Middle Pleistocene Thames terrace deposits at Globe Pit, Little Thurrock,and their contained Clactonian industry

D. R. Bridgland* and P. Harding'[

BRIDGLAND, D. R. & HARDING, P. Middle Pleistocene Thames terrace deposits at GlobePit, Little Thurrock, and their contained Clactonian industry. 1993. Proceedings ofthe Geologists'Association, 104,263-283. Section cleaning and a small-scale archaeological excavation have beenundertaken at Globe Pit, Little Thurrock, a site in the Corbets Tey Formation of the LowerThames. Gravel outcropping at this site had previously yielded a substantial assemblage ofPalaeolithic artefacts. Significant numbers of additional artefacts were discovered during thecourse of the work described here and served to confirm that a Clactonian industry is represented.The occurrence of this industry in the Corbets Tey Formation has hitherto been regarded asanomalous and indicative of an early and temporary incision to this level by the Thames.

The recent work has shown that the artefacts do not occur in an isolated early remnant of gravelperched above the main level of the Corbets Tey Formation, but in the 'feather-edge' of theCorbets Tey Gravel itself, in the oldest part of the formation. Complicated sequences of down­cutting and aggradation are no longer needed to explain either the occurrence of Clactonianartefacts at Little Thurrock or the distribution of interglacial sediments within the Lower Thamesterrace sequence.

A new interpretation of this formation, and the Lower Thames sequence as a whole, is nowproposed. This holds that the C1actonian gravel at Globe Pit represents deposition in the latter partof Oxygen Isotope Stage 10, although the material may have been knapped at an earlier date.Stratigraphically higher, younger divisions of the Corbets Tey Formation are thought to date fromStage 9 (interglacial fossiliferous brickearth) and Stage 8 (upper gravel). The younger divisionsof the Corbets Tey Formation, at nearby Purfleet, contain artefacts made using the Levalloistechnique.

* Earth Science Consultancy, 41 Geneva Road, Darlington DL14NE.t Wessex Archaeology, Portway House, Old Sarum, Salisbury SP4 6E8.

1. INTRODUCTION

Globe Pit is one of several Chalk quarries in the areaof Grays, Essex, that have provided exposures inPleistocene Thames terrace sediments. The pit issituated to the southeast of Grays town centre, at LittleThurrock; most references to sections at Little Thurrockrefer to this site, although not necessarily to the smallarea in which the deposits now survive (Fig. 1). Asequence of Pleistocene gravels and finer-grained,fossiliferous deposits was once visible here, the formeryielding Palaeolithic artefacts and the latter rich inmolluscan remains. The sequence has been describedrecently as part of the Corbets Tey Formation (Bridg­land, in press), a downstream equivalent of the LynchHill Gravel Formation of the Middle Thames (equiva­lent to the Lynch Hill Member of Gibbard (1985)).

The fine-grained deposits represent part of thecelebrated 'Grays brickearth' , a rich source ofPleistocene mammalian remains in the days whenexcavation was by hand. Further west this deposit wasalso exploited in pits to the south of Orsett Road. Faunalassemblages attributed to Grays are an amalgamation ofmaterial from all these various pits. A fossiliferous siltyclay that occurs in association with a later gravel forma­tion, the Taplow-Mucking Gravel, is also represented in

the Grays area, outcropping to the west of the towncentre, at West Thurrock (Bridgland, in press). Thislater deposit has also been the source of mammalianremains and, unfortunately, these were not separatedfrom the material from Grays and Little Thurrock bymany of the early collectors.

The remaining sections in the eastern part of GlobePit have been recognized as a Site of Special ScientificInterest by the Nature Conservancy Council for England('English Nature', formerly the Nature ConservancyCouncil and before that the Nature Conservancy) sincethe 1950s. Regrettably this did not prevent the survivingreserves of fossiliferous sediment being destroyed by theend of the 1970s. However, an important remnant ofartefact-bearing gravel has been preserved within theSSSI and has been the subject of this investigation. Theassemblage comprises abundant Clactonian artefacts ingood condition, seemingly uncontaminated by materialfrom other industries. However, the Lynch Hill/CorbetsTey Gravel is considered to substantially post-date theappearance ofthe Acheulian culture in this region, sinceAcheulian hand axes are very common in the older BoynHill/Orsett Heath Gravel, which forms the highestterrace in the Lower Thames. Furthermore, at Purfleet,7 km to the west, a Proto-Levalloisian assemblage has

264 D . R . BRIDGLAND AND P . HARDING

Alluvium

Brickearth

TaplowlIMucking Gravel

Lynch Hill/Corbets Tey Gravel

Boyn Hill/Orsett Heath Gravel

Thanetsand

oa:

otrIII~

Celcon yard

o,metres

10, 20,

Fig. l. Map of the site, with insets showing relation to the Lower Thames terraces of the Grays area and location in southernEngland.

been described from gravels that are also attributed tothe Corbets Tey Formation (Wymer, 1968; Bridgland,1988, in press).

2. PREVIOUS LITERATURE

A full review of the literature on the Pleistocene sites inthe Grays area has been provided recently by Bridgland(in press) . Early exposures in and fossils from the Grayspits were described by Morris (1836), Dawkins (1867),

Tylor (1869), Hughes (in Whitaker, 1889, p. 420),Woodward (1890) , Reid (1897), Hinton & Kennard(1900) and many more. Hinton & Kennard (1990,p. 364) illustrated a section at the Globe Pit, in whichthey showed gravel 'washed down from valley to thenorth (High Terrace Series derived)' overlying theThanet sands, but in turn overlain by gravel and brick­earth, their 'Middle Terrace Series'. A record bySpurrell (1892, p . 194) of 'numerous "waster" flintflakes' from 'the easternmost pit at Little Thurrock' is

THAMES TERRACE D EPOSITS AND THE CLACTONIAN INDUSTRY 265

probably the earliest citation of the Globe Pit industry .Two years later Smith (1894, p. 271) illustrated a'worked' red deer antler that, along with numerousother fragments of antlers , bones, tusks and 'keen flakesand implements' , he claimed to have found in situ on 'thePalaeolithic floor at Little Thurrock'.

The only record of a Palaeolithic implement from theGlobe Pit , as opposed to cores and flakes , was providedby Kennard (1904). Kennard described and illustrated a'side scraper', probably of Acheulian affinity, andreported that this was found in situ in the 'Middle Ter­race' gravels at the site. He suggested that this artefacthad been reworked from the 'High Terrace' (the BoynHilUOrsett Heath Gravel). Kennard (1916, p. 256)subsequently reported that he and Hinton found nodistinctive implements in their explorations ofthe Graysbrickearths, but that 'the few flakes found .. . may wellbe considered as of St Acheul type'. He referred inparticular to 'gravel overlying the brickearth at theGlobe Pit , Grays', which he claimed to have yielded anumber of implements, including the one that he himselfhad described in 1904. This presumably refers to thelater gravel , now quarried away, that was illustrated byWymer (1985, see Fig. 2).

