The Lower Palæozoic Rocks of Austwick and Horton-in-Ribblesdale, Yorkshire

I. Introduction The area dealt with in this communication is one of the small exposures of Lower Palæozoic rocks forming part of the edge of the rigid block which, near the Craven faults, appears from beneath the great spread of almost horizontal Carboniferous strata of the Mid-Pennine area. The late Prof. J. E. Marr suggested that this rigid block was formed in the main of Pre-Cambrian rocks with a fringe of Lower Palæozoic strata deposited against its flanks, the whole having been compacted in pre-Carboniferous times. In the Austwick-Horton area, therefore, we may expect to find evidence of successive transgressions with special marginal fades and signs of numerous breaks in the succession, which features are absent or not well defined in the more central parts of the Lower Palæozoic trough of the Lake District and southern Scotland. It is with the hope of throwing some light on these matters that we venture to add yet another to the long list of papers on this district of Yorkshire. The mapping and collecting of material has been carried out by both authors. The detailed mapping was begun in 1920 by Mr. Wilcockson, and he also collected the greater part of the fossil material. Professor King took the Cambridge field-mapping classes here from 1920 to 1931 inclusive, and during that time examined many of the exposures and determined certain fossil localities. Trenches were dug by Mr. Wilcockson in 1920 with the aid of grants from the British Association, and two trenches were dug