Chronology of the Lower and Middle Palaeolithic in NW Europe: developer-funded investigations at Dunbridge, Hampshire, southern England

Proceedings of the Geologists’ Association 123 (2012) 584–607

Contents lists available at SciVerse ScienceDirect

Proceedings of the Geologists’ Association journal homepage: www.elsevier.com/locate/pgeola

Chronology of the Lower and Middle Palaeolithic in NW Europe: developer-funded investigations at Dunbridge, Hampshire, southern England Phil Harding a,*, David R. Bridgland b, Peter Allen c, Philippa Bradley a, Michael J. Grant a,d, David Peat e, Jean-Luc Schwenninger e, Rebecca Scott f, Rob Westaway g,h, Tom S. White i a

Wessex Archaeology, Portway House, Old Sarum, Salisbury SP4 6EB, UK Department of Geography, Durham University, South Road, Durham DH1 3LE, UK Department of Geography, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK d Centre for Earth and Environmental Science Research, School of Geography, Geology and the Environment, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey KT1 2EE, UK e Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK f Department of Prehistory and Europe, British Museum, 56 Orsman Road, London N1 5QL, UK g Faculty of Mathematics, Computing and Technology, The Open University, Gateshead NE8 3DF, UK h NIReS, Newcastle University, Newcastle upon Tyne NE1 7RU, UK i Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK b c

A R T I C L E I N F O

A B S T R A C T

Article history: Received 6 June 2011 Received in revised form 9 March 2012 Accepted 12 March 2012 Available online 6 April 2012

This paper reports important findings relating to the chronology of Palaeolithic occupation, artefact typology and Quaternary fluvial deposits from a geoarchaeological watching brief undertaken over 17 years at Kimbridge Farm Quarry, Dunbridge, Hampshire. Sections were recorded and sampled and 198 artefacts, principally hand axes, were collected, with the primary aim of enhancing understanding of the geological context of the richest Lower Palaeolithic assemblage from Hampshire. Digital terrain modelling was used to characterize the three-dimensional form of the fluvial geology. Two gravel terraces have been confirmed: an upper Belbin Formation, which contained most of the archaeological artefacts, and a lower Mottisfont Formation. Results of specific note included recovery of artefacts demonstrating elements of ‘proto-Levallois’ technology from within the Belbin Gravel deposition. Fully developed Levallois technology was present across both the Belbin Gravel and the Mottisfont Formation at Dunbridge, the latter having an otherwise relatively sparse Palaeolithic content. Previously published OSL dating, supplemented by new data, has been combined with uplift modelling to suggest dates of MIS 9b and MIS 8, respectively, for these two gravels. This fits well with evidence from other sites in England and the near Continent for the timing of the earliest Levallois at around MIS 9. The results from the Dunbridge watching brief have demonstrated that this response provides a relatively cost effective method by which important scientific data can be salvaged from commercial quarrying. ß 2012 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved.

Keywords: Middle Pleistocene Levallois Solent OSL dating River terrace stratigraphy

1. Introduction Pleistocene river gravels in the Hampshire Basin, southern England, have long been recognized as important sources of Lower and Middle Palaeolithic artefacts (Bury, 1923; Calkin and Green, 1949; Wymer, 1999). These gravels form terraces of the erstwhile River Solent (Prestwich, 1898; Everard, 1954; Allen and Gibbard, 1993; Bridgland, 2001; Westaway et al., 2006; Briant et al., 2006; Bates and Briant, 2009; Bates et al., 2010) and of its north-bank tributaries, most of which continue to drain southwards to the coast, the parent river having been submerged to form the strait

* Corresponding author. E-mail address: [email protected] (P. Harding).

between Hampshire and the Isle of Wight (Fig. 1). One of the most prolific sites was at Dunbridge, Hampshire, in the valley of the River Test (Fig. 1), where almost 1000 hand axes were found (Roe, 1968a, 1981; Wessex Archaeology, 1993). It was one of only a handful of truly rich sites in the Solent catchment (Fig. 1), along with Woodgreen, in the Avon (Bridgland and Harding, 1987), Corfe Mullen, in the Stour (Green, 1947; Calkin and Green, 1949), and Moreton, in the Frome (Arkell, 1947). These ‘super sites’ (Ashton and Hosfield, 2010) each contributed more than 10% of all the hand axes collected from their respective terraces. They shared a common geomorphological setting at the boundary between the Chalk uplands and Tertiary beds of the Hampshire Basin. This coincidence Ashton and Hosfield (2010) and Hosfield (2011) have attributed to the reduced gradient as the rivers issued from constricted valleys through the Chalk, as well as the ready supply

0016-7878/$ – see front matter ß 2012 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.pgeola.2012.03.003

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

585

Fig. 1. Location of the Dunbridge project site and other quarries nearby; inset shows the geology of the region, with other important archaeological sites located.

of flint from the sides of these valleys and the enhanced quantities of material that were flushed into them from the Chalk upland. The disused gravel pit that was the source of the Dunbridge assemblage was designated as a Site of Special Scientific Interest (SSSI) in the mid-1980s, an outcome of the Geological Conservation Review carried out by the UK Government conservation agency

(cf. Bridgland and Harding, 1987). At much the same time (1987), Halls Aggregates (South Coast Limited; now Cemex), sought consent for gravel extraction from farmland to the south of the SSSI, a proposal that met with considerable local opposition and was subject to a lengthy planning enquiry. The perceived scientific and archaeological importance of the deposits, some of them

586

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

contiguous with those within the SSSI, led to the eventual planning consent carrying the constraint that regular developer-funded archaeological and geological monitoring should take place. Thus from 1991 to 2007 a systematic watching brief was in operation during gravel extraction at the Kimbridge Farm quarry, Dunbridge. This project aimed to establish the geological context of the Dunbridge artefacts from the River Test terrace gravels, which were believed to be of more than a one period (Bridgland and Harding, 1993). A sequence of eleven terraces is recognized in the Test downstream of Romsey (BGS, 1987), but detailed mapping of the gravels in the Dunbridge area has never been undertaken, a shortcoming that has hampered interpretation and correlation of the Dunbridge assemblage. Nonetheless it has long been clear that Dunbridge is important to the chronology of the Palaeolithic in Britain and NW Europe, since the site records the appearance in the region of Levallois technology (Middle Palaeolithic); three flakes made using this core-preparation technique were known from the extant collections (Roe, 1968a). During the protracted watching brief 198 additional artefacts were recovered, the find-spots for 190 of which could be mapped with reasonable accuracy, allowing the extent of the Palaeolithic artefact scatter and its relationships to the geological deposits to be established. Most importantly this also included the recovery of additional Levallois material, including three ‘proto-Levallois’ and three developed Levallois cores. Since the initiation of the project at the Kimbridge Farm pit, a technique of use for the direct dating of clastic fluvial deposits (including those that lack organic material or other fossils) had become routine, this being optically stimulated luminescence (OSL) dating of sand grains (e.g., Jain et al., 1999; Wallinga, 2001; Toms et al., 2005; Briant et al., 2006; Schwenninger et al., 2006, 2007; Busschers et al., 2007; Bateman et al., 2008; Bates et al., 2010; Bennett et al., 2011). A pilot study was undertaken to ensure that sufficient quantities of quartz grains could be retrieved for dating and to establish whether characteristics were suitable for full analysis (Schwenninger, 2009). In addition deposit modelling was undertaken, based on pre-extraction boreholes and the watching brief archive, to interpret the Pleistocene geology of the quarried area and place the Dunbridge fluvial gravels in their correct Quaternary context. 2. Previous records from the Dunbridge locality The Kimbridge Farm pit exploited an area on the western side of the Test valley (centred on NGR SU 321 255), 19 ha in extent and approximately 900 m from the present river channel, ca. 500 m south of its confluence with the tributary River Dun (Fig. 1). The quarried land sloped from 47 m O.D. in the north to 36 m O.D. in the south, although rising steeply to 60 m O.D. in the west, beyond the outcrop of terrace gravel. The Dunbridge SSSI, now heavily wooded, lies to the north. The solid geology is the Palaeogene (Palaeocene) Reading Formation (formerly Reading Beds), generally a well-bedded (typically cross-bedded) medium-fine sand, with staining and partial cementation by iron and/or manganese. Beds of well-rounded flint pebbles occur sporadically and were observed beneath the Pleistocene terrace gravels in parts of the quarry area (Bridgland and Harding, 1993), with large lenses of clay occurring less frequently. Extraction of the Dunbridge gravel appears to have commenced in the late 19th century; a small pit, accessed from Dunbridge Lane, was mapped in 1874, approximately 300 m north of the most recent quarry. By 1911 the embryonic pit had extended southwards, with additional workings to the west of Sandpits Copse. It is likely that these two pits, with an additional quarry at Kimbridge, approximately 1 km to the south, represent the extent of quarrying prior to the work of Dale (1912, 1918) and White (1912), encompassing the sections and producing the artefacts

they described. Dale (1912) confirmed that two pits had been worked at Dunbridge, noting that the easternmost, by then no longer active, had produced a large number of implements. Extraction expanded southwards during World War I (Dale, 1918) to include the areas subsequently designated as the SSSI (Fig. 1). Subsequent mapping suggests that extraction was completed by 1945, as no further amendments to the quarried area were surveyed after that date. White (1912) suggested that there were two ‘levels’ or ‘stages’ of terrace gravels in this area that yielded palaeoliths, an upper ‘Belbin Stage’ (named after Belbin’s Pit, Romsey) and a lower ‘Mottisfont Stage’. He ascribed the gravel exploited in the original Dunbridge pit to the Belbin Stage and that quarried at Kimbridge, at a lower topographic level, to the Mottisfont Stage, noting further gravel deposits connecting these on the intervening slope. Terraces attributable to the Belbin Stage have been a rich source of palaeoliths wherever they have been uncovered, including Belbin’s Pit at Romsey (Kelley, 1937; Roe, 1968a). Quarries further downstream at Warsash have also yielded Levallois artefacts (e.g., Burkitt et al., 1939; Roe, 1968a,b; Wessex Archaeology, 1993), although these are poorly provenanced and, at one site (Newbury’s Pit; SU 497 061; Burkitt et al., 1939), it has been inferred from the limited detail of stratigraphic description that they were possibly from colluvial overburden above fluvial terrace deposits (e.g., Westaway et al., 2006; Ashton and Hosfield, 2010). The quarries at Dunbridge, however, have remained the most prolific in Hampshire (Harding, 1998). One of the main artefact collectors, Dale (1912), considered the gravels from Dunbridge and Kimbridge to be closely related, despite their altitudinal difference. He subdivided the gravels based on colour, differentiating a lower dark red gravel, a middle yellow–brown gravel and an upper white gravel. He noted that conflicting opinions were prevalent between geologists, who considered the deposits to represent a single deposit that had been affected by leaching, and archaeologists who maintained that implements from the lower body of the gravel were frequently heavily rolled and therefore considerably older than those from the upper parts of the gravel, which contained implements that were relatively unrolled. By 1918 he favoured the argument that this represented gravels of two periods, with the fresh hand axes in the upper six feet of the white gravels considered to be of later character than those in the lower gravel (Dale, 1918). He also noted that these two deposits were separated by a ferruginous band that extended widely around the Dunbridge pit, although he recognized that this could be the result of postdepositional modification by percolating ground water. Roe (1964, 1968a) catalogued 967 implements and rough outs from Dunbridge, representing 95% of the extant collections, in a pilot metrical study of hand axe morphology, but omitted it in a subsequent study (Roe, 1968b) as an unreliable sample, subsequently grouping it with sites that might have yielded coherent assemblages, but are otherwise of limited value (Roe, 1981). He noted the Dunbridge material to be disturbed, badly collected and possibly also mixed with implements of other unrelated traditions (Roe, 1981). Pointed implements, mainly in a rolled and stained condition, predominate, supplemented by ovate forms, many in a similar condition. However, there are also finely made pointed and ovate hand axes, cleavers, elements of Levallois technology and a bout coupe´ hand axe, which are less heavily rolled and patinated white and were considered by Roe likely to be stratigraphically and chronologically later. A sub-sample of 168 hand axes from the site was subsequently re-examined by Hosfield and Chambers (2004) in a review of early prehistoric behaviour using assemblages from secondary archaeological contexts. They concluded that, although horizontal and vertical reworking of material influenced the data set, assemblages such as that from Dunbridge were indeed representative of peaks

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

and troughs in the presence of human populations in the Lower and Middle Palaeolithic. Their analysis confirmed Roe’s (1981) conclusions that the assemblage was mixed, contained a large number (42%) of pointed implements with a range of other forms and included no diagnostic manufacturing techniques, such as twisted profiles. No further scientific study of the site was undertaken until 1986, when three hand-dug sections were documented as part of the Geological Conservation Review (Bridgland and Harding, 1987). This work produced an unrolled, unstained and unpatinated pointed hand axe in talus derived from the upper part of the section, thereby confirming the occurrence of implements in mint condition in that part of the deposit. Further work was undertaken to assist the planning application for gravel extraction. A transect of machine-dug evaluation test pits (Collcutt et al., 1988), supplemented by borehole data, led to the conclusion that two separate Test terrace formations were represented within the planning area: a higher ‘Dunbridge’ unit in the north-western part of the site (synonymous with the Belbin Gravel) and a lower ‘Barley Hill’ division to the south-east. The latter (equivalent to the Mottisfont Gravel) was suggested to be the

587

upper edge of the terrace remnant exploited by the Kimbridge Pits (White, 1912), which was also a source of palaeoliths, although less prolific than the higher-level Dunbridge deposits. A small number of Palaeolithic artefacts, in a rolled condition, were recovered, thereby confirming that the implements had once been part of fluvial bedload. Bridgland and Harding (1993), reporting on the early years of the Dunbridge watching brief, noted that Dale’s (1912) stratigraphy could be matched only in parts of the quarry, based on the four sections recorded by that date (sections 1–4 in Fig. 2). These represented the higher-level Belbin Gravel, the ‘Dunbridge’ division of Collcutt et al. (1988). From about 1997 quarrying extended the workings into the Mottisfont deposits, which are thus reported below for the first time. 3. Wider context: terrace correlation and dating in the Test valley British Geological Survey (BGS) 1:50,000 BGS sheet 299 (Winchester) from 1949 shows only undifferentiated terrace gravel, although the most recent published (2002) and online

Fig. 2. Distribution of boreholes, test pits and exposed sections used within the deposit model and shown in Figs. 5–7. Outline of the deposit model area and extent of Dunbridge quarry are also shown.