Following consideration of material from the typelocality at Clacton (Warren, 1922, 1926), a distinctivePalaeolithic industry , characterized by stone-struckflakes and cores and lacking hand axes, was definedunder the name Clactonian (Breuil , 1932). King &Oakley (1936) made the earliest observation that theLittle Thurrock material belonged to this Clactonianindustry, while Oakley & Leakey (1937) illustratedthree Clactonian flakes from Little Thurrock in theirreport of excavations at Clacton . King & Oakley pro­posed a correlation between the Palaeolithic deposits at

Grays and Clacton, supported by a comparison of thefauna recorded from the two sites. They proposed theterm 'Clacton-on-Sea Stage' for this phase of Thamesdevelopment and placed this stage between the depo­sition of the Lower Loam and the Lower Middle Gravelat Swanscombe , implying that the river's floodplainlevel fell to the elevation of the 'Middle Terrace' at thistime and then was built back up to the highest levels ofthe 'High Terrace'. Other 'Middle Terrace' deposits,including those at Crayford and Northfleet, wereregarded by these authors as younger than the youngestsediments of the 'High Terrace'. Their scheme for inter­preting the Lower Thames terraces, largely based on thearchaeology, thus invoked a complexity of relative upliftand subsidence in the London area , rather than theprogressive lowering of base level that would normallybe associated with a simple flight of terraces. The riverwas held by King & Oakley to have flowed at the 'HighTerrace' level during two different periods and at the'Middle Terrace' level during two different periods , aview that was seldom challenged prior to the most recentwork in the Lower Thames.

The association between the Little Thurrock depositsand the Clactonian industry was confirmed by Wymer(1957), who pinpointed the source of artefacts to a smallremnant of gravel overlying a 'bench' at 49 ft (15mOD)- the remnant of Corbets Tey Gravel described above.Wymer collected 289 flakes and 5 'Chopper cores' fromthis gravel, many of the former showing secondaryworking and over half in mint or fairly sharp condition,indicating minimal transport (Wymer , 1957, 1968). NoAcheulian implements or finishing flakes were encoun­tered, leading Wymer to conclude that the collectionrepresents a single industry , with no mixing of materialreworked from any other.

N

Metres 0 .0.

25No artefacts known

Deposits of the Lynch Hill / Corbets Tey Formation s

20

15

10

5

Bullhead Bed

Chalk

Location of Figure 3I \

I I ClactonianI artefactsI

Acheulian side scraper(Kennard , 1904 , 1916)

Base level in Globe Pit : 6 metres 0 .0. (Wymer. 1985)Base level 0.2 kilometres to the west: c. -10 metres 0.0. (Tyler , 1869)

I!IlIllillll Slope deposits ~ Taplow/Mucking Gravel ~ Brickearth E::::J Gravel ~ Boyn Hill/Orsett Heath Grave l

Fig. 2. Section through the Corbets Tey Formation at Globe Pit (modified from Wymer , 1985).

266 D . R . BRIDGLAND AND P . HARDING

Hart (1960) referred the Clactonian deposits at theGlobe Pit to the Taplow Terrace, describing the depositsas 'brickearth with gravelly partings ' , the Clactonianartefacts occurring in the latter. In an undated, un­published report on file with English Nature (Bridgland,in press) , Hart recorded gravel containing Clactonianartefacts and mammalian remains occupying a channelwith a base level of 6.5 m OD at Globe Pit. The occur­rence of deposits yielding (mainly sharp) Clactonianmaterial at this level has been confirmed recently byWymer (1985), who published a complex diagrammaticsection through the deposits at Globe Pit , includingthose now quarried away (see Fig. 2) .

A further excavation of the Clactonian deposits inGlobe Pit was undertaken in 1961 by Snelling (1964).Some 280 worked flints were obtained, including twohammerstones, two waste cores and very occasionalcore tools similar to those described by Wymer. West(1969) carried out pollen analyses of samples collectedfrom the brickearth banked up against and overlying theClactonian deposits in the Globe Pit. He recorded asection similar to that described by Hart , with a baselevel of 9mOD , comprising up to 0.5 m of gravel, over­lain by 3 m of brown silt and sand (brickearth) con­taining the bivalve Corbicula fluminalis (Miiller) . Thepollen showed that the deposits were of interglacialorigin but was insufficiently distinctive to permitallocation to a particular stage. However, since brick­earth at comparable elevations at Aveley and Ilford,8 km and 19km (respectively) to the northwest, hadyielded pollen sequences attributed to the Ipswichian(West , Lambert & Sparks, 1964; West , 1969), West(1969) proposed a similar age for the Gr ays deposit. Thissuggestion was disputed by Conway (1970), whofavoured a Hoxnian age on palaeontological andarchaeological grounds , as originally implied by King &Oakley. West (1969) countered the archaeological argu­ment by suggesting that the Clactonian gravels at 49 ft(15 m) OD had been 'sludged' down a south-facing slopeof post-Clactonian age and were then overlain by thefluvial aggradation of the Ipswichian brickearth.

The most recent previous study of the deposits atGlobe Pit was by Hollin (1977), who reinterpreted :existing published descriptions and carried out newanalyses at a number of sites in the Lower Thames area,with a view to identifying evidence for sea-level change.He supplemented the pollen analyses obtained by Westfrom Globe Pit and was able to demon strate enhancedevidence for an Ipswichian age, which he consideredmost probable, although not certain. He interpreted thelaminated brickearth as a tidal deposit and suggestedthat it represented estuarine aggradation to 14 metresabove OD , related to an Antarctic ice surge during theIpswichian Interglacial. However, a preliminaryattempt at establishing a Pleistocene stratigraphybased on amino-acid epimerization in fossil molluscs(Miller , Hollin & Andrews, 1979) has suggested thatC. fluminalis shells from Grays (presumably Little

Thurrock) are of comparable age to shells of the samespecies at Swanscombe (Dierdens Pit) and StokeNewington and that they are markedly older thanCorbicula shells from Aveley , Ilford and Crayford.Bowen , Hughes , Sykes & Miller (1989) confirmed theseresults using additional species. They noted , in addition ,that shells from classic Ipswichian sites (those yieldinghippopotamus) such as Trafalgar Square show markedlyless epimerization than those from sites such as Aveley.The implication of the latest amino acid data is that noneof the familiar Lower Thames sites date from the sameinterglacial as Trafalgar Square ; all are older (Bowenet al. , 1989; Bridgland, in press).

This review of previous descriptions and interpret­ations of the Little Thurrock site indicates that, despiteconsiderable attention from geologists and archae­ologists, the age of the deposits and their position withinthe Lower Thames terrace succession remains un­certain. For this reason the Geological Review Unit ofthe then Nature Conservancy Council organized the re­excavation of sections in the Clactonian gravels at GlobePit in the spring of 1983, primarily in order to allowgeological investigation but with close archaeologicalsupervision , all Palaeolithic finds being carefullyrecorded.

3. DESCRIPTION OF mE 1983 SECTIONS

Pleistocene deposits of several different ages areexposed around the sides of this large, exhausted Chalkquarry. At the northern end gravel mapped as 'BoynHill' (Geological Survey, Sheet 271) overlies ThanetSand at 20.5 mOD. Further south , a small remnant ofgravel on the eastern side of the pit , behind the gardenson the south side of Overcliff Road (Fig. 1), is all thatremains of the deposit from which the Clactonianartefacts have been recovered. In this area thePleistocene deposits thin rapidly northwards, bankedagainst Thanet Sand bedrock. It appears that theartefact-bearing gravel was all but removed by theerosion that preceded the deposition of the above­mentioned Grays brickearth, which is banked againstit, almost ent irely covering it at the surface, so that onlybrickearth appears on the Geological Survey map. Thearea has been partly excavated for gravel and it isdifficult to decide how much of the original land surfaceremains .

Sadly, the 'brickearth' has been almost entirelyquarried away at Globe Pit, the last bedded, shellybrickearth having been removed since its descriptionby West (1969), leaving only a structureless, de­calcified feather-edge (Fig. 3). According to Hart (inBridgland, in press) and Conway (in Wymer , 1985), thebrickearth also contained Clactonian artefacts , probablyreworked from the underlying gravel.

