| Abstract: |
A programme of palaeoenvironmental assessment and scientific dating was undertaken on two borehole sequences from New Covent Garden Market, including WS1 from Phase A2 (Wessex Archaeology 2021a) and WA-16 from Phase B (Wessex Archaeology 2023). The assessment followed programme of borehole survey and deposit modelling at Phase B, undertaken as part of a staged approach to the geoarchaeological investigations. The assessment was undertaken in order to determine the depositional history and age of the deposits, the level of preservation and concentration of palaeoenvironmental remains, the archaeological and geoarchaeological potential of the deposits, and to make recommendations for any for further work. The sequence of superficial geological deposits recorded overlying the London Clay bedrock at the site comprises Pleistocene fluvial sands and gravels, in places overlain by Holocene alluvium, and modern Made Ground. In one sequence, WA-16, the Holocene alluvial sequence includes a unit of peat directly overlying the gravel, whilst in WS1 the peat was recorded within a tripartite sequence of Holocene alluvium. The sands and gravels at the site comprise the Late Devensian Shepperton Gravel, formed within palaeochannels cut through the earlier Kempton Park Gravel terrace. The more substantial of these channels is more widely known as the Battersea Channel (Morley, 2009/10), which itself forms an important component of the Battersea Channel Project (BCP; EH 2014). The Battersea Channel underlies the western margin of the Phase B site, where the Gravel surface is recorded at levels between c. -1 and -3m OD.
In borehole WA-16 the Holocene alluvial sequence includes a unit of peat directly overlying the sands and gravels at between -1.17 and -2.12 m OD; at the Phase A2 site (Wessex Archaeology 2021a) peat was recorded in two boreholes, 2.1m thick in WS1 and 1.28m thick in WS4, varying in depth between -0.01 to -2.11 m OD (WS1) and -0.19 to -1.47 m OD (WS04). In WS1, the results of the radiocarbon dating indicate that the peat is of Late Neolithic through to Iron Age date. However, significantly older dates were obtained on the base of the peat in WA-16. The radiocarbon dates here range between Late Upper Palaeolithic (within the Lateglacial Interstadial) and Late Mesolithic/Early Neolithic. However, given the disparity between the dates on the peat in WS1 and WA-16, there is some uncertainty as to the chronology of the peat sequence in WA-16.
The results of the palaeoenvironmental assessment yielded variable results on the basis of preservation. Overall they were found to contain very limited pollen assemblages in WA-16, with variable plant macrofossil preservation also recorded in WS1. However, evidence is provided for a similar vegetation history to that recorded in other peat sequences within the Battersea Channel Project area, with an initially relatively closed landscape followed by an expansion of herbaceous taxa (and opening up of the landscape) in the Bronze Age. Large grass pollen grains, potentially providing evidence for cereal cultivation, are recorded and increase in abundance in later deposits, though such pollen grains may also represent wild grasses typical of estuarine influenced wetlands.
On the basis of an Iron Age date for the top of peat in WS1, this horizon represents a relatively rare occurrence of organic deposits of this date in the BCP project area. Further pollen analysis of samples from this horizon is recommended, primarily focussed on the organic alluvium overlying the peat, and the top of the peat. |