588

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

mapping (BGS DigMap) shows the deposits throughout the quarried area (including the lower-level Kimbridge quarries) as ‘River Terraces 2 to 3’. However, it is possible to extrapolate from the detailed mapping on the BGS Southampton sheet (1:50,000 sheet 315; BGS, 1987), the boundary of which is only 2–3 km to the south of Dunbridge. That map shows eleven Test terraces, numbered upwards, both upstream and downstream of Southampton (Edwards et al., 1987; Edwards and Freshney, 1987; BGS, 1987), all of them post-dating the so-called ‘Older River Gravels’ that crop out on the Test–Avon interfluve. However, correlation downstream from Dunbridge into this mapped area is far from straightforward, due to inconsistencies of the terrace scheme on the map, in comparison with the accompanying memoir (cf. Wessex Archaeology, 1993; Westaway et al., 2006, including online supplements). Westaway et al. (2006) noted instances where terrace numbering is miscorrelated between reaches; for

example Terrace 4 in the NW part of the Southampton map becomes Terrace 3 in its SE part, where no Terrace 4 has been identified (although, according to BGS DigMap, Terrace 4 resumes immediately east of the area of the Southampton sheet, as illustrated in Fig. 3). Westaway et al. (2006) thus erected a new scheme of named terraces (see Figs. 3 and 4). The higher and older Belbin Gravel at Dunbridge was included by Westaway et al. (2006) in their Belbin Terrace, which they traced downstream for 25 km to the Hamble area. Throughout this reach it correlates with Terrace 4 of Edwards and Freshney (1987), as indicated in Fig. 4. Further downstream, however, Terrace 4 is not mapped but Westaway et al. (2006) recognized its continuation as their Warsash Terrace, which coincides with the northern (valley-side) edge of Terrace 3 (Fig. 3) of Edwards and Freshney (1987) and occurs at a height of 25 m O.D. in the Warsash area. This correlation was criticised by Ashton and

Fig. 3. Terraces of the River Test. Ornaments follow the named terrace scheme of Westaway et al. (2006), with BGS terrace numbering (from Edwards and Freshney (1987) and adjoining areas covered by BGS DigMap) is also indicated. Note that in some cases numbers applied to what is here regarded as the same deposit differ in different reaches (see text).

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

589

Fig. 4. Longitudinal profile, projected SE with distances measured from zero at NGR SU 320 280, of the terraces of the River Test around and downstream of Dunbridge (after Fig. 17 of Westaway et al., 2006). Compiled using outcrop data from Edwards and Freshney (1987) and BGS (1998). Key sites: 1 – Dunbridge, Belbin Gravel; 2 – Dunbridge, Mottisfont Gravel; 3 – Hunt’s Farm Sports Ground, Timsbury; 4 – Solent Breezes caravan park; 5 – Hook; 6 – Ridge; 7 – Yewtree Farm, Mottisfont; and 8 – Spearywell Woods, Mottisfont. 9 – Pauncefoot Hill Pit, Romsey. 10 – Fleet End Pits, Warsash; 11 – Newbury’s Pit, Warsash. The Belbin gravel is represented using data from boreholes BH 7/84 and BH 9/84, the Mottisfont gravel by boreholes FA-BH1604 and BH 21/84 (cf. Fig. 2). Terraces have been labelled using the Westaway et al. (2006) nomenclature, which is crossreferenced to the Edwards and Freshney (1987) scheme, and with the age estimates from the present study, which supersede those from Westaway et al. (2006). It is suggested that the newly designated Lower Warsash terrace be defined using the type locality provided by the Burkitt et al. (1939) stratigraphic section at Newbury’s Pit, Warsash (SU 497 061). Terrace tie lines interpreted by Westaway et al. (2006), but which are no longer considered tenable, are omitted or depicted using fainter ornament.

Hosfield (2010), who pointed out that the artefact-bearing quarries at Warsash (10 and 11 in Fig. 4) were at a lower height than shown in the Westaway et al. (2006) long-profile diagram (their Fig. 17). This error has been corrected in the updated map in Fig. 3 and long-profile projections illustrated in Fig. 4, which recognize two terraces, equivalent to Terraces 3 and 4 further upstream, within what is mapped as Terrace 3 in the Warsash area. Indeed, throughout much of the wide expanse of Terrace 3 hereabouts there is a subdued break of slope between 15 and 20 m O.D., presumably a degraded bluff between the two terraces. These ‘upper’ and ‘lower’ Warsash terraces correlate, respectively, with the Belbin and Mottisfont terraces further upstream. Given that the artefact-producing quarries were in the lower of these terraces, the implication is that the Levallois technology at Warsash is from the Mottisfont Formation. Ashton and Hosfield (2010) concluded that the Levallois artefacts came from overburden rather than from the fluvial deposits of the Lower Warsash terrace, although this is not readily apparent from the text of Burkitt et al. (1939). Bates and Briant (2009, Figs. 2.2 and 2.5) and Bates et al. (2010, Fig. 13) have provided an independent extension of the BGS terrace scheme upstream from the Southampton map sheet to the Dunbridge area. It is apparent, however, that this adds further inconsistencies in terrace numbering; in their scheme the Belbin and Mottisfont terraces are numbered 5 and 4, rather than 4 and 3, as suggested above. Similar numerical mismatches occur at many other localities in the Test. The present authors therefore prefer to persevere with the scheme of named terraces, based on the principles of lithostratigraphy (cf. Schreve et al., 2002; Bridgland et al., 2011), proposed by Westaway et al. (2006), albeit with the above-mentioned modification. It should be noted that Bates and Briant (2009) and Bates et al. (2010) also numbered the ‘upper ‘and ‘lower’ Warsash terraces as 5 and 4, respectively, thus implying the same correlation with the Belbin and Mottisfont formations as is proposed above (cf. Fig. 4).

3.1. Previous OSL dating Prior to the present study, OSL dating had been undertaken at seven sites in Test terrace deposits and/or in deposits of the main Solent River in the vicinity of its confluence with the Test (Schwenninger et al., 2006, 2007; Bates et al., 2010, Fig. 1). Five of these sites have yielded meaningful numerical ages (Table 1), the other two yielding dates that significantly underestimate the ages of the river terraces concerned, probably because they represent later ‘overburden’ (see Table 1 caption). From Hunt’s Farm Sports Ground, Timsbury, near Romsey (Fig. 3 and Table 1), Bates et al. (2010) sampled gravel forming a terrace 5 m above the modern River Test, i.e. within their Terrace 1 (= the Broadlands Farm Terrace of Westaway et al., 2006). The resultant OSL age estimate of 70 ka indicates deposition during the early Devensian, c. MIS 4, somewhat older than the MIS 2 age assumed for it by Westaway et al. (2006). If this date is correct, the implication might be that the MIS 2 terrace in that part of the Test valley is buried beneath the alluvium of the inner part of the estuary. The four dates from the Solent Breezes Caravan Park (Fig. 3), all suggesting an age within MIS 7 (Table 1), are perhaps overestimates; this site falls within the Hamble Terrace of Westaway et al. (2006), who attributed it to MIS 6. The OSL dates from Hook (Mallards Moor Terrace) and Yewtree Cottage (Bitterne Terrace) would appear to be underestimates of the likely ages (Fig. 3 and Table 1). From Ridge (also Mallards Moor Terrace (Fig. 3), despite being part of a higher-numbered terrace in their scheme), Schwenninger et al. (2006, 2007) reported two OSL dates, 410 and 280 ka (Table 1). Given that this site and Hook are stratigraphically equivalent (cf. Fig. 4), it would be appropriate to calculate a weighted mean age for both (excluding sample X1646 from Hook, which Schwenninger et al. (2006, 2007) identified as unreliable). The resulting age determination is 314  24 ka (2s), indicating a 95.4% confidence limit for an age-distribution of sediments within this terrace between 338 and 290 ka. Given that 3 data components contribute to this

590

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Table 1 Summary of recent OSL dating of the Solent terrace system. Site

Context

MIS stage

NGR

Source

Lab code

Age (1s; ka)

Comments

Hunt’s Farm

Broadlands Farm terrace

MIS 4

SU 346 250

(1,3)

X1577

69  11

Solent Breezes

Hamble terrace

MIS 6

SU 505 039

(1,3) (1,3) (1,3) (1,3)

X1481 X1482 X1483 X1484

213  25 204  18 231  24 221  20

Slight Slight Slight Slight

Hook

Mallards Moor terrace

MIS 10

SU 523 058

(1) (2)

X1646 X1647

237  37 292  20

Underestimate of true age Slight underestimate of true age

Ridge

Ganger Wood terrace

MIS 10

SU 342 182

(1) (2)

X1575 X1576

413  26 280  19

Overestimate of true age Slight underestimate of true age

Yewtree Cottage

Bitterne

MIS 13b

SU 316 275

(1,3)

X1734

380  34

Underestimate of true age

Valid numerical age overestimate overestimate overestimate overestimate

of of of of

true true true true

age age age age

Data from Bates et al. (2010) and Schwenninger et al. (2006, 2007). Context denotes the terrace deposit of Westaway et al. (2006) in which the site is located. MIS denotes the Marine Isotope Stage deduced for the formation of this terrace in the present study. Sources: (1) Schwenninger et al. (2006), (2) Schwenninger et al. (2007), (3) Bates et al. (2010). Numerical ages and quoted uncertainties are always from the most recent reference source. The most significant difference in numerical age between publications is for the sample from Yewtree Cottage, for which source (Allen and Gibbard, 1993) reported an age of 206  20 ka. Sites that yielded numerical ages that considerably underestimate the true ages of the terraces have been excluded. This includes Chilling, in the Mottisfont terrace near Warsash, where brickearth overlying the fluvial terrace deposits yielded a numerical age of 29  2 ka, and Spearywell Woods, in the Bitterne terrace near Mottisfont Abbey, which yielded a numerical age of 11  2 ka.

age-determination, the weighted mean age can also be expressed as 314  14 ka (2 s, s being the standard error in the mean). This age range post-dates MIS 12 but is too old for MIS 8; it potentially includes MIS 10 and MIS 9b, both stages to which terraces within the Solent system have been assigned previously (cf. Westaway et al., 2006). 3.2. Age of Palaeolithic assemblages A case for using Palaeolithic assemblages as a means for dating the terrace sequence in the Solent catchment was proposed by Westaway et al. (2006), based on previous observations by Bridgland (1994, 1998, 2001), White (1998) and White and Ashton (2003). Westaway et al. (2006) regarded first appearances as of particular importance: (1) of artefacts per se, (2) of artefacts made using Levallois technique and (3) of Mousterian of Acheulean Tradition (MTA; specifically, bout coupe´) handaxes. These provided key age constraints for their terrace modelling, which were taken to be (1) MIS 15–13, (2) MIS 9–8 and (3) MIS 3. The potential age-significance of assemblages with large quantities of twistededged ovate handaxes, suggested by White (1998) to occur in MIS 11, was used as a further constraint. Ashton and Hosfield (2010) have undertaken a study to determine whether the archaeology and geology of the Solent could be used to estimate the density of human activity in Britain. They specifically aimed to identify whether the supposed absence of humans after MIS 6 (cf. Sutcliffe, 1995; Bridgland, 1998, 2006) was reflected in the archaeological record. This work drew attention to the fact that, in contrast to the Thames (cf. Wymer, 1999), very little Levallois technology has been identified in the Solent valley and what has been recorded, principally from Warsash, has been poorly provenanced. The rarity of Levallois artefacts led to Ashton and Hosfield (2010) excluding them from their survey, in which only hand axes were used. They did not consider that this dearth of Levallois material reflected collection bias but rather postulated that it might be due either to decreasing populations from MIS 9 or to the prevalence of other technologies. They were generally sceptical about the value of artefacts, and of Levallois in particular, as evidence of age.

pit. This agreement, for which no precedent existed (for review see online supplement, Appendix 1), allowed access for an archaeologist and any related specialists, as required, to record the geological deposits and search for artefacts on one full day or two half days each month. Quarrying commenced in April 1991 and concluded in May 2007, when the reserves were deemed uneconomical. Extraction was initially undertaken using a 3608 tracked excavator, which provided vertical quarry faces that could be examined and representative detailed sections cleaned, logged and photographed. Periodically the position of the quarry face was surveyed and the profile drawn to provide data for three-dimensional terrain modelling. Spoil heaps at the quarry and >40 mm processed material (‘rejects’) were scanned for artefacts. By 1996 the extraction included exploitation of the Palaeogene pebble beds, which reduced the rate at which the Pleistocene fluvial gravel was being quarried. Visits were therefore reduced in 1997, with the agreement of the County Archaeologist, to only one half day visit per month. Extraction became less systematic, employing a shovel loader to dig the gravel, which created irregular pit faces. The fluvial gravel thinned to the south, coincident with the extent of the Belbin Gravel, and was routinely mixed with Palaeogene pebbles on the reject heap; in some cases gravel was imported from neighbouring sites for processing. These circumstances combined to reduce the benefits for regular visits to a minimum. Apart from a rapid increase in extraction in the early part of 2002, when heavily stained gravel, almost certainly from the Mottisfont Formation, was being quarried, subsequent entries in the site day book note no substantial changes to the pit face until its closure. The number of visits and the total number of artefacts recovered annually is shown in Table 2. Artefacts recovered at the quarry could be provenanced with some certainty; material found at the washing plant was recorded by date of discovery, relating this to the known extensions or additions to the quarry face since the previous visit. This methodology provided a consistent, if imprecise, sample of the material being quarried, from which artefacts could be located to general areas within the pit. It could not take any account of stockpiled material that may have been introduced into the washing plant.

