and around the Warwickshire Coal-field. 545 



The Stocking ford Shales. 



The shales which overlie the quartzite occupy a considerably larger 

 area. They extend from a little south of Bedworth to Waste Hill, 

 one mile and a half north-west of Atherstone, a total distance of nine 

 miles and a half. They are divisible into two perfectly conformable 

 subdivisions, the lower, which rests quite conformably on the 

 quartzite, being distinguished by a bright red tinge and by the pre- 

 sence of minute Brachiopods of the genera Lingulella and Obolella, 

 the upper consisting of olive-coloured, grey, and thin black shales, 

 with Agnostus and Olenus. 1 The shales are fine-grained and laminated 

 and contain only a few harder and more sandy micaceous bands. 

 They are altogether uncleaved, and present so close a resemblance 

 to Coal-measures, as to have led (in the absence of fossil evidence 

 and in view of their apparent confonnity with the productive 

 measures) to their having been originally classed as Lower Coal- 

 measures. 



They are traversed by very numerous sheets of intrusive diorite, 

 etc. These igneous rocks are frequently found to follow a bedding- 

 plane for many yards, and on a general view indicate the strike of 

 the shale very accurately. On a close examination it becomes 

 evident that the shale overlying each sheet of igneous rock is as 

 highly altered as that below, and that frequently the igneous rocks 

 break obliquely across the beds, or even swell out into bosses, 

 forcibly contorting and thrusting aside the surrounding shales. 

 These facts, indicating the intrusive character of the rock, were 

 clearly recognized by the Eev. J. Yates in the year 1824. 



The southern termination of this range of Lower Silurian shales 

 is concealed by Drift. But the beds seem to have been found in a 

 colliery shaft at Hawkesbury Basin, one mile south of Bedworth, 

 where the following section was proved : 2 — 



ft. in. 

 l Bind, rock, and fire-clay -with coal and ironstone 182 11 



Coal-measures, J Black shale-rock 6 



( "White rock-binds 1 6 



Alternations of hard black bat and granite- 

 like rock in boulders 172 9 



357 8 

 Mr. Howell remarks that the "granite-like rock " was not a granite, 

 but that, not having seen it in situ, he is unable to say whether it is 

 trap or an altered sedimentary rock. It seems extremely probable, 

 however, that the f^ock described as hard black bat was the altered 

 Lower Silurian shale, and the granite-like rock some of the dioritic 

 intrusions which are so numerous in this part of the shale, as seen 

 at Chilvers Coton. 



The most southerly exposure is at Marston Jabet in the old quarry 

 in diorite figured in the Memoir on p. 39, but the first surface 



1 This subdivision consists of two zones according to Prof. Lapworth, an upper 

 zone characterized by Sphcerophthalmus alatus, Beck., and a lower zone with 

 Aynoslus sociale, Tullberg, Geol. Mag. for 1886, p. 321. 



2 The Geology of the Warwickshire Coal-field (Geol. Survey Memoir), p. 20. 



DECADE III. YOL. III. NO. XII. 35 



