Plumstead Portal (Crossrail XSW11)

Abstract

• This archive describes the archaeological evaluation and watching brief work carried out at the Plumstead Portal site by the Museum of London Archaeology (MOLA). The North Woolwich portal is located within the existing railway corridor of the former North London Line (NLL), between Factory Road and Albert Road, in the London Borough of Newham, National Grid Reference 542700 180000. All fieldwork was conducted between 11/04/12 and 09/06/14 and supervised by Portia Askew (MOLA Supervisor), Virgil Yendell (MOLA Senior Geoarchaeologist) and Jason Stewart (MOLA Geoarchaeologist), and included the following: The two evaluation trenches showed natural sands and gravels overlain by peats and alluvial clays. The surface of the Pleistocene\Early Holocene deposits indicated a series of braided river channels within a low-lying area on the western margins of a main channel. A borehole survey showed this channel to be over 200m wide and c.3m deep. This feature would have formed a major part of the floodplain landscape from the Early Holocene and probably became a major drainage feature when the other Holocene channels to the west became abandoned. It is possible that the channel forms an abandoned arm of a former course of the Great Breach Dyke, which existed from the Early Holocene period into the Bronze Age. A Mesolithic land surface was identified with rising sea levels leading to widespread peat formation by the early Neolithic into the Bronze Age, Within the peat deposits were worked timbers which may have formed parts of a structure, possibly a trackway constructed to access or traverse the wetlands. The overlying alluvial silts and clays are likely to be of Iron Age, medieval and historic date representing an inundation of the floodplain. The upper 1.20m comprised dumps which represent making up and levelling of the site prior to the construction of the railway and associated buildings in the vicinity. The foundations of a chimney of the adjacent Listed power station were also recorded. Three window samples afforded opportunities to sample the alluvial sequence above Shepperton Pleistocene Thames gravel. A variable sequence was recorded across the site. The sequence within the windows samples on the site shows gravels and sands overlain by clays and sands then peats and sealed by alluvial clays. The elevation of the surface of the Pleistocene/Early Holocene confirms the previous deposit model of a series of braided river channels (LZ3) within a low lying area of the floodplain and separated or fringed by channel bars to later wetlands (LZ2). The northern, eastern and western extent of the channel has been refined by the variously sourced borehole and trench data. The channel is still estimated to be more than 200m wide and up c 3m deep. This feature formed a major part of the floodplain landscape from the Early Holocene, and probably became a major route of drainage and transport. It is possible that the channel forms an abandoned arm of a former course of the Great Breach Dyke, which existed from the Early Holocene into the Bronze Age period.