THE NATURE OF THE JUNCTION BETWEEN THE LOWER CARBONIFEROUS AND THE MILLSTONE GRIT OF NORTH-WEST YORKSHIRE.

Abstract

The greater part of North-West Yorkshire is composed of almost horizontal Lower Carboniferous rocks capped by Millstone Grit. The Lower Carboniferous, divided into Great Scar Limestone and Yoredale Series, is exposed over most of this area in the dales eroded by the Yorkshire rivers, and the Millstone Grit occurs as isolated outliers on the hills dividing one dale from the other. In the east, however, the general easterly dip of both Millstone Grit and Lower Carboniferous results in the occurrence of the Millstone Grit at a lower level, where it forms extensive tracts of moorland. The area under discussion includes the upper part of Swaledale, Wensleydale and Arkengarthdale in the north, and Semerdale, Bishopdale, Upper Coverdale and Wharfedale as far as Grassington in the south. The geology of part of the area has been described in the Mallerstang and Ingle-borough Memoirs (Sheet Memoirs 97 N.W. and 97 S.W.), while the entire area is geologically mapped on the One Inch Sheets 97 and 92 S.E. (Old Series). The mapping by the members of the Geological Survey was largely lithological. The rocks are exposed in a series of stream sections, and the intermediate country is usually covered with drift or scree detritus. As the lithology of the Lower Carboniferous gradually changes from north to south from a series of sandstones, shales and limestones to a facies composed of limestone only, the relation of the Lower Carboniferous and the Millstone Grit is not brought out. The work of Professor Garwood and Miss Goodyear ...