OR/16/034 Model assumptions, geological rules used etc.
| Barron, A J M. 2016. Metadata report for GSI3D cross sections along the HS2 route in Area 9 (Birmingham spur). British Geological Survey Open Report, OR/16/034. |
In many cases the borehole data/interpretation conflicted with the memoir figures (Powell et al., 2000[1]), either because the borehole data was not used for the figure or more recently acquired, the present author disagreed with the earlier interpretation, or the figure was poorly drawn or generalized. A judgement was made on the individual case but generally the borehole interpretation took precedence. Nonetheless, the general pattern of structure/rockhead contours in the figures was honoured as far as possible. This continued throughout the modelling.
In the memoir (Powell et al., 2000[1], p.81), most/all of the glacigenic deposits in the area are inferred to be Anglian/Wolstonian (i.e. Middle Pleistocene) in age and have been modelled as such in Area 7. However, in DiGMapGB-50 v7 as used in the model shape files, they are attributed as Devensian (i.e. Late Pleistocene; e.g. GFDUD rather than GFDMP), presumably as a result of more recent research, although this interpretation is known to be controversial/not yet well substantiated. To fit Area 7, Middle Pleistocene units are used here, except in NS1 at SP 184 924.