4. Methodology 5. Geological data Planning consent was granted for gravel extraction at Dunbridge subject to the implementation of a geo-archaeological watching brief, to be operable throughout the working life of the

Descriptions of the early exposures in the Belbin Gravel (sections 1–4 (a and b); see Figs. 2 and 5) were provided in the

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

591

Table 2 Summary of Dunbridge watching brief details showing artefact recovery by type and year. Visits

Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Total Total Total Total Total Total Total Total Total Total Total Total Total Total Total Total Total

Grand total

15 visits 22 visits 21 visits 22 visits 22 visits 19 visits 9 visits 8 visits 10 visits 9 visits 5 visits 3 visits 2 visits 2 visits 1 visit 3 visits 1 visit

Cores

Broken Cores/Core Fragments

Flakes

Scrapers

Hand axes

Debitage

TOTAL

0 2 0 1 3 3 3 0 1 0 1 1 0 0 0 0 0

0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0

2 8 14 17 23 32 4 2 3 3 1 0 0 0 1 3 1

0 0 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0

0 4 5 7 16 11 5 2 1 3 0 3 0 0 0 3 1

0 0 0 1 1 0 0 0 1 0 0 0 0 0 0 0 0

2 14 21 28 43 46 13 4 6 6 2 4 0 0 1 6 2

15

1

114

4

61

3

198

interim report on the Dunbridge watching brief by Bridgland and Harding (1993). Their interpretation envisaged a single gravel body that had been modified in situ; they found well-bedded gravel, typical of fluvial deposition, to be invariably present in the basal parts of the recorded sections, with bedding becoming increasingly poorly preserved upwards through the sequence, as a result, they suggested, of general pedogenic processes and, in particular, cryoturbation. Where Dale’s (1912) divisions could be recognized, with an upper bleached gravel separated from a lower oxidized gravel by an iron–manganese pan, they regarded this too as the product of pedogenic processes, with the pan probably formed by the downward translocation of mineral salts as part of the bleaching of the upper gravel: essentially a podsolization process. This is not to say that there could not also have been progressive aggradation of the sequence, with hiatuses, such as might explain the variation in artefact occurrence and condition observed by Dale (1918; see above). An additional section in Belbin Gravel was later recorded from the western face of the pit (section 13); although comparable with the earlier sections, it showed a covering of nongravelly overburden (Fig. 6). Exposures, available later during the watching brief, of the Mottisfont Formation (sections 14, 15, 16 and 28/29; see Figs. 2, 6 and 7) again showed fluvially bedded gravel, although often with a loamy or clayey matrix and with large rip-up clasts of poorly consolidated material from the underlying Palaeogene (e.g. the clay clast, 0.4 m across, near the base of section 16: Fig. 6). It seems likely that soliflucted material was being added to the fluvial bedload at this north-western margin of the Mottisfont Gravel floodplain from the slope leading up to the Belbin Gravel, undoubtedly leading to the incorporation of reworked gravel clasts (including occasional artefacts) as well as the finer-grained bedrock-derived material. Iron/manganese staining and panning was again observed at points within the sand and gravel sequences, with a notable pan typically found at the base of the Pleistocene deposits (Fig. 6). Thin beds of open-framework gravel and cross-bedded sand were also recorded, confirming the fluvial origin of the sequence. Pronounced scouring into the bedrock was observed at the bases of sections 14 and 28/29 (Figs. 6 and 7). The upper parts of the geological sequence at certain points within the quarried area comprised non-fluvial ‘overburden’, particularly slope deposits but perhaps including wind-blown material. Any artefacts from such overburden might be considerably later than the indigenous archaeology from the underlying

terrace deposits, only the latter being constrained by the dating framework that is provided by a progressively incised river terrace staircase (cf. Bridgland et al., 2004). Indeed, it has been suggested recently (Ashton and Hosfield, 2010) that Levallois artefacts amongst the collections from Dunbridge and comparable sites in the Test, such as Romsey (Belbin’s Pit) and Warsash, have been derived from non-fluvial overburden. As such clayey ‘overburden’ material was removed from above the gravel prior to quarrying, it was preserved only in sections at the margins of the extraction area, such as section 13 (Fig. 6), which showed two upper layers, a lower one relatively free of gravel clasts and possibly incorporating wind-blown silt; both can probably be attributed to solifluction. Even where recorded sections were at the quarry margins, the uppermost ‘stripped’ layers were poorly exposed at the time of recording, as in sections 28 and 29, which were sampled for the OSL dating (Fig. 7). Elsewhere overburden thickness could be reconstructed from boreholes and other records and incorporated in the digital terrain modelling (see online supplement, Appendix 2, Fig. S1 [all figure numbers with an S prefix refer to this Appendix]). This showed concentrations of thicker overburden on the western side of the pit, including the vicinity of section 13 (see Fig. S2), and above the bluff between the two terraces, where no in situ fluvial gravel occurred. It was notable that the areas in which certain critical artefacts were found (see below) coincided with thin (<0.5 m) overburden (compare Fig. S1 with Fig. 8). As noted above, the uppermost levels were commonly cryoturbated, showing involutions and occasional ice-wedge pseudomorphs. If the cryoturbated layer involved clayey overburden, it was stripped off prior to quarrying (see Fig. S1); if the upper parts of relatively clean sandy gravel were cryoturbated, these structures could be observed at the top of gravel sections (e.g. section 3, Fig. 5). 5.1. Composition of the gravels Thirteen gravel samples were processed for clast analyses, with two size fractions analysed, 16–32 and 11.2–16 mm (as recommended by Bridgland (1986)). Lithological analyses were carried out for all samples, whereas angularity/roundness analyses were conducted on seven selected samples (Table 3). Sample 208 was from the Palaeogene marine gravel. The Test gravels are somewhat dull in composition, consisting of little else but flint. The most significant variation is in the proportion of this flint that represents marine pebbles reworked

592

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Fig. 5. Sections through the Belbin Gravel, Dunbridge compiled during the watching brief (from Bridgland and Harding, 1993).

from the Palaeogene. Such material is greatly boosted in the basal samples (e.g., sample 204 from basal Belbin Gravel and 209 and 211 in basal Mottisfont Gravel; see Figs. 5 and 6), suggesting that the first gravels to be deposited incorporated material reworked from the eroding bedrock beneath. The greatest abundances of Palaeogene flint pebbles were in samples from close proximity to the gravel–bedrock contact. Non-flint material, which is never common, also tends to be richest in these basal samples, pointing to enhanced reworking from bedrock sources. Samples from higher within the Pleistocene show less bedrock-derived material, perhaps indicating that the main source of gravel had switched to reworking from pre-existing fluvial deposits (higher gravel terraces).

5.2. Digital terrain modelling of the Pleistocene sediment bodies Digital terrain modelling was undertaken in order to characterize the three-dimensional form of the Pleistocene fluvial sediment bodies, these being the context for the Palaeolithic archaeology at Dunbridge. Its key objectives were to model the surface of the underlying Palaeogene bedrock at the site, the distribution of Pleistocene gravel deposits, and to determine the extent to which these have influenced the distribution and taphonomy of the artefacts relative to the terrace geology. The detailed recording of the quarry sections during the watching brief, and the analysis of clast composition and angularity–roundness, have confirmed that the Pleistocene gravels are of fluvial origin,

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

593

Fig. 6. Section 13 in the Belbin Gravel with sections 14–16 through the Mottisfont Gravel from the Dunbridge watching brief.

probably laid down under cold-climate conditions in a fast-flowing gravel-bed river (Bridgland and Harding, 1993; Harding, 1998). The topography of the bedrock surface included a system of elongated scoured ‘deeps’ trending north-east to south-west, two of which had widths of 15–40 m and depths of up to 6.5 m; the gravels filling these features dominated the north-east corner of the workings (Harding, 1998, Fig. 11.1.3). Deposit modelling of Kimbridge Farm Quarry and adjacent areas (totalling 42 ha), was undertaken to further assess the distribution of the terrace sediment bodies within this area; it used data from 260 boreholes, test pits and exposed quarry sections (Fig. 2). The quality of information from each of these data sets varied from detailed sedimentary descriptions to mere datum levels relating to the key stratigraphical units. Records of lithology were variable between each data set and absent in over half of the records used. To undertake the deposit modelling it was therefore necessary to utilize stratigraphical units alone, of which four basic divisions were defined:  Topsoil.  Upper Clay: a band of clay-dominated sediments was found at the top of some sequences (16 sample points), perhaps related to the presence of overburden (e.g., colluvium) or to modification by pedogenesis (see above).

 River Terrace Deposits (RTD): the deposits of principle interest in this study. These are gravel dominated and often defined as ‘hoggin’ within the geotechnical reports.  Tertiary bedrock: predominantly Palaeogene Reading Beds, with pebble beds and, if present, Eocene London Clay. The area of the resultant deposit model has been constrained by a polygon around the margin of all the sample points, including the area of most recent workings, to minimize extrapolation of the results beyond the available data set (see Fig. 2). All data were processed using Rockworks 2006, with 2-D and 3-D stratigraphical maps plotted, using the gridding method of Inverse Distance Weighting. All position data is presented in 12 unit OSGB format, with the ground surface datum in metres measured against Ordnance Datum Newlyn (O.D.). 5.3. Modelling results The topography of the bedrock surface shows a general decline from west to east across the study area (average reduction 44– 32 m O.D.), with the highest elevation associated with the hill beneath Hyde Farm Cottage (reaching 50 m O.D.) in the south (see Figs. 1 and 9a). The bedrock topography can be divided into three main areas: two wide terrace platforms separated by an inclined

594

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Fig. 7. Sections 28 and 29, showing the Mottisfont Gravel and the locations of OSL samples.

‘bluff’ running through the centre of the study area in a north– south direction (37–40 m O.D. contours). The westernmost terrace has an inclination of 0.788, with that in the east inclining at 0.988, whereas the ‘bluff’ between them, measuring approximately 50– 150 m in width, has a dip of 2.878 (all slopes trend approximately eastwards). Modelled RTD thickness (Figs.), along with the 37 and 40 m O.D. bedrock-surface contours (Fig. 9a), demarcates the two terraces at the site (also shown in 3D in Fig. S3). There is a distinct thinning of the RTD in the centre of the study area (9b and S3), coinciding with the 40 m O.D. bedrock-surface contour (Fig. 9a) and suggesting attenuation towards the leading edge of the upper terrace. The thickest RTD are present in the central parts of the upper terrace, coinciding in part with the location of the channel ‘deeps’ identified by Harding (1998), although the distinction of separate deeps is not possible due to the spatial distribution of the sample points. The RTD thickness also increases in the south-western part of the study area, contiguous with the lower terrace sediments. However, being above the 40 m O.D. bedrock-surface contour, this is probably an extension of the upper terrace (see Figs. 8 and 9); the apparent connection with the lower terrace perhaps results from the wider distribution between sample points hereabouts. The lower terrace reaches its maximum thickness below the 37 m O.D. bedrock-surface contour, running beneath Dunbridge Lane and extending to the south-east of the study area. The northwest (upper) boundary of this terrace probably lies close to the 40 m O.D. bedrock-surface contour, coincident with a break in

slope as plotted in the watching brief (Fig. 9a). Recorded sections (14–16, 28 and 29) confirm that gravel thickens to the south east. Thus the boundary of the lower terrace has been extended in a north-west direction towards the edge of the Belbin Formation. The apparent continuation of the lower terrace into the area of the erstwhile Kimbridge quarries suggests equivalence with the deposits there, which serves to confirm that only two Pleistocene river terraces are present in the area, an upper Belbin Formation and a lower Mottisfont Formation (see Fig. 8). The modelled sediment bodies can be readily reconciled with the reconstructions by Westaway et al. (2006) of the Belbin and Mottisfont formations. The Dunbridge upper terrace has an average altitude of between 44.8  1.9 m O.D. (top) and 42.0  1.9 m O.D. (base), compared with an altitudinal range for the Belbin Formation in the Dunbridge area from Westaway et al. (2006) of 41–48 m O.D. The lower Mottisfont Gravel has an average altitude of between 38.2  2.3 m O.D. (top) and 35.7  2.9 m O.D. (base), which compares with an altitudinal range for the Mottisfont Formation the Dunbridge area of 30–38 m O.D. according to Westaway et al. (2006). 6. Palaeolithic archaeology The additional 198 flint artefacts from the watching brief (Table 4) are shown by artefact type and recovery point, with comparable quantification of the 1021 objects in the extant collection (Roe, 1968a). Cores and flakes were proportionally more

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

595

Fig. 8. Artefact distribution plotted over the approximate terrace footprints as derived from the digital terrain modelling. Numbered points show the reconstructed location of key finds.

prevalent from the former in contrast to more easily recognized and collectable hand axes from the latter, thus providing a more balanced sample of the Palaeolithic artefact typology at the site. The stripping of overburden prior to extraction (see above) has increased the probability that all the artefacts from the watching brief are from the fluvial deposits. There were no faunal remains or palaeo-environmental material from the project. Thirty per cent (60) of the artefacts from the watching brief were collected from the quarry. These were primarily flakes recovered from weathered talus at the base of the quarry face or from surface bunds; however artefact recognition from freshly excavated material at the quarry was limited by the heavy clay matrix of the fluvial gravels. Recovery rates were improved by routinely scanning processed gravel in the >40 mm washed gravel (reject) heap, which produced the remaining 70% (138) of the artefacts. Screened material of <40 mm was not scanned; this undoubtedly biased artefact recovery against smaller pieces, which are likely to have been present amongst this material in limited numbers. No artefacts from the watching brief corresponded with Dale’s ‘white series’ of unrolled artefacts with a white patina, which were thought likely to originate from the upper part of the terrace deposit (Roe, 1981). However pieces with a white patina and in a rolled condition, and others with staining overlying surface patination, were recorded from the watching brief.