The initial site cleaning operation of 1983involved theremoval of topsoil and accumulated spoil from two mainsections within the SSSI. This was carried out with the

THAMES TERRACE DEPOSITS AND THE CLACTONIAN INDUSTRY 267

NORTH

Section 1b16

15

c::i 140

"' 13~~ 12E

11

10

9o 1I

2 3 4 5 metres

SOUTH

16

15

143!Po

13 rno

12 0

11

Fig.3. Sections excavated in 1983/4 (composite view).

mimmum disturbance of in situ deposits. Section 1(now 1a) proved to be near the edge of the Pleistocenedeposits, with only 20-40 em of gravel and sand remain­ing in its vicinity, partly as a result of former quarrying(Figs 1 & 4). In cleaning this section, overburden wasremoved over a rectangular area of c. 15m2

, providing anew N-S vertical section to the west, Section 1b (Figs 1,3 & 4), which proved more informative than the originalW-E section. Section 2 revealed considerably thickerPleistocene material, including the wedge of clayey sand(brickearth) described above. Thanet Sand was notreached here initially, but by excavating a steppedsection at right angles down the bank into the mainquarry (Fig. 1) it was reached at the extreme southern

end of the site (Section 2a - Figs 3 & 6). In addition,a small pit was excavated down to the bedrock sand atthe northern end of section 2 (Section 2b - Figs 3 & 5).These sections, together with a series of auger holesbetween them, show the progressive southward declineof the Thanet Sand surface (Fig. 3), as the Pleistocenedeposits thicken towards the worked-out area.

Some 82 artefacts were recovered in situ from the twosections cleared in 1983. The following summer it wasdecided that the remaining veneer of in situ Pleistocenematerial should be removed from the area of Section 1,since it was becoming vegetated and clearly would havebeen destroyed or severely damaged in a very shorttime. Considerable information about the form of the

16

14

NORTH

metres0.5I

o16 f-I----+------1

SOUTH

15

c::io"'~1iiE

14"-

Bedding in Thanet Sand. or Groundwater effect?

Fig. 4. Section lb. The position of Gravel Sample 1 is shown.

Na-­00

NORTH SOUTH

15 15TOPSOI L

o~

Cl:c6o~Zo)zo:-0:t):coZo

13

ci0CIl

~QjE

12

14

• ""' . .. . ' ~ . ' ~ 0

,.~" ,,b;~· ;'~i;:}~"i..

FEATHER EDGE OF 'BRICKEA RTH?

metreso 0 .5

I I I

~" O "' .'_ ' " . CLAYEY SANDt::t2:~~~:;':f:}:;~·~~·:~:'~q. &_J _ . .__

THA NET SAND

... . '. . - '. .

~:·i'~·t~;~~:~~~~~~~~~~_·~~·13

12

14

cioCIle;;E

Fig. S. Section 2a. The positions of artefacts are shown (by projection in the case of some of those from the trial pit at the northern end), Closed trianglesindicate the positions of flakes, open triangles broken flakes, The position of Gravel Sample 3 is shown,

THAMES TERRACE DEPOSITS AND THE CLACTONIAN INDUSTRY 269

Thanet Sand surface was obtained from this excavation,which yielded a further 108 artefacts and also resultedin the deepening of sections la and lb. A Geologists'Association excursion party visited the site in December

0 .5

1984 and were shown the new sections and a selection ofthe artefacts collected from them, as well as recordsof earlier work, kindly displayed by John Wymer andBernard Conway.

me tre sWEST

13 -

12 -

6­,...1 1 -

- . --- -r-r-

• • • - . " , ... 00 " " . ~ .. - . 0 . .. _

-.-; -' -..:-= ---~~', ~.- .~ ~

....,.-.

- 10 -

9 -

THANET SAND

Fig. 6. Section 2b. The positions of artefacts are shown. Closed triangles indicate the positions of flakes, open triangles brokenflakes. The position of Gravel Sample 2 is shown.

270 D. R. BRIDGLAND AND P. HARDING

4. GEOLOGY

The Pleistocene sediments

Two separate Pleistocene deposits were recognized inthe 1983 sections: the 'Clactonian gravel' and the clayeysand ('Grays Brickearth'). Studies have been enti.relyconfined to the former, since very much better sectionsin the latter were described by West (1969) and Hollin(1977), when more of the deposit remained (foss!l­iferous remnants of this 'brickearth' have been dIS­covered elsewhere in the Grays area, but there seemslittle prospect for its serious study at this site). The'Clactonian gravel' comprises well-bedded gravels andsands the latter occurring mainly within the lower partof the sequence at the southern end of the site, wherethe beds are thickest (Figs 3, 5 & 6). At the very baseof section 2b, the sand showed signs of penecon­temporaneous deformation (Fi~. 6), perh~ps.as a res~lt

of burial by the overlying sediments while It wa~ stillwaterlogged. Above this, poorly preserved npplelaminations were observed, but the deposits were other­wise entirely horizontally bedded, with alterationsshowing coarser and finer gravel clasts as w~ll as co~rser

and finer sand in the matrix. Three clasts of iron-stainedclay were present near the base of the section; theseshowed signs of rolling and are considered to have beenfluvially deposited (Fig. 6). The full sequence of graveland sand, observed to below 10m OD, is interpretedhere as a single in situ fluviatile aggradation, contra­dicting earlier views that fluvial gravel was restrict~d to a'bench' at 15m and that below this level the matenal wasof colluvial origin (see above).

The remnant of Boyn Hill/Orsett Heath Gravel pre­served at the northern end of the pit was also investi­gated, by the (manual) excavation of two trial pits.These showed bedded but cryoturbated sand and sandygravel beneath pebbly, sandy subsoil. Pit 1 reachedThanet Sand at 1.75 m beneath the land surface, which isat c. 23 m OD at this point. The second pit extendedto 1.9 m below ground level but did not reach !he bas~ ofthe Pleistocene. Two samples for clast-lithologicalanalysis were collected from pit 1 (Globe Pit north 1a &1b) and one from pit 2 (see Table 1).

The Thanet Sand surface

Wherever the Thanet Sand surface was uncovered atGlobe Pit it proved to be extremely uneven. Initialimpressions from the base of section 2b and the pit at thebase of section 2a were that the bedrock surface was'pot-holed'. The much larger area of Th~net ~an~

surface uncovered in 1984 in the area of section 1 indi­cated a linear trend to the undulations, however (Fig. 7).The largest of these features, at the southern end ofsection 1, appears to be coincident with the 'step' in thebedrock surface observed by Wymer (1957) several

metres to the east. This feature has been undercut on itsnorthern side.

Few previous descriptions of the form of bedrocksurfaces beneath Pleistocene gravels have been pub­lished, although 'swirl-holes' in the Oxford clay ~ere

recorded beneath the Wolvercote Channel Deposits atOxford (Bell, 1894), while an intensely irregular scouredLondon Clay surface was recorded beneath grave~ atStoke Newington following a recent archaeologicalexcavation (Harding & Gibbard, 1984). At StokeNewington there were a number of rounded, some­times undercut, gravel-filled hollows resembling pot­holes. As at Globe Pit, the alignment of these featuresshowed a clear linear trend. They were interpreted asthe result of erosion of the London Clay, concentratedalong the line of channels in a river bed (Harding &Gibbard, 1984). A highly irregular Chalk surfacebeneath Thames gravel at Furze Platt, Maidenhead, wasrecently described and illustrated in these Proceedings(Harding, Bridgland, Madgett & Rose, 1991). Here,too there were indications of scoured pot-hole featureswith linear trends, but the situation was complicated bysolution of the Chalk.

