossils indicate the presence of regional boreal forest with Pinus and Picea during the major part of the channel 2 filling, when relatively quiet water conditions allowed the growth of aquatic taxa and bordering reedswamp, possibly in a floodplain abandoned channel. However, towards the top of the sequence, conditions change, with a loss of these taxa, an increase in Ericales pollen (indicating the presence of heathland), appearance of dryland taxa and an increase in reworked pre-Quaternary microfossils. The changes indicate an alluvial infilling of the channel, accompanied by deteriorating climate. The analyses of Coleoptera clearly indicate an ‘intense episode of arctic climate’ near the top of the channel 2 sequence. Therefore overall the sequence of channels apparently represents a period of climatic deterioration from temperate to arctic conditions.

2.3. Brandon FWS, Warwickshire At Brandon [NGR: SP 394762] (Fig. 1) a lens of grey clay and silt occupied a wellmarked channel interfingering with sands, cut-out to the north, occurred within c. 6.5 m of bedded Baginton-Lillington Gravel (Baginton Formation). At the centre of the channel the silts were c. 2 m thick. The silts were grey with a finely dispersed organic content. The top of the channel was marked by a strong break with solifluction at this horizon (Fig. 2). The flora and the small vertebrate and invertebrate fauna obtained from the channel and described by Kelly (1968) and Osborne and Shotton (1968) indicate the contemporary cold climate and ecology. The pollen diagram shows a typical cold stage pollen assemblage, with low tree pollen percentages, high Poaceae, Cyperaceae, a variety of non-tree taxa, including Plantago maritima Linnaeus, 1753, Artemisia etc. The plant macrofossils include Betula pubescens Ehrhart, 1789, Salix, Linum, Herniaria, etc. The faunal evidence supports this interpretation. A similar, disturbed clay bed within the Baginton Formation gravels was described by Shotton (1929, p. 207; 1968) from Lillington, and several grey silty clay lenses occurred in the gravels in the Brandon area. Most of these beds showed some postdepositional disturbance and the most contorted band parallels the Lillington occurrence. Immediately following the filling of the channel there was a period of cryoturbation. Logically, Shotton (1968) concluded that these clay beds represent pools or standing-water channel fills in a gravel-bed river environment. The strong cryoturbation, however, provided an important indication of a periglacial climate, corroborating the conclusions drawn from the channel's fauna and flora. Prior to the discovery of this silt-filled channel, the Baginton-Lillington Gravels (Baginton Formation) had only yielded vertebrate remains (Shotton, 1953), comprising Mammuthus primigenius, Palaeoloxodon antiquus, Coelodonta antiquitatus Blumenbach, 1799, Bos or Bison, Rangifer tarandus (Linnaeus, 1758), Equus caballus (ferus) (Linnaeus, 1758),and possibly Sus scrofa Linnaeus, 1758. Despite the

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undoubted presence of two teeth of Palaeoloxodon antiquus, the much more abundant Mammuthus primigenius and the other animals leave no doubt about the coolness of the climate, the environment being one of grassland with scattered woodland (Lister, 1989). 2.4. Brandon, Pools Farm At this site (Maddy et al., 1994) [NGR: SP 384763] (Fig. 1) the Brandon Gravel again overlies the Mercia Mudstone bedrock and consists of clast-supported, medium to coarse gravel with much coarse interstitial sand (facies Gm; facies nomenclature after Miall, 1977). The gravels reach a maximum thickness of 3.5 m (Fig. 2). Lithologically the gravels are correlated with the Baginton facies of the BagintonLillington Gravel Member described by Shotton (1953). They are predominantly massive, although crude sub-horizontal bedding suggests that aggradation resulted from the superimposition of successive bar-core sediments, or successive gravel sheets. By analogy with similar Pleistocene sediment associations in lowland Britain, the predominance of coarse depositions suggest deposition under relatively highenergy fluvial conditions (Bryant, 1983; Briggs and Gilbertson, 1973; Clarke and Dixon, 1981). The Brandon Lower Organic Sands and Silts occurred as a channel-like bed within the Brandon Gravels (Fig. 2). Their upper bounding surface, was erosional and planar truncating the silts. The Sands and Silts unit sequence consisted of a basal clast-supported gravel (up to 0.3 m), overlain by variable thicknesses of massive and laminated organic sands and silts (facies FI), ranging in thickness from 0.39 m to 2.1 m. Where the sands and silts are thickest they include isolated lenses of massive, sandy, fine to medium gravels. The fine-grained sediments indicate deposition in a lower energy fluvial environment punctuated by periodic higher energy flow events, indicated by the isolated gravel lenses which represent periodic flood events with faster moving water invading the channel. The silts and sands have yielded a fossil assemblage, the presence of a former vegetation cover in the immediate area is indicated by the numerous plant macrofossils present within the sediments. The assemblages obtained indicate a boreal forest community, indicated by the pollen of Pinus, Picea and Alnus which were well-represented. Poaceae pollen was abundant and was accompanied by low percentages of Ericales pollen and that of herb taxa. Abundant cones and needles of Pinus and Picea were recovered, whilst the fossil Coleoptera indicate temperate climate. This assemblage was compared with that recovered from Waverley Wood (above) and therefore was assumed to be of similar age. A second channel-like unit the Brandon Upper Organic Silts and Clays (Profile C) occurred within the overlying Baginton Sand (Maddy et al., 1994) (Fig. 2). The pollen diagram from this unit was remarkably similar to that Kelly (1968) obtained from his site nearby (above) in contrast to the Lower Organic Silts at the site. This evidence conforms the prevailing cold-climate environmental conditions during deposition of the Baginton Formation. The Brandon sequence almost certainly resulted from the migration of the main flow channel(s), of the braided Brandon (Baginton Formation) river, away from this part

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of the braidplain, leaving partially filled channels, with the immediate local areas being colonised by plants. Renewed migration of the main flow channels of the river resulted in the reoccupation of the area and the deposition of further gravels and sands, implying that the river continued flowing throughout the whole period indicated by the sequence at this site. Although the Brandon Gravel Member did not preserve any direct evidence of the climate prevailing during deposition of the unit, the Organic Sands and Silts channel fill indicated a temperate boreal forest flora and accompanying fauna. However, the sediments could represent a fluvial depositional environment that persisted through the transition from a temperate to a cold stage since the main body of the sediments accumulated under a cold-climate as indicated by the assemblage from the Upper Organic Silts and Sands bed. The Brandon Gravels must have accumulated under conditions of plentiful sediment supply and highly seasonally variable discharges. Such sediment availability probably reflects slope instability as vegetation cover is being lost in response to a contemporaneous cooling climate. The shifting of the active channel zone away from the fine-channel fill locations on the floodplain could explain the temporary accumulation of lower energy fluvial deposits in a minor channel before the return of the active channel zone and the recommencement of gravel accumulation. 2.5. Frog Hall Organic silt at this site [NGR: SP 416736] (Fig. 1), recorded from 3.6 m to 7.4m below surface, lying between gravel beds, was analysed for pollen and macroscopic remains (as well as for insects, ostracods and molluscs) (Keen et al., 1997) (Fig. 2). The pollen diagram through the organic silt showed a single pollen assemblage biozone with tree and shrub frequencies reaching 30-50 % of total land pollen and spores. The spectra were dominated by Betula, with consistently low percentages of Pinus, Picea, Corylus and Salix, with Quercus, Ulmus, Abies, Alnus and Carpinus pollen present in low numbers (cf. Thomas, 2001). Grasses and sedges are wellrepresented, together with low frequencies of a wide variety of herbs. Analysis of macroscopic plant remains showed the presence of 67 taxa. Betula was the only tree recorded as a macrofossil, with abundant fruits and cone scales (including B. cf. pendula) being recovered. A wide variety of marsh and aquatic species were also present, with a trend upwards towards percentage decrease of marsh and aquatic taxa, which may have resulted from upward silting of the channel. The environment indicated was temperate, with shallow water (2-3 m), still or slowly flowing, with local birch woodland, the organic silt interpreted as sediment in a cut-off channel on a river floodplain. The pollen diagram is remarkable in showing little change over 3.6 m of the silt bed, a strong contrast to pollen sequences in temperate stages recorded in lake sediments. The sequence in the channel starts as it finishes, the channel filling recording a time subsequent to the abandonment of the channel. The pollen diagram thus represents an apparently stable pollen source, suggestive of local and regional vegetation which was present over an unknown period, long enough for at least 7.4 m of sediment to accumulate. This stability does not suggest that the period represented should be

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placed at the beginning of a temperate stage (pre-temperate substage of Turner and West, 1968). Rather it suggests a period of stability, in which Betula communities colonised the immediate area, accompanied by a rich local herbaceous flora, terrestrial and aquatic. Such a situation might occur on a major gravel floodplain. The consistent low frequencies of other tree and shrub pollen may be interpreted as a background pollen rain, including that from conifers and temperate trees in the pollen source area. It should be noted that fluviatile sediments are liable to contain reworked pollen and spores. It is worth noting, however, that the presence of low frequencies of Picea pollen from the base of the sequence upwards would argue against an interpretation that the assemblages are early interglacial, since Picea is generally a late arrival in known fully interglacial vegetational histories. It is possible to regard this episode of vegetational history as a period of non-glacial conditions when forest spread to the Midlands. Whether it is interglacial or interstadial cannot be determined in the lack of a fuller vegetational sequence and agreement about what these terms mean. The time was related to an early part of a temperate stage, possibly the Hoxnian Stage; however, the stratigraphical relationships in the Frog Hall area have shown that the organic silts predate the late Wolstonian glaciation (Gibbard et al., 2012). 2.6. Brooksby In the Wreake valley, northern Leicestershire, a borehole (SK61NE67) [NGR: SK 46763156] (Fig. 1) at Brooksby, waterlain fine and medium sands, 7.8 m thick resting on the Triassic bedrock (Rice 1991). These sands included two organic strata approximately one metre below the base of the overlying Baginton Gravel (Fig. 2). These sands were included in the Brooksby Sand and Gravel Member, a unit underlying the Baginton Sand and Gravel Formation, in turn overlain by glacial deposits. A second borehole (61 SE4) near Rearsby, again encountered a unit of gravelly sands 5.9 m thick. Lithological samples from both the sand units could not be distinguished from the overlying Baginton Formation gravel. From the evidence available it was not possible to determine the extent nor distribution of the Brooksby Sand and Ggravel. However, the Brooksby deposits were interpreted as sediments lying in a narrow valley in the bedrock indicating milder conditions than those indicated by the Baginton Formation Sand and Gravels, known to contain syngenetic ice-wedges. The Brooksby deposits were thought to cover ‘a substantial time interval’ rather than a single short-lived event. The organic horizons yielded both pollen and macroscopic plant remains. The pollen spectra from the two horizons, c. 2 m apart, were similar and showed the presence of boreal forest with high frequencies (64 %, 44 %) of Pinus pollen, lower frequencies (10 %, 12 %) of Picea pollen, accompanied by low frequencies of Poaceae, Calluna and Ericales pollen and Sphagnum spores. Abies pollen was also present (2 % in each sample). Macroscopic remains of Picea were present in both samples, together with a wide variety of herb taxa and also mosses. Several aquatic and marsh taxa were noted in the list of macroscopic plant remains, suggesting that the organic sediments may have been deposited in abandoned channels in a sandy floodplain. The palaeobotany is significant in providing evidence of a period of mild climate with