6.1. Artefact types 6.1.1. Cores Most of the cores demonstrate similar variations in condition and staining to the hand axes. They include three unipolar ‘proto-Levallois’ flake cores (513, 588 and 653) and three others (538, 671 and 685) demonstrating fully developed Levallois technology, (Mode 3: Boe¨da, 1995; Barton, 1997). The former (Fig. 10 and Appendix 2, Fig. S4) are all rolled and stained and typical of material from the main body of the Belbin Gravel (they are also matched to this formation by their date of discovery). They are all produced from relatively small nodules of flint and are characterized by the removal of a limited number of parallel flakes from a flaking face with a prepared striking platform. The three fully developed, bipolar Levallois flake cores have carefully prepared faceted striking platforms, cortical backs and hard-hammer mode with relatively controlled removals from the flaking face. One core shows predetermined flaking of the lateral core edges (Fig. 10, 671). Not only are the technology and morphology identical, they are also remarkably similar in size and weight, ranging 110–120 mm in length, 76–87 mm width, 31– 41 mm thickness and 317–407 g weight. The Levallois cores all have a light yellow surface stain overlying a patina, indicating

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

596

Table 3 Clast lithological data. A. Clast lithology of 16–32 mm gravel fractions B. Clast lithology of 11.2–16 mm gravel fractions. C. Angularity/Roundness analyses, all flints included. D. Angularity/Roundness of flint, with unbroken Palaeogene pebbles excluded. A. Clast lithology (16–32 mm) Sample

201 202 203 204 205 206 207 209 210 211 212 215 216

FLINT Palaeogene pebbles

Nodular

Broken

Weathered

Total

8.0 4.2 4.2 50.5 4.9 9.7 21.9 47.1 4.2 57.4 15.5 9.3 7.6

21.3 18.8 12.8 12.5 17.6 17.2 13.1 9.6 17.1 6.6 12.6 6.1 10.3

5.6 7.8 8.0 2.6 7.0 4.4 5.0 2.5 3.3 4.2 3.3 1.6 0.8

64.7 69.1 74.6 30.2 70.5 73.1 59.7 40.4 75.2 31.6 68.3 80.2 78.6

99.6 100.0 99.6 95.8 100.0 100.0 99.7 99.6 99.8 99.8 99.8 97.1 97.3

Non-flinta

Total

0.4 – 0.4 4.2 – – 0.3 0.4 0.2 0.2 0.2 2.9 2.7

249 190 264 192 244 227 320 488 456 408 419 325b 267c

Non flinta

Total

0.1 0.5 0.6 7.0 – 0.2 0.4 0.6 0.3 0.9 0.1 1.9 0.9

757 380 327 226 522 406 534 770 986 570 1000 487d 544e

B. Clast lithology (11.2–16 mm) Sample

201 202 203 204 205 206 207 209 210 211 212 215 216

FLINT Palaeogene pebbles

Nodular

Broken

Weathered

Total

7.3 5.8 4.3 47.7 6.1 9.9 22.1 42.7 7.4 21.2 23.0 11.4 8.3

5.9 8.4 3.7 2.5 7.9 7.9 5.6 4.4 3.7 5.4 4.6 2.1 1.5

7.0 3.9 4.6 4.5 5.2 7.9 4.9 6.9 6.4 9.1 6.2 1.9 0.9

79.8 81.3 86.9 38.3 80.8 74.1 67.0 45.3 82.3 63.3 66.1 82.8 88.2

99.9 99.5 99.4 93.0 100.0 99.8 99.6 99.4 99.7 99.1 99.9 98.1 99.1

C. Angularity/roundness analysis, all flints Sample

wr

r

sr

sa

a

va

Total

201 202 204 205 208 215 216

0.8 – 31.0 0.8 26.7 3.8 4.1

1.2 – 14.1 0.4 5.2 1.0 2.6

2.0 4.7 2.7 2.1 2.6 0.3 0.8

41.3 34.2 15.8 41.7 – 11.4 37.6

42.9 43.2 26.1 41.7 – 81.3 54.1

11.7 17.9 10.3 13.2 65.5f 1.6 0.8

247 190 184 242 116 315 266

D. Angularity/roundness analysis of flint, excluding unbroken Palaeogene pebbles Sample

wr

r

sr

sa

a

va

Total

201 202 204 205 215 216

– – – – – –

– – – – – –

2.1 4.7 2.1 2.1 0.3 0.8

42.1 34.2 29.5 42.3 12.1 40.7

43.8 43.2 50.5 42.3 85.9 58.4

12.0 17.9 20.0 13.4 1.7 0.8

242 190 95 239 298 246

a Minor components include Greensand chert, various ironstones and various non-durable local (Palaeogene) material, such as laminated siltstone/mudstone, as well as contemporaneous iron pan (the last is excluded from totals for the purpose of calculation). b Includes 12  iron pan – calculations are based on a total of 313. c Includes 5  iron pan – calculations are based on a total of 262. d Includes 5  iron pan – calculations are based on a total of 482. e Includes 17  iron pan – calculations are based on a total of 527. f Very angular flint: frost shattered in situ.

probable derivation from the upper part of the gravel sequence, which is of a similar colour. The remaining cores include elements of migrating platform or alternate flaking (Mode 1: Barton, 1997), which from their condition and location are of Palaeolithic date; however a core from the top of the gravel (presumably after overburden removal) may be of Neolithic or Early Bronze Age date.

6.1.2. Flakes The 114 flakes and broken flakes form the largest component (58%) of the assemblage from the watching brief. They demonstrate most clearly that tool manufacture was undertaken locally and that flake and core tool industries are both represented. They also indicate details of raw material selection and, with reference to artefact condition, provenance from within the gravel. All the

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

597

Table 4 Artefact assemblages from Dunbridge showing recovery by the watching brief from the quarry and washing plant with comparable figures from the extant collections. Watching brief

Roe (1968a)

Artefact

Quarry

%

Hand axe Rough out Flake Core Retouched/scraper Debitage

9 1 44 5 1 0

15 2 73 8 2 0

Total

60

Washing plant 45 6 70 11 3 3 138

%

Total

%

33 4 51 8 2 2

54 7 114 16 4 3

27 4 58 8 2 1

198

No 953 14 27 3 16 8

% 93.3 1.3 2.6 0.3 1.5 0.7

1021

Taken from Roe (1968a).

flakes are likely to be of Palaeolithic age with the exception of three from the stripped surface of the gravel. The technology of these pieces, which have a white surface patina, suggests that they might be from the Neolithic or Bronze Age. Flake recovery, both in the quarry and from the reject heap, was biased in favour of easily recognizable, large (60–80 mm but up to 123 mm), unbroken, undiagnostic pieces. This results in part from scanning only the >40 mm reject heap; however it also reemphasizes the availability and selection of large nodules and might well reflect the true size range of flakes at the site. Smaller flakes, generally found only at the quarry, in the bund and talus material, are of minimum 41 mm length. Enhanced recovery of smaller flakes, and therefore a clearer impression of overall sizerange, would have been improved by searching the smaller fraction reject piles, something that should perhaps be adopted by future watching brief projects.

The flakes are primarily characterized by plain butts and hardhammer mode. Some are by-products of hand-axe preparation, Newcomer’s (1971) Stage 1; however, deliberate flake–core technologies, representing Mode 1 and 3, are also evident at the site. Diagnostic examples of hand-axe thinning and shaping, Newcomer’s (1971) Stage 2, are rare. Only two flakes definitely resulted from the thinning and shaping of hand axes, of these only one shows characteristics of soft-hammer percussion. There were ten other possible thinning and shaping flakes and one tranchet sharpening flake, which confirms hand-axe production in the area. The paucity of thinning and shaping flakes has undoubtedly resulted from these being less robust and, like many of the small flakes, more susceptible to breakage and dispersal by fluvial activity. One flake (Fig. 10, 500), removed from a unipolar core, is in a similar condition and surface staining to the developed Levallois

Fig. 9. Output from digital terrain modelling: a–Contours on the Palaeogene bedrock surface; b–RTD thickness with 40 and 37 m O.D. contours from the underlying Palaeogene geology topography shown.

598

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Fig. 10. Proto-Levallois cores 513 and 653, developed Levallois cores 538, 671 and 685 and Levallois flake 500 from Dunbridge. Core 538 reproduced from Harding (1998), Fig 11.1.1.

cores from the site. Other flakes, with unidirectional flake scars, hard-hammer mode and well-controlled management of the flaking angle, are rolled and show varying levels of surface staining. These pieces might be by-products of preliminary stages of hand-axe manufacture but could equally have been removed from single platform ‘proto-Levallois’ flake cores.

6.1.3. Hand axes The 61 hand axes and hand-axe rough outs constitute 31% of the watching brief assemblage; of these 12 have been broken in antiquity, with a further five broken as a result of gravel extraction and processing. The implements from the watching brief have been classified according to the scheme of Wymer (1968) to be

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

compatible with a sample of 168 implements analysed by Hosfield and Chambers (2004). Pointed implements, often with flattened, cortical butts, remain prevalent; however, as in previous surveys, ovates are also represented, as well as two ficrons and three cleavers, one of which is sufficiently squat to suggest that it may have undergone resharpening. The majority of hand axes (60%), are in a rolled and stained condition, with the observed correlation between heavily rolled and heavily stained pieces maintained. There were also seven unfinished rough outs that confirmed elements of hand axe manufacture and two hand axes with a distinctly plano-convex cross section may have been made from large flake blanks. The unbroken hand axes, including rough outs, have ranges of 65–186 mm (mean 116 mm) in length, 54–153 mm (mean 82 mm) in width and 93–1511 g in weight. Of potential significance is the butt of what appears to be a bout coupe´ hand axe (Harding, 1998, Fig. 11.1.2; Fig. S5), which was found when the Belbin Gravel was being exploited. This implement seems likely to have come from Dunbridge; although the site archive expresses some doubt, there is nothing to indicate that gravel was being processed from elsewhere, at the time of its discovery (1992). The implement has a pale yellow stain and is in a slightly rolled to rolled condition, similar to other material attributed to the upper part of the Belbin Gravel. 6.1.4. Flake tools The watching brief produced a retouched flake and three scrapers, one a large end-scraper made on a tertiary flake. This implement, stained light yellow and only slightly rolled, was found near the junction of the Belbin and Mottisfont gravels. By way of comparison, Dale (1912) noted that large, slightly rolled flakes that had been trimmed along one edge were found near the base of the Mottisfont Gravel, in association with heavily rolled ovate implements. A scraper ‘of Le Moustier type’ (Dale, 1912, Fig. 2) is cited as an example of this type of implement from Kimbridge, although the caption states that it was found at Dunbridge. These pieces are chronologically undiagnostic within the Palaeolithic, but confirm the production of flake tools in tandem with hand axes. 6.2. Artefact distribution and relation to geology Artefact distribution, within the outline of the Kimbridge Farm quarry, has been overlaid onto the two demarcated terraces defined by the terrace modelling (Fig. 8). The results for the 190 artefacts that could be plotted show clearly that most material was recovered from the high-level Belbin Gravel. Very few artefacts were recovered from the lower Mottisfont Gravel (Fig. 8). This contrast accords with variations in implement density from the old workings, in which artefacts were more plentiful in the higher Belbin Formation at Dunbridge than in the lower Mottisfont Gravel at Kimbridge (Roe, 1968a). More detailed examination of the horizontal distribution of artefacts from the Belbin Gravel suggests that the greatest artefact density occurred along the southern margins of the terrace where the deposit thinned. In contrast no artefacts were recorded from the area of the deepest gravel, to the north east. A diffuse linear concentration, aligned north to south, can also be detected in the deeper gravel to the north-west. This appears to run parallel to, but does not coincide with, the alignment of the ‘deeps’. It is debatable whether this distribution reflects material that has been swept into a channel feature within the body of the gravel, in much the same way that, during an experimental project on artefact taphonomy in a gravel bed river, implements became incorporated into a deep water channel of the Afon Ystwyth (Harding et al., 1987, Fig. 14.2). The distribution of the Levallois cores and the Levallois flake (Fig. 10) require special consideration as potential chronological

599

indicators of material in the gravels. The ‘proto-Levallois’ cores were found at the processing plant before quarrying of the Mottisfont Gravel began, and so must have come from deposits within the Belbin Formation. The developed Levallois material was also primarily recovered from the reject heap, although approximate locations can be reconstructed (Fig. 8). Core 538 (Fig. 10) was found well within the area of the Belbin Gravel as was flake 500. Both are in a sharp condition, however, and such damage as can be observed cannot equivocally be attributed to fluvial processes rather than the quarry washing plant, since both were found amongst processed gravel. Core 671 (Fig. 10), which is also in a sharp condition, was found on a bund in bleached gravel approximately 20 m south of the edge of the Mottisfont Gravel, and may have come from either deposit. It displays a number of incipient cones of percussion typical of material derived from a fluvial environment. This was the only core found at the quarry, which removes the likelihood that these features resulted from the processing plant, as is possible with the other cores. The site archive noted that a band of bleached gravel, approximately 0.5 m thick, overlay heavily stained material near the surface of the Mottisfont Formation in that area. This confirms that the bleached gravel was not restricted to the upper parts of the Belbin Gravel but continued across both terrace features (cf. Dale, 1912). Core 685 (Fig. 10) was found at the washing plant and could not be plotted with any certainty. It was found in 2002, by which time the Mottisfont Formation was being extracted and any stockpiled aggregates from the Belbin Gravel are likely to have been processed. It is the only Levallois core that shows clear evidence of being slightly rolled with dulled, stained areˆtes separating flake facets on both the flaking face and more notably on the back (see online supplement, Fig. S4). Although artefacts were undoubtedly distributed throughout the deposits, the observed upwards decrease in the grain size of the sediment bodies makes it more likely that the larger, heavier pieces occurred in the main body of the gravel, rather than the upper, finer layers. Vertical distribution can also be assessed by condition and staining. There was a marked correlation (Fig. 11) between the more heavily rolled artefacts in the terrace gravels and the intensity of staining. Surface staining of artefacts was predominantly yellow (37%), reddish yellow (18%), yellowish red (11%) or strong brown (3%). Heavily stained gravel was frequently more common in the lower parts of the Belbin Formation, below the bleached horizon. All three ‘proto-Levallois’ cores were rolled and stained, which indicates that the most likely source of these pieces is the body of the Belbin Formation. The upper ‘bleached’ gravels, in contrast, were more commonly patinated and stained pale brown

Fig. 11. Graphic illustration of patination and degree of rolling of the Dunbridge watching brief artefacts.

