Series: Quaternary Scientific (Quest) unpublished report series

A programme of geoarchaeological fieldwork (including two boreholes) and deposit modelling (incorporating the results of previous geotechnical investigations) was carried out at the site, in order to (1) clarify the nature of the sub-surface stratigraphy across the site; (2) to clarify the nature, depth and extent of any alluvium and organic/peat deposits, and (3) to investigate the palaeoenvironmental and archaeological potential of the site. The results of the deposit modelling indicate that the sediments recorded at the site are similar to those recorded elsewhere in this area of Reading, with Chalk bedrock/Late Devensian Shepperton Gravel overlain by a sequence of Holocene alluvial sediments, buried beneath modern Made Ground. At the site and across the modelled area, the relief features of the Chalk bedrock and Shepperton Gravel surfaces indicate that the site lies on the floodplain of the River Kennet, and that the surface of the Late Devensian Gravel is relatively even, generally lying at between ca. 33.5 and 35.3m OD. The Gravel is overlain by Holocene alluvium, generally between 1 and 3m in thickness, and described as mineral-rich (sandy/clayey/gravelly silt), the surface of the alluvium relatively even at between ca. 36 and 36.5m OD. In contrast to other sites nearby, no peat or organic-rich horizons are recorded within the alluvium at the site. Perhaps significantly, the deposits of the Lower Alluvium are recorded at similar elevations here to the peat ca. 100m to north, perhaps indicative of subsequent erosion of the peat by fluvial (channel) activity in the area of the site. On this basis, no further environmental archaeological investigations are recommended, and the prehistoric archaeological potential of the site is considered to be limited.

Following the results of the geoarchaeological deposit modelling, a programme of environmental archaeological assessment was undertaken on one borehole sequence from the site. The sequence recorded here is similar to that at Bramcote green immediately to the west. Radiocarbon dating indicates that a sequence of calcareous and organic deposits accumulated during the Lateglacial Interstadial, during which type sedge fen or reed swamp and aquatic conditions were present. This was followed by a sequence of Holocene alluvial sedimentation. The peat deposits at the site date to the Late Mesolithic through to the Early Bronze Age, and are indicative of alder carr on the floodplain with mixed deciduous woodland on the surrounding dryland. Further analysis of the sequence is recommended, as well as archaeological evaluation of the site.

A single borehole was put down at the site, thought to be towards the centre of the former Bankside Channel. The results revealed the surface of the basal Shepperton Gravel lies at -2.80m OD and is overlain by a sequence of mineral-rich sediments that become finer upwards. Made Ground caps the alluvial sediments from 0 to +2.50m OD. No Peat is present in the 185 Park Street borehole as it is at the neighbouring 135 Park Street site; a thin (9cm) horizon of organic-rich sediment was recorded at approximately the same elevation, but it is impossible to determine the chronological relationship between this and the Peat deposits from the neighbouring site. Due to the inorganic nature of the stratigraphic sequence, which has very limited potential for radiocarbon dating, no further work is recommended.

Geoarchaeological and palaeoenvironmental investigations have revealed a sequence of London Clay, overlain by Pleistocene Gravel, Holocene alluvium (in places including peat), ground-raising/levelling deposits and modern Made Ground. The Gravel is overlain at the site by variable thicknesses of Holocene alluvium, recorded to levels between ca. 1.75 and -0.80m OD. The alluvium is predominantly fine-grained and mineral-rich; however, a peat unit dated to the Saxon period was recorded between 0.2 and -0.35m OD. Above this, the ground-raising/levelling deposits incorporate alluvial sediments from the underlying unit, including organic matter, and contain anthropogenic material of Saxon date onwards (including charcoal, bone, worked wood and shell). The sediments appear to represent natural foreshore deposits associated with the floodplain of the River Thames, overlain by alluvium and a series of ground-raising/levelling deposits. They are very similar in character to those recorded at Adelphi House and 18-20 York Buildings. The biological remains in both the naturally accumulated and reworked/redeposits organic deposits are very similar. A generally open, damp and disturbed environment is indicated, with a range of herbaceous taxa recorded potentially representing their growth in a number of open habitats, including wetlands, meadow, pasture, disturbed/waste ground with crops and their associated weeds.