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boreal forest at a time before or during the early deposition of the Baginton Sand and Gravels in the Wreake valley. Palaeolithic artefacts have been recovered from these sediments (cf. below). 2.7. Witham-on-the-Hill The sequence at this site [NGR: TF 030177] (Fig. 1) was exposed in the 1990s and was summarised by Lewis (1989, 1993). It consisted of a basal gravel and sand comprising abundant Jurassic limestone, quartz and quartzite clasts, derived from the Midlands' Mesozoic rocks, resting on bedrock at 45 m OD, reaching a maximum thickness of c. 9 m (Fig. 2). Ice-wedge casts occurred in the gravel and sand unit. The gravel was overlain by stratified sands up to 3 m thick which were, in turn overlain by laminated and massive diamicton of glacial origin, according to Lewis (1993) equivalent to the Heath Till unit, 4.5 m thick in total. The beds immediately underlying the diamicton units at this site are deformed in the direction of ice movement, i.e. N-S to NW-SE. A bed of silt up to 1 m thick occurred at the site and was sampled in a borehole sunk by Rose (in Lewis, 1989). There appears to be some confusion concerning the precise stratigraphical position in which this grey silty sand bed occurred. The bed was laminated in part. According to Lewis (1989, p. 126) the fossiliferous unit occurred 'within the sand and gravel', however, in the same paragraph it is stated that the unit 'occurs between the sand and gravel and the cross-bedded sand'. Judging from the occurrence of the fossil-bearing unit at other sites mentioned above, it is likely that the silt could potentially have occurred lower stratigraphically in the sequence, possibly near its base and below the level containing the ice-wedge casts. A pollen diagram through the silty sand to sandy silt to silty sand yielded a uniform assemblage representing a single Pinus-Picea pollen assemble biozone, with Pinus 2530 % (total land pollen and spores), Picea 10-20 %, and low frequencies of Betula and Alnus pollen. Poaceae and Cyperaceae showed percentages of 5 to 10 %, with Ericales, Asteraceae and other herbs 1 to 5 %. The pollen spectra indicate regional boreal forest, with indications of heath and herb communities. No significant vegetational changes are present (Gibbard and Peglar, 1989). 2.8. High Lodge, Mildenhall, Suffolk The sequence at High Lodge [NGR: TL 738756] (Fig. 1) includes up to c. 2 m of clayey silt, deformed and sheared, overlying Lowestoft Formation diamicton (Ashton et al., 1992; West et al., 2014) (Fig. 2). The clayey silt has been regarded as either an overbank alluvial sediment, with periodic flooding or more recently as an infill of a sinkhole in the Chalk. The pollen diagrams through the clayey silt shows high percentages of Pinus, low percentages of Picea, with lower percentages of Poaceae and Filicales. The assemblages again indicate regional boreal forest. The interpretation, especially with reference to the taphonomic problems associated with the sediments concerned, are discussed by Turner (1978, unpublished) and Hunt (1992). A detailed pollen diagram through the clayey silts by Turner (1973, 1978, unpublished) shows spectra similar to those by Hunt (1992), but with more detail,

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consistent low presence of Betula and Alnus, and higher percentages of Poaceae with a range of non-tree pollen taxa. Turner (1978, unpublished) suggested that the assemblages indicated open boreal forest, and considered the higher frequencies of Pinus and Picea towards the base and the top of the section to be a result of differential weathering; also that the diagram is likely to contain unrecognisable repeated sequences as a result of the visible shearing of the sediments. Turner (1978, unpublished) also analysed the abundant plant macrofossil flora from the more organic parts of the clayey silt. Apart from fragments of Picea wood, most of the macrofossils represented fringing marsh communities or aquatic vegetation. He considered that the assemblages were similar to those recorded from sediments of the present-day Breckland meres, in contrast to a posited overbank origin of the sediment, since overbank sediments of modern and early Holocene rivers fail to preserve pollen or macroscopic assemblages because of their state of oxidation. The High Lodge palaeobotanical evidence indicates the presence of boreal woodland (Turner, 1973, 1978). But there is conflict as to the time interval represented. Rose (1992) considered the age to be pre-Anglian, a fact that has been restated subsequently, most recently by Lewis et al. (2019). However, the geological evidence from the High Lodge area, from nearby Warren Hill (Three Hills) to the south and from numerous fen edge sites to the north (Gibbard et al., 2009, 2012, 2018, 2019; West et al., 2014), demonstrates that the clayey silts are younger and belong to a temperate event before the invasion of ice in the Wolstonian into Fenland at c. 180160 ka, in the time before the Fenland had undergone a long and active degradation and incision at a time of lower sea levels. The silts include important finds of Palaeolithic artefacts. 2.9. East Farm Barnham, Suffolk The sequence of deposits at this site [NGR: TL 875787] (Figs 1, 2) was investigated by Paterson (1937, 1939, 1942) and Wymer (1985) and was recently re-examined and described by Ashton et al. (1998), whose lithological units are referred to herein. Although locally very variable, in principle it comprises a succession of fine-grained deposits, predominantly silty clays (unit 5) resting on chalk-rich to brown diamicton (units 3-2), this overlying a basal sand and gravel unit (unit 1). The clays are overlain by a possible palaeosol (‘black clay, unit 6: Ashton et al., 1998) that intervenes between them and the subsequent sand, clay, the sequence being capped by brown silt (unit 7: ‘brickearth’). Overall this sequence reached a maximum of over 19.5 m, although it thins markedly laterally, infilling a depression in glacial sediments, the latter underlain by Chalk bedrock. Despite a claim by Ashton et al. (1998) that the sediments represent a fluvial channel fill, the depression appears to represent a closed basin with still to very slow-moving water, flow decreasing upwards in the sequence and terminating with a palaeosol on the dry, subareal, infill surface. West (2018) concluded that it represents a doline infilling, in common with similar sites in the district, including that at High Lodge (West et al., 2014), Beeches Pit, Icklingham (Preece et al., 2007) and Elveden (Ashton et al., 2005), such depressions being frequent in the region even today. The basal glacial deposits are correlated to the Lowestoft Formation and as such are

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of Anglian glacial age, whilst the overlying sequence of clays predominantly yielded temperate floral assemblages that are typical of the temperate climate event correlated to the Hoxnian Stage interglacial (~MIS 11). The thermoluminescence dating of burnt flints recovered from the site (414±3 ky: Preece et al., 2007) broadly confirms the overall geology and the biostratigraphical correlation. The overlying materials post-date the temperate beds and appear to be of colluvial origin infilling the depression, presumably deposited under cold-climatic conditions. As noted, the palynological analyses from the main body of the fine sediments indicated a typical interglacial sequence, however, the assemblage from the uppermost fossiliferous stratum, the so-called gritty clay (unit 5c), immediately underlying the black clay palaeosol, was atypical, being dominated by coniferous tree pollen, notably including high frequencies of Picea pollen (biozone 6: Hunt, in Ashton et al., 1998). The palynology indicates a boreal forest assemblage unlike that found elsewhere in late Hoxnian sequences (cf. West 1980), and therefore implies a later event, suggesting that the sediment potentially post-dates the interglacial and may indeed represent a younger interval. This is supported by ESR dates from this unit that gave an age of 200-300 ka (Ashton et al., 1998). 3. Discussion 3.1. Problems of interpretation of sites Before considering how these sequences might be interpreted in detail, it is necessary to describe several problems which await the interpreter of the sections. The first is a question of nomenclature. The sites considered here present pollen diagrams indicating the presence of coniferous woodland which could be parts of interglacial periods or of interstadial periods sensu Jessen and Milthers (1928). Here they are considered here as events indicating a temperate climate, without a definite relation to an interglacial or interstadial event, and are called temperate events. A further division of interglacials, apposite to the present account, was suggested by Zagwijn (1989) who distinguished two modes of NW European interglacial conditions; ‘full interglacials’ such as the Eemian or Holsteinian, characterised by oceanic conditions and high eustatic sea level, and those characterised by cool, more continental climates, and lower sea level (see below). Secondly, as a background to the interpretation of the pollen diagrams, it is helpful to be aware of pollen diagrams indicating comparable interstadial conditions during the younger, Devensian Stage which are within a secure stratigraphy. At Chelford, Cheshire, organic sediments lie in a shallow channel within the Middle Sands of the Cheshire Plain (Simpson and West, 1958; Worsley, 2015). The pollen diagram shows substantial frequencies of Betula and Pinus pollen and low frequencies of Picea pollen, with abundant macroscopic remains of Picea abies, including cones and wood. There are no changes in the vegetational history which would indicate that this period is part of an interglacial. If found in a borehole, it would appear as an event which might be interstadial or interglacial. At Beetley, Norfolk, a post-Ipswichian organic fill within a shallow depression within a gravelly sequence, c. 1.5 m deep, showed a complete cycle of change, leading to the establishment of coniferous