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

600

(2%) or pale yellow (6%). These features, which are also characteristics of the fully developed Levallois material, make it almost certain that these latter artefacts came from the upper part of the fluvial sequence and form part of Dale’s (1912) ‘middle series’. Deep staining was also characteristic of the main body of the Mottisfont Gravel, which accords with Dale’s (1912, p. 110) observation that the gravel at Kimbridge was very red and iron rich towards the base, a staining ‘‘which coats the flints with a deep ochreous deposit and sometimes cements them together’’. 7. New OSL dating Twelve samples were collected for OSL dating from the bestpreserved remaining sections at Dunbridge, all within the Mottisfont Formation. The distribution of the samples within the exposed stratigraphy is indicated in Fig. 7; samples 2 and 9 were from underlying Palaeogene (Reading Formation) sand, the remainder from the Mottisfont Gravel. 7.1. Methodology OSL dating was first applied to quartz by Huntley et al. (1985), and the technique was further developed by Smith et al. (1986) and Rhodes (1988). Optical dating was demonstrated to work well for aeolian samples (Smith et al., 1990; Stokes et al., 1997) but was also shown to provide useful age estimates for a range of sedimentary contexts including fluvial deposits (Wallinga, 2001). Further developmental research by Murray and Wintle (2000a,b) introduced palaeodose measurements based on a ‘single aliquot regenerative-dose’ (SAR) protocol. In recent years, this SAR technique has been applied with varying degrees of success to Middle Pleistocene fluvial deposits in southern England (e.g., Toms et al., 2005; Briant et al., 2006; Schwenninger et al., 2006); this technique is also adopted in the present study. In situ NaI gamma-ray spectrometry measurements using a portable field spectrometer were made at five sampling locations (see Table 5) and the instrument was calibrated against the Oxford blocks (Rhodes and Schwenninger, 2007). The environmental dose rate was obtained by combining these direct radiation

measurements (external gamma dose rate) with laboratory-based geochemical analysis of sub-samples of sediment taken from the OSL container. The concentrations of radioisotopes were determined by ICP-MS using a fusion preparation method. Luminescence measurements were made using automated Risø luminescence readers, the samples being prepared according to standard laboratory procedures in order to yield sand sized (180– 250 mm) quartz grains. Further details regarding the adopted instrument settings and preparation procedures are provided by Schwenninger et al. (2011). All OSL measurements were made at a raised temperature of 125 8C for 100 s. The signal detected in the initial 2 s (with the stable background count rate from the last 10 s subtracted) was corrected for sensitivity change using the OSL signal regenerated by a subsequent test dose. To ensure removal of unstable OSL components and dose-quenching effects, and to stimulate re-trapping and ensure meaningful comparison between naturally- and laboratory-irradiated signals, pre-heating was performed prior to each OSL measurement. Following each regenerative dose as well as the natural dose, a pre-heat at 260 8C for 10 s was used whereas in the case of the test dose, a reduced pre-heat of 220 8C for 10 s was applied. The OSL measurements incorporated a post-IR blue OSL stage in which each OSL measurement is preceded by an IRSL measurement at 50 8C, to reduce the potential effects of residual feldspathic components (Banerjee et al., 2001) but the standard SAR procedure was otherwise unchanged. For each sample a typical set of 8–16 small (4 mm) multigrain aliquots were measured. Deliberate bleaching using blue LED illumination for 100 s at room temperature was applied to two aliquots of each sample in order to erase the natural signal. These aliquots were then given a known laboratory dose (110 Gy) in order to obtain a recovered dose. This provides a good additional means of testing whether or not the adopted measurement procedures and instrument settings are suited to the dating of a particular sample. 7.2. Results The OSL and radioactivity measurements, and the resulting age estimates are summarized in Table 5. The grouping of the apparent ages of the samples, including the outliers considered unreliable, is

Table 5 Summary of OSL dating results. Field code

d

1A 1Bd 1Cd 2 3 4 5 6 7 8 9 10

Laboratory code

X3641 X3642 X3643 X3644 X3645 X3646 X3647 X3648 X3649 X3650 X3651 X3652

Radioisotopesa

Field water

In situ external g-dose rateb 1

; 1s)

K (wt%)

Th (ppm)

U (ppm)

%

(Gy ka

0.42 0.43 0.55 0.23 0.35 0.38 0.41 0.54 0.20 0.22 0.19 0.12

2.3 2.4 2.8 1.5 2.3 2.3 2.8 4.0 1.4 1.4 1.1 0.8

0.5 0.5 0.6 0.4 0.5 0.4 0.5 0.8 0.5 0.6 0.3 0.3

7–17 7–17 7–17 3–9 7–13 7–13 7–13 7–17 3–9 3–9 3–9 3–9

0.2100.021 0.2100.021 0.2100.021 0.1830.018 0.2800.028 0.2800.028 0.2900.029 0.2690.027 0.2360.024 0.2360.024 0.1240.013 0.2800.028

Cosmic dose rate (Gy ka

1

; 1s)

0.0820.012 0.0820.012 0.0820.012 0.0860.013 0.1200.028 0.1170.026 0.1170.026 0.1150.025 0.0800.011 0.0740.010 0.0690.009 0.1070.021

Total dose rate (Gy ka

1

; 1s)

0.650.04 0.650.04 0.750.05 0.360.02 0.720.05 0.720.05 0.770.05 0.870.05 0.540.03 0.550.09 0.380.02 0.520.04

Palaeodosec

OSL agec

(Gy; 1s)

(ka; 1s)

183.0611.43 202.8630.43 195.5529.33 [260.8749.88] [284.6798.92] 247.0212.65 233.416.04 293.2033.77 [229.2227.60] [218.0032.50] [433.1032.04] [235.8549.33]

28326 31051 26243 [733149] [396140] 34129 30221 33545 [42858] [39362] [1152108] [456101]

a Measurements of radioisotope concentrations were made on dried, homogenised and powdered material by fusion ICP-MS with an assigned systematic uncertainty of 5%. Dry beta dose rates calculated from these activities were adjusted for the measured field water content expressed as a percentage of the mass of the sample. b Based on in situ measurements using a portable gamma ray spectrometer equipped with a 3  3 inch NaI scintillator crystal and calibrated against the Oxford blocks (Rhodes and Schwenninger, 2007). Due to adverse weather conditions, spectroscopy measurements could only be obtained for samples 1A, 1B, 1C, 2, 5, 6 and 8. For samples 3 and 4, the external gamma dose rate was based on the mean of readings obtained for nearby samples 5 and 6. Similarly, for sample 7 the external gamma dose rate was derived from spectra collected at the location of sample 8 (in the same stratigraphic unit). In the case of sample 10, which was taken from a sandy pocket within the gravel, it was decided that the external dose rate would best be represented by measurements obtained from similar configurations associated with the locations of samples 1, 5 and 6. For sample 9, located in the basal sand unit of presumed Palaeogene age, the external dose rate was calculated from the concentrations of K, Th and U as determined by ICP-MS. c Palaeodose values and resulting age estimates in brackets are problematic mainly because of suspected partial bleaching and/or mixed grain populations. Pending more advanced future analyses using single grain measurements, the calculated OSL age estimates for these samples are considered unreliable. d Samples 1A, 1B and 1C are near replicates taken from the same stratigraphic unit and located within 15 cm horizontal distance of each other.

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Fig. 12. Plot of total dose rate against palaeodose for the Dunbridge OSL samples (Table 5). The samples considered unreliable, and thus excluded from calculations of the age of the Mottisfont Gravel, are labelled using fainter ornament. On this type of graph, the gradient of a line joining the point representing a sample to the origin is inversely proportional to the age of the sample. The relatively tight grouping of the apparent ages of the samples considered unreliable is thus visually evident.

illustrated using the plot of total dose rate against palaeodose in Fig. 12. More detailed information, including typical OSL signal plots, growth curves, palaeodose distributions, luminescence characteristics, and geochemical composition of individual samples, can be found in Schwenninger et al. (2011). The yield of quartz grains derived from these sandy samples was plentiful and aliquots showed good response to laboratory irradiation. Visual checks of the initial signal intensity and the form of the decay curve show a fast decrease in OSL intensity which is characteristic of quartz. This is further evidenced by a well defined 110 8C TL peak; stimulation using infrared laser diodes, which also confirmed the purity of each aliquot with negligible contributions from potential feldspathic contaminants (<1%; see Table 2 of Schwenninger et al., 2011). Furthermore, a low irradiation dose was repeated at the end of each measurement cycle to test the SAR sensitivity correction procedure. If this correction is adequate then the ratio of the signal from the repeated dose to that from the initial regeneration dose will be 1.0  0.1. Recycling ratios close to unity were indeed recorded for all the Dunbridge samples (see Table 2 of Schwenninger et al., 2011), confirming that this procedure was working as expected. Excluding the samples (2 and 9) derived from bedrock, the results (Table 5) show a range of ages for the Mottisfont Gravel from 456  101 to 262  43 ka (each 1s). There appears to be no stratigraphical consistency, with these oldest and youngest age estimates (samples 10 and 1, respectively) both coming from horizontally bedded sandy gravel midway within the sequence: the former from near the top and the latter from near the bottom of this unit, in a clear age inversion. The majority of the intermediate age estimates are indistinguishable at 1s. Somewhat surprisingly, the two samples from bedrock sand have yielded finite ages, older than any from the Mottisfont Gravel but still within the Pleistocene (1.15  0.11 and 0.73  0.15 Ma; each 1s). Whereas these age estimates are considerably younger than the age of the Reading Formation (55 Ma), the results from the Mottisfont Gravel are all rather older than anticipated for this formation if the Westaway et al. (2006) modelled age of MIS 8 is correct. Excluding the bedrock samples, as well as sample 3 (which yielded very scattered palaeodose values and is thus considered unreliable), sample 10 (which yielded such a high numerical age that it may well not have been reset during deposition), and samples 7 and 8 (which are likewise considered unreliable as a result of the analyses presented in Table 5), the weighted mean age of the remaining eight measure-

601

ments is 305  25 ka (2s), which is similar to the mean of the dates by Bates et al. (2010) from a higher terrace deposit (see above). Since 6 data components contribute to this estimate, the associated mean value can also be reported as 305  10 ka (2 s). Two of the splits of sample 1 have yielded numerical ages that are noticeably younger than any of the other samples; as a result, sample 1 overall yielded an age range of 311–267 ka at 1s, which overlaps the MIS 9–8 boundary at 277 ka. A weighted mean OSL age can also be calculated for samples 1A, 1B and 1C by combining their individual palaeodose values (from Table 5) to obtain a mean of 186.69  10.05 Gy (1s) and their total dose rates (also from Table 5) to obtain a mean of 0.674  0.025 Gy ka 1 (1s), then by taking the ratio of these values to obtain an age estimate of 277  18 ka (1s). Overall, these different methods of combining the data from the various samples and splits suggest that the Mottisfont Gravel was emplaced during MIS 8 or during one of the cold substages of MIS 9. 8. Uplift modelling The additional age constraints now available, both from geochronology (this paper and various publications in recent years: Briant et al., 2006, 2009; Schwenninger et al., 2006, 2007; Briant and Schwenninger, 2009) and the new Palaeolithic evidence from the Dunbridge watching brief, make it worth revisiting the upflift modelling by Westaway et al. (2006). The rationale for the original modelling of the Test terraces was detailed in Appendix 3 of Westaway et al. (2006). In this they reviewed the evidence for the occurrence of Levallois artefacts at sites such as Dunbridge and Warsash, in what they regarded as a single terrace despite different numbering at those localities, coming to the conclusion that the Levallois material at Warsash was probably from non-fluviatile overburden. This suggested that the fluvial gravels of this terrace dated from MIS 10, which provided a plausible modelling solution, allowing them to suggest a viable correlation with their revised terrace scheme for the main Solent River. From the modelling of uplift throughout that system, largely calibrated by the Palaeolithic archives (but also by the few instances of biostratigraphical control), they concluded that the best modelling solutions were obtained if the earliest evidence of Levallois technology was dated to MIS 9b, rather than the beginning of MIS 8, as they had supposed at the outset of their work. It should be noted that the Westaway et al. (2006) modelling was carried out before any OSL dating became available for any part of the Solent river system; the Briant et al. (2006) OSL dataset from Solent River gravels upstream of its confluence with the Test appeared while the former paper was in press, allowing a note to be added in proof discussing the OSL results. Despite the numerical ages obtained from OSL being highly scattered, the exclusion of statistical outliers made it possible to calculate weighted mean ages of sufficient precision for correlation with marine isotope stages and there was generally good agreement with the uplift modelling (Westaway et al., 2006, note added in proof). The age constraints now available for the lower reaches of the Solent (Table 1; see also above) require the Broadlands Farm Terrace to date from MIS 4, or thereabouts, rather than MIS 2 as previously thought. Meanwhile the confirmation, from the present project, that Levallois artefacts occur within the upper body of the Belbin Gravel means that the terrace formed by the latter can be no older than MIS 9b, younger than the MIS 10 age assigned to it by Westaway et al. (2006); the shorter interval between these terraces thus requires a higher uplift rate than was calculated by those authors. Furthermore, the OSL evidence suggesting that the Ganger Wood–Mallards Moor Terrace dates from MIS 10 or MIS 9b, rather than MIS 12, as Westaway et al. (2006) thought, likewise requires faster uplift and is consistent with the new archaeological

602

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

sites of Solent Breezes and Hook, supports the terrace-dating scheme inferred in Fig. 13, including an age of MIS 9b for the terrace deposit at Warsash. Thus in the revised modelling (Figs. 13 and 14) the Belbin–Highfields–Warsash Terrace is seen as the Test equivalent of MIS 9b terraces in other parts of the Solent system, such as the Ensbury Park Terrace of the Stour, the High Cliff Terrace of the Avon and the Beckton Farm Terrace of the main River Solent. Compared with Test age model 1 of Westaway et al. (2006) the new solution incorporates the following changes:

Broadlands Farm Terrace Hamble Terrace Mottisfont terrace Belbin–Highfields–Warsash Terrace Ganger Wood–Mallards Moor Terrace Nursling-Bursledon Terrace Bitterne Terrace Rownham’s Farm–Midanbury terrace(s) Castle Hill Terrace Toot Hill–Netley Hill Terrace Lordswood Lane–West End Terrace Chilworth Terrace

Westaway et al. (2006)

This paper

MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS

MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS MIS

2 6 8 10 12 13b 14 16–15b 18 22 26 36

4 6 8 9b 10 12 13b 14 16 18 20 22

As can be seen, the new solution adjusts the higher part of the terrace staircase to younger ages. This brings it into agreement with the other parts of the Solent system in-so-far as the succession now starts at MIS 22. Westaway et al. (2006) reported that the earliest accredited in situ archaeology had been found in the Nursling terrace (Fig. 4), which adjusts from MIS 13b to MIS 12 as a result of the present study. However, Schwenninger et al. (2006) reported in situ flake artefacts at Spearywell Woods, Mottisfont (c. SU 312 282), in fluvial gravel between 73 and 77 m O.D., which places them within the Midanbury Terrace of the Test (Fig. 4), for which an age of MIS 14 is now inferred from the new uplift modelling. These artefacts would thus imply human