At Globe Pit there is some evidence that loading ofthe gravel into the top of the Thanet Sand may ~ave

operated in the development of these features; sectIonscut into the sand in the area of the undercut 'scourfeature' at the southern end of section 1b revealedlineation within the Thanet Sand closely following theshape of the infilling gravel body, suggesting upwardsqueezing of the bedrock. This lineation was emph~­

sized by colour changes that proba~~y owed the~r

existence to groundwater effects, raising the pOSSI­bility that the latter may have been responsible. for theentire lineation phenomenon. Whether loadmg hastaken place or not, there has clearly been erosion of !heThanet Sand surface beneath the edge of the Clactoniangravel at Globe Pit. Despite the difference in bedrocktype, the 'scour-features' at this site are r~markably

similar to those in London Clay at Stoke Newmgton.

Analysis of the gravel

The analysis of clast lithology has been undertaken onsamples from the sections in the Corbets Tey Gravel atthe conservation site and from the trial pits in the OrsettHeath Gravel at the northern edge of the Globe PitChalk quarry (Table 1). Two different-sized fractionswere analysed, 1l.2-16mm and 16-32mm. These areboth sizes commonly used in Pleistocene gravel analysis(Bridgland, 1986a) and allow comparison with datacollected from other sites (Bridgland, 1983, 1988), someof which are included in Table 1.

Not surprisingly, all the samples had a compositiontypical of Lower Thames gravels downstream from theconfluence with the River Darent. As the data in Table 1

THAMES TERRACE DEPOSITS AND THE CLACTONIAN INDUSTRY 271

55

PH

t 49

04

+ 50+

A-II

Ir:';. 6

15.00

~

A-A-

+ I::. + A- A- t 536

A- A-

,Q + + + 52.... 14.80

=Q:::~

rI:J

+ 51

1

01

+

Contours in m. 0.0

6 Broken flakes

A- Unbroken flakes

o...Fig. 7. Contour plan of the excavation area, with a plan of the artefact find spots and a projection of finds onto section lb.

272 D. R. BRIDGLAND AND P. HARDING

Table 1. Data from clast-lithological analysis of selected Lower Thames gravels. 16-32 mm counts are in plain text, 11.2-16in italics. A 'D' after the sample number indicates a position downstream from the confluence with the River Darent

Flint

Formation (Member) Site Sample Tertiary Nodular Total Chalk*

Kempton Pk/E. Tilbury E. Tilbury Mshs 1 D 58.9 9.9 96.2Marshes 11.2-16 1 D 49.5 6.6 92.2

TaplowlMucking Lion Pit - upper gravel 1 D 67.1 5.9 95.311.2-16 1 D 59.4 3.2 94.2lower gravel 1 D 47.8 35.9 97.5 (1.1)*11.2-16 1 D 50.2 19.6 95.7 (0.3)

Mucking lA D 64.0 9.3 97.011.2-16 1A D 57.7 4.9 92.1

IB D 37.4 13.3 92.5

Lynch HilVCorbetsTey Stifford lA 51.6 8.4 94.0IB 52.5 92.9

11.2-16 1B 39.2 8.3 88.3Belhus Park, organic bed 1 47.5 9.8 90.2 (0.3)Belhus Park, upper gravel 1 49.0 9.7 93.8Purfleet, Esso Pit lA 44.8 16.9 91.8

11.2-16 1A D 36.3 7.6 86.6lBD 47.7 18.1 95.0 (37.3)

Globe Pit 1 D 57.9 11.2 93.111.2-16 2 D 47.8 6.1 91.3

2 D 50.2 10.5 93.211.2-16 2 D 40.7 5.4 90.5

3 D 64.6 8.9 94.4Barvills Fm Pit 1 D 67.9 11.8 92.9

11.2-16 1 D 55.6 5.6 91.8

Boyn HillIOrsett Heath Hornchurch 1 41.8 0.7 92.6Railway cutting 2 28.9 11.7 90.2Hornchurch Dell 1 54.0 7.7 91.7Globe Pit North lA D 41.4 9.0 90.4

IB D 53.2 9.3 95.111.2-16 1B 50.1 5.3 90.1

2 D 62.0 9.4 94.411.2-16 2 D 48.1 6.3 92.6

Linford 1 D 64.6 11.6 96.02 D 84.2 4.0 95.7

11.2-16 2 D 28.0 3.6 91.3

(Swanscombe Lower Barnfield Pit 1 D 58.2 9.8 93.9Middle Gravel) 11.2-16 1 D 50.9 5.3 89.9

2 D 48.5 12.7 92.711.2-16 2 D 41.6 5.5 89.7

(Swanscombe Lower Barnfield Pit 3 D 55.5 8.3 94.3Gravel) 11.2-16 3 D 36.5 5.9 89.0 (0.1)

4 D 30.5 11.8 94.1 (0.4)11.2-16 4 D 28.1 8.8 90.6 (0.3)

* Onlydurableclasts included; Chalkshown as % durables. Nodularflintnot separately recorded inStifford lB.

THAMES TERRACE DEPOSITS AND THE CLACTONIAN INDUSTRY 273

Southern ExoticsNational

Greensand Carboniferous Rhaxella Ratio Total Gridchert Total Quartz Quartzite chert chert Igneous Total Qtz: qtzt count Reference

0.9 1.1 0.9 0.7 0.5 0.3 0.3 2.7 1.40 745 TQ688078431.5 1.6 3.2 1.4 0.6 0.2 0.1 6.1 2.21 979

0.8 0.8 3.5 3.9 255 TQ597878091.1 1.1 1.9 1.5 0.4 0.4 4.7 1.29 4650.7 0.7 0.7 1.1 1.8 0.67 276 TQ597878210.6 0.6 1.8 0.9 0.6 0.3 3.7 2.00 3271.1 1.1 0.9 0.6 0.1 1.8 1.50 708 TQ689281541.9 1.9 3.1 1.2 1.1 0.2 0.1 6.0 2.55 9014.9 4.9 1.2 0.6 0.6 0.3 2.6 2.00 345

0.4 0.4 2.9 1.2 0.6 0.1 0.4 5.5 2.33 730 TQ 590079080.9 1.0 3.5 1.4 0.5 0.1 5.9 2.46 9181.1 1.4 6.0 2.6 1.1 0.2 0.1 10.3 2.30 12770.7 0.7 2.0 4.4 2.0 0.7 9.1 0.46 297 TQ5758811

3.5 1.4 0.7 0.7 6.2 2.50 1450.5 0.5 2.5 3.0 1.6 7.4 0.82 366 TQ560778371.0 1.1 3.9 3.7 3.1 0.5 0.2 11.7 1.04 6181.5 1.5 0.8 1.5 0.8 0.4 3.5 0.50 2603.2 3.5 0.8 1.1 1.1 0.2 3.4 0.71 653 TQ625178303.9 4.1 0.5 2.6 0.5 0.5 0.3 4.6 0.21 11123.1 3.1 1.3 0.7 0.7 0.8 3.7 2.00 617 TQ625178284.4 4.7 2.1 0.8 1.2 0.2 0.1 4.5 2.73 14562.4 2.4 1.5 1.0 0.4 3.2 1.40 463 TQ625178283.3 3.3 1.7 1.1 0.4 0.1 3.6 1.50 722 TQ681177742.7 2.9 2.2 1.1 1.1 0.3 0.3 5.3 2.08 1138