Two phases of geoarchaeological fieldwork consisting of the monitoring of geotechnical works was carried out at the site prior to the generation of a deposit model for the site. The results of the investigation revealed a basal Shepperton Gravel surface that sloped steeply downwards from the south-western corner of the site towards the north. This was overlain by a sequence of Holocene Alluvium (including Peat) capped by Made Ground. Due to the location of the site adjacent to the floodplain edge, in combination with the presence of a thick horizon of Peat, and location of a Neolithic trackway structure to the north of the site at Belmarsh West, the potential for cultural and/or palaeoenvironmental remains was considered high.

A programme of environmental archaeological assessment of a borehole from the 20 Horn Lane site was undertaken, following the recommendations of previous geoarchaeological fieldwork and deposit modelling. This work was undertaken in order to (1) establish the age of the peat recorded at the site; (2) assess the palaeoenvironmental potential of the sequence; (3) highlight any indications of nearby human activity, and (4) provide recommendations for further analysis. The results of the environmental archaeological assessment have revealed a similar sedimentary sequence to that at other sites on Greenwich Peninsula, and more specifically those overlying comparatively low (<-3m OD) Shepperton Gravel topography. The site is located within a large, broadly east-west aligned depression in the Gravel surface, thought to represent a palaeochannel that would have been a significant component of the prehistoric landscape. The alluvial sequence infilling this channel includes a peat horizon of early/middle Neolithic to middle Bronze Age date; these dates for the peat are consistent with those recorded elsewhere on the Greenwich Peninsula, including at sites located within this channel ca. 1km to the west. The results of the assessment indicate that the preservation and concentration of biological remains (diatoms, waterlogged plant remains and pollen) is limited, unlike at other sites located within this channel; evidence for significant changes in vegetation composition or human activity cannot be defined. On this basis, no further environmental archaeological analysis of the sequence is recommended.

A programme of geoarchaeological field investigations and deposit modelling were undertaken at the site in order to (1) clarify the nature of the sub-surface stratigraphy across the site; (2) clarify the nature, depth and extent of any alluvium and peat deposits; and (3) make recommendations for any further environmental archaeological assessment of the sequence at the site. The results of the deposit modelling have revealed a sequence of Late Devensian Shepperton Gravel, the surface of which generally lies at between ca. -0.90 to -2.10m OD, the site lying just to the east of an area of elevated Gravel topography that underlies much of the north-western area of the Isle of Dogs. The Shepperton Gravel is overlain at the site by a sequence of Holocene alluvium, in places containing peat. This episode of peat formation is indicative of a transition to a more stable valley floor, encouraging the development of semi-terrestrial conditions across much of the site. The peat here is generally recorded at levels between ca. 0 and -1.5m OD, and present in thicknesses of between 0.3 and 1.2m; in the new geoarchaeological borehole it was recorded between -0.94 and -0.13m OD, potentially representing up to ca. 800 years of peat accumulation. A programme of environmental archaeological assessment is recommended on the geoarchaeological borehole collected from the site. The results of the deposit modelling have revealed a sequence of Late Devensian Shepperton Gravel, the surface of which generally lies at between ca. -0.90 to -2.10m OD, the site lying just to the east of an area of elevated Gravel topography that underlies much of the north-western area of the Isle of Dogs. The Shepperton Gravel is overlain at the site by a sequence of Holocene alluvium, in places containing peat. This episode of peat formation is indicative of a transition to a more stable valley floor, encouraging the development of semi-terrestrial conditions across much of the site. The peat here is generally recorded at levels between ca. 0 and -1.5m OD, and present in thicknesses of between 0.3 and 1.2m; in the new geoarchaeological borehole it was recorded between -0.94 and -0.13m OD, potentially representing up to ca. 800 years of peat accumulation. At the nearby Wood Wharf site (Young et al., 2018a), the peat varied in thickness between 0.15 and 2.3m, its surface was recorded at similar levels of between ca. 0.5 and -1.5m OD. At Wood Wharf, the results of the radiocarbon dating of the peat indicated that accumulation began during the middle to late Neolithic, with peat cessation more variable and occurring between late Neolithic to late Bronze Age/early Iron Age, and potentially representing two separate periods of peat formation on the floodplain (see Young et al., 2018a).

