I—Notes on the Geological Horizon and Palæontology of the ‘Soapstone Bed,’ in the Lower Coal-Measures, Near Colne, Lancashire

Abstract

The ‘Soapstone bed,’ which has yielded the specimens about to be described by Dr. Henry Woodward, was so named by the late George Wild. It is a thin band of light-grey shale lying from 4 to 7 feet above the ‘Mountain Four Feet’ mine in the neighbourhood of Colne and Trawden.The shale contains an abundance of small flattened nodules, varying in size from half an inch to six inches in length, and from half an inch to two and a half inches in breadth. The vertical thickness rarely exceeds an inch and a half. The shale readily breaks down into a soft unctuous clay on weathering, whilst the outer surface of the nodules undergoes oxidation and breaks away in thin coats. The nodules consist of earthy carbonate of iron, and it is to the oxidation of the latter that breaking up takes place by a process of concentric scaling.Between the ‘Soapstone bed’ and the ‘Mountain Four Feet’ mine are black shales with dark ironstone nodules often full of Gonialites, Fterinopecten, etc. The horizon from the top of the coal-seam to the ‘Soapstone bed’ is the most prolific in organic remains in the Lower Coal-measures, in whatever locality it may be met with.Whilst the horizon of the Soapstone nodule bed is constant over a large area, the beds immediately subjacent to it are not. The Mountain Four Feet mine, upon which it rests under and around the whole of the Burnley coalfield, is seen when traced southwards to be formed by the union of two coal-seams, the ‘Gannister mine’ and the ‘Bullion mine’ respectively.