St Helens Isle of Wight WTW Geoarchaeological and Archaeological Monitoring of Ground Investigation Works

Wessex Archaeology has been commissioned by Stantec ('the Client') to produce a report outlining the results of geoarchaeological and archaeological monitoring of Ground Investigation (GI) works at St Helens Water Treatment Works (WTW) in the Isle of Wight (the 'Site'). The Site is centred on NGR 462490 088521 (Figure 1). Review of British Geotechnical Survey (BGS Geoindex) mapping identified the possible presence of landforms associated with Quaternary geological deposits within the Site. These deposits include Tidal River or Creek deposits comprising Holocene aged minerogenic and possibly organic alluvium (including peats) associated with the inlets of the River Yar, a former tributary of the palaeo-Solent. Both Pleistocene river terrace deposits and Head may also be present across the Site. Such geological deposits may have potential to contain archaeology, as well as environmental remains reflective of past human activity, landscapes and environments. Assessment of the geoarchaeological resource associated with Quaternary deposits is 'deposit-led', with the aim to provide lithostratigraphic and chronostratigraphic frameworks and to assess the archaeological and palaeoenvironmental potential of different deposits. In order to help inform on both the geoarchaeological and archaeological potential of Quaternary deposits within the Site and to mitigate against impacts, a requirement for both archaeological and geoarchaeological monitoring of selected GI interventions was identified. Geoarchaeological and archaeological monitoring of GI works has informed on the nature and distribution of the Quaternary lithostratigraphy in the Site and has enabled an initial assessment of their geoarchaeological and archaeological potential. The sequence at the Site comprises Head, overlain by Made Ground to the east and by Topsoil to the west. These Head deposits are characteristic of downslope movement of sediments through freeze-thaw, or solifluction, processes under periglacial conditions. These deposits frequently contain fine to extensive pockets of orangish brown sands and gravels, suggested to represent fluvial deposits derived from either the Carpenters Farm Gravel Member to the west or, and most likely, terrace plateau gravels of the Wootton Gravel Complex Member to the north of the Site. It is therefore possible that these local pockets within the Head may contain reworked Early Palaeolithic lithic artefacts dating to between MIS 11-Despite this, the potential for in situ artefactual or significant palaeoenvironmental material to be preserved is considered low. Geoarchaeological and archaeological monitoring of GI works has demonstrated that Quaternary geological deposits with significant archaeological or geoarchaeological potential are unlikely to occur within the Site. Consequently, no purposive geoarchaeological work is recommended.