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woodland with Picea abies followed by a reversal to open conditions (site BD: Phillips, 1976). Near the base was an horizon with abundant leaves of Picea abies, although the pollen percentages of Picea were low. The sequence represents an interstadial, which would be recognizable if found in a borehole. Thirdly, in assembling pollen data relating to the sequences considered here, there is the problem of the taphonomy of the pollen assemblages. The taphonomy will vary from site to site. For example, assemblages from large lakes, from small ponds and from sediments associated with fluvial conditions will have a very different taphonomy. In particular, assemblages from a fluvial environment are likely to contain reworked pollen or spores, and care has to be taken in their interpretation. Sections described are often limited in exposure, with an unknown relation to the wider environment, which makes for a problem in the assessment of their taphonomy. In addition to the question of taphonomy, the representation of Picea in pollen diagrams also presents a problem. Picea abies is usually regarded as a low pollen producer and its representation in pollen diagrams appears very variable. Thus at some sites regarded as interstadial, an abundance of macroscopic remains of Picea abies is accompanied by very low pollen frequencies, e.g. the Devensian sites of Chelford (Simpson and West, 1958), Beetley BD (Phillips, 1976). 3.2. Comparison of sites Taking the evidence presented, a consistent picture emerges of an interval or intervals of boreal woodland dominated by coniferous taxa, characteristically including Picea, the presence of which is represented not only in the pollen spectra but in the majority of cases by macrofossils of cones and wood. Other taxa present indicate that the woodland was open and included a lower storey of a range of herbs and ericaceous shrubs. This assemblage is striking for its consistency in indicating a cool, continental climate, evidence for which is supported by both the vertebrate and invertebrate faunal evidence available at individual sites. Whilst this alone does not demonstrate the age equivalence of the localities, the palaeontological evidence, combined with that indicated by the stratigraphical situation of the localities discussed implies a consistency that justifies further investigation. In discussion of the Baginton Formation and its equivalent deposits of the Midlands, Gibbard et al. (2013) noted the consistent occurrence of the organic fine-grained sediments within the fluvial gravel and sands. Part of the basis of this recent reinterpretation was the discovery of these local fossil-bearing, channel-fill beds, at sites including Brandon, Brooksby and Witham-on-the-Hill, that yielded consistent evidence for interstadial-type, boreal, conifer-dominated forest vegetation growth under a cool, continental climate (Old et al., 1987; Maddy et al., 1994, discussed above). However, in contrast, some stratigraphically higher, and therefore younger sequences, within the gravel and sands have indicated colonisation of local area by a cold-climate steppe or treeless, subarctic flora and fauna (Shotton, 1953; Kelly, 1968; Osborne and Shotton, 1968; Gibbard and Peglar, 1989 a). The occurrence of these two sequences, deposited under contrasting climatic regimes, demonstrates that a climatic change from boreal, interstadial to subarctic, full-glacial conditions took place during the quasi-continuous deposition of the Baginton Formation (Gibbard

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and Peglar, 1989 a; Gibbard et al., 2013); deposition that continued into fully glacial conditions represented by the Wolston Formation glacio-lacustrine and ultimately till deposits. The conclusion that the accumulation of the Baginton Formation deposits was initially deposited under a cool, continental climatic regime is reinforced by the finds of large mammalian fossils from the unit. These discoveries do not give a precise indication of their age beyond late Middle to Late Pleistocene, apart from R. tarandus (reindeer) which is rare before the Hoxnian Stage, whilst Coelodonta antiquitatis (woolly rhinoceros) is unknown before this stage (Shotton, 1983 a, b; above). (Shotton, 1983 a, p. 269) concludes that 'this evidence for a post-Hoxnian age would appear to be conclusive', an opinion confirmed by Lister (1989). 3.3. Age of the Mathon deposits Concerning the age of the Mathon deposits, the striking palaeontological resemblance between the Brays Bed assemblage and those from Brandon, Pools Farm (Maddy et al., 1994) and Waverley Wood (Shotton et al., 1993) in the English Midlands was already noted by Coope et al. (2002). The consistent evidence for boreal coniferous forest in all these beds, together with their overlying cold-climate fluvial deposits implies that the sequences span a temperate to glacial climatic transition. Although, the fossil assemblages are potentially environmentally controlled, the palaeontological similarities overall suggest the deposits are of the same age. This correlation is strengthened by the occurrence of the exotic beetle taxa noted above (section 3.1). Although in the original publication the vegetational evidence for the age of the Warwickshire deposits, and therefore that at Mathon, was based principally on the occurrence of coniferous forest assemblages, it now appears that the recurrence of similar assemblages at different times implies that the correlation to an early Middle Pleistocene interglacial event was premature. Given the remarkably similarity of the Brays stratigraphical sequence to those in Warwickshire, at all three sites the organic deposits are overlain by a fluvial sands and gravels and in turn by till; the Coddington Till at Mathon and the Thrussington Till at the Warwickshire sites, it is therefore highly probable that they represent the same time interval (cf. below). The previous correlation of the Herefordshire glacial deposits to the Anglian Stage (Barclay et al., 1992, Richards, 1998), the Risbury Formation representing the only evidence of Anglian-Stage glaciation in western England, and, in turn, the Brays Bed therefore being equated to an early Middle Pleistocene (Cromerian Complex Stage) interglacial event, is now questioned. Reappraisal of the age of the Midlands glacial sequence, already noted, together with the conclusion that the correlative sequences described below are significantly younger, strongly implies that the Mathon Formation deposits must also be younger, i.e. they date from the post-Hoxnian to pre-Wolstonian glaciation interval. 3.4. Age of Waverley Wood channel deposits

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Having highlighted the striking consistency of the occurrence of the temperate, conifer-dominated units in the basal Baginton Formation, there is one problem that has to be addressed. That is the fact that despite the Waverley Wood deposits yielding a floral assemblage comparable to that at sites such as Brandon, Brooksby and Witham, the deposits have been biostratigraphically correlated with a Cromerian Complex Stage interglacial (cf. Jones and Keen, 1993). This conflicts with the Late Wolstonian age of the Baginton Formation proposed by Gibbard et al. (2013 and references therein). Since there are no grounds for suspecting that the latter formation represents a much longer period of time than previously thought, the correlation of the Waverley Wood deposits need to be be re-examined to determine whether there is coincidentally a remarkably similar fossil assemblage from sites of different ages, or whether the correlation of the Waverley Wood deposits was incorrect. Whilst the majority of the evidence for the age and therefore their correlation is equivocal, in detail the evidence for the age of the Waverley Wood deposits hinges principally on the significance of the recovery of the molluscan assemblage that, in part, comprised a relatively rich fluvial assemblage including Valvata macrostoma Mörch, 1864, Unio crassus Philipsson, 1788, and Pisidium clessini Neumayr, 1875. Significantly, all the Bithynia were referable to B. troschelii (Paasch, 1842), “which imparted a distinctly ‘Cromerian’ look to this otherwise undiagnostic assemblage.” (Preece, 2001). These freshwater river and lake gastropods are generally absent from sediments deposited during cold intervals, but they have been recorded in interstadial sequences. In analyses the opercula of either Bithynia tentaculata (Linnaeus, 1758), a species abundant throughout much of Europe, or Bithynia troschelii. The latter is now extinct in Britain although it is found across central Europe to eastern Siberia. The occurrence of B. troschelii, rather than B. tentaculata in the Waverley Wood deposits appears to suggest correlation with a warm-climate event within the 'Cromerian Complex' Stage (cf. Preece, 2001). However it should be regarded as tentative at best, since the former appears to favour continental climatic habitats, in contrast to more oceanic environments. Moreover, according to Currant (in Lister, 1989) the limited vertebrate fauna includes the water vole Arvicola cantiana (Hinton, 1910) and pigmy shrew Sorex (Drepanosorex) savini Hinton, 1911, their occurrence implying a broadly Middle Pleistocene age. If this evidence from Waverley Wood is taken in context, together with the fact that the total fossil assemblage reflects a cool, continental climate, and that there appears some confusion over the detailed sequence of individual channel fills at the site, and the fact that the coleopteran evidence indicates a marked climatic deterioration in the uppermost part (cf. above), it seems reasonable to question the correlation of the sequence with a ‘Cromerian Complex’ Stage interglacial. Instead it appears more likely that it represents the same event as the deposits at the other sites within the Baginton Formation gravels. If this is the case, the deposit is most likely of Late Wolstonian age (cf. Gibbard, 1992, unpublished report), notwithstanding the questionable AA age determinations, relating the sequence to MIS 15 determined by Bowen et al. (1989) and Penkman et al. (2013). 3.5. Age of the Brandon deposits

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The resemblance of the palaeontological and stratigraphical occurrence of the temperate Lower Organic Sands and Silts at Brandon and that at Waverley Wood, mentioned in the discussion of the Pools Farm, Brandon sequence, is striking (Maddy et al., 1994; Gibbard and Peglar, 1989a). Indeed these authors noted that the two could represent fragments of the same event. As stated above the Brandon Lower Organic Sands and Silts included palaeobotanical assemblages, dominated by boreal forest, but they occur within, rather than beneath, the Baginton Formation. Moreover, their occurrence within the gravels clearly indicates a deteriorating climate, indicated by both the palaeobotanical assemblages and also the sedimentary environments in which they occur. These authors commented '..it is not inconceivable therefore that the Waverley Wood channel [fills] represent an earlier phase of the same forested interstadial/interglacial event as that represented in the early part of the Baginton Formation' (Maddy et al., 1994; cf. Gibbard, unpublished report 1992). As already noted, the event represented in the Brandon Lower Organic Sands and Silts deposits has been correlated with that at Brooksby and Witham-onthe-Hill. 3.6. Age of the Frog Hall channel deposits In common with the Baginton Formation sequences discussed above, the organic silts at the Frog Hall locality (cf. above) have also been interpreted as representing a temperate event that predates the Wolstonian glaciation, the underlying gravels possibly representing a cooler climate interval immediately preceding the temperate event (Gibbard et al., 2013). The question, therefore, is could this channel-fill sequence represent part of the same event as that discussed above? Based on the palynological assemblage, this concept is perfectly conceivable, indeed if that is the case the Frog Hall temperate deposits might represent an earlier portion. This is based on the mutual frequency of Betula versus Pinus pollen, the latter dominating the Waverley Wood sequence, in contrast to Frog Hall. Assuming that the correlation proposed is correct, the vegetational development of the temperate event can be reconstructed by combining the palaeobotanical records from these three sites. The sequences indicate that initial vegetation was dominated by Betula reaching frequencies of almost 50 % of total land pollen and spores (tlp), with Pinus later, peaking at only 10 % during this first phase; Picea arrived at approximately the same time at less than 10 %. As noted above, other trees are present in low frequencies. To judge from the Waverley Wood and Brandon A profiles, Pinus later expands at the expense of Betula to become the dominant tree, while Picea pollen increases its contribution to c. 10 % tlp. The abundance of Picea cones and wood at Brandon indicates that it became locally very frequent. Picea is a low pollen producer and is therefore potentially under-represented in the pollen spectra from these sequences. The high frequencies of Poaceae, Cyperaceae pollen, together with a range of other herbs indicates that the woodland was open, with acidic soils locally indicated by the Ericales pollen present. The climatic deterioration recorded in the overlying sequences is not represented in the pollen spectra. This appears to result from silting up of the channels, possibly accompanied by removal

