V.—The Inclination of Overfolds in Relation to the Larger Folds in which they are Contained

Abstract

While spending a few days recently examining the sections on the North Devon coast, with a view to obtaining a clearer conception of the tectonic structure of that region, I was deeply impressed by the great number of minor overfolds and with the great uncertainty in the relations of the various beds thereby brought about. In many cases where the dip appears to be constantly to the south, through a considerable thickness of strata, closer examination shows repeated isoclinal folds. The western face of Little Hangman Hill at Combe Martin exhibits such a condition very well. Throughout the whole coast which I examined, from Combe Martin to the southernmost part of Bideford Bay, the axes of the minor folds are inclined to the north in this way, so as to frequently produce the appearance of steady southern dip and greatly to increase the apparent thickness of the strata. In speculating as to the possible cause of the constant direction in which the axes of these folds are inclined, an explanation occurred to me which I believe to be the correct one, and which may be applied generally to a large number of cases. As I have been unable to find it in the works I have been able to consult, it may be desirable to publish it, since it may aid considerably the elucidation of the true structure and history of complicated districts.