A Contribution to the Petrography of the New Red Sandstone in the West of England

Abstract

I. Introduction. In a former paper communicated to this Society I dealt with the mineralogical constitution of the great Pebble-Bed, as developed in Devon and Somerset. The results obtained encouraged me to undertake a similar study of the other members of the New Red Sandstone Series in that district ; and, in the following communication, I have endeavoured to point out the mineralogical and physical differences exhibited by the microscopic particles which form the finer portions of the deposits. The classification and subdivision of the New Red Sandstone Series in Devon and Somerset has gradually evolved from the labours of several geologists, and I propose to use those subdivisions which are now adopted by the Geological Survey. The New Red Sandstone in the area under consideration may be divided as follows, commencing with the older beds :— These subdivisions are founded solely on lithological characters, and therefore form the most natural basis for a petrographical study. The Lower Breccias are well-developed, and have been examined on the south coast at Teignmouth and Dawlish, along the western side of the Exe estuary on the flanks of the Haldon Hills, in the Exeter district, and in the Crediton and Stogumber valleys. They usually consist of deep-red breccias, sands, and sandstones, most often loose and incoherent, but occasionally compacted into rocks of more solid character. The Lower Sandstones, which for the most part occupy a position above the breecias, have been studied on each side of the Exe estuary, in the vale of