Fig. 13. Revised modelling of the uplift history indicated by the disposition of River Test terraces in the area of Chilworth: (a) observed and predicted uplift history; (b) enlargement of the younger part of a; (c) predicted history of uplift rate variation. Terrace height data are the same as used by Westaway et al. (2006), uplift now being measured from a reference level of 0 m O.D. Solid symbols indicate preferred ages of terrace deposits; open symbols indicate alternative possibilities. Model prediction uses Wi = 11 km, u = 13 8C km 1, k = 1.2 mm s 1, to1 = 18 Ma, DTe1 = 8.0 8C, to2 = 3.1 Ma, DTe2 = 1.2 8C, to3 = 2.0 Ma, DTe3 = 1.9 8C, to4 = 0.9 Ma, and DTe4 = 2.7 8C. For explanation of these model parameters see, for example, Westaway et al. (2006). This prediction is for the component of regional uplift in this vicinity; the local effect of active folding on the Portsdown anticline, which transects the Test valley in this area (Westaway et al., 2006), has been estimated to have contributed an additional 26 m of uplift, occurring at a uniform rate, since 0.9 Ma.

constraint. The best-fitting solution (Fig. 13) assigns the Belbin– Warsash Terrace to MIS 9b and the Ganger Wood–Mallards Moor Terrace to MIS 10. The resultant attribution of the Levallois archaeology in the Belbin Terrace to MIS 9b implies that it is broadly contemporaneous with that from other sites in the Solent system, notably those in the Ensbury Park Terrace of the River Stour, in the Bournemouth area (cf. Westaway et al., 2006). Revised uplift modelling of the eastern Solent, near the downstream limit of the reach of the Test covered by Fig. 4, adjoining the key Palaeolithic site of Warsash and the OSL dating

Fig. 14. Revised uplift modelling for the eastern Solent (Portchester), representing the downstream end of the Test valley sequence and using both fluvial and marine data. The height data are the same as used by Westaway et al. (2006), except the Cams Hall raised beach (r.b.) has been adjusted to 18 m O.D. and the Mallards Moor fluvial terrace to 33 m O.D. For the fluvial data, uplift has been estimated relative to a reference level of 8 m O.D.; for the marine data, uplift has been measured relative to the estimated sea level for each interglacial, assumed to be as follows: MIS 13c, 0 m or 5 m; MIS 13a, 5 m; MIS 11c, 0 m; MIS 11a, 5 m; MIS 9e, 0 m; MIS 9c, 10 m, MIS 9a, 10 m; MIS 7e, 0 m or 5 m; MIS 7c, 5 m; MIS 7a, 5 m; MIS 5e, 0 m, MIS 5c, 5 m; MIS 5a, 5 m. Labelling is as for Fig. 13, except that different ornament is used for fluvial and marine sites and the Isle of Wight sites included for comparison are labelled in purple. This prediction is for the component of regional uplift in the vicinity; the local effect of active folding on the Portsdown anticline, which adjoins the Portsdown area (Westaway et al., 2006), has been estimated to have contributed an additional 20 m of uplift, occurring at a uniform rate, since 0.9 Ma. Prediction uses the same model parameters as for Fig. 12 except Wi = 10.5 km, DTe1 = –8.0 8C, DTe2 = –1.4 8C, DTe3 = –1.4 8C, and DTe4 = –3.0 8C.

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Fig. 15. Revised uplift modelling of the Sussex raised beaches (based on Boxgrove). The height data are the same as were used by Westaway et al. (2006), except the height of the Aldingbourne raised beach (r.b.) has been revised to 22 m O.D. (cf. Bates et al., 2010; see text). Prediction uses the same model parameters as for Fig. 12 except Wi = 8.5 km, DTe1 = –4.0 8C, DTe2 = –0.8 8C, DTe3 = –1.3 8C, and DTe4 = – 3.0 8C. It also uses the same set of estimates for interglacial se levels as Fig. 12 and the same labelling as for Figs. 12 and 13.

occupation of the area during MIS 15, pushing the earliest evidence of human presence in the Solent catchment back one climate cycle earlier than was recognized by Westaway et al. (2006) and fully in keeping with the expected initial human presence in the region during the latter stages of the Cromerian Complex (cf. Parfitt et al., 2005, 2010; Westaway, 2009a,b, 2011). Another substantive aspect to the ‘new’ chronology suggested by Bates et al. (2010) was their suggestion, again from OSL dating, that the Aldingbourne raised beach dates from early MIS 7 (i.e. MIS 7e) rather than MIS 9, as previously thought. Fig. 15 shows an uplift modelling solution for the Sussex raised beaches, fitted to the age and height data for the Aldingbourne raised beach as recommended by Bates et al. (2010). The different terrace age model for the Test and resulting slightly higher uplift rates required by that adjustment are consistent with the younger age of the Aldingbourne raised beach when applied further east along the Solent. In addition to the above-mentioned implications for the chronology of human occupation and for the Test terrace staircase, this revised uplift modelling has further implications regarding the rate of localized deformation on the Portsdwn Anticline (Fig. 3), for the physical properties of the Earth’s crust in the study region, and for the dating of other sites in the region; these implications are covered in the online supplement. 9. Discussion The OSL dating results obtained in this study (Table 5) warrant further comment. The most coherent and reliable set of dates were obtained from OSL samples 1A, 1B and 1C, all collected within a sandy lens in the lower Mottisfont gravel. These samples were also characterized by the lowest degree of variability between individual palaeodose determinations. Using the weighted mean palaeodose and dose-rate for these three samples, a date of 277  18 ka (1s) is obtained. However, if the results from the other samples are also included then as earlier analysis indicated a weighted mean age of 305  10 ka (2 s) is obtained. This is older than the anticipated age for this terrace deposit, in MIS 8, based on both the previous analysis by Westaway et al. (2006), which used calibration from a range of available evidence, including archaeological and palaeontological assemblages, and the revised uplift modelling from the present study. This leads to the conclusion that a substantial number of samples from the Mottisfont gravel at Dunbridge have been affected by systematic error, which has caused

603

the numerical ages of the samples to exceed the true age of the deposit. In general, two effects can cause OSL dates to exceed the true age of a deposit: (1) incomplete bleaching of the sample material on deposition (Olley et al., 1998); (2) leaching by groundwater of radioactive elements from the sediment, which results in the present-day measured radiation dose rate being less than the timeaveraged dose rate since deposition and thus the calculation of an overestimated age (Li et al., 2007, 2008). The opposite effect, of OSL dates underestimating the probable ages of samples, has also been recognized in samples from southern England, and has been tentatively attributed to uptake of radioactive elements (Brown et al., 2010). In the case of Dunbridge, it is also possible that the OSL age estimates are affected by a systematic offset in the water content. Sampling was undertaken during a period of bad weather and the sediment from the exposed sloping section may have experienced an excess uptake of water during the days preceding the sampling. The reported values presented in Table 5 may thus represent artificially inflated moisture contents. Due to the attenuating effect of water, this would cause an underestimation of the received dose and thus lead to an age overestimate. For OSL samples 1A, 1B and 1C a reduction in the mean water content from 12 to 10% would have reduced the dates by 5 ka. It is intriguing to note that, despite the sandy texture of all the samples, some were found to have substantially lower water contents, down to 4–6% (see Table 5). It is worth pointing out, however, that the errors attached to the modern-day moisture contents are sufficiently large (5%) to accommodate for such variations and therefore such an effect should not cause major concern. The most plausible interpretation of the Mottisfont Gravel dates, however, is that they generally suffer from systematic error as a result of incomplete bleaching of the mineral grains during Pleistocene fluvial deposition. The superposition of the Mottisfont Gravel above Palaeogene sandy bedrock means that much of the sand in this Middle Pleistocene fluvial deposit has probably been reworked from the underlying sediment. It has already been suggested that sample 10 may not have been completely reset (i.e. not fully bleached) during emplacement in the fluvial terrace deposit, on account of its extreme numerical age. Furthermore, the elemental concentrations of K, Th and U for this sample are very similar to those recorded for the sandy bedrock (samples 2 and 9). This reinforces the view that the bulk of the sediment contains grains directly derived from the underlying Reading Formation. Samples 7 and 8, which came from the basal part of the Mottisfont Gravel, have also yielded particularly high numerical ages with large uncertainties in palaeodose, suggesting that they too may include significant proportions of incompletely bleached sand grains. Both samples were located adjacent to an area in which the bedrock is considered to be affected by pronounced scouring and therefore it is not surprising that the dating should turn out to be problematic. By analogy, the remaining samples, especially those characterized by a high degree of scatter in the palaeodose values, may likewise contain smaller, but variable, proportions of grains retaining a residual signal from the Palaeogene parent material, the lowest proportion being evidently in sample 1, which has yielded the lowest numerical age (Table 5) and the closest to the expected age of the deposit. Some of the OSL dates obtained from terrace deposits of the main Solent River by Briant et al. (2006) are significantly older than the expected ages of the fluvial deposits, likewise suggesting a degree of incomplete resetting of the OSL signal at deposition (cf. Westaway et al., 2006 [note added in proof]; Briant et al., 2009; Briant and Schwenninger, 2009). Further indications of systematic errors in the full set of OSL dates now available for the River Test, from Bates et al. (2010)

604

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

(Table 1) and from the present study, are also evident. For example, as already noted, the weighted mean of the three dates from the Ganger Wood–Mallards Moor terrace deposit (expected age: MIS 10) is indistinguishable from the weighted mean of the new OSL dates from the Mottisfont Gravel (expected age: MIS 8), whereas the terrace stratigraphy (Fig. 4) precludes the possibility that these distinct fluvial deposits are of the same age. It is indeed evident that the earlier phase of OSL dating has overestimated the age of the Hamble terrace deposits (Table 1) as well as the Mottisfont Gravel, but has underestimated the ages of the Bitterne and Ganger Wood–Mallards Moor terrace deposits (Table 1). A similar mismatch, with some dates too old and others too young, was indeed noted by Westaway et al. (2006) in their summary of the OSL dating evidence from Briant et al. (2006). These observations indicate a requirement for caution in the use and interpretation of OSL dating of Middle Pleistocene fluvial deposits, especially in a system such as the Solent, where more than one fluvial terrace has formed during some 100 ka climate cycles. It is evident from this, as well as previous studies, that OSL dating can result in numerical ages that are neither precise (i.e. reproducible) nor accurate (i.e. corresponding to the true ages of the sediments). Some of the dates are nonetheless of value in providing a general indication of the true ages; for example, the weighted mean age of the samples from the Mottisfont Gravel is within one 100 ka climate cycle of the expected age of the deposit. However, uncritical use of the extant OSL dataset from the study region, without due consideration to specific sedimentological or geomorphic processes as well as age-constraints provided by archaeology, biostratigraphy or from uplift modelling, could result in unnecessary confusion. 9.1. Significance of the Archaeological record The watching brief has successfully placed the archaeological assemblage from Dunbridge within a more secure geological context than was possible previously, by establishing that the principal source of Lower Palaeolithic material is the Belbin Formation. Hand axes persist throughout the sequence as the principal retouched tools from the site, complementing the assemblage catalogued by Roe (1968a). Importantly, the occurrence of both proto- and fully developed Levallois has been documented. The three ‘proto-Levallois’ cores from Dunbridge were undoubtedly derived from the Belbin Formation, as their condition, staining and date of discovery confirm. This embryonic form of the Levallois technique is most closely associated with the site at Purfleet, Essex (Wymer, 1968; White et al., 2006), where ‘protoLevallois’ technology is superseded by developed Levallois technology. The sequence at Dunbridge is reminiscent of, but not necessarily comparable with, that at Purfleet, which has been dated to MIS 8 (Schreve et al., 2002) or perhaps MIS 9b (Bridgland et al., 2012). However cores demonstrating similar ‘protoLevallois’ characteristics are known from a number of locations predating MIS 9 (Scott, 2011), from which it has been argued that Levallois technology might well have developed from skills learned in the manufacture of hand axes (White and Pettitt, 1995; White and Ashton, 2003). ‘Proto-Levallois’ cannot therefore be used uncritically as a diagnostic chronological indicator. Nevertheless, a situation in which it is followed by the appearance of developed Levallois technology is likely to be significant and it is tempting, given the arguments from terrace stratigraphy and OSL dating, to consider the Dunbridge and Purfleet sequences to be broadly contemporaneous (always noting that the Solent system, unlike the Thames, has generated terraces at the rate of more than one per 100 ka glacial–interglacial cycle: Bridgland and Westaway, 2008; Bridgland, 2010).

