Published online by Cambridge University Press: 01 May 2009
The Permian in Durham is the most internally disturbed of the newer or covering beds of England. In deep borings it is a dark dolomitic rock full of sulphates and chlorides; at the surface it has quite a different appearance. The Permian and overlying Secondary beds seem to have been lowered by downwarping. During the subsequent differential uplift and denudation the area remained a land surface and the sulphates were removed by penetrating water, not by subaerial weathering. Horizontal and low angle thrusts occur in the Sunderland area above about the middle of the underlying Coal Measure basin. The movements may have been induced by diminution in rock volume following solution and segregation accompanied by attraction or packing together of the mass of the formation.