Mosslands School, Wallasey: Geoarchaeological Assessment

In total, six window sample (WS) boreholes were located by the monitoring geoarchaeologist using a GNSS, and undertaken by the geotechnical contractor. The lithology of the boreholes was recorded using the sediment classification system of Troels-Smith (1955). The scheme breaks down a sediment sample into four main components and allows the inclusion of extra components that are also present, but that are not dominant. Key physical properties of the sediment layers are darkness (Da), stratification (St), elasticity (El), dryness of the sediment (Sicc) and the sharpness of the upper sediment boundary (UB). The descriptive logs were supplemented by digital photography carried out using a DSLR with a minimum sensor size of 10 megapixels. All photography adhered to Historic England guidance for Digital Image Capture and File Storage (HE 2015b). Graduated metric scales of appropriate lengths were used, ensuring the use of vertical scales used against deep sections in combination with horizontal scales. Digital photographs intended for archive purposes will comply with AAF and ADS guidance (i.e. high quality non-proprietary raw files (DNG) or TIFF images). Stratigraphic data was acquired from the earlier GI works undertaken at the site (Tier 2025) and incorporated alongside the data acquired by this study to produce deposit models to assist in illustration and interpretation of stratigraphic deposits. Deposit modelling followed procedures set out within the Historic England Guidance for Deposit Modelling and Archaeology (HE 2020). Based on the inputted stratigraphic data, modelled surfaces and a model- based project section was created to aid visualisation using Rockworks The lowermost deposits at the site are glacial till which was deposited in the Late Devensian. The surface of this till has been demonstrated to slope down to the south of the site, forming a ridge which descends from around 4.00-5.00m OD down to around 0.00-1.00m OD. This till slope forms the northern part of what would have been an east-west orientated valley which formed in the underlying glacial till (Kenna, 1978 pp. 31). This valley is roughly reflected in the present-day topography of the region as shown in the LiDAR where a lowland stretch extends from Wallasey Pool in the east through Bidston Moss, and over to Leasowe and Moreton in the west at the coast. Against this slope was a soft, inorganic grey sandy silt (tidal deposits) followed by peat which extended upwards to between 1.00-2.50m BGL. Within window samples WS04, WS05 and WS06 there was a firm blue clay (further tidal deposits) overlying the peat up to between 0.60-1.20m BGL. This peat is the result of deposition during the early Mesolithic, where sea level rise led to the area around Bidston Moss becoming a complex mosaic of perimarine swamps, meres and Fens (Tooley 1982). The overlying silty clay likely relates to marine inundation which post-dates 3,371-3,622 cal BC (95.4% probability) and is recorded both at Bidston Moss (Cowell and Innes, 1994) as well as the wider area to the north-west on the Wirral during the early 4th millennium BC (Tooley, 1978). Although radiocarbon dating has demonstrated that the sedimentary sequence at Mosslands School broadly matches that of Bidston Moss, the preservation of palaeoenvironmental remains at Mosslands School is distinctly poorer. Both pollen and diatom remains were very poorly preserved, with post-depositional processes having likely resulted in the degradation of what remains were present. What remains are present are in such a small quantity and condition that they would be unable to provide further insights beyond what were already provided by the nearby Bidston Moss site (Cowell and Innes, 1994). The majority of the Mosslands School development is located within areas that have a superficial geology characterised as glacial till underlying made ground.