The discovery of unequivocal evidence of developed Levallois technology at Dunbridge is extremely significant. As noted above, Ashton and Hosfield (2010) concluded that the paucity of material from the Test valley and poor levels of archive nullified the value of using the introduction of Levallois technology, and its distribution in the Solent region, as a reliable indicator of terrace age. They could locate only 36 pieces, of which 24 were from the pits at Warsash. As with the artefacts from Belbin’s and Chivers pits, north of Romsey, these were all only slightly abraded and were characterized by a creamy patination, a description that is reminiscent of the developed Levallois cores from the Dunbridge watching brief. These pieces contrast markedly with the condition of the hand axes, which are generally rolled and iron-stained. Drawing particularly on the work of Burkitt et al. (1939, especially Figs. 4.3 and 4.4) who was himself unsure of the source of the artefacts from Warsash, Ashton and Hosfield (2010) nevertheless concluded that the Levallois material from that site, and from Belbin’s and Chivers pits as well as Dunbridge, probably came from deposits overlying the terrace gravel and could not be used to date the latter. The new material from Dunbridge now makes it necessary to review the similarities and contrasts in the material from Warsash, much of it now housed at the British Museum, especially in view of the likelihood that they are from time-equivalent terrace deposits. Both industries represent fully developed Levallois technology but adopt different reduction strategies. That from Dunbridge demonstrates bipolar flaking patterns, whereas that from Warsash is characterised by centripetal removals. However the principal issue relates to condition, especially in its role as an indicator of provenance, about which the evidence is less conclusive. Both industries are remarkably fresh, which led Hosfield and Ashton to conclude that at both sites the Levallois material was derived from overburden. However individual pieces, including that illustrated by Burkitt et al. (1939, Fig. 4, No. 3) and described as being ‘very slightly rolled’ (op. cit., p. 50), do show distinct dulling of the areˆtes sufficient to raise an issue of doubt that the material was from overburden. At Dunbridge, although most of the material was found at the processing plant, it is known that overburden was removed prior to quarrying reducing the likelihood that any of the artefacts came from that source. In contrast there is evidence of fluvial activity, unrelated to gravel processing, on some artefacts, which increases the likelihood that the Levallois material came from the upper parts of the gravel sequence. The appearance of Levallois technology in fluvial sequences at around MIS 9–8 is also seen in northern France, in the River Somme valley. Here interglacial sediments capping the Epinette Formation, which forms the fourth terrace (counting upwards), have been dated to MIS 9 using the ESR method, with Levallois technology appearing in the next terrace in the sequence, representing MIS 8 (Bridgland et al., 2006; Antoine et al., 2007). As in the Thames, there are records from older sediments of artefacts suggestive of Levallois technology (i.e. ‘proto-Levallois’), but which might be by-products of handaxe manufacture (Tuffreau and Antoine, 1995); these occur in Garenne Formation, from which ESR dates of 400  101 ka (Tuffreau and Antoine, 1995) and 448  68 and 443  53 ka (Antoine et al., 2003) have been obtained. Levallois technology appears within the Maas/Meuse sequence of the Netherlands in deposits at Maastricht-Belve´de`re, within the Caberg Terrace (van Kolfschoten et al., 1993). Although these have been widely attributed to MIS 7 (e), recent reappraisal of Dutch and wider north-west European post-Elsterian temperate-climate fossiliferous sites, based on amino acid analyses of molluscan shells, led Meijer and Cleveringa (2009) to attribute them to MIS 9. While the findings related to the Levallois technology have confirmed its potential as an indication of age, the credentials of

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

another supposed chronologically significant Palaeolithic artefact type are perhaps compromised by data from Dunbridge. The enigmatic bout coupe´ hand-axe fragment recorded during the watching brief represents a type of implement considered diagnostic of a Devensian (Last Glacial) age (White and Jacobi, 2002), particularly representing MIS 3. The Dunbridge specimen is rolled, showing that it has come from the body of the Belbin Formation; nevertheless it conforms to features described by Tyldesley (1987) and reaffirmed by White and Jacobi (2002). A bout coupe´ hand axe was found previously at Dunbridge (Roe, 1981) but is unrolled and unstained and so may have come from deposits overlying the gravels. Other anomalous examples are known, which White and Jacobi (2002, 1123) acknowledged might necessitate ‘special pleading’ to refute their presence from pre-Last Interglacial contexts. 10. Conclusions Evidence from section monitoring during 17 years of gravel extraction at Kimbridge Farm quarry has provided significant insights into the context of the largest assemblage of Palaeolithic artefacts from Hampshire. Coupled with the results of digital terrain modelling, this evidence has demonstrated that two distinct Pleistocene river terrace deposits were exploited by the quarry. The uppermost terrace can be equated with the Belbin Stage of White (1912), now termed the Belbin Gravel Formation. This body of sediment has yielded the majority of Palaeolithic finds from both the area of modern quarrying and from the neighbouring Dunbridge gravel pit SSSI. This terrace can be equated with the Belbin Formation of the Westaway et al. (2006) scheme (adopted here in slightly modified form), which projects downstream into Terrace 4 of Edwards and Freshney (1987), and with Terrace 5 of Bates and Briant (2009; cf. Wilkinson, 2007). Westaway et al. (2006) proposed that the Belbin Formation dates from MIS 10; however, the identification of artefacts demonstrating features of ‘proto-Levallois’ technology from the main body of this gravel has led to reconsideration of its age, which is now considered to be MIS 9b. Westaway et al. (2006) suggested that Levallois technology first appeared in the Solent in MIS 9b, based on their original modelling, although Ashton and Hosfield (2010) raised doubts about this conclusion, expressing concern over the low numbers of finds, the lack of scrutiny of the published identifications or actual contexts and the paucity of dating constraints. The Dunbridge project has addressed these concerns and has provided more rigorous evidence in support of the occurrence of ‘proto-Levallois’ in quantity within this gravel formation. Despite the reservations about the application of OSL dating, expressed above, the improved age constraints provided by the technique (cf. Bates et al., 2010) have required modification of the terrace chronology for the Test and the Solent River downstream of its confluence with the Test; the remainder of the Solent system is, however, unaffected. The incorporation of this improved dating and the newly established constraint, from this present project, of ‘proto-Levallois’ technology from within the body of the Belbin Gravel into revised uplift modelling (see above), has brought the terrace age model for the Test into line with that for other parts of the Solent river system, notably with regard to the age of the highest and oldest terrace (MIS 22). The lower terrace at Dunbridge can be correlated with White’s (1912) Mottisfont Stage, based on its disposition, which implies equivalence with the Mottisfont terrace of the Westaway et al. (2006) scheme, which projects downstream into Terrace 3 of the Edwards and Freshney (1987) scheme, and with Terrace 4 of the Bates and Briant (2009) and Wilkinson (2007) scheme. The dating for this lower terrace is again largely in agreement between the two schemes, both implying an age in MIS 8. Finds of Levallois

605

flakes from the Kimbridge Pits (Roe, 1968a), which are considered to have exploited this lower terrace, are potentially significant. Their origin and context are unclear, although Dale (1912) reported that flake implements, in a relatively fresh condition, were found with heavily rolled material towards the base of the Kimbridge pit. The MIS 8 age is confirmed in the revised uplift modelling undertaken and is further supported by some of the new OSL age estimates presented here. Acknowledgements Specific thanks are extended to English Heritage, who funded the post-excavation analysis, programme of OSL dating and full reporting of the project through the Aggregates Levy Sustainability Fund (ALSF). The help of English Heritage through the assessment and post-excavation process is gratefully acknowledged; in particular the late Sarah Jennings, Helen Keeley, Barney Sloane and Kath Buxton are thanked for their help during the project. David Hopkins (Hampshire County Council) provided funding for an initial study of the watching brief archive for which Wessex Archaeology is very grateful. The watching brief could not have been undertaken without funding from Halls Aggregates (South Coast Ltd.), specifically to Rosemary Box who coordinated the initial stages of the watching, and latterly to Cemex, especially to Richard Small for his help arranging access, for providing plant to collect OSL samples and for borehole data. The work at Dunbridge became a long term project during which time a large range of individuals were involved at the quarry in one capacity or another. These people became friends and made the work enjoyable; to them all go prolonged thanks. The completion of the report has been made possible by the efforts of Elizabeth James who completed the illustrations and Dr. Julie Gardiner, who undertook an internal review of the report for Wessex Archaeology. The archive is currently stored at the offices of Wessex Archaeology under project codes W436, 34351, 69590–92. The archive, comprising the paper record and artefact assemblage, will be deposited with the Hampshire Museums Service.

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.pgeola.2012.03.003. References Allen, L.G., Gibbard, P.L., 1993. Pleistocene evolution of the Solent River of southern England. Quaternary Science Reviews 12, 503–528. Antoine, P., Auguste, P., Bahain, J.J., Coudret, P., Depaepe, P., Fagnart, J.P., Falgueres, C., Fontugne, M., Frechen, M., Hatte´, C., Lamotte, M., Laurent, M., LimondinLozouet, N., Locht, J.L., Mercier, N., Moigne, A.M., Munaut, A.V., Ponel, P., Rousseau, D.D., 2003. Pale´oenvironnements ple´istoce`nes et peuplements pale´olithiques dans le bassin de la Somme (Nord de la France). Bulletin de la Socie´te´ pre´historique Franc¸aise 100, 5–28. Antoine, P., Limondin Lozouet, N., Chausse´, C., Lautridou, J.-P., Pastre, J.-F., Auguste, P., Bahain, J.-J., Falgue`res, C., Galehb, B., 2007. Pleistocene fluvial terraces from northern France (Seine, Yonne, Somme): synthesis, and new results from interglacial deposits. Quaternary Science Reviews 26, 2701–2723. Arkell, W.J., 1947. The Geology of the Country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the Geological Survey, London. Ashton, N., Hosfield, R., 2010. Mapping the human record in the British early Palaeolithic: evidence from the Solent River system. Journal of Quaternary Science 25, 737–753. Banerjee, D., Murray, A.S., Bøtter-Jensen, L., Lang, A., 2001. Equivalent dose estimation using a single aliquot of polymineral fine grains. Radiation Measurements 33, 73–94. Barton, R.N.E., 1997. Stone Age Britain. English Heritage, Batsford, London, p. 144. Bates, M.R., Briant, R.M., 2009. Quaternary sediments of the Sussex/Hampshire Coastal Corridor: a brief overview. In: Briant, R.M., Bates, M.R., Hosfield, R.T.,

606

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607

Wenban-Smith, F.F. (Eds.), The Quaternary of the Solent Basin and West Sussex Raised Beaches: Field Guide. Quaternary Research Association, London, pp. 21– 41. Bateman, M.D., Buckland, P.C., Chase, B., Frederick, C.D., Gaunt, G.D., 2008. The LateDevensian proglacial Lake Humber: new evidence from littoral deposits at Ferrybridge, Yorkshire, England. Boreas 37, 195–210. Bates, M.R., Briant, R.M., Rhodes, E.J., Schwenninger, J.-L., Whittaker, J.E., 2010. A new chronological framework for Middle and Upper Pleistocene landscape evolution in the Sussex/Hampshire coastal corridor, UK. Proceedings of the Geologists’ Association 121, 369–439. BGS, 1987. Southampton. British Geological Survey Geological Map Sheet 315 (England and Wales), 1:50,000 Scale. The Ordnance Survey, Southampton. BGS, 1998. Fareham. British Geological Survey Geological Map Sheet 316 (England and Wales), 1:50,000 Scale. The Ordnance Survey, Southampton. Boe¨da, E., 1995. Levallois: a volumetric construction, methods, a technique. In: Dibble, H.L., Bar-Yosef, O. (Eds.), The Definition of Levallois Technology, Monographs in World Archaeology, vol. 23. Prehistory Press, Madison, Wisconsin, pp. 41–67. Briant, R.M., Schwenninger, J.-L., 2009. Solent river gravels at Badminston Farm, Hampshire SU 463 019. In: Briant, R.M., Bates, M.R., Hosfield, R., WenbanSmith, F.F. (Eds.), The Quaternary of the Solent Basin and West Sussex Raised Beaches: Field Guide. Quaternary Research Association, London, pp. 189–197. Briant, R.M., Bates, M.R., Schwenninger, J.-L., Wenban-Smith, F.F., 2006. A long optically-stimulated luminescence dated Middle to Late Pleistocene fluvial sequence from the western Solent Basin, southern England. Journal of Quaternary Science 21, 507–523. Briant, R.M., Wenban-Smith, F.F., Schwenninger, J.-L., 2009. Solent River gravels at Barton on Sea, Hampshire SZ 230 930. In: Briant, R.M., Bates, M.R., Hosfield, R., Wenban-Smith, F.F. (Eds.), The Quaternary of the Solent Basin and West Sussex Raised Beaches: Field Guide. Quaternary Research Association, London, pp. 161–170. Bridgland, D.R., 1986. Clast Lithological Analysis. Technical Guide 3. Quaternary Research Association, Cambridge. Bridgland, D.R., 1994. Quaternary of the Thames. Chapman & Hall, London. Bridgland, D.R., 1998. The Pleistocene history and early human occupation of the River Thames valley. In: Ashton, N., Healy, F., Pettit, P. (Eds.), Stone Age Archaeology. Essays in Honour of John Wymer. Oxbow Monograph, vol. 102. Oxbow Books, Oxford, pp. 29–37. Bridgland, D.R., 2001. The Pleistocene evolution and Palaeolithic occupation of the Solent River. In: Wenban-Smith, F.F., Hosfield, R.T. (Eds.), Palaeolithic Archaeology of the Solent River, Occasional Paper 7. Lithic Studies Society, pp. 15–25. Bridgland, D.R., 2006. The Middle and Upper Pleistocene sequence in the Lower Thames; a record of Milankovitch climatic fluctuation and early human occupation of southern Britain. Henry Stopes Memorial Lecture. Proceedings of the Geologists’ Association 117, 281–305. Bridgland, D.R., 2010. The record from British Quaternary river systems within the context of global fluvial archives. Journal of Quaternary Science 25, 433–446. Bridgland, D.R., Harding, P., 1987. Palaeolithic sites in tributary valleys of the Solent River. In: Barber, K.E. (Ed.), Wessex and the Isle of Wight: Field Guide. Quaternary Research Association, Cambridge, pp. 45–57. Bridgland, D.R., Harding, P., 1993. Preliminary observations at the Kimbridge Farm Quarry, Dunbridge, Hampshire: early results of a watching brief. Quaternary Newsletter 69, 1–9. Bridgland, D.R., Westaway, R., 2008. Climatically controlled river terrace staircases: a worldwide quaternary phenomenon. Geomorphology 98, 285–315. Bridgland, D.R., Maddy, D., Bates, M., 2004. River terrace sequences: templates for Quaternary geochronology and marine–terrestrial correlation. Journal of Quaternary Science 19, 203–218. Bridgland, D.R., Antoine, P., Limondin-Lozouet, N., Santisteban, J.I., Westaway, R., White, M.J., 2006. The Palaeolithic occupation of Europe as revealed by evidence from the rivers: data from IGCP 449. Journal of Quaternary Science 21, 437–455. Bridgland, D.R., Innes, J.B., Long, A.J., Mitchell, W.A., 2011. Late Quaternary Landscape Evolution of the Swale–Ure Washlands. Oxbow Books, North Yorkshire, Oxford. Bridgland, D.R., Harding, P., Allen, P., Candy, I., Cherry, C., Horne, D., Keen, D.H., Penkman, E.H., Preece, R.C., Rhodes, E.J., Scaife, R., Schreve, D.C., Schwenninger, J.-L., Slipper, I., Ward, G., White, M.J., Whittaker, J.E., 2012. An enhanced record of MIS 9 environments, geochronology and geoarchaeology: data from construction of the Channel Tunnel Rail Link and other recent investigations at Purfleet, Essex. Proceedings of the Geologists’ Association, doi:10.1016/ j.pgeola.2012.03.006, in press (manuscript PGEOLA-D-10-00004R1). Bennett, J.A., Brown, A.G., Schwenninger, J.-L., Rhodes, E.J., 2011. Holocene channel changes and geoarchaeology of the Exe River, Devon, UK, and the floodplain paradox. In: Brown, A.G., Basell, L.S., Butzer, K.W. (Eds.), Geoarchaeology, Climate Change and Sustainability. Special Paper 476. Geological Society of America, pp. 135–152. Brown, A.G., Basell, L.S., Toms, P.S., Bennett, J.A., Hosfield, R.T., Scrivener, R.C., 2010. Later Pleistocene evolution of the Exe valley: a chronostratigraphic model of terrace formation and its implications for Palaeolithic archaeology. Quaternary Science Reviews 29, 897–912. Burkitt, M.C., Paterson, T.T., Mogridge, C.J., 1939. The Lower Palaeolithic industries near Warsash, Hampshire. Proceedings of the Prehistoric Society 5, 39–50. Bury, H., 1923. Some aspects of the Hampshire plateau gravels. Proceedings of the Prehistoric Society of East Anglia 4, 15–41. Busschers, F.S., Kasse, C., Van Balen, R.T., Vandenberghe, J., Cohen, K.M., Weerts, H.J.T., Wallinga, J., Johns, C., Cleveringa, P., Bunnik, F.P.M., 2007. Late Pleistocene

