Fieldwork report for archaeological monitoring at C25145 Twyford Padbury Brook

Recording of sediments followed established guidance (Jones et al., 1999; Historic England, 2015b; Technical Standard-Specification for Historic Environment Investigations Doc No: HS2-HS2-EV-STD-000-000035). A written record of each individual context was created on site for each location, following standard geological criteria (Troels-Smith, 1955; Jones et al., 1999; Tucker, 2003) on pro-forma logs sheets. Photographs were also taken of site survey works whilst they were in progress. Mechanical excavation was undertaken in 200-300mm depth spits, 100 litres of sediment from at least every fifth machine bucket was sieved, recording location in meterage, and separating notable layers. In total 1400 litres were sieved. Sieving focused on the gravel deposits where there was potential for palaeolithic faunal remains and where the sieving method was most appropriate. Fined-grained deposits were not recorded. Organic deposits were bulk sampled with the aim to take 4 0litres but this was not possible in the one instance a bulk sample was required. A bulk sample was taken from a very ephemeral organic deposit (1008) but due to the access restrictions and sampling from the machine bucket no more 10 litres was recovered. A subsample of the bulk sample was processed by hand for plant macrofossil remains, the remaining sample was processed for faunal and carbonised remains. Processing and environmental assessment was undertaken by appropriately qualified specialists in accordance with established guidelines. The deposit sequence included approximately 2m of terrace gravel (1004); a very ephemeral organic deposit (1008) was noted in the bottom c. 0.1m of the gravel. This was predominantly a loose grey clayey sand with organic fragments and ephemeral organic staining (Plate 1, Appendix 2). Specialist reports detailing the findings from the bulk sample taken from this organic deposit are provided in Appendix 5 and record no worked flint or faunal remains. Although, wood and grass remain do survive they are poorly preserved. Possible periglacial features or Pleistocene palaeochannel features (1005/1006/1007) were also recorded in the gravel. Overall, the organic horizon indicates a period of stabilisation and vegetation growth (trees and grass) before being overlain by further gravel units and the formation of the later periglacial/palaeochannel features. The gravel was overlain by c. 0.25m of thin weathered silt alluvium (1003) and sealed by subsoil (1002), measuring c. 0.1m in depth, and topsoil (1001), measuring c. 0.3m in depth. No lithic artefacts or faunal remains were recovered during works at Twyford Padbury Brook.