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of any sediments representing this phase as a consequence of migration of flow channels of the rivers in which the sediment sequences accumulated. 3.7. Age of the East Anglian sequences This reconstruction is further reinforced by comparison with the two East Anglian sites presented above, High Lodge and East Farm Barnham, Suffolk. The close resemblance of the biota, and particularly the pollen assemblages, already suggested the equivalence of these sequences, as noted by Jones and Keen (1993, p.63, 70); these authors further noting that the vegetation was of 'Chelford-type….rather than that of an interglacial' – alluding to the Early Devensian Substage forested interstadial event first recognised by Simpson and West (1958) (cf. above). The correlation of the Waverley Wood channel deposits is reinforced by the interpretation of the High Lodge sequence as representing a forested interstadial-like temperate interval predating the Late Wolstonian glaciation of Fenland basin (Gibbard et al., 2018). It is possible that the gritty clay (unit 5c) at the East Farm Barnham site is of the same age given its stratigraphical position and biostratigraphy. 3.8. Baginton Formation river development The interpretation presented above has important implications for understanding the evolution of Midlands Baginton Formation (proto-Soar or ‘Bytham’) river. Shotton’s opinion (1953), that it was a relatively short-lived drainage line that only flowed in the interval between the Anglian and Wolstonian glaciations was strongly supported by Gibbard et al. (2013). The latter authors concluded that deposition of the Baginton Formation and equivalent deposits in the Midlands seems to have initially occurred under temperate conditions but continued into a period characterised by more severe subarctic climate, to judge from the palaeontology of channels fills at Brandon, Brooksby and Witham-on-the-Hill. At the time Gibbard et al. (2013) did not include the Waverley Wood channel fills, apparently underlying the Baginton Formation gravels and sand, within the temperate interval, stating that 'that the only sites actually containing unequivocal evidence for potential preAnglian artefacts are the channel sediments underlying the Baginton Formation at Waverley Wood and the lacustrine deposits at High Lodge, Suffolk'. Re-evaluation of both localities demonstrates that there is a substantial likelihood that they are not as previously supposed of pre-Anglian age but represent the same event as those at the other sites mentioned above (Gibbard et al., 2009, 2013), i.e. they are at least 250 ky younger than previously thought. The implication for the age of the Baginton Formation is that the downcutting to the base of the unit must have occurred during or more probably immediately before the temperate event (under cold-climate conditions). This confirms that the Waverley Wood channel sediments should indeed therefore be considered as a member of the Baginton Formation (cf. Maddy, 1999). Throughout the Midlands’ there was a major period of fluvial incision and associated landscape remodelling in the interval between the end of the Hoxnian Stage interglacial and the deposition of the Baginton Formation. This period also saw marked landscape evolution in eastern

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England during which the modern drainage system was established following both the Anglian Stage glaciation and the immediately following the Hoxnian Stage interglacial (West, 1963, 1968; Gibbard, 1991). The deposits appear to show a transition not only in climate but in river form, beginning in the temperate interval the river apparently adopted a narrow channelised course, potentially with floodplains (cf. Collcutt, 1999; Gibbard and Lewin, 2002), but this was replaced by the river adopting a wide, multi-channelled braided pattern, presumably in response to declining temperatures, possibly increased seasonality and sediment supply. Typical cold-climate regimes with highly peaked flow discharges were reestablished. These provided the energy for stream rejuvenation, channel enlargement, remobilisation of coarse debris, rapid removal and reworking of fines and fossils, and importantly, substantial incision into accumulated floodplain deposits. The re-activation of conditions for gravel transport, initially in the absence of full loading of cold-climate materials, resulted in valley incision, fine alluvial sediment being removed (Gibbard and Lewin, 2002), particularly where valley width was restricted. A parallel development apparently occurred in the Welsh borderland to judge from the close similarities of the Mathon sequence, already described, the southwardflowing Mathon river occupying an earlier, possibly Anglian–age glacial overflow channel (Coope et al., 2002). Since there is now a substantial concensus, throughout northern Europe, that the major glaciation was restricted to the latter part of the period (i.e. late Wolstonian/Saalian, early in MIS 6: Gibbard and Clark, 2011; Ehlers et al., 2011; Boswell et al. 2019), on balance it appears that the earlier predominantly cold intervals (i.e. MIS 10, 8) within the Wolstonian/Saalian Stage were dominated by severe cold, non-glacial conditions in lowland Britain and on the adjacent midContinent (Hughes and Gibbard 2019). Moreover, as in the Fenland region of eastern England, post-glacial drainage therefore developed on the newly deglaciated surfaces in the latest Wolstonian period. The occurrence of subsequent last (i.e. Ipswichian / Eemian Stage) interglacial fluvial sequences within the modern valleys, confirms that the present drainage system was established by this time (Gibbard et al., 2018). In addition, this evidence has implications for the interpretation of Palaeolithic artefact assemblages associated with the Baginton Formation river and correlative sequences (see below). The conclusions regarding the age of the sediments and therefore their contained artefacts demonstrates that all of the sites associated with the temperate event must be late Middle Pleistocene age. In other words, none of the sites are of pre-Anglian age, as previously thought (Gibbard et al., 2013). Nevertheless, despite this weight of evidence Lewis et al. (2019) disagree with this conclusion, but see Gibbard et al. (2019) for a rebuttal of their views. 3.9. Comparison with other post-Hoxnian – pre-Ipswichian stage sequences As already discussed there are many sequences which have been placed within the Wolstonian Stage 260 ky interval on various bases. Although there is no modern synthesis of these events, a review by Jones and Keen (1993, Ch. 7) lists 26 localities

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from which temperate climate deposits have been related to this period. Interestingly none of the sites discussed herein were identified by these authors as being of this age. Of the characteristics of the sites placed in this period few appear to be consistent in either their stratigraphical setting or their biostratigraphy. Rather their assignment to this interval appears to be based on a range of criteria that is mainly negative evidence. This may, in part, be that they represent more than one interval, as Jones and Keen (1993) note; indeed this is almost certainly the case (cf. for example, Penkman et al., 2013). However, none of the sequences they discuss apparently include the characteristic Picea-Pinus interstadial forest assemblage identified in this study, and none appear to be as firmly fixed in their lithostratigraphical setting as those discussed above. One site where potentially equivalent deposits might occur is Marsworth in Buckinghamshire [NGR: SP 9314] (Fig. 1). Here at least two temperate and an intervening periglacial episode during the Middle and Late Pleistocene have been assigned to MIS 7 (i.e. Late Wolstonian) and MI Substage 5e (Ipswichian Stage) on the basis of Uranium-series dating of tufa from the lower channel deposits (Green et al., 1984; Candy and Schreve, 2007). An intervening sheet of chalky periglacial slope deposits (coombe rock) was equated to MIS 6 (= Late Wolstonian) (Murton et al., 2001, 2015; Murton, 2013). Sequence unit C13 here yielded a molluscan fauna whose climatic significance is thought to record a change from warmer to colder conditions and increased aridity. Murton et al. (2015) attributed this unit (interpreted as a cooltemperate channel fill) to MIS 7b or 7a (cf. Murton et al., 2001). Molars of Mammuthus primigenius from the Lower Channel are also interpreted to indicate a time towards the end of MIS 7, whereas fully temperate conditions are indicated during MI substages 7e and 7c. These age attributions are supported by the geochronology from the Marsworth sequence (Murton et al., 2015). Whilst it is beyond the scope of this article to assess each of the many sequences related to this interval by other workers, what emerges from the present investigation is that there is firm evidence for a forested temperate interval dominated by coniferous trees. Questions concerning this interval remain, since it is uncertain whether it was a single fully interglacial event, the interstadial-character of the deposits described being the end of a longer episode, or whether this phase never achieved the full interglacial biological characteristics associated with the typical interglacials recognised in the region (cf. West, 1980). Moreover, it appears that, beyond the details presented herein, the period does not seem to display specific biostratigraphical characteristics, at least within the palaeobotanical assemblages, that allow it to be unequivocally differentiated from other temperate events in the later Middle Pleistocene. The detail of the evidence hints that the phase was more complex, possibly with two or more peaks in warm climate (cf. Candy and Schreve, 2007). What is certain is that this temperate event represented in the Midlands and the Fenland region sites described above, progressively passed through deteriorating climate to periglacial and ultimately glacial conditions. A similar apparent climatic sequence was recorded at Norton Bottoms in the River Trent valley, Nottinghamshire where a silt and sand channel fill, underlying the Balderton Sands and Gravels, yielded evidence of temperate fluvial conditions (Bridgland et al., 2014). Since these sequences are now known to have occurred

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during the Late Wolstonian Stage (i.e. Late Saalian, MIS 6), it is highly likely that the temperate event is equivalent to part of the immediately preceding MIS 7 complex. Moreover, since this event apparently occurred at the end of the warm-climate interval, it most likely represents the Late Wolstonian MI Substage 7a-c (sensu Railsback et al., 2015), termed here the Waverley Wood temperate event (Appendix 1). The implication, therefore is that the downcutting that produced the channels occupied by the temperate deposits dates from immediately before the event, i.e. it relates either to a cold interval in MIS 7, termed substage 7d (a substantial, shortlived cold or glacial phase, ~235-220 ka: Ruddiman and McIntyre, 1982; Tzedakis et al., 2004; Railsback et al., 2015; Lang and Wolff, 2011), or possibly the end of MIS 8 (~245 ka; Middle Wolstonian Substage). Since the base of MIS 6 occurred at ~190 ka, this implies that the interval including the Waverley Wood event could have spanned some 30 ky, assuming it represents MI substage(s) 7a-c s.s. (i.e. ~ 220-190 ka: Tzedakis et al., 2004; Railsback et al., 2015). 4. Possible equivalent correlatives on the near Continent The fragmentary nature of the deposits identified as potentially belonging to the temperate climate event immediately predating the Wolstonian glaciation s.s., makes it difficult to be certain how much of the MIS 7 interglacial complex is represented at any one locality (cf. Candy and Schreve, 2007). Whilst it appears likely that the Waverley Wood temperate event indeed represents the younger part of this interval, the evidence seems to imply that a possible earlier phase or phases may have occurred. For this reason it is necessary to compare the sequences presented with potentially equivalent localities on the near Continent to determine whether a more complex picture emerges. The comparison is validated by the fact that Britain was joined with the Continent for much of the time during this period. What is immediately obvious from this comparison is that there are only a few places where possibly equivalent units are known. Of these only six localities appear to show some resemblance to the Midlands' and East Anglian sequences. Perhaps the best studied is that at Schöningen, near Helmstedt in Lower Saxony. Here the eponymously named full interglacial occurs, this event having been correlated to the early part of MIS 7 and followed by a period of climatic oscillations during which two milder climate events, the Buddenstedt Interstadials I and II, were identified by Urban (1995). The latter are overlain by the Saalian-age glacial sediments. These 'intra-Saalian' events clearly indicate a period of climatic instability that pre-dates the arrival of the Saalian glacial ice in MIS 6. The Schöningen Interglacial pollen spectra include a significant component of temperate trees, with Picea and Pinus pollen being continuously present. The same period is represented at the Nachtigall site, near Höxter, in Germany, where similar climatic oscillations potentially record the same event (Kleinmann et al., 2011). The Schöningen Interglacial has been correlated with the 'upper' interglacial deposits at Wacken, Dömnitz, and the Bilzingslaben III tufa in Germany (Vandenberghe, 1995; Mania, 1995) and the Lublinian Interglacial in Poland (Lindner et al., 2013). Heijnis (1992) dated the former to c. 180 to 227 ka BP using the U-series method, supporting correlation with the Late Saalian Substage, MIS 7 s.l. (Litt et al., 2007, 2008),