A programme of geoarchaeological investigations were carried out at the 30-44 Crown Street, Acton site in order to carry out a suitable assessment of its palaeoenvironmental and Palaeolithic archaeological potential. Due to access restraints, only mini digger with a maximum machine arm depth of 1.4m was available during the excavations; the sequence within the test pits (TP1 and TP2) was therefore limited to Made Ground, in both pits to their maximum depth of 1.4m below ground level. The contact between the Made Ground and the natural sequence at the site was therefore not observed in the test pits, and it remains unclear if any remnant of the Lynch Hill Gravel survives below ca. 1,4m bgl. However, it is perhaps of note that in the geotechnical logs, these units are described only as 'slightly gravelly clay' or a 'sandy clay'; in addition, the London Clay, recorded as a firm brown slightly sandy clay in the geotechnical boreholes, can be fairly confidently identified in the logs below ca. 2 to 3m bgl, perhaps indicating that significant thicknesses of gravel are unlikely to survive at the site. Depending on the likely depth of impact of the development at the site, and future access for either a larger mechanical excavator and/or boreholes, any future interventions should be put down to a minimum depth of 3.0m bgl to examine the sequence in more detail.

Four geoarchaeological boreholes were put down across the site at selected locations. Combined with previous geotechnical records, a model of the sub-surface stratigraphy indicates a sequence of Shepperton Gravel overlain by sands and organic sands, alluvium (including peat) and made ground. The Shepperton Gravel undulates across the site from >-2m OD in the north, to approximately 0m OD at its centre. This topographic high point may represent a gravel eyot: a possible foci for human activity. The thickness of the overlying sands and alluvium reflects that of the underlying topography. Further environmental archaeological assessment work was recommended.

A programme of geoarchaeological field investigations and deposit modelling was undertaken at the site, in order to (1) enhance our understanding of the sub-surface stratigraphy at the site; (2) to evaluate the potential of the sequences to contain evidence for Palaeolithic archaeology or biological remains; and (3) make recommendations for any further geoarchaeological or archaeological investigations at the site. The results of the deposit modelling have revealed a sequence of Chalk bedrock, overlain by middle Pleistocene Gravel (likely to equate to the Boyn Hill Gravel of Gibbard (1985)), and modern Made Ground. A very clearly expressed difference in level of the gravel surface between the northern (ca. 46.5 to 47.5m OD) and southern (ca. 50.0 and 50.5m OD) halves of the site appears to be entirely due to quarrying in the northern half. For this reason, greater thicknesses of gravel are recorded in the south (4.6 to 4.8m) than in the north (0.4 to 1.4m). The ground level in the unquarried southern half of the site accords closely with the level recorded by Gibbard (1985) at the Boyn Hill type site, and it is likely to be this Gravel unit that is recorded across the present site. Although the Boyn Hill Gravel has been a significant source of Palaeolithic artefacts elsewhere in Maidenhead, including very close to the present site (Wymer, 1968), no lithic artefacts or faunal remains were identified in any of the gravel sub-units identified across the five test pits. The results of the geoarchaeological investigations are relatively conclusive in that the Gravel at 54 Furze Platt Road represents Boyn Hill, rather than Lynch Hill, Gravel, and to that end support the view of Gibbard (1985), Bridgland (1994) and Harding et al., (1991). In addition, no lithic artefacts or faunal remains were identified in any of the five test pits at the site; on this basis, no further geoarchaeological or archaeological investigations are recommended at the site.