Fossils and conditions of deposit, a theory of coal formation

Abstract

This paper is the result of a study of the fossil lists of the Geological Survey Memoirs and other papers dealing with the Coal-Measure deposits, combined with the experience the author has gained in the field during the revision of the Carboniferous rocks by the Geological Survey. It is an attempt at finding the best method of approaching the study of the fossils in relation to the deposits in which they occur, and as to how far this method might help in solving the problem of formation of coal seams. Groups of fossils, which must, for this very reason, be looked upon as the remains of organisms which lived in natural association, recur again and again in similar deposits in these rocks, and may be classified as follows:— 1. Clear-water marine forms, including species of foraminifera, corals, encrinites, echinoids, polyzoa, lamellibranchs, gasteropods, cephalopods, brachiopods, and crushing teeth of fish. These occur in detrital limestones and calcareous light blue shales. The shale becomes more argillaceous at a distance from the limestone, and when of any thickness is usually dark in colour from organic impurity or sulphides of iron. As a typical example of such a deposit, we have a limestone and shale at Dunbar which has been termed the Middle Skateraw Limestone by the Geological Survey. As to the method of formation of such limestones, it is evident that they are the detritus from remains of calcareous organisms which have accumulated beyond the reach of terriginous sediment. The