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Geochemical analysis of sediments recovered from test pitting. A geoarchaeological study of sub-surface strata at Pump House Farm, Rodney Stoke, Somerset was carried out between November 2021 and January 2022. The purpose was to assess the archaeological and palaeoenvironmental significance of a buried organic layer that had been revealed in a prior archaeological evaluation. Three test pits were excavated using a mechanical excavator and to 1.0-1.2m depth below ground level (bgl), and the layers exposed in one wall from each described using standard geological criteria, photographed and (in the case of two of the test pits) sampled with monolith tins. These latter were taken through an organic-rich stratum that had previously been suggested to be a Romano-British palaeosol. The strata in the test pit walls comprised (i) silt/clays with evidence of former rooting, overlain by (ii) 0.13 (Test Pit 3) to 0.04m (Test Pit 1) organic rich silt/clay (the putative palaeosol), (ii) with 0.48-0.62m of iron stained and rooted silt/clay completing the sequence. The modern soil has developed in the top of the latter. In the laboratory the monolith samples were described and photographed. Sub-samples were collected for 14C measurement (n=1), sedimentological and geochemical study (n=48) and foraminiferal assessment (n=8). The last of these were submitted to Dr Matthew Law of L-P Archaeology, but following processing no foraminiferal tests (or indeed any other macrofossils) were found. The absence of biological macrofossils also meant that there was no suitable material for 14C dating. The sedimentological/geochemical samples were measured for their magnetic susceptibility, weight loss-on-ignition at 550oC, and element constituents, the latter using portable X-ray fluorescence. The laboratory sedimentology study demonstrated low magnetic susceptibility throughout the sequences indicating that burnt mineral matter is not present in the sequence. Weight loss-on-ignition measurements demonstrated that c. 6-14% of the sediment is organic matter, but that peaks of higher organic concentration do not coincide with the possible palaeosol. The geochemical measurements showed variations in iron and aluminium that correspond to changing bedrock-derived mineral content. However, in TP3, lead contents varied according to a different pattern. They increased through the basal silt/clay to peak at the top of the putative palaeosol, a phenomenon that was also observed in a sequence at Nyland Hill 1.7 km to the north and where it has been attributed to Romano-British mining of the metal.

Hand auger survey of the lithology. A geoarchaeological auger survey was undertaken of land encompassed by a revised layout of Junction 28 of the M25 motorway in the London Borough of Havering. The particular focus of the study was the floodplain of Weald Brook and the surrounding valley sides. Fieldwork was carried out in November 2022, while the purpose of the work was to determine the depth, nature and archaeological/palaeoenvironment potential of strata subcropping on the site. Thirty-four geoarchaeological auger holes were completed using manually operated Edelman augers. Strata in the auger heads were described in the field and lithostratigraphic data obtained from the auger holes was combined in a Rockworks database with those from 15 geotechnical boreholes and 3 geotechnical test pits. The database was then used to plot composite cross sections and deposit models. Technical summary of the stratigraphy Five stratigraphic units are present on the site. Strata of the Early Eocene age London Clay Formation form the bedrock basement and were found underlying superficial deposits across the entirety of the site. Matrix-supported flint gravels overlie London Clay Formation deposits on the western flanks of the Weald Brook valley and have an upper subcrop elevation of c. +35.5 to +31.5m OD. Further gravel with similar properties were found in the Weald Brook floodplain at +31.8 to +28.7m OD, while geotechnical boreholes demonstrated that these deposits were up to 2.5m thick. It is likely that the gravels are either remnants of a single unmapped Late Pleistocene fluvial terrace or of two such terraces, one Late Pleistocene and the other Late Pleistocene or Holocene. It is notable that one geotechnical borehole (GE ATK090) encountered deposits containing organic remains beneath the gravel. The archaeological potential of the gravel is dependent on age, which is presently unknown. However, in situ archaeological remains are unlikely. Organic preservation beneath the gravel in one floodplain location demonstrates localised moderate palaeoenvironmental potential. Moderately sorted silt/clays with occasional to moderate gravel overlie strata of the London Clay Formation and the gravel to the west of the Weald Brook floodplain. These deposits are thickest in the west of the study area (up to 4m in one of the geotechnical boreholes [GE ATK058]), but they feather out on the floodplain edge. The strata are colluvial deposits (Head) and are most likely of Late Pleistocene and Holocene age. They have a low archaeological and palaeoenvironmental potential. Moderately to well sorted brown and grey silt/clays form the surficial outcrop in the Weald Brook floodplain. Such deposits are up to 2.8m thick, and lack both organic remains and visible sedimentary structures. These strata are likely alluvium that has accreted by overbank flooding of the Weald Brook during the Holocene. The deposits have a low archaeological and palaeoenvironmental potential. Poorly sorted gravels containing cultural material (brick, concrete etc) are found as localised subcrops to the east of the Weald Brook floodplain. These deposits are Made ground, most likely forming as a result of activities associated with industrial units attached to Grove Farm. The Made ground has no archaeological or palaeoenvironmental potential.

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