THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. II. 



No. X. — OCTOBER, 1905. 



OK,XC3-II<rjLXj .^ISTIGXiES. 



I. — Notes on the Geological Horizon and Paleontology of 



THE ' SOAPSTONE BeD,' IN THE LoWER COAL-MEASURES, NEAR 



CoLNB, Lancashire. 

 By Herbert Bolton, F.E.S.E., Curator of the Natural History Museum, Bristol. 



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 Qoniatites, 

 Pterinopecten, 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. These, in the Rossendale area, 

 are separated by a thickness of 40 feet of sandstone and shale, which 

 thins out along a north-west and south-east line between Bacup and 

 Burnley, the thinning out being due to the curving upwards of the 

 lower or Gannister seam to meet the overlying Bullion mine. 



DECADE V. — VOL. II. — NO. X. 28 



