Abstract

In a written contribution Dr. G. H. Mitchell said: Of the many problems of Lake District tectonics two in particular are outstanding. One is the relationship of the Borrowdale Volcanic Group to the Skiddaw Slates. The other concerns the nature of the junction between the Coniston Limestone Group and the Borrowdale Volcanic Group. Over the past too years these two junctions have provided geologists with the problem of tectonic relationships. The upper junction is now generally held to be an unconformity.

The lower junction has been described as conformable; at other places an unconformity has been invoked while elsewhere a normal fault, a thrust, or a lag fault have been postulated.

Unfortunately exposures of the actual junction between the Borrowdale Volcanic Group and the Skiddaw Slates are for long distances poor and obscured by drift deposits, or disturbed by the passage of ice. There is often ample excuse for controversy regarding the structural relationships. Furthermore it is clear that the incidence of cleavage varies greatly from place to place and from bed to bed.

Nevertheless during the last few years much new mapping has been done and it is good to attempt to correlate present knowledge. This Dr. Moseley has done, including in his account the Caledonian, end-Silurian, Variscan and Alpine movements and so providing information for discussion of the tectonics of the north-west of England as a whole. The road to the solution of these problems lies in detailed field surveys covering the whole district. Meanwhile Dr. Moseley's present