2.3 2.3 2.0 1.4 0.6 0.6 5.1 1.17 352 TQ546487391.6 1.9 1.9 2.3 1.6 0.9 0.9 7.9 0.80 429 TQ546487391.5 1.5 2.1 2.8 1.2 0.4 6.7 0.78 676 TQ 544086754.1 4.4 0.6 1.4 1.6 0.3 5.2 0.40 365 TQ624578552.0 2.2 0.7 0.7 1.0 0.3 2.7 1.00 4083.3 4.1 1.4 3.1 0.9 0.3 0.1 5.9 0.46 7863.0 3.6 1.3 0.6 1.9 486 TQ624678552.7 3.2 1.0 1.8 0.4 0.4 0.3 4.2 0.56 9022.2 2.4 0.7 0.2 0.2 1.7 424 TQ668180281.4 1.6 0.5 0.2 1.2 2.7 6251.1 1.2 3.9 2.3 0.6 0.2 0.5 7.4 1.73 665

0.9 1.2 2.4 1.8 0.5 4.8 1.37 1081 TQ597374302.1 2.3 4.4 2.0 0.8 0.1 7.7 2.21 17031.9 2.0 1.9 1.8 0.5 0.1 0.2 5.0 1.05 992 TQ597574303.0 3.1 3.5 1.5 0.5 0.2 0.2 6.8 2.42 1785

1.0 1.0 2.3 1.3 0.5 0.2 0.1 4.5 1.75 931 TQ597474302.5 2.7 4.0 2.9 0.5 0.1 0.1 8.3 1.40 13912.7 2.8 1.1 0.8 0.4 0.1 2.7 1.29 857 TQ597474343.5 3.8 2.7 1.5 0.9 0.2 5.6" 1.74 1494

274 D. R. BRIDGLAND AND P. HARDING

show, this confluence boosts the amount of southernmaterial in the gravels, most of which is chert from theLower Greensand. Note that all non-flint material isgenerally more common at the 11.2-16mm size, which,coupled with the larger numbers that are usually presentin this fraction, makes this the best size range forobserving the rarer elements of the gravel, such asoccasional igneous rocks. The latter are usually acidtypes and are often porphyritic. They may have beenreworked from earlier Thames gravels upstream fromLondon, in which such material is more common(Green, Hey & McGregor, 1980), or from Anglianglacial deposits. The consistent presence of Rhaxellachert provides corroboratory evidence for the post­Anglian-glaciation age of all the gravels, as this rock isbelieved to have been brought to the London Basin bythe Anglian ice sheets (Bridgland, 1986b). The possibleprovenances of the various rocks found in Thamesgravels have been discussed at some length by Bridgland(1986b).

5. THE ARCHAEOLOGICAL EXCAVATION

Introduction and techniques

The gravel veneer south of section 1a was excavated bytrowel, within an area east of gridline 02 and north ofgridline 53 (Fig. 7) sieved through 10mm mesh torecover any knapping chips that might have survived.All artefacts found in situ were recorded in three dimen­sions. Wherever possible, records were kept to indicateangle of rest, orientation and whether dorsal or ventralsurfaces lay uppermost.

The archaeological material recovered in 1983/4 isrecorded in Table 2. Pieces in situ in the Corbets TeyGravel were recorded sequentially as 1/1, 1/2 etc. and2/1, 2/2 etc. from sections 1 and 2 respectively.

Unstratified pieces found when excavating the twosections were labelled I/O or 2/0. The 'later prehistoric'category in Table 2 includes a distinctive patinatedbladelet fragment with an abraded butt. Wymer (1957)recorded a Neolithic scraper from the topsoil of hissection at Globe Pit. The column headed 'others'includes a burnt core from 1/0 and a quartzite hammer­stone (Fig. 9) from 2/0.

All unbroken flakes were analysed to establish detailsof morphology and technology. Unstratified flakes wereincluded in the analyses, to maximize the sample size.

Distribution of artefacts

The distribution of broken and unbroken flakes from theexcavation are shown in plan on Fig. 7; pieces foundwest of gridline 02 are projected onto the N-S section.Material from section 2 was recorded by tacheometryand plotted onto the section drawings (Figs 5 & 6). Inboth sections, flakes were distributed throughout thedeposits down to the Thanet Sand surface. This supportsthe conclusion that they are derived. They appear to bemore common in the gravel than in the sand, as would beexpected in the case of derived material; the sand bedspresumably result from low-energy flow that was in­sufficient to carry pebble-sized material, includingflakes. The relation between the size of the material andthe associated gravel, and the absence of flakes less than20mm in length (Fig. 8), are presumably further resultsof water transportation and winnowing. This is con­firmed by weights; 88% of the flakes weigh more than10g but 58% weigh less than 30 g (individual pieces over200 g were recorded). This probably explains the generalabsence of cores, as was concluded previously by Wymer(1957).

The area of excavation was small and no concen­trations were apparent in plan; the fact that more pieces

Table 2. Artefacts from Globe Pit, 1983/4. This shows the total number of flakes found fromeach context. No cores were found. Flakes found in situ in section la and in the excavation areawere labelled 1/1 etc. and unlocated pieces 1/0. A similar system was used for section 2 (2/1 etc.)

Total Later Broken MeasuredContext recorded Deleted prehistoric pieces Others flakes

I/O 49 9 2 10 3 252/0 47 8 0 14 1 241/1 202 85 0 35 6 762/1etc. 87 14 0 23 5 45

Total 385 116 2 82 13 170

Note: The column headed 'deleted' refers to flakes collected during the excavation that have probably formed asa result of gravel collision in the river. Flakes of this type were first considered in detail by Warren (1920). Theyare recognized here using criteria established at Furze Plait, Maidenhead (Harding et al., 1991), namely small,narrow butts, heavily crushed platform edges, diffuse bulbs of percussion (Oakley 1949)) and cortical orthermally fractured dorsal surfaces.

FLAKE LENGTH FLAKE BREADTH FLAKE BREADTH:LENGTH

-I:t»3:mVJ

~;:d;:d»otTl

tItTl"0oVJ

~»ztI-I:trnor'»~z>zZtIcVJ-I;:d-<

Sample size 170 flakes

2:5 3:5 4:5 5:5 6:5 7+:5

NIR - Not recorded

%

0-3 4-6 7-9 10-12 13-15 16-18 19+ NIR

FLAKE BUTT WIDTH

%

0-9 10-1920-2930-3940-49 50+

%

FLAKE WEIGHT

50 75 10025o

10-1920-2930-3940-4950-5960-69 70+

CORTEX

%

%

<1;0 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85+ NIH

0-4 5-9 10-14 15-1920-2425-29 30+

10-1920-2930-3940-4950-5960-69 70'"

FLAKE PERCUSSION ANGLE

FLAKE THICKNESS

10

30

30

20

10

10

40

30

% 20

% 20

%

Fig. 8. Histograms showing the frequency of various attributes of flakes from the 1983 and 1984excavations.

N-.JU1

276

o

D. R. BRIDGLAND AND P. HARDING

150mm

Fig. 9. I1Iustration of hammerstone from Section 2 (unstratified).

were recorded in the northern part of the area merelyreflects the preservation there of thicker gravel. Smallflakes and chips of the type produced during knapping,which would be readily dispersed by flowing water, wereabsent; nor were there any conjoining pieces. Mostflakes appeared to be lying flat in the gravel, althoughtwo were found on edge and two more were upright withthe butt down. Similar observations of flakes in gravelwere made by Wymer (in Singer, Wymer, Gladfelter &Wolff, 1973, p. 12) at Clacton.