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potentially its latter part. The Waverley Wood 'intra-Wolstonian' temperate event presumably represents either the end of the Schöningen Interglacial or less likely one of the Buddenstedt interstadials. Comparable sequences in the Netherlands that have been equated to this 'intraSaalian' complex occur at Wageningen-Fransche Kamp (van Kolfschoten, 1991; De Jong, 1991; Ruegg, 1991), Hoogeveen and the subsequent Bantega Interstadial (Zagwijn, 1973; De Jong, 1988; Westerhoff et al., 2003) and notably MaastrichtBelvédère, (van Kolfschoten et al., 1993; Vandenberghe, 1995). The latter produced a vertebrate fauna of fully temperate character, and although it lacked fossil pollen, the molluscan fauna notably included Bithynia troschelii (Meijer, 1985, 1986), which matches the record of this taxon at Waverley Wood (cf. above). This author included the fauna from Maastricht-Belvédère interglacial in his Malacozone 4a (which is characterised by an almost total lack of extinct species). The pollen spectra from Wageningen are of interglacial/interstadial character and are comparable to those from Waverley Wood. They were correlated to the Hoogeveen Interstadial which includes significant frequencies of Picea in biozones SIVa and IVb (de Jong, 1991; Westerhoff et al., 2003), whilst the pollen assemblage differs from those from the younger Bantega interval (Zagwijn, 1973; De Jong, 1988, 1991; Westerhoff et al., 2003). The Wageningen fauna has also been correlated with the same temperate interval as Hoogeveen and Maastricht-Belvédère (van Kolfschoten, 1991; Meijer, 1991), however doubts remain as to whether the Hoogeveen Interstadial indeed represents the same event as that at the latter (van Kolfschoten et al., 1993). It is possible therefore that these sequences could represent an earlier warm-climate interval(s) within the MIS 7 complex, i.e. substages 7c or 7e (cf. Westerhoff et al., 2003). Further afield, similar climatic instability has been recorded during this ‘intraSaalian’ interval on the Velay plateau of the Massif Central in France by de Beaulieu and Reille (1995) and de Beaulieu et al. (2001). Here maar lake deposits record a 'complete' sequence of climatic events through the Middle to Late Pleistocene, and include apparent equivalents to the interglacial and interstadials of northern Germany. As at Schöningen, the Bouchet complex includes an interglacial (Bouchet I) and two interstadial intervals (Bouchet II and III), both of the latter are characterised by coniferous tree pollen, including significant frequencies of Picea. These events are therefore potentially the equivalents of the Buddenstedt Interstadials, whilst Bouchet I may be equated with the Schöningen Interglacial. However, Picea is represented only in low numbers during the interglacial event in the Velay plateau (de Beaulieu et al., 2001). Therefore, given the considerable distance of these sites from Britain, together with their contrasting geological and geomorphological settings, it is difficult to be certain precisely which event might be the equivalent of that recognised in the English Midlands. Nevertheless, comparison with the Continental sequences does reinforce the view that the Waverley Wood temperate event represents an interval in the complex MIS 7 period (i.e. MI substages 7a-c or 7e), with the stratigraphically younger, cold-environment deposits recording the climatic deterioration into early MIS 6 (Morton or Tottenhill Stadial (Gibson, 2019) = Drenthe Stadial) (Table 1; Appendix 1).

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Having said that, the question of the relationship to the deep-sea record can be broadly assessed. As van Kolfschoten et al. (1993) state, the ‘warm-climate phases’ of the MIS 7 complex (substages 7a-c, 7e) are notable for having relatively low peaks in oxygen isotope ratio, compared to those equivalent to the Holocene Series, Eemian and Holsteinian stages. Despite that, MI substages 7a-c and 7e were sufficiently warm enough to be considered 'interglacial' in character in southern Europe (Tzedakis et al., 2004; Lang and Wolff, 2011). These cooler climates were attributed by Shackleton (1987) to there being more extensive polar ice and lower sea-levels during these former interglacial-type events, in contrast to the 'full interglacials' like the Eemian Stage. This offers a possible explanation for the cool, continental conditions represented during these warm-climate phases. Moreover, as Van Kolfschoten et al. (1993) point out, this explanation reinforces the view advanced by Zagwijn (1989), that in NW Europe there are at least two modes of interglacial (temperate) climate events, that with characteristics like the 'full interglacial' events Holocene, Eemian (Ipswichian) and Holsteinian (Hoxnian), typified by oceanic climate and high sea-levels, and a second type with lower sea-level and more continental climate; the Waverley Wood interval being clearly of the latter type. The environmental implications of this latter mode in northern Europe are poorly understood, but the conclusion that global relative sea-level failed to reach above -15 m throughout MIS 7, supported by Dutton et al. (2009), further reinforces the interpretations presented herein. 5. Palaeolithic Archaeology As already noted Palaeolithic stone tools have been found within the deposits at a number of the sites discussed. In particular, the implements predominantly occur within coarse, ‘lag-like’ gravel at the base of the Baginton Formation, as well as within channel deposits, the latter including four handaxes recovered at Waverley Wood (Shotton, 1989; Lang and Keen, 2005) and similar finds from Brooksby (McNabb, 2001; Graf, 2002). A situation parallel to that is seen at Warren Hill where reworked palaeoliths are found in quantity in the proglacial deposits of the Tottenhill glaciation. A Palaeolithic flake industry notably also occurs in the silts at High Lodge immediately underlying the proglacial gravels (West et al., 2014; Lewis et al., 2019, Gibbard et al., 2019). At this site the artefacts are in situ, indicating human occupation during the temperate interval recorded there, whereas at other sites the possibility remains that the artefacts could, in part, be reworked. Palaeolithic materials have also been recovered from the potential Continental equivalent events at Schöningen (Serangeli et al., 2018), Maastricht-Belvédère (Kolfschoten et al., 1993) and Wageningen-Fransche Kamp (Stapert, 1991). It is interesting to note that at the last site flint flakes showing Levalloisian technique were identified since this technique has been recognised from Wolstonian-age deposits (Mellars, 1974). 6. Conclusions

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The occurrence of certain conifer (Pinus-Picea) pollen assemblages which have been recorded in a number of Quaternary sites in glaciated parts of lowland England suggest that several of the sites, but not all, represent northern temperate type of forest or woodland that colonised the region during one or more time periods of milder climate during the late Middle Pleistocene. The fauna associated with this period, consistently with the flora, includes Mollusca, Insecta and vertebrates all of which typically indicate a generally continental climatic environment. The evidence available suggests this temperate event is comparable in character, but not chronologically equivalent to, the Early Weichselian/ Devensian Brørup/Chelford Interstadial. The fact that it occurred immediately before a major glaciation event is interesting in this context, but its significance in that sense remains uncertain. Moreover, judging from the mode of occurrence of the deposits apparently representing this event, it seems that the accumulations spanned the climatic deterioration from interglacial/interstadial to fully glacial (i.e. cold-climate) conditions. Multiple lines of stratigraphical evidence strongly imply that the event occurred during the Late Wolstonian Substage, immediately predating the Wolstonian glaciation s.s., i.e. Late Wolstonian, c. MIS 6. A potential stratotype site for the event is described in Appendix 1. Palaeolithic humans were present during this period, their artefacts having been found associated with sediments at several of the sites related with this event, and in particular are present in place at High Lodge in Suffolk. Given this evidence, it appears that the temperate event represented could be equivalent to part of the complex interval identified in ocean-floor isotope sequences as MIS 7. Whilst few reliable numerical dates are available from this period in Britain, those that are available, either from the sediments themselves or associated overlying accumulations, broadly confirm this correlation. The Brays Bed at Mathon and the Lower Channel fill sediments at Waverley Wood, including a tufa, previously correlated with part of the Cromerian Complex Stage, potentially represent part of the same temperate event, the complex structure of which suggests that the Pinus-Picea event represents the latest part, in which case it represents ~MIS 7a. It is important, however, to note that not all sites dated to MIS 7 in the literature actually represent this event. It is vital that correlation should, in all cases, be developed on the basis of multi-disciplinary stratigraphy with critical assessment of the validity of numerical age dating. The event is potentially equivalent to that indicated by the sequences at Nachtigall and Schöningen in Lower Saxony, etc. in northern Germany, both being identified to the Schöningen Interglacial (?=MIS 7a-c or 7e) and the comparable sequences at Hoogeveen, Maastricht- Belvédère and Wageningen Fransche-Kamp in the Netherlands. However, the complexity of these 'intra-Saalian' events implies that any correlation to a specific interval remains tentative at the present state of knowledge, a problem also encountered in deep-sea records. It is notable that Palaeolithic artefactual material has been recovered from these sequences, except those at Nachtigall and Hoogeveen. The stratigraphical significance of the proposed correlation is that it offers a possibility to begin recognising the internal chronological structure of the Wolstonian Stage in lowland Britain and potentially beyond, a period which, up to

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now, has been generally characterised by erosion under cold-climate conditions. This stage represents an interval that is over twice the length of the Devensian/Weichselian Stage and potentially more complex in terms of climatic and therefore environmental evolution. That said this reconstruction provides a tantilising glimpse into the structure of the Wolstonian Stage. Future research should be directed towards attempting to provide a better-defined chronology of events during the stage in general, and during the Waverley Wood temperate event identified here, in particular. It would also be important to continue to clarify potential correlation with events on the eastern side of the North Sea with those in Britain. The apparent rarity of depositional sequences representing this Late Wolstonian/ Late Saalian Substage temperate complex in lowland NW Europe emphasises the absence of suitable accommodation space. One possible explanation is that the previous intervals of the stage (Early and Middle Wolstonian substages) were dominated by periglacial, rather than glacial landscape processes. Acknowledgements We thank Philip Stickler (Department of Geography, University of Cambridge) who assisted with the cartography. We have benefitted from enthusiastic discussions with many colleagues, especially Doctors C. Turner and S. Gibson. We thank Dr F. Busschers for providing assistance with accessing an article. We also thank the editors for accepting this publication and for helpful comments. REFERENCES Ashton, N.M., Cook. J., Lewis, S.G., Rose, J. (Eds), 1992. High Lodge: Excavations by G. de G. Sieveking, 1962-8 and J. Cook, 1988. British Museum Press, London. Ashton, N., Lewis, S.G., Parfitt, S., 1998. Excavations at the Lower Palaeolithic site at East Farm, Barnham, Suffolk, 1989-94. London: British Museum Occasional Paper 125. Ashton, N., Lewis, S., Parfitt, S., Candy I, Keen D, Kemp R, Penkman K, Thomas G, Whittaker J, White M. 2005. Excavations at the Lower Palaeolithic site at Elveden, Suffolk, UK. Proceedings of the Prehistoric Society 71, 1–61. Barclay, W.J., Brandon, A., Ellison, R.A., Moorlock, B.S.P., 1992. A Middle Pleistocene palaeovalley-fill west of the Malvern Hills. Journal of the Geological Society 149, 75-92. Boswell, S.M., Toucanne, S., Pitel-Roudaut, M., Creyts, T.T., Eynaud, F. and Bayon, G., 2019. Enhanced surface melting of the Fennoscandian Ice Sheet during periods of North Atlantic cooling. Geology, 47, 664-668. Bowen, D.Q., Hughes, S., Sykes, G.A., Miller, G.H., 1989. Land-sea correlations in the Pleistocene based on isoleucine epimerisation in non-marine molluscs. Nature 340, 49-51. Bowen, D.Q., 1999. On the correlation and classification of Quaternary deposits and land-sea correlations. Special Report Geological Society London, No.23.

