THE PETROGRAPHY OF THE CARSTONE AND ASSOCIATED BEDS IN YORKSHIRE AND LINCOLNSHIRE

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Abstract
(Read, March 13th, 1926.) The original aim of this work was to investigate the conditions under which the Carstone and Red Chalk of Yorkshire and Lincolnshire were accumulated. It has, however, been found necessary to examine the beds over a somewhat larger area, and also to study for some purposes the Neocomian strata underlying them. Observations on these latter beds are including in this paper, but the authors do not claim to have studied exhaustively these strata. The study of the Red Chalk has resolved itself into parts—mineralogical and chemical. Details regarding the mineralogy are incorporated in this paper, but the authors feel that the investigations into the colouration of the Red Chalk have not been carried sufficiently far to warrant any definite conclusions. The field work and mineral separations have been carried out by the junior author while the petrographical work has been done jointly. The Carstone. The general lithology and stratigraphical relations of the Carstone have been well described by Sir A. Strahan,1 and the authors have little to add. The rock is very variable in grade and in matrix, but fairly uniform in composition, the only notable exception being a strong conglomerate near the base of the Carstone at Hunstanton from which notable phosphatised fossils are recorded.2 In Lincolnshire and Norfolk, phosphatic concretions are common, usually appearing in bands preserving a certain amount of parallelism. Even when the rock thins, the nodule lines still remain but at a less distance apart. This suggests that they represent certain stages when deposition ...