evolution of the Rhine–Meuse system in the southern North Sea basin: imprints of climate change, sea-level oscillation and glacio-isostacy. Quaternary Science Reviews 26, 3216–3248. Calkin, J.B., Green, J.F.N., 1949. Palaeoliths and terraces near Bournemouth. Proceedings of the Prehistoric Society 15, 21–37. Collcutt, S.N., Bridgland, D.R., Gamble, C.S., Newbury, M., 1988. The Proposed Extraction of Hoggin and Sand at a site on Kimbridge Farm, Kimbridge, Hampshire. Evaluation of the Pleistocene Contexts and their Archaeological Implications. Unpublished report by Oxford Archaeological Associates Ltd., Oxford. Dale, W., 1912. On the implement-bearing gravel beds of the lower valley of the test. Proceedings of the Society of Antiquaries, London Series 2 24, 108–111. Dale, W., 1918. Report as local secretary for Hampshire. Proceedings of the Society of Antiquaries, London Series 2 30, 20–23. Edwards, R.A., Freshney, E.C., 1987. Geology of the Country around Southampton. Memoir for 1:50,000 Geological Map Sheet 315 (England and Wales) HMSO, London. Edwards, R.A., Scrivener, R.C., Forster, A., 1987. Applied Geological Mapping: Southampton Area. Main Report and Appendix (Area Covered by 1:50 000 Geological Sheet No 315 (Southampton) and OS 1:10 000 sheets SU 31 and 41 and parts of SU 20, 21, 22, 30, 32, 40, 42, 50, 51 and 52). BGS Research Report no. IC50/87/2, Vol. 1. British Geological Survey, Keyworth, Nottingham. Everard, C.E., 1954. The Solent River, a geomorphological study. Transactions of the Institute of British Geographers 26, 41–58. Green, J.F.N., 1947. Some gravels and gravel pits in Hampshire and Dorset. Proceedings of the Geologists’ Association 58, 128–214. Harding, P., 1998. An interim report of an archaeological watching brief on palaeolithic deposits at Dunbridge, Hants. In: Ashton, N., Healy, F., Pettitt, P. (Eds.), Stone Age Archaeology. Essays in Honour of John Wymer, Oxbow Monograph 102. Occasional Paper 6. Lithic Studies Society, pp. 72–76. Harding, P., Gibbard, P.L., Lewin, J., Macklin, M.G., Moss, E.H., 1987. The transport and abrasion of flint hand axes in a gravel-bed river. In: Sieveking, G.de G., Newcomer, M.H. (Eds.), The Human Uses of Flint and Chert. Proceedings of the Fourth International Flint Symposium. Cambridge University Press, Cambridge, pp. 115–126. Hosfield, R.T., 2011. Rolling stones: understanding river-rolled Paleolithic artifact assemblages. In: Brown, A.G., Basell, L.S., Butzer, K.W. (Eds.), Geoarchaeology, Climate Change and Sustainability. Special Paper 476. Geological Society of America, pp. 37–52. Hosfield, R.T., Chambers, J.C., 2004. The Archaeological Potential of Secondary Contexts English Heritage Project Report (Project No. 3361) English Heritage Archive Report, London, doi:10.5284/1000291. Huntley, D.J., Godfrey-Smith, D.I., Thewalt, M.L.W., 1985. Optical dating of sediments. Nature 313, 105–107. Jain, M., Tandon, S.K., Bhatt, S.C., Singhvi, A.K., Mishra, S., 1999. Alluvial and aeolian sequences along the River Luni, Barmer District: physical stratigraphy and feasibility of luminescence chronology methods. Memoir of the Geological Society of India 42, 273–295. Kelley, H., 1937. Acheulian flake tools. Proceedings of the Prehistoric Society 3, 15– 28. Li, B., Li, S.-H., Wintle, A.G., 2007. Overcoming environmental dose rate changes in luminescence dating of waterlain deposits. Geochronometria 30, 33–40. Li, B., Li, S.-H., Wintle, A.G., Zhao, H., 2008. Isochron dating of sediments using luminescence of K-feldspar grains. Journal of Geophysical Research 113, F02026, doi:10.1029/2007JF000900. Meijer, T., Cleveringa, P., 2009. Aminostratigraphy of Middle and Late Pleistocene deposits in The Netherlands and the southern part of the North Sea Basin. Global and Planetary Change 68, 326–345. Murray, A.S., Wintle, A.G., 2000a. Application of the single-aliquot regenerativedose protocol to the 375C quartz TL signal. Radiation Measurements 32, 579– 583. Murray, A.S., Wintle, A.G., 2000b. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32, 57–73. Newcomer, M.H., 1971. Some quantitative experiments in hand axe manufacture. World Archaeology 3, 85–94. Olley, J., Caitchoeon, G., Murray, A.S., 1998. The distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz: Implications for dating young sediments. Quaternary Science Reviews 17, 1033–1040. Parfitt, S.A., Barendregt, R.W., Breda, M., Candy, I., Collins, M.J., Coope, G.R., Durbidge, P., Field, M.H., Lee, J.R., Lister, A.M., Mutch, R., Penkman, K.E.H., Preece, R.C., Rose, J., Stringer, C.B., Symmons, R., Whittaker, J.E., Wymer, J.J., Stuart, A.J., 2005. The earliest record of human activity in northern Europe. Nature 438, 1008–1012. Parfitt, S.A., Ashton, N., Lewis, S.G., Abel, R.L., Coope, G.R., Field, M.H., Gale, R., Hoare, P.G., Larkin, N.R., Lewis, M.D., Karloukovski, V., Maher, B.A., Peglar, S.M., Preece, R.C., Whittaker, J.E., Stringer, C.B., 2010. Early Pleistocene human occupation at the edge of the boreal zone in northwest Europe. Nature 466, 229–233. Prestwich, J., 1898. The Solent River. Geological Magazine 35, 349–351. Rhodes, E.J., 1988. Methodological considerations in the optical dating of quartz. Quaternary Science Reviews 7, 395–400. Rhodes, E.J., Schwenninger, J.-L., 2007. Dose rates and radioisotope concentrations in the concrete calibration blocks at Oxford. Ancient TL 25, 5–8. Roe, D.S., 1964. The British Lower and Middle Palaeolithic: some problems, methods of study and preliminary results. Proceedings of the Prehistoric Society 30, 245– 267.

P. Harding et al. / Proceedings of the Geologists’ Association 123 (2012) 584–607 Roe, D.A., 1968a. A Gazetteer of the British Lower and Middle Palaeolithic Sites. Council for British Archaeology Research Report 8. Council for British Archaeology, London. Roe, D.A., 1968b. British Lower and Middle Palaeolithic Handaxe Groups. Proceedings of the Prehistoric Society 34, 1–82. Roe, D.A., 1981. The Lower and Middle Palaeolithic Periods in Britain. Routledge and Kegan Paul, London. Schreve, D.C., Bridgland, D.R., Allen, P., Blackford, J.J., Gleed-Owen, C.P., Griffiths, H.I., Keen, D.H., White, M.J., 2002. Sedimentology, palaeontology and archaeology of late Middle Pleistocene River Thames terrace deposits at Purfleet, Essex, UK. Quaternary Science Reviews 21, 1423–1464. Schwenninger, J.-L., 2009. Feasibility Study for OSL Dating of Fluvial Sand and Gravel Deposits near Dunbridge, Hampshire. Unpublished Report, Research Laboratory for Archaeology and the History of Art. University of Oxford. Schwenninger, J.-L., Harding, P., Bridgland, D.R., Allen, P., Bradley, P., Peat, D., 2011. Dunbridge, Hampshire: Optically Stimulated Luminescence Dating of Pleistocene Fluvial Sand and Gravel Deposits. Research Report Series 113–2011. English Heritage, Portsmouth. Schwenninger, J.-L., Rhodes, E.J., Bates, M.R., Briant, R.M., Wenban-Smith, F., 2006. Optically Stimulated Luminescence (OSL) Dating of Quaternary Deposits from the Sussex/Hampshire Coastal Corridor. Research Department Report Series 20/ 2006. English Heritage, Portsmouth. Schwenninger, J.-L., Bates, M.R., Briant, R.M., Wenban-Smith, F., 2007. Further Optically Stimulated Luminescence (OSL) Dating of Quaternary Deposits from the Sussex/Hampshire Coastal Corridor. Research Department Report Series 55/ 2007. English Heritage, Portsmouth. Scott, B., 2011. Becoming Neanderthals. The Earlier British Middle Palaeolithic. Oxbow Books, Oxford. Smith, B.W., Aitken, M.J., Rhodes, E.J., Robinson, P.D., Geldard, D.M., 1986. Optical dating: methodological aspects. Radiation Protection Dosimetry 17, 229–233. Smith, B.W., Rhodes, E.J., Stokes, S., Spooner, N.A., Aitken, M.J., 1990. Optical dating of sediments: initial results from Oxford. Archaeometry 32, 19–31. Stokes, S., Thomas, D.S.G., Washington, R.W., 1997. Multiple episodes of aridity in southern Africa since the last interglacial period. Nature 388, 154–159. Sutcliffe, A.J., 1995. Insularity of the British isles 250,000-30,000 years ago: the mammalian, including human evidence. In: Preece, R.C. (Ed.), Island Britain: a Quaternary Perspective. Geological Society of London Special Publication, 96, pp. 127–140. Toms, P.S., Hosfield, R.T., Chambers, J.C., Green, C.P., Marshall, P., 2005. Optical Dating of the Broom Palaeolithic sites, Devon and Dorset. Centre for Archaeology Report 16/2005, English Heritage. Tuffreau, A., Antoine, P., 1995. The earliest occupation of Europe: continental northwestern Europe. In: Roebroeks, W., van Kolfschoten, T. (Eds.), The Earliest Occupation of Europe. University of Leiden Press, Leiden, pp. 147–163. Tyldesley, J.A., 1987. The bout coupe´ hand axe. A Typological Problem. British Archaeological Reports. British Series, vol. 170. Oxford. .

607

van Kolfschoten, T., Roebroeks, W., Vandenberghe, J., 1993. The Middle and Late Pleistocene sedimentary and climatic sequence at Maastricht–Belvedere: the Type Locality of the Belvedere Interglacial. Mededelingen Rijks Geologische Dienst 47, 81–91. Wallinga, J., 2001. The Rhine–Meuse System in a New Light: Optically Stimulated Luminescence Dating and its Application to Fluvial Deposits. Netherlands Geographical Studies, vol. 290. The Royal Dutch Geographical Society. Wessex Archaeology, 1993. The Southern Rivers Palaeolithic Project Report No. 1 1991–1992. The Upper Thames Valley, the Kennet Valley and the Solent Drainage System. Wessex Archaeology, Salisbury. Westaway, R., 2009a. Calibration of decomposition of serine to alanine in Bithynia opercula as a quantitative dating technique for Middle and Late Pleistocene sites in Britain. Quaternary Geochronology 4, 241–259. Westaway, R., 2009b. Quaternary vertical crystal motion and drainage evolution in East Anglia and adjoining parts of southern England: chronology of the Ingham River terrace deposits. Boreas 38, 261–284. Westaway, R., 2011. A re-evaluation of the timing of the earliest reported human occupation of Britain: the age of the sediments at Happisburgh, eastern England. Proceedings of the Geologists’ Association 122, 383–439. Westaway, R., Bridgland, D., White, M., 2006. The Quaternary uplift history of central southern England: evidence from the terraces of the Solent River system and nearby raised beaches. Quaternary Science Reviews 25, 2212– 2250. White, H.J.O., 1912. The Geology of the Country around Winchester and Stockbridge. Memoir of the Geological Survey, London. White, M.J., 1998. Twisted ovate bifaces in the British Lower Palaeolithic: some observations and implications. In: Ashton, N., Healey, F., Pettit, P. (Eds.), Stone Age Archaeology: Essays in Honour of John Wymer. Oxbow Monograph 102, Lithic Studies Occasional Paper 6. Oxbow Press, Oxford, pp. 98–104. White, M.J., Jacobi, R.M., 2002. Two sides to every story: Bout coupe´ hand axes revisited. Oxford Journal of Archaeology 21, 109–133. White, M.J., Pettitt, P., 1995. Technology of early Palaeolithic Western Europe: innovation, variability and a unified framework. Lithics 16, 27–40. White, M.J., Ashton, N.M., 2003. Lower Palaeolithic core technology and the origins of the Levallois method in north-western Europe. Current Anthropology 44, 598–609. White, M.J., Scott, B., Ashton, N.M., 2006. The Early Middle Palaeolithic in Britain: archaeology, settlement history and human behaviour. Journal of Quaternary Science 21, 525–541. Wilkinson, K., 2007. The Palaeolithic of Hampshire, Solent Thames Research Framework, http://www.buckscc.gov.uk/assets/content/bcc/docs/archaeology/A_ST_ Hamp_1_Hants_Pal_Res_Ass_KW_v3_18_Jan_07_.pdf (accessed June 2010). Wymer, J.J., 1968. Lower Palaeolithic Archaeology in Britain as Represented in the Thames Valley. John Baker, London. Wymer, J.J., 1999. The Lower Palaeolithic Occupation of Britain, 2 vols. The Trust for Wessex Archaeology, Salisbury, Wiltshire.