Difference between revisions of "OR/14/013 Modelled faults"

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Latest revision as of 15:39, 5 May 2015

Monaghan A A, Arkley S L B, Whitbread K, McCormac M. 2014. Clyde superficial deposits and bedrock models released to the ASK Network 2014: a guide for users Version 3 . British Geological Survey Internal Report, OR/14/013.
Figure 4 Overview of faults modelled in the Central Glasgow bedrock model, looking from above.

Dipping faults were included in the Central Glasgow bedrock model (Figure 4). Some faults have long-established names, while others are designated informally (e.g. f23). With a few exceptions relating to the inclusion of smaller structures on NS66SW, faults were included in the model if over 30 m throw or 2 km in length.

In the Central Glasgow bedrock model, fault dips were calculated where data were available using the XYZ positions recorded in subsurface mine abandonment plans and linked to the surface outcrop position. The data were mainly available on NS66SW, showing that the majority of faults have dips of c. 60°. One fault, the Burnside Fault (Figure 4), has a c. 45° dip. Occasionally, fault information was encountered in boreholes. However, the amount of fault subsurface position information from mining and boreholes is generally very limited (and not enough to make a fault defining pointset). Thus, faults were created by projection from their mapped outcrop position at 60° (apart from Burnside at 45°).

The availability of mining information on NS66SW meant that faults could be analysed for their continuation at depth. Smaller faults were observed to terminate within 100 m of rockhead (e.g. F6, Figure 4) whereas larger structures (e.g. Rutherglen) extend to the depth of the whole of the model. On NS66NW and NS56SE, mining information was more limited and faults incorporated in the model were generally larger in terms of length (and therefore probably depth also), such that faults on these sheets were extended to a standard depth of 1 km.

Only faults with larger throws of greater than tens of metres and lengths of kilometres were included in the Clyde Catchment scale bedrock model. Generally the modelled position of faults is consistent between the two models, though two faults have a differing dip in the Clyde Catchment bedrock model due to evidence available outside the Central Glasgow area. In the buffer zone provided to the ASK Network there are over 100 parts of modelled faults.