Excavation of the feather-edge of the brickearth wasrestricted to section cleaning and no artefacts or fossilswere found.

Raw material and condition

The flint from the analysed sample has been sorted usingthe divisions defined by Wymer at Clacton to indicatebroad trends of raw material selection (Singer et al.,

1973, p. 35). The occurrence and relative condition ofeach group is shown in Table 3.

The raw material is variable and probably derivedfrom several sources, of which only Bullhead(indigenous) and bi-zoned (from north Kent) can beidentified in hand specimen. It is uncertain how much ofthe flint used to make the artefacts was collected fromthe Chalk and how much comes from Pleistocenegravels. The sections at Globe Pit give no indication ofwhether large nodules were available in the local gravelor whether the Bullhead Bed was exposed nearby at thetime of occupation. The proportion of Bullhead flintmay be under-represented in Table 3, as the charac­teristic green exterior over a deep orange-stainedmarginal zone may not have survived the knappingprocess or subsequent weathering.

The fact that identifiable flint types recur amongst theflakes suggests that selection of raw material wasdeliberate. These specific flint types were supple­mented by casual use of flint clasts from pre-existing

Table 3. Artefacts from Globe Pit (1983/4): raw material and condition

Mint Sharp Slightly rolled

Dark 3 17 18Flint Bullhead 1 10 20

raw material Bi-zoned 10 20Unclassified 31 39

Total 4 68 87

Rolled Total

3831

2 329 69

11 170

THAMES TERRACE DEPOSITS AND THE C L A CTO N IA N INDUSTRY 277

Thames gravels , as is indicated by a number of little­rolled flakes that have heavily rolled cortex. The factthat the 'deleted' flakes (see Table 2) comprise pre­dominantly gravel-flint, together with a few of Bullheadorigin, tends to substantiate their interpretation as theresults of accidental collision in the fluvial environ­ment.

The flakes are unlikely to have moved far from theiroriginal location. Table 3 shows that most were in asharp or slightly rolled condition, using the classi­fication scheme of Wymer (1968 , pI. Xl) and , therefore,comparable with material from Wymer's (1957) section3 at Globe Pit (see Fig. 1). Occasional flakes showpatination or staining, which may have occurredbefore redeposition in the gravel. The uniformity ofcondition suggests that the material was derived froma common source and the quantity recovered indicatesthat this source was very rich.

6. THE GLOBE PIT INDUSTRY

The Clactonian industry as defined at Clacton has beendescribed by Warren (1922 , 1951) , Oakley & Leakey(1937) and Wymer (in Singer et al. ; 1973) as a flakeindustry supplemented with some chopper-core tools ,with no predetermined blank form. Flakes of this typecan be produced from single platform cores (e.g. Fig.10.1), flaked from opposed platforms or from many un­related platforms (e.g. Fig. lOA), or by alternate flaking(Fig. 10.5).

The most likely method of production is direct percus­sion using a stone hammer, but striking cores againsta fixed hammer, the 'block on block' technique , alsoproduces flakes of this type. Wymer (1968) listedfour characteristics of the ' typical Clactonian flake ':prominant bulbs and cones of percussion ; wide strikingplatforms; low flaking angles; and pronounced,irregular concavities on the reverse side (dorsal surface).Most authors have stressed that 'Clactonian flakes' arenot diagnostic of the Palaeolithic, but can be producedby any industry using this basic technology (Newcomer,1971; Roe, 1981).

The flakes from the 1983/4 excavations have beencompared with previous assembl ages from Globe Pit(Wymer, 1957; SneIling, 1964) and found to be broadlysimilar (Fig. 8) . Flake dimensions are shown by length(measured perpendicular to the butt) breadth (parallelto the butt) and maximum thickness. Shape is shown asa breadth: length ratio (Bohm ers & Wouters , 1956).These figures show that 65% (length) and 67% (breadth)measure 30-59 mm with 60% 10-19 mm thick. SmalI,thin flakes are probably under-represented, althoughthe absence of careful core preparation makes it unlikelythat such material was ever numerous. Most flakes aresquat, 71% having a breadth : length ratio between3 :5 and 5: 5. Some 6% of flakes have breadth: lengthratios of 2 : 5, sufficiently elongate to be classified

as blades. This small proportion is likely to have beenproduced by chance and does not indicate that bladeswere a deliberate product.

Some 73% of the flakes show characteristics of hardhammer percussion (e .g. Fig. 10.5) ; they have well­defined points and cones of percussion, pronouncedbulbs of percussion, conchoidal ripples on their bulbs ofpercussion and unlipped butts (Ohnuma & Bergman,1984) . The unstratified quartzite hammerstone (Fig. 9)from section 2 and the two flint hammerstones found bySnelling (1964) would have produced flakes with thesecharacteristics. Evidence of platform faceting, formedduring the preparation of a striking platform prior to thedetachment of a flake, is absent. Some flakes also showwell-developed incipient cones of percussion on thedorsal surface or on the butt (Fig. lOA), probablyresulting from miss-hits . Similar features were noted onClactonian material from Clacton (Singer et al., 1973).They frequently indicate blows that were located too farback on the striking platform to remove a flake. In con­trast, small dispersed incipient cones of percussion,common on both dorsal and ventral flake surfaces , arethought to have been produced by gravel coIlision in thefluvial environment.

Warren (1951) measured the 'flaking angle', asrepresented by the 'operative angle' (see Fig. 10.8), in asample of Clactonian flakes and found that 50% laybetween 55 and 67°. The current sample, of which 153could be measured , also has a characteristically lowangle of percussion with 57% within the above range.

The survival of cortical surfaces indicates that mostcores were not flaked to exhaustion, 56% of all flakeshaving 50% or more cortical cover. Wymer (in Singeret al. , 1973) argued that this was consistent with theproduction of chopper-cores where no more than 5 to12 flakes were removed from each core . No particularpattern of dorsal flake-scars is dominant in theassemblage from the recent Globe Pit excavation . Manyflakes were apparently removed from multi-platformcores or from those shaped by alternate flaking.Consequently, the most common type of flake at GlobePit is that with a plain non-cortical butt (68%) . How­ever, flakes with cortical butts (20%) or thermal buttsare also present. Flake butts are broad (Fig . 8), a featureindicative of technologies in which the point of percus­sion is set well back on the striking platform.

A specific technique for flake production was identi­fied by Wymer (1957) , in which blanks were removedfrom a cylindrical nodule. He illustrated a core (1957,fig. 504) from which flakes had been struck like slicesfrom a 'swiss roll' . The resulting discoidal flakes werecharacterized by cortex around all or most of the circum­ference - the so-called 'salami-slice' flake. The recentexcavations have confirmed the presence of flakes of thistype: e.g. Fig. 10.2, flake 1/152. However, neither flake1/152 nor Wymer's original core provide unequivocalevidence for the use of a distinctive technique. Such

278 D. R. BRIDGLAND AND P. HARDING

o:

tJ_~,~

Fig. 10. Illustration of flakes from the 1983 and 1984 excavations at Globe Pit. See text for explanation of numbering andinterpretation. 1: 2/0; 2: 1/152; 3: 1/0; 4: 1/3; 5: 1/0; 6: 1/0; 7: 1/67; 8: 2/0; 9: 1/35.

evidence might be expected to be more common if adeliberate technique of this type was employed.