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Bridgland, D.R., Howard, A.J., White, M.J., White, T.S. (Eds), 2014. Quaternary of the Trent. Oxbow Books: Oxford. Briggs, D.J., Gilbertson, D.D., 1973. The age of the Hanborough terrace of the River Evenlode, Oxfordshire. Proceedings of the Geologists' Association 84, 155-173. Bryant, I.D., 1983. The utilization of Arctic river analogue studies in the interpretation of periglacial river sediments from southern Britain, in: Background to Palaeohydrology, 413-431. Wiley, Chichester. Candy, I., Schreve, D., 2007. Land–sea correlation of Middle Pleistocene temperate sub-stages using high-precision uranium-series dating of tufa deposits from southern England. Quaternary Science Reviews 26, 1223–1235. Clarke, M., Dixon, A.J., 1981. The Pleistocene braided river deposits in the Blackwater Valley area of Berkshire and Hampshire, England. Proceedings of the Geologists' Association 92, 139-157. Collcutt, S.N., 1999. Huncote Quarry, Huncote, Leics: Appraisal of the potential for Lower Palaeolithic Archaeology. Oxford Archaeological Associates, unpublished report for Acresford Sand and Gravel Ltd for review of 1969 planning permission, in Leicestershire & Rutland SMR, planning archaeology site file, Huncote Quarry. Coope, G.R., Field, M. H., Gibbard, P.L., Greenwood, M., Richards, A., 2002. Palaeontology and biostratigraphy of a Middle Pleistocene river channel beneath the Mathon Sand and Gravel Member, at Mathon, Herefordshire, England. Proceedings of the Geologists’ Association 113, 237-258. de Beaulieu, J., Reille, M., 1995. Pollen records from the Velay craters: a review and correlation of the Holsteinian Interglacial with isotopic stage 11. Mededelingen Rijks Geologische Dienst 52, 59–70. de Beaulieu, J.L., Andrieu-Ponel, V., Reille, M., Grüger, E., Tzedakis, C., Svobodova, H., 2001. An attempt at correlation between the Velay pollen sequence and the Middle Pleistocene stratigraphy from central Europe. Quaternary Science Reviews 20, 1593-1602. De Jong, J., 1988. Climatic variability during the past three million years, as indicated by vegetational evolution in northwest Europe and with emphasis on data from The Netherlands. Philosophical Transactions of the Royal Society of London B 318, 603-617. De Jong, J., 1991. Pollen-analytical investigation on sediments of Pleistocene age at Wageningen (The Netherlands). Mededelingen Rijks Geologische Dienst 46, 6570. De Rouffignac, C., Bowen, D.Q., Coope, G.R., Keen, D.H., Lister, A.M., Maddy, D., Robinson, J.E., Sykes, G.A., Walker, M.J.C., 1995. Late Middle Pleistocene interglacial deposits at upper Strensham, Worcestershire, England. Journal of Quaternary Science 10, 15-31. Dutton, A., Bard, E., Antonioli, F., Esat, T.M., Lambeck, K., McCulloch, M.T., 2009. Phasing and amplitude of sea-level and climate change during the penultimate interglacial. Nature Geoscience 2, 355-359. Ehlers, J., Gibbard, P.L., Hughes, P.D. (Eds), 2011. Introduction, in: Ehlers, J., Gibbard, P.L., Hughes, P.D. (Eds), Quaternary Glaciations - Extent and

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Chronology - A Closer Look. Chapter 1 Developments in Quaternary Science 15, p. 1-14. Elsevier, Amsterdam. Field M.H, Gibbard, P.L., Brandon, A., 1997. The first record of Larix from the British Pleistocene. Geological Magazine 134, 317-322. Gibbard, P.L., Clark, C.D., 2011. Pleistocene Glaciation Limits in Great Britain, in: Ehlers, J., Gibbard, P.L., Hughes, P.D. (Eds), Quaternary Glaciations - Extent and Chronology - A Closer Look. Chapter 7 Developments in Quaternary Science 15, p. 75-94. Elsevier, Amsterdam. Gibbard, P.L., Peglar, S.M., 1989a. Palynology of the fossiliferous deposits at Brandon, Warwickshire, in: Keen, D.H. (Ed.), West Midlands field guide. Quaternary Research Association, Cambridge, 21-23. Gibbard, P.L., Peglar, S.M., 1989b. Palynology of the fossiliferous deposits at Witham-on-the-Hill, Lincolnshire, in: Keen, D.H. (Ed.), West Midlands field guide. Quaternary Research Association, Cambridge, pp. 35-37. Gibbard, P.L., Turner, C., 1988. In defence of the Wolstonian Stage. Quaternary Newsletter 54, 9-14. Gibbard, P.L., 1991. The Wolstonian Stage in East Anglia, in: Lewis, S.G., Whiteman, C.A., Bridgland, D.R. (Eds), Central East Anglia and the Fen Basin, Field Guide, Quaternary Research Association, London, 7-14. Gibbard, P.L., Lewin J., 2002 Climate and related controls on interglacial fluvial sedimentation in lowland Britain. Sedimentary Geology 15, 187-210. Gibbard, P.L., West, R.G., Boreham, S., Rolfe, C., 2012. Late Middle Pleistocene glaciofluvial sedimentation in Norfolk, England. Netherlands Journal of Geosciences 91, 63-78.. Gibbard, P.L., Pasanen, A., West, R.G., Lunkka, J.P., Boreham, S., Cohen, K. M., Rolfe, C., 2009. Late Middle Pleistocene glaciation in eastern England. Boreas 38, 504–528. Gibbard, P.L., Turner, C., West, R.G., 2013. The Bytham river reconsidered. Quaternary International 292, 15-32. Gibbard, P.L.,West, R.G., Hughes, P.D., 2018. Pleistocene glaciation of Fenland, England, and its implications for evolution of the region. Royal Society Open Science 5, 170736, 52 p. http://dx.doi.org/10.1098/rsos.17073 Gibbard, P.L., West, R.G., Hughes, P.D., 2019. Human occupation of northern Europe in MIS 13: Happisburgh Site 1(Norfolk, UK) and its European context: a response to Lewis et al. (2019). Quaternary Science Reviews 223, 1-3. Gibson, S., 2019. The Pleistocene history of the Birmingham district. PhD thesis University of Cambridge. 329 pp. Graf, A., 2002. Lower and Middle Palaeolithic Leicestershire and Rutland: progress and potential. Leicestershire Archaeology and History Society 76, 1-46. Green, C.P., Coope, G.R., Currant, A.P., Holyoak, D.T., Ivanovich, M., Jones, R.L., Keen, D.H., McGregor, D.F.M., Robinson, J.E., 1984. Evidence of two temperate episodes in late Pleistocene deposits at Marsworth, UK. Nature 309, 778. Head, M.J., Gibbard, P.L., 2015. Early-Middle Pleistocene transitions: Linking terrestrial and marine realms. Quaternary International 389, 7-46. Heijnis, H., 1992. Uranium/thorium dating of Late Pleistocene peat deposits in NW Europe. Doctoral dissertation, Rijksuniversiteit Groningen.

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Hughes, P.D. Gibbard, P.L., 2019. The ‘Missing Glaciations’ of the Middle Pleistocene. Quaternary Research in press. Hunt, C.O., 1992. Pollen and algal microfossils from the High Lodge clayey-silts, in: Ashton, N.M., Cook, J., Lewis, S.G., Rose, J. (Eds), High Lodge: Excavations by G. de G. Sieveking, 1962-8 and J. Cook, 1988, 109–115. British Museum Press, London. Jones, R.L. Keen, D.H., 1993. Pleistocene environments in the British Isles. Chapman & Hall, London. 346 p. Keen, D. H., Hardaker, T., Lang, A.T.O., 2006. A Lower Palaeolithic industry from the Cromerian (MIS 13) Baginton Formation of Waverley Wood and Wood Farm Pits, Bubbenhall, Warwickshire, UK. Journal of Quaternary Science 21, 457–470. Keen, D.H., Coope, G.R., Jones, R.L., Field, M.H., Griffiths, H.I., Lewis, S.G., Bowen, D.Q., 1997. Middle Pleistocene deposits at Frog Hall pit, Stretton-on-Dunsmore, Warwickshire, English Midlands, and their implication for the age of the type Wolstonian. Journal of Quaternary Science 12, 183-208. Kelly, M.R., 1968. Floras of Middle and Upper Pleistocene age from Brandon, Warwickshire. Philosophical Transactions of the Royal Society of London B 254, 401-415. Kleinmann, A., Müller, H., Lepper, J., Waas, D., 2011. Nachtigall: A continental sediment and pollen sequence of the Saalian Complex in NW-Germany and its relationship to the MIS-framework. Quaternary International 241(1), 97-110. Lang, N., Wolff, E.W., 2011. Interglacial and glacial variability from the last 800 ka in marine, ice and terrestrial archives. Climates of the Past 7, 361–380. www.climpast.net/7/361/2011/doi:10.5194/cp-7-361-2011 Lewis, S.G., 1989b. Huncote, Leicestershire, in: Keen, D.H. (Ed.), West Midlands. Field Guide. Quaternary Research Association, London, pp. 111-116. Lewis, S.G., 1989b. Witham on the Hill, Lincolnshire, in: Keen, D.H. (Ed.), West Midlands. Field Guide. Quaternary Research Association, London, pp. 123-130. Lewis, S.G., 1993. The status of the Wolstonian glaciation in the English Midlands and East Anglia. PhD thesis, University of London. Lewis, S.G., Ashton, N., Field, M.H., Hoare, P.G., Kamermans, H., Knul, M., Mücher, H.J., Parfitt, S.A., Roebroeks, W., Sier, M.J., 2019. Human occupation of northern Europe in MIS 13: Happisburgh Site 1 (Norfolk, UK) and its European context. Quaternary Science Reviews 211, 34-58. Lindner, L., Marks, L., Nita, M., 2013. Climatostratigraphy of interglacials in Poland: Middle and Upper Pleistocene lower boundaries from a Polish perspective. Quaternary International 292, 113-123. Lister, A.M., 1989. Mammalian faunas and the Wolstonian debate. In: Keen, D.H. (ed.) West Midlands. Field Guide. Quaternary Research Association, London, pp. 5-11. Litt, T., Behre, K.E., Meyer, K.D., Stephan, H.J., Wansa, S., 2007. Stratigraphische Begriffe für das Quartär des norddeutschen Vereisungsgebietes. Eiszeitalter und Gegenwart 56, 7-65. Litt, T., Schmincke, H.U., Frechen, M. and Schlüchter, C., 2008. Quaternary, in: McCann, T. (Ed.), The geology of central Europe 2, 1287-1340.

