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121. However, large areas of seismic blanking, interpreted as representing accumulations of shallow gas, have been identified within BNB (Figure 17.5). These have been included within the list of palaeolandscape features (Figure 17.2, Appendix 17.3), as they suggest the presence of intact organic material within the sediment, and the most extensive are 75459 and 75544 (see Appendix 17.3 for full list).


122. The source of the gas may be uncertain, however. The largest accumulations of gas (75459 and 75544) appear to be generally associated with the largest of the Lower Brown Bank Formation/Eem Formation features (75490 and 75543), and are orientated along the same general NNW - SSE alignment. This possibly suggests the actual source of the gas may be within these earlier features, not in the BNB blanket deposit itself. However, the correlation is not entirely consistent and this interpretation remains uncertain.


123. The post-Devensian (Flandrian), Holocene geology of East Anglia Three comprises two units; a pre-transgression unit and post-transgression unit. The pre- transgression unit is represented by a series of small, scattered cut and fill and channel features cut into the upper layer of BNB. The largest of these are features 75454, 75511 and 75517 though a number of smaller individual cut and fills are also present (Figure 17.2, see Appendix 17.3 for full list).


124. These are relatively small features, with poorly defined basal reflectors and either an acoustically transparent of well-layered fill (Figure 17.7). They have not been sampled by boreholes, but they are interpreted as fluvial features representing the remnants of the post-Devensian) land surface.


125. These features possibly date from the very Late Upper Palaeolithic and Mesolithic Periods (MIS 2 - 1, and as such have the potential to contain both in situ and derived archaeological artefacts, along with palaeoenvironmental material.


126. The post-transgression Holocene sediments are represented by a deposit of marine sediment, found by boreholing to comprise fine to coarse sand, which is silty and contains organic matter in some areas (probably reworked). This sediment varied in thickness from a thin veneer to sand banks up to 10m thick, and the boundary between it and the underlying BNB unit is often unclear. These sediments are not considered to be of archaeological potential in themselves, though they could periodically bury and expose sites such as shipwrecks in areas of mobile sediment, and thicker sand deposits could protect earlier land surfaces.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Appendix 17.2 Archaeological Review of


Geophysical and Geotechnical Data: Technical Report


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