Ambrose, K. 2015. GSI3D model metadata report for HS2 Area 8 (Drayton Bassett to Rugeley). British Geological Survey. (OR/15/074).
A number of normal geological faults are mapped within the model area. Figure 5 shows the current mapped faults in the DiGMapGB-50 dataset and Figure 6 shows the revised fault network represented in the Area 8 model. Four of these faults are major structures: the Birmingham Fault runs NNE–SSW across the area and the north-south trending Western Boundary Fault of the Warwickshire Coalfield just clips the south eastern corner of the area and continues south into Area 7. These faults form a graben that links the Needwood Basin to the north with the Knowle Basin to the south. These sedimentary basins and the graben were active during the Triassic, resulting in synsedimentary movement during the Permian and Triassic and a much thicker (c.1000 m) sequence of these deposits within the graben. Carboniferous aged Warwickshire Group rocks that crop out on the upthrow side of this fault are absent in the floor of the graben. Carboniferous rocks reappear in the extreme west of Area 8 on the upthrow side of the north-south trending Great Barr Fault, which forms the eastern boundary to the South Staffordshire Coalfield. A number of other faults, mainly showing a N–S to NE–SW orientation, occur within Area 8 together with a number showing a general E–W trend. These faults show variable downthrows and some significant structures with throws of up to 100 m. The Hints Fault trends NE-SW across the model area and downthrows the rocks to the east by an estimated 200 m in the southern part of the model area, diminishing northwards. This fault was extended north-east following a recent re-survey of 1:10 000 scale map sheets in the area.
Faults are modelled using the GSI3D superficial engine as steps in the geological surfaces rather than as a faulted bedrock model where the unit is in contact across the fault.
File:OR15074fig5.jpgFigure 5 Current Area 8 mapped faults shown in DigMapGB-50 (red).
File:OR15074fig6.jpgFigure 6 Revised Area 8 faults modelled (red), model area outlined in green.