27

1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283

Maddy, D.M. 1999. English Midlands, in: Bowen, D.Q (Ed.), A revised correlation of the Quaternary deposits in the British Isles. Geological Society Special Report no.23, pp. 28-44. Maddy, D., Coope, G.R., Gibbard, P.L., Green, C.P., Lewis, S.G., 1994. Reappraisal of the Middle Pleistocene deposits near Brandon, Warwickshire and their significance for the Wolston glacial sequence. Journal of the Geological Society 151, 221-233. Mania, D., 1995. Die geologischen Verhältnisse im Gebiet von Schöningen. Archäologische Ausgrabungen im Braunkohlentagebau Schöningen, Landkreis Helmstedt, Hahnsche Buchhandlung, Hannover, pp.33-43. McNabb, J., 2001 The East Midlands and the Palaeolithic Archaeology of Western Doggerland. (Unpublished contribution to East Midlands Archaeological Research Framework, Leicestershire and Rutland SMR). (http://www.le.ac.uk/archaeology/pdf_files/emidpal/pdf) Meijer, T., 1985. The pre-Weichselian nonmarine molluscan fauna from MaastrichtBelvédère (southern Limburg, the Netherlands). Mededelingen Rijks Geologische Dienst 39, 75-98. Meijer, T., 1986. Non-marine biozonation of Quaternary deposits in the Netherlands, in: Proceedings of the 8th International Malacological Congress, Budapest 1983. 161-163. Meijer, T., 1991. Molluscan investigation of ice-pushed Pleistocene deposits near Wageningen, the Netherlands. Mededelingen Rijks Geologische Dienst 46, 5664. Mellars, P.A., 1974. The Palaeolithic and Mesolithic. in: Renfrew, C. (Ed.), British prehistory: a new outline. London: Duckworth, 41-99. Miall, A.D., 1996. The geology of fluvial deposits. Springer, Berlin. Mitchell, G.F., Penny, L.F., Shotton, F.W., West, R.G., 1973. A Correlation of Quaternary deposits in the British Isles. Geological Society of London Special Report 4, 99 pp. Murton, J.B., 2013. Marsworth/Pitstone SSSI (SP9341), in: Catt, J. Murton, J.B. Brown, E. Maton, C. (Eds), Quaternary History of the Chiltern Plateau and Scarp: Little Heath and Marsworth/Pitstone – Scientific and Conservation Problems. Field Guide. Quaternary Research Association: London. pp. 14-22. Murton, J.B., Baker, A., Bowen, D.Q., Caseldine, C.J., Coope, G.R., Currant, A.P., Evans, J.G., Field, M.H., Green, C.P., Hatton, J., Ito, M., Jones, R.L., Keen, D.H., Kerney, M.P., McEwan, R., McGregor, D.F.M., Parish, D., Robinson, J.E., Schreve, D.C., Smart, P.L., 2001. A Late Middle Pleistocene temperate– Periglacial-temperate sequence (Oxygen Isotope Stages 7–5e) near Marsworth, Buckinghamshire, UK. Quaternary Science Reviews 20, 1787–1825. Murton, J.B., Bowen, D.Q., Candy, I., Catt, J.A., Currant, A., Evans, J.G., Frogley, M.R., Green, C.P., Keen, D.H., Kerney, M.P., Parish, D., Penkman, K., Schreve, D.C., Taylor, S., Toms, P.S., Worsley, P., York, L.L. 2015. Middle and Late Pleistocene environmental history of the Marsworth area, south-central England. Proceedings of the Geologists' Association, 126, 18-49. Old, R.A., Sumbler, M.G., Ambrose, K., 1987. Geology of the country around Warwick. Memoir British Geological Survey, The Stationary Office: London.

28

1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329

Osborne, P.J., Shotton, F.W., 1968. The faunas of the channel deposits of early Saalian age at Brandon. Philosophical Transactions of the Royal Society of London, B254, 417-424. Paterson, T.T., 1937 Studies in the Palaeolithic succession in England: No.1. The Barnham sequence. Proceedings of the Prehistoric Society 3, 87-135. Paterson, T.T., 1939. Pleistocene stratigraphy of the Breckland. Nature 143, 822. Paterson, T.T., 1942. Lower Palaeolithic Man in the Cambridge district. PhD thesis University of Cambridge, 196 pp. Penkman K.E.H., Preece, R.C., Bridgland, D.R., Keen, D.H., Meijer, T., Parfitt, S.A., White, T.S., Collins, M.J., 2013. An aminostratigraphy for the British Quaternary based on Bithynia opercula. Quaternary Science Reviews 61, 111134. Penkman, K.E.H., Preece,R.C., Keen, D.H., Collins, M.J., 2010. Amino- acid geochronology of the type Cromerian of West Runton, Norfolk, UK. Quaternary International 228, 25–37. Phillips, L., 1976. Pleistocene vegetational history and geology in Norfolk, with an appendix on the non-marine mollusca from Swanton Morley. Philosophical Transactions of the Royal Society of London B 275, 215-286. Preece R.C., 2001. Molluscan evidence for differentiation of interglacials within the ‘Cromerian Complex’. Quaternary Science Reviews 20, 1643-1656 Preece, R.C., Parfitt, S.A., Bridgland, D.R., Lewis, S.G., Rowe, P.J., Atkinson, T.C., Candy, I., Debenham, N.C., Penkman, K.E., Rhodes, E.J., Schwenninger, J.L., 2007. Terrestrial environments during MIS 11: Evidence form the Palaeolithic site at West Stow, Suffolk, U.K. Quaternary Science Reviews 26, 1256–1300. Railsback, L.B., Gibbard, P.L., Head, M.J., Voarintsoa, N.R.G., Toucanne, S., 2015. An optimized scheme of lettered marine isotope substages for the last 1.0 million years, and the climatostratigraphic nature of isotope stages and substages. Quaternary Science Reviews 111, 94-106. Rice, R.J., Douglas, T., 1991. Wolstonian glacial deposits and glaciation in Britain, in: Ehlers, J., Gibbard, P.L., Rose, J. (Eds), Glacial Deposits in Great Britain and Ireland, Rotterdam, Balkema, pp. 25-36. Rice, R.J., 1991. Distribution and provenance of the Baginton Sand and Gravel in the Wreake Valley, north-eastern Leicestershire, England: implications for interregional correation. Journal of Quaternary Science 6, 39-54. Richards, A.E., 1998. Re-evaluation of the Middle Pleistocene stratigraphy of Herefordshire. Journal of Quaternary Science 13, 115-136. Richards, A.E., 1999. Middle Pleistocene glaciation in Herefordshire: sedimentological and structural evidence from the Risbury Formation. Proceedings of the Geologists' Association 110, 173-192. Rose, J., 1987. Status of the Wolstonian glaciation in the British Quaternary. Quaternary Newsletter 53, 1-9. Rose, J., 1992. Regional context and geological background, in: Ashton, N.M., Cook, J., Lewis, S.G., Rose, J. (Eds), High Lodge. Excavations by G. de G. Sieveking, 1962-8 and J. Cook, 1988, British Museum Press, London. pp. 13–24. Ruegg, G.H.J., 1991. Summary of results of the Wgeningen-Fransche Kamp investigations. Mededelingen Rijks Geologische Dienst 46, 97-99.

29

1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375

Schenninger, J.-L., Bridgland, D.R., Howard, A.J., White, T.S., 2007. Optically stimulated luminescence dating of the Trent Valley sediments: problems and preliminary results, in: White, T.S., Bridgland, D.R., Howard, A.J., White, M.J. (Eds), The Quaternary of the Trent Valley and adjoining regions field guide, pp. 62–65. Quaternary Research Association: London. Serangeli, J., Rodríguez-Alvarez, B., Tucci, M., Verheijen, I, Bigga, G., Böhner, U., Urban, B., van Kolfschoten, Th., Conard, N.J., 2018. The Project Schoningen from an ecological and cultural perspective. Quaternary Science Reviews 198, 140-155. Shotton, F.W. West, R.G., 1969. Stratigraphical table of the British Quaternary. Proceedings of the Geological Society 1656, 155-157. Shotton, F.W., 1929. The geology of the country around Kenilworth, Warwickshire. Quarterly Journal of the Geological Society 85, 167-222. Shotton, F.W., 1953. The Pleistocene deposits of the area between Coventry, Rugby and Leamington, and their bearing on the topographic development of the Midlands. Philosophical Transactions of the Royal Society of London B 237, 209-260. Shotton, F.W., 1968. The Pleistocene succession around Brandon, Warwickshire. Philosophical Transactions of the Royal Society of London B 254, 387-400. Shotton, F.W., 1976. Amplification of the Wolstonian Stage of the British Pleistocene. Geological Magazine 113, 241-250. Shotton, F.W., 1983a. The Wolstonian Stage of the British Pleistocene in and around its type area of the English Midlands. Quaternary Science Reviews 2, 261-280. Shotton, F.W., 1983b. Observations on the type Wolstonian glacial sequence. Quaternary Newsletter 40, 28-36. Shotton, F.W., 1989. The Wolston sequence and its position within the Pleistocene, in: Keen, D.H. (Ed.), West Midlands. Field Guide. Quaternary Research Association, London, pp. 1-4. Shotton, F.W. Keen, D.H., Coope, G.R., Currant, A.P., Gibbard, P.L., Aalto, M., Peglar, S.M., Robinson, J.E., 1993. Middle Pleistocene deposits at Waverley Wood Farm pit, Warwickshire, England. Journal of Quaternary Science 8, 293-325. Simpson, I.M. West, R.G., 1958. On the stratigraphy and palaeobotany of a late‐ Pleistocene organic deposit at Chelford, Cheshire. New Phytologist 57, 239-250. Stapert, D., 1991. Archaeological research in the Fransche Kamp pit, near Wageningen, (Central Netherlands). Mededelingen Rijks Geologische Dienst 46, 72-88. Straw A., 2000. Some observations on ‘Eastern England’ in ‘A Revised Correlation of Quaternary deposits in the British Isles’, (ed. DQ Bowen, 1999). Quaternary Newsletter 91, 2–6. Straw, A., 2005 Glacial and pre-glacial deposits at Welton-le-Wold, Lincolnshire, Exeter. Studio Publishing, UK. 39 pp. Straw, A., 2011 The Saale glaciation of eastern England. Quaternary Newsletter 123, 28–35. Straw, A., 2015 The Quaternary sediments at Welton-le-Wold, Lincolnshire. Mercian Geologist 18, 228–233.