One small artefact that was found in situ (flake 1/35;Fig. 10.9) may represent a hand axe finishing flake. It isin a slightly rolled condition and has a mottled light bluelsoft white patinated dorsal surface, although the ventralsurface is unpatinated. This artefact stands out from thebulk of the material from the site, which is largely un­patinated. It has semi-convergent flake scars and aslightly dipping profile, both characteristic features of

flakes produced during the finishing of hand axes. Thelinear butt is characteristic of finishing flakes where theblow is positioned on the edge of the hand axe. NeitherWymer (1957) nor Snelling (1964) found any evidence ofAcheulian technology at Globe Pit, so this small findmay provide the first indication that debitage from handaxe making might be mixed with the Clactonian industryat the site. Its contrasting surface condition indicatesthat it is unrelated to the Clactonian assemblage.

THAMES T E R R A C E DEPOSITS AND THE C L A CTO N IAN INDUSTRY 279

Chips

Approximately 300 small flakes and chips, with a totalweight of 270g, were recovered from the sieved area.None could be identified positively as by-products ofknapping, providing confirmation that the assemblage isnot in primary context.

Retouch

Retouch forms at Clacton have been described byWarren (1922, 1951) and Oakley & Leakey (1937).Warren (1951) also recognized high-angle edgechipping, producing prominent notches , but heattributed this to post-depositional movement underpressure and not to human agencies. He distinguishedthe results of this natural damage from more concavenotches, which he considered indicative of separatelydirected blows, although he was reticent about attribut­ing even these phenomena to human activity. Wymer(1957) and Snelling (1964) both recorded retouchedmaterial from Globe Pit. Wymer listed a number ofbacked flakes , beaked pieces , hollow scrapers and othertools modified to points or with miscellaneous trimming.Snelling (1964) considered that flakes were generallyunmodified and that much of the apparent 'retouch' wasthe product of gravel abrasion. Amonst the flakes fromthe latest excavation, most pieces display natural edgedamage. Only two flakes can be suggested as showingretouch. Flake 1167 (Fig. 10.7) has its proximal endretouched by a series of small flakes, forming a 'truenotch ' (sensu Bordes, 1979). Retouch of this typeproduces a strong concave scraping edge . An unstrati­fied flake from section 2 (Fig. 10.8) shows the charac­teristically low angle of percussion and broad butttypical of flakes removed during the manufacture of a'Clactonian notch ' (Bordes, 1979). This method ofretouch produces a sharp concave edge by the removalof a single flake.

A review of the potentially retouched artefactsamongst the material recovered by Wymer and Snellinghas shown a similar paucity of unequivocally genuineretouch (J . McNabb , pers. comm.) . This is in keepingwith other Clactonian sites, where retouch is extremelyrare . Only at High Lodge, Mildenhall , are sophisticatedretouching techniques recognized in a flake industry thatis unassociated with hand axes (Cook & Ashton , 1991;Cook, Ashton, Coope, Hunt, Lewis & Rose, 1991;Ashton, 1992; Ashton & McNabb , 1992). The unrolledmaterial from the various Clactonian assemblagescontains notches and spalls, some of which must beviewed with circumspection. The possibility that notchescan have resulted from natural collision in the fluvialbed-load gravel has been confirmed (Harding, Gibbard,Lewin, Macklin & Moss, 1986). The general lack ofretouch at Globe Pit and sites with similar assemblages

suggests that the main purpose of Clactonian knappingwas the production of flakes with sharp edges. Indeed,notching as a Clactonian technique was probably used toenhance the sharpness/usefulness of an unretouchededge.

Previous authors (Wymer, 1957; Snelling, 1964) havesuggested that many Clactonian flakes were probablyutilized without retouch. Jones (1980) reported that anunretouched flake edge was more suitable than a handaxe for making an incision. Strathern (1969) alsodescribed unspecializcd flake tools in New Guinea thatwere selected for their sharp edge and used, withoutretouch, for a wide range of purposes. An assessment ofthe analysed sample , based on edge angle , edge lengthand the absence of cortex, has led to the conclusion thatat least 40% of the flakes possess at least one functionaledge .

Interpretation of the archaeology

The assemblage from Globe Pit is considered to repre­sent a single industry, of Clactonian type , a conclusionthat accords with the views of previous authors (Wymer ,1957, 1968; Snelling, 1964). Although no flake coreswere found during this excavation , the material isbelieved to represent a flake industry . Despite thepresence of a single unassociated possible hand axefinishing flake, no indications of hand axe manufacturenor of Levallois technique can be seen in the Globe Pitindustry. This industry thus conforms with those fromother Lower Palaeolithic non-hand axe sites tradition­ally labelled as Clactonian,such as Clacton-on-Sea ,Swanscombe (Lower Gravel and Lower Loam) andBamham (McNabb , 1992).

Ohel (1979) had considerable difficulty in acceptingthe Clactonian affinities of Wymer's material fromGlobe Pit . He suggested that the lack of any charac­teristic hand-axe debitage is the only reason for assign­ing the site to the Clactonian and concluded that theflake element contained examples of debitage types thatwere characteristically non-Clactonian. One of thesedebitage types comprised flakes that had been proxi­mally notched. However , proximal notching is in fact adiagnostic feature of the Clactonian (see below) thatoccurs frequently at both Swanscombe and Clacton.Ohel also considered the presence of a 'Levalloiselement' in Wymer 's assemblage as precluding theclassification of the Globe Pit assemblage as Clactonian.There is in fact no Levallois element in any of the GlobePit assemblages, neither is there any evidence for thefacetting of platforms. Apart from the trimming of the'overhang' on a core 's edge, there is no indication of corepreparation amongst the collection.

The archaeological finds and archive have beendeposited in the British Museum, to join material fromprevious excavations at the site .

280 D . R . BRIDGLAND AND P . HARDING

7. DISCUSSION AND CONCLUSIONS

The Clactonian industry at Globe Pit has been regardedas 'out of place' in the 'Middle Terrace' (Corbets TeyGravel) . This and the palaeontology of the overlyingbrickearth have led to the interpretation of thesedeposits as older than their position within the terracesequence would otherwise suggest . This view has onlyrecently been challenged (Bridgland, 1988; in press) .Bridgland (in press) has interpreted the artefact-bearinggravel at Globe Pit as the lowest of three divisions of theCorbets Tey Formation of the Lower Thames. TheGrays brickearth belongs to his middle division and theupper gravel (Fig. 2), now quarried away, to his upperdivision . These same three divisions , which represent asequence of cold, temperate and cold climatic episodes,are recognized at other sites in the Corbets Tey Forma­tion, notably Belhus Park and Purfleet . Bridgland(in press) has suggested that Clactonian artefacts arecharacteristic of the lower division of the Corbets TeyGravel , pointing out that they occur at this same strati­graphie level at Purfleet (Palmer, 1975; Wymer, 1985) aswell as at Globe Pit. He has suggested a correlationbetween the Corbets Tey Formation and the Lynch HillGravel, which has also yielded Clactonian artefacts atDeep Lane, Burnham (Wymer, 1988).

