On the Correlation of the Upper Jurassic Rocks of the Swiss Jura with those of England

Abstract

In the summer of 1884 the author was sent out by the University of Cambridge, with a grant from the Worts Fund, to study the Jurassic rocks of the Jura. He was accompanied by Mr. E. W. Small, M.A., Christ's College. Some of the results then obtained are given in the present paper. The Jura range of mountains is formed in great part of rocks of Jurassic age, which have been thrown into a series of folds running more or less parallel to each other in a north-east and south-west direction. These folds are usually quite simple, and it only rarely occurs that the foldings have gone on to such an extent that the beds are inverted. If one examines a geological map of the district, it will be seen that the surface of the ground is occupied principally by Upper Jurassic Rocks; indeed all the higher ground is so formed, and it is only in the valleys and gorges which run transversely across the folds, or in the centre of the folds where the upper portion has been removed by denudation, that older beds are seen. In this paper it is proposed to deal only with the Upper Jurassic Rocks. In this term are included all the beds which lie between the base of the Callovian and the summit of the Purbeckian, and as such it is generally understood by English geologists. This classification, however, differs from that given by many foreign authors, since what is here included in