30

1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419

Sumbler, M.R., 1989. The Frog Hall sand and gravel: a ‘Wolstonian’ fluvial deposit near Coventry. Quaternary Newsletter 58, 3–8. Sumbler, M.G., 1983a. A new look at the type Wolstonian Glacial deposits. Proceedings of the Geologists’ Association 94, 23-31. Thomas, G.N., 2001. Late Middle Pleistocene pollen biostratigraphy in Britain: pitfalls and possibilities in the separation of interglacial sequences. Quaternary Science Reviews 20, 1621-1630. Turner, C., 1970. The Middle Pleistocene deposits at Marks Tey, Essex. Philosophical Transactions of the Royal Society of London B, 257, 373-437. Turner, C., 1973. High Lodge, Mildenhall, TL 739753, in: Rose, J., Turner, C. (Eds), Clacton Field Guide, (unpaginated). Quaternary Research Association, Cambridge. Turner, C., 1978. Vegetational remains from the lacustrine deposits at High Lodge. Unpublished report: British Museum, London. Turner, C., West, R.G., 1968. The subdivision and zonation of interglacial periods. Eiszeitalter und Gegenwart 19, 93–101. Tzedakis, P.C., Roucoux, K.H., de Abreu, L., Shackleton N.J., 2004. The duration of forest stages in southern Europe and interglacial climate variability. Science 306, 2231-2235. Urban, B., 1995. Palynological evidence of younger Middle Pleistocene interglacials (Holsteinian, Reinsdorf and Schöningen) in the Schöningen open cast lignite mine (eastern Lower Saxony, Germany). Mededelingen Rijks Geologische Dienst 52, 186. Van Kolfschoten, T., 1985. The Middle Pleistocene (Saalian) and Late Pleistocene (Weichselian) mammal faunas from Maastricht-Belvédère. Southern Limburg, the Netherlands). Mededelingen Rijks Geologische Dienst 39, 45-74 Van Kolfschoten, T., 1991. The Saalian mammal fossils from Wageningen-Fransche Kamp. Mededelingen Rijks Geologische Dienst 46, 38-53. Van Kolfschoten, T., Roebroeks, W., Vandenberghe, J., 1993. The Middle and Late Pleistocene sedimentary and climatic sequence at Maastricht-Belvédère: the type locality of the Belvédère Interglacial. Mededelingen Rijks Geologische Dienst 47, 81-91. Vandenberghe, J., 1995. Timescales, climate and river development. Quaternary Science Reviews 14, 631-638. West, R.G., 1957. Interglacial deposits at Bobbitshole, Ipswich. Philosophical Transactions of the Royal Society of London B 241, 1-31. West, R.G., 1963. Problems of the British Quaternary. Proceedings of the Geologists' Association 74, 147-186. West, R.G., 1968. Pleistocene geology and biology, with especial reference to the British Isles. Longmans Green, London. West, R.G., 1980. Pleistocene forest history of East Anglia. New Phytologist 85, 571– 622. West, R.G., 2018. Breckland meres and Palaeolithic archaeology. Bulletin of the Geological Society of Norfolk 67, 3-18.

31

1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465

West, R.G., Gibbard, P.L., Boreham, S., Rolfe, C., 2014. Geology and geomorphology of the Palaeolithic site at High Lodge, Mildenhall, Suffolk, England. Proceedings of the Yorkshire Geological Society 60, 99-121. Westerhoff, W.E., Geluk, M.C., de Mulder, E.F.J., 2003. Geschiedenis van het Kwartair, in: de Mulder, E.F.J., Geluk, M.C., Ritsma, I., Westerhoff, W.E., Wong, Th.E. (Eds), De ondergrond van Nederland. Geologie van Nederland, Deel 7, 167-246. Nederlands Instituut voor Toegepaste Geowetenschappen TNO. White, T.S., Bridgland, D.R.., Westaway, R, Howard A.J., White, M.J., 2010. Evidence from the Trent terrace archive, Lincolnshire, UK, for lowland glaciation of Britain during the Middle and Late Pleistocene. Proceedings of the Geologists' Association 121, 141–153. White, T.S., Bridgland, D.R., Westaway, R, Straw, A., 2017. Evidence for late Middle Pleistocene glaciation of the British margin of the southern North Sea. Journal of Quaternary Science 32, 261–271. Worsley, P., 1987. Permafrost stratigraphy in Britain—a first approximation. Periglacial Processes and Landforms in Britain and Ireland. Cambridge University Press, Cambridge, 89, p.99. Worsley, P., 2015. Late Pleistocene geology of the Chelford area of Cheshire. Mercian Geologist 18, 202-212. Wymer, J.J., 1985. Palaeolithic sites of East Anglia. Geobooks, Norwich. Zagwijn, W.H., 1973. Pollenanalytic studies of Holsteinian and Saalian Beds in the northern Netherlands. Mededelingen Rijks Geologische Dienst 24, 139—156. Zagwijn, W.H., 1989. Vegetation and climate during warmer intervals in the Late Pleistocene of western and central Europe. Quaternary International 3, 57-67.

Appendix 1. Possible stratotype section for the Waverley Wood temperate event As Penkman et al. (2013, p. 123) state 'No formally defined British type-site exists for MIS 7, although the site at Strensham in the Avon valley in Worcestershire (de Rouffignac et al., 1995) has been proposed as the type-site for this particular ‘aminozone’ (Bowen, 1999)'. They continue: 'Our new data … show that the extent of protein degradation in the opercula from Strensham is greater than that from the Ipswichian type-site at Bobbitshole near Ipswich, but less than that from the aforementioned MIS 9 sites'. They therefore equate the Strensham deposit with their MIS 7 (or Late Wolstonian as it should be termed). The Strensham Member (Avon Valley Formation: Maddy 1999) deposits [NGR: SO 904397] (Fig. 1), comprising grey clay 40 cm thick, underlie a terrace of the River Avon in Warwickshire (de Rouffignac et al., 1995). Apart from giving AA estimates from fossil Mollusca the fossiliferous sediments also contained pollen and plant macrofossils, Coleoptera and notably skeletal remains of a mammoth. The evidence indicated that the deposits accumulated in a slowly flowing river channel, the surrounding area supporting marsh and species-rich grassland with few, if any trees. This sequence has been compared to the Lower Channel sequence at

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1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511

Marsworth (Murton et al., 2001). If correct this suggests that the Strensham sequence might represent a fragment of the same event as in the Midlands sites. As regards the suitability of the Strensham site as a type-locality, the poorly constrained site and local geology, combined with the lack of development of the palaeontological assemblages, the conclusions being based on isolated ‘spot’ samples, and, as already stated the fact that AA determinations from many sequences appear unreliable and therefore reliance on these results as the primary criterion for correlation is weak, the locality is not ideal as a reference sequence. Furthermore, the fact that the Avon river valley is incised into the Wolston and Baginton Formation sequences precludes the possibility that the Strensham deposit could be equivalent of those described above. On the contrary the Strensham sequence must post-date the Wolstonian glaciation s.s. (Morton Stadial; Gibson, 2019) since the valley of the River Avon did not come into existence until after that occurred (Shotton, 1953). Together this indicates that the Strensham sequence is unsuitable as a reference stratotype for the temperate event discussed in this article, nor indeed is it suitable for any other event that might be proposed in future, there being a high probability that it dates either from the latest, post-glacial interval of the Wolstonian Stage (Pershore Stadial = Warthe Stadial: Gibson, 2019: Table 1), or else it must post-date that event. Given these points, correlations proposed with this sequence based on AA determinations also fall into question, but these lie beyond the scope of the present study. Whilst the Marsworth sequence demonstrates the relationship of the Late Wolstonian temperate deposits to both periglacial slope materials and the overlying last interglacial fluvial channel fill, the sequence, although highly detailed, is of very local character. In contrast, based on the character and regional relationships of the sequences presented here it seems appropriate to propose that the Waverley Wood channel fill (details) should be adopted as the stratotype for the temperate event discussed herein, whilst the basal boundary of the subsequent Morton Stadial (Gibson, 2019) should also be located in this sequence at the point where coldclimate flora and fauna are recognised.

Figure captions Figure 1. Location map showing the location of the sites discussed in the text and the maximum limit of glaciation during the Late Wolstonian Substage (modified from Gibson, 2019; Gibbard et al., 2018). The National Grid co-ordinates system is shown on the map margins. Figure 2. Summary logs of the principal sites discussed in the text. The lithological divisions use standard facies abbreviations and the lithostratigraphical formations are also shown. The colours (in the web version of the figure) are: blue, cold-climate environment, red, temperate climate environment; yellow Baginton Formation arenaceous deposits. For further explanation, see text.

33

1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522

Table caption Table 1. Geological timetable of events in the English Midlands region and their correlation to the near Continent during the Middle to Late Pleistocene subseries (modified from Gibbard et al., 2013). The NW European chronostratigraphy/climatostratigraphy is based on Litt et al. (2007, 2008). For further explanation see text.

34

Glacial events

Climate/ environment

Aggradation of temperate floodplain and channel sediments

Temperate

Downcutting and aggradation of gravel and sand in river valleys Non-deposition Downcutting and aggradation of gravel and sand in river valleys, e.g. Balderton Member (Trent system)

Periglacial

Eemian

~5e

Warthe Stadial 6

Wolstonian glaciation s.s. lacustrine ponding of river valleys. (Wolston, Risbury and Feltwell Formations).

Periglacial / glacial

Late

Aggradation of gravel and sand in river valleys (Baginton Formation, Mathon Formation, etc.)

Approx. Marine Isotope (Sub-) Stage (MIS)

Human Continental chronostratigraphy / occupation climatostratigraphy

Drenthe Stadial

Deposition of Waverley Wood, and associated deposits. Mathon, Brooksby, High Lodge, ?Frog Hall deposits silt deposits. Complex ‘temperate’ channel fills.

Boreal / temperate

*

Downcutting and aggradation of gravel and sand in river valleys

Periglacial

*

Non-deposition

Periglacial

Downcutting and aggradation of gravel and sand in river valleys.

Periglacial

?Schöningen Interstadial/ Interglacial

~7a-c, ?7e

Early /Middle

Early /Middle

Wolstonian

Late

Ipswichian

Fluvial events

Saalian

British chronostratigraphy / climatostratigraphy

?

8-~11b

?Fuhne Stadial Hoxnian

Infill of lake basins, incoherent river system, e.g. Nechells, Quinton

Temperate

*

Holsteinian

~11c

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

none

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