Note on the Determination of the Limit between the Silurian and Devonian Systems

Abstract

IN a recently published paper on the “Highest Silurian Rocks of the Clun Forest District, Shropshire” the present writer gave an account of an area where the series of “passage-beds”, marking a gradual transition from Silurian to Old Red Sandstone conditions, is well seen. The succession there is practically identical with that established by Miss Elles and Miss Slater in the Ludlow District. From November, 1918, to October, 1919, whilst engaged in a study of Belgian Tertiary rocks, I have had an opportunity of visiting some of the more important sections of the Gedinnian in the Ardennes and also of examining the palæontological collections at Brussels, Lille, and elsewhere. This work has thrown very considerable light on the English succession, and it seems desirable to give here a resumé of the conclusions reached.