Thursday 20th November, Malcolm Butler from the UK Onshore Geophysical Library will give a talk “2D musings on 3D geology in the Welsh Borderlands”.
Abstract:
Interpretation of a compiled 2D seismic section from Chepstow to the Longmynd is presented to show the strong erosion beneath the Shelveian Unconformity outside basinal areas. This unconformity is overlain by rocks of lower Llandovery age in the area south of Craven Arms but lies immediately below rocks ranging in age from Upper Ordovician to Wenlockian north of the Church Stretton Fault complex.
The interpretation demonstrates the presence of a widespread regional high to the east of the Malvern Hills over which the Llandovery sequence appears to lie immediately on lower Cambrian or Precambrian rocks. This stripping (or non-deposition) of rocks beneath the Shelveian Unconformity appears to also occur beneath the Worcester Graben and the western part of the Oxfordshire Coalfield, although widespread erosion beneath the Variscan Unconformity confuses the situation. Where seismic data are available off the western flanks of the Malvern Hills, the lack of significant thinning in the Silurian and Lower Devonian section may indicate that no separate Malvern High existed at this time.
The talk may be downloaded from: