A summary of the project fieldwork report, documenting the principal fieldwork undertaken in the Axe Valley during phase two of the project, is included below (and a pdf version of the fieldwork report is available here). Full details of the OSL sampling will be included in the dating report to be submitted to English Heritage upon completion of the project (along with the final project report).
Work at Kilmington Pit (identified as a major area of interest in Phase I) focused upon the well-exposed upper halves of the fluvial deposits (the lower halves of the sections are generally slumped and vegetated). The pit is now disused (and generally overgrown), although two Acheulean bifaces and several flakes attributed to the Palaeolithic were recovered during its working life.
The southern, western and eastern faces consist of in situ gravels, while the northern face is dominated by backfill. However there has also been considerable slumping of the in situ gravels, leaving a total section exposure of c. 9 m. Clast analysis, sedimentary logging, OSL sampling, topographic surveying, and pollen sampling was undertaken.
There are clear cryoturbation features in the uppermost units (heaves and clusters) of the in situ gravels, while the lower units tend to exhibit some horizontal bedding and imbrication. Manganese and iron staining occurs in patches throughout the gravels, while discontinuous sand, silt and clay lenses of varying sizes have also been found within nearly all the main gravel units. Some of these lenses have been disrupted by cryoturbation, although there are also bedding and cross bedding structures. The deposits show evidence of channel and bar features and the variation in the composition of the sedimentological units are clearly indicative of different flow rates and fluvial processes. All of the units exhibited the same basic lithology (dominated by chert). Stereographic plots of clast dip and orientation showed clear evidence of palaeoflow directions.
Four OSL samples were processed, yielding dates of 309,000±26,000, 273,000±26,000, 174,000±18,000 and 154,000±19,000 BP. The dates would appear to be associated with two major units: lower (309 and 273 kya [OIS-8]) and upper (174 and 154 kya [OIS-6]). Records do not document from which unit the Kilmington artefacts were collected from. If it was the lower unit, then the Kilmington artefacts are likely to be broadly contemporary with those from Broom, elsewhere in the Axe valley (it is probably also likely that the artefacts represent occupation during warmer climatic conditions of the OIS-9 interglacial, or an OIS-8 interstadial). The upper unit dates argue against this unit as the origin of the artefacts, since wider evidence from the UK has highlighted a general abandonment of Britain during OIS-6 (although the artefacts may of course be re-worked from earlier deposits), while handaxe manufacture also declines (although such artefacts do not disappear) after the end of OIS-8.
Topographical mapping has highlighted clear altitudinal differences between discontinuous terrace patches, suggesting that the pre-existing classification of the deposits as undiffereniated terraces should be re-visited.
Chard Junction Pit
A small number of handaxes have been recovered from this active pit (including that found by the late John Wymer on a QRA/INQUA trip (Wymer 1977). Extensive exposures of fluvial deposits are available for study at Chard Junction Pit (the gravels extend a maximum thickness of 15m), with continuing extraction revealing new exposures at regular intervals. As with the Kilmington work, sedimentary logging, organic sampling, topographic survey, and OSL sampling was undertaken.
Two major units were recorded at the Hodge Ditch Location. The uppermost unit resembles a debris flow deposit, whilst the lower unit is a fluvial deposit. Cryoturbation features (including heaves, clast clusters and ice cracks) are visible to varying degrees throughout these units. There is considerable lateral and vertical variability in the composition of the major units at the pit. Sand- and silt-filled channel features are evident (many with distinct bedding structures), alongside imbricated gravels. The orientation of the channel features and imbrication indicate a dominant palaeoflow direction similar to that observed in the Axe Valley today, with the multiple channels indicating a braided stream environment.
OSL samples were extracted from four separate sections (at different depths and locations) in the active pit, with a further sample taken from the base of an extant section in an area now being used as a silt pond. The youngest dates lie at the junction between the upper debris flow deposits and the lower fluvial deposits, and date the top of the fluvial unit to OIS-5c and 5b (98,000±8,000 and 94,000±9,000). At the very base of the currently exposed deposits, a date of 174,000±18,000 (OIS-6). A further preliminary date of 274,000±74,000 (OIS-8) was achieved on the sample taken from the base of the section in the former workings (now a silt pond).
Lithologically, all of the units were dominated by chert and flint, although occasional pieces of basalt were also found. This material is not currently found in the local area, and the nearest in situ basalt is in Ireland. These occasional clasts may be derived from Tertiary deposits or reworked from the Budleigh Salterton Pebble Beds.
Two GPR survey transects were run across the floor of the Railway Ballast Pit at Broom and from Pratt’s New Pit to the River Blackwater. The GPR data was unable to detect the base of gravels (unsurprising in light of the probable depth of the Broom lower gravels), however the GPR did detect sedimentological variation within the gravels.
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