At Purfleet, however, Clactonian material is mixedwith Acheulian hand axes. The upper gravel at Purfleet,which was deposited in a later cold episode, containsLevallois artefacts, which are also found at Lynch Hillsites in the Middle Thames, such as Baker's Farm(Lacaille, 1940; Wymer, 1968). It would appear, there­fore, that during the time interval represented bythe Lynch Hill/Corbets Tey Formation, Clactonianknapping methods ceased to be employed and the

MetresO.D

Levallois technique was first used in the Thames valley.An important unanswered question , however , iswhether these two changes were related. The fact thatthe most important Clactonian industries exclude handaxes , whereas most if not all assemblages with evidencefor the use ofthe Levallois technique include hand axes ,would seem to argue against there being any relationbetween the Clactonian knappers and those whosubsequently used the Levallois technique.

Bridgl and (in pre ss) has proposed a radical re­interpretation of the lower Thames terrace sequence.Terrace form ation in this part of the valley is seen,according to this new scheme, as having been driven byclimatic fluctuation. Four terrace formations are recog­nized east of London: the Boyn Hill/Orsett HeathGravel; the Lynch Hill/Corbets Tey Gravel ; the Taplow/Mucking Gravel; and the Kempton Park/East TilburyMarshes Gravel (Bridgland, 1988, in press). Each ofthese incorporates locally preserved interglacial sedi­ments sandwiched between cold-climate gravel deposits(Fig . 11). Four separate interglacials are thus repre­sented. The se must all post-date the Anglian glaciation,since the Lower Thames only came into being when theriver was diverted into its modem route through Londonby the build up of Anglian ice in its old valley through theVale ofSt Albans (Gibbard, 1977). The widely held viewthat the Anglian correlates with Oxygen Isotope Stage12 of the deep sea record (Bowen, Rose , McCabe &Sutherland, 1986; Campbell & Bowen, 1989) leadsinexorably to the suggestion that the four interglacialscorrelate with the four warmest peaks on the oxygenisotope curve after Stage 12, those of stages 11, 9, 7 and5 (Sub-stage 5e). In fact , there is good evidence fromamino acid ratios to support these correlations in thecases of the Stage 11 and 7 and Sub-stage 5e peaks

60

40

20

o

-20

Swanscombedeposits

Interglacial depositsat Purfleet. Grays(Little Thurrock).IIford (Cauliflower pit),Belhus Park.

Interglacial deposits atAveley, West Thurrock.IIford (Uphall Pit) andCrayford

BuriedChannel

-40 ..L- -J

c:=J Alluv ium [,,:::w: l Interglacial deposits c:::J Co ld-<:Iimate Gravels CJ Till

Fig. 11. Idealized transverse section through the terraces of the Lower Thames (after Bridgland, in press) .

THAM ES TERRACE DEPO SI TS AND T H E CLACT O N IA N INDUSTRY 281

(Bowen et al., 1989; Bridgland, in press; Fig. 11) andratios indicating correlation with Stage 9 have beenobtained from the Corbets Tey Formation at BelhusPark (Bowen , 1991). The artefact-bearing gravel at theGlobe Pit is attributed, in this scheme, to depositionduring the latter part of Oxygen Isotope Stage 10,whereas the overlying interglacial brickearth isattributed to Stage 9. If conventional terminology ispreferred, it is necessary to ascribe the entire sequenceat Globe Pit to the Saalian Stage (this term is usedinstead of the British term Wolstonian , which is largelydiscredited - for explanation see Bridgland, in press).This stage appears to encompass Oxygen Isotope Stages10-6 inclusive and include the two interglacials thatcorrelate with Oxygen Isotope Stages 9 and 7. Irrespec­tive of the age of the Hoxne type locality, which is thesubject of controversy (Bowen et ai. , 1989), within theLower Thames sequence the term Hoxnian (sensuSwanscombe) has been applied to the first interglacialafter the Anglian, that correlated here with OxygenIsotope Stage 11 (Bridgland, in press) .

This recent reinterpretation of the Globe Pit industryrefutes the idea that it pre-dates the hand axe industriesat Swanscombe , which occur in the deposits of thehigher Orsett Heath Formation and are believed to datefrom Oxygen Isotope Stage 11, the 'Swanscombe inter­glacial' of Bowen et al. (1989). There are importantrepercussions for Palaeolithic archaeology, and inparticular the dating of different technologies, in thisnew interpretation of the Lower Thames sequence. TheClactonian Industry is represented in deposits attributedto Oxygen Isotope Stage 11 (possibly late 12), at Swans­combe (and at the Clacton type locality) and Stage 10,at Globe Pit and Purfleet.In the post-interglacial gravelsof the Corbets Tey Formation, which are attributed toStage 8, the Clactonian is not found , but instead there isevidence for the first use of the Levallois technique inthe 'Proto-Levallois' industry of Botany pit , Purfleet(Wymer, 1968; Bridgland, in press) . Later in Stage 8 theriver cut down to the level of the Mucking Formationand deposited gravels that again yield artefacts showingthe use of Levallois technique, found at sites such asCrayford and West Thurrock. The Acheulian is repre­sented throughout this sequence, hand axes occurring inthe Stage 11 deposits at Swanscombe, in the Stage 10gravels of the Orsett Heath Formation and in the Stage 8gravels in the upper part of the Cor bets Tey Formationand the basal part of the Mucking Formation. All typesof artefacts can, of course, occur as reworked specimensin any of the terrace deposits that were laid downsubsequent to their first appearance in the sequence.

As was noted above , the Clactonian and Acheulianindustries , although overlapping in time, appear to be

quite separate, perhaps reflecting two co-existing groupsof early humans. The industry of Globe Pit probablyresults from the activities of a group of Clactonianknappers on or near the north bank of the Thames in theproximity of the present site. The considerable abun­dance of debitage in the gravel in the small area of theSSSI, as well as the sharp condition of most of theartefacts, indicates that the material has been locallyincorporated into the edge of theCorbets Tey Gravel ,with minimal transportation. The Globe Pit industry isthus a concentration of Clactonian material within agravel deposit (the lowest division of the Lynch HiIVCorbets Tey Formation) that contains, in other areas ,both Clactonian and Acheulian artefacts. A concen­tration such as this should be set against a 'backgro und'of less frequently occurring artefacts representing thegravel as a whole. The possible hand axe thinning flake(Fig. 10; see above) may represent this 'background',although it would be dangerous to argue strongly from asingle find . Its distinctive condition does add somesupport to this argument, however. The only other non­Clactonian artefact recorded from Globe Pit, the sidescraper illustrated by Kennard (1904; see above) isthought to have come from the later gravel, above thebrickearth (Wymer, 1985; Fig. 2), which is thought todate from Oxygen Isotope Stage 8.

The occurrence of the Clactonian assemblage atGlobe Pit should no longer be thought of as anomalous,nor be taken as evidence of an age comparable with theSwanscombe deposits ; the complex sequence of down­cutting and aggradation events used by King & Oakley(1936) to explain the archaeological record from theLower Thames need no longer be invoked. The artefact­bearing gravel at Globe Pit is still seen as 'early' in thecontext of the 'Middle Terrace', but this merely reflectsits position at the base of the stratigraphic sequence ofdeposits forming this terrace , now classified as theCorbets Tey Formation.

ACKNOWLEDGEMENTS

The authors wish to acknowledge John McNabb formuch useful discussion of earlier drafts of this paper.He, Paula Blackford (now Paula Bridgland) and PennyRobinson helped in the excavations. John Wymer,Andrew Snelling and Bernard Conway kindly providedinformation on their earlier work at the site. All con­cerned are indebted to Mr and Mrs A. Croot, of Over­cliff Road , for allowing the use of their garden for accessto the site and for their generous hospitality . Assistancewith the diagrams was kindly provided by the CityCartographic Unit at the London Guildhall University,where David Bridgland is an honorary fellow.

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