﻿Vol. 64.] CAKBONIFEROUS LIMESTONE OP THE MIDLAND AEEA. 55 



The uppermost beds represent a high level in D^, and the whole 

 of the series, down to the lava (2), clearly belongs to this subzone.^ 

 The series underlying the lava presumably represents D^, but, in 

 the failure to record any characteristic fossils of that subzone, 

 I have not obtained any palseontological evidence to prove this. 

 Fossils are rare in the grey limestones (3), and in the dolomitic 

 series the fossils, if originally present, have been largely obliterated, 

 casts of crinoid-ossicles alone having been detected. 



(b) The Matlock district. 



Numerous sections of D^, more or less extensive, are to be found 

 in the area adjacent to Matlock, but I have not examined them in 

 detail. The Carboniferous Limestone of this district is being 

 investigated by Mr. C. B. Wedd, of H.M. Geological Survey, Avho 

 has already given a preliminary account of the succession.^ For 

 the present purpose, of comparison with the lithological sequence 

 in other parts of the area, the following brief description of the 

 succession in this district will suffice. The thinly-bedded, blue or 

 dark-grey limestones with chert, which constitute the uppermost 

 division of the Carboniferous Limestone, have an average thickness 

 of about 50 feet, and include only a small part of D.,, Locally, 

 indeed, where the cherty limestones are reduced in thickness, they 

 are all included in Dg, and the whole of J)^ consists of white or 

 light-grey limestones without chert. 



(c) The Wirksworth quarry-sections. 



At Wirksworth, the Middlepeak Quarries and adjacent quarries 

 lying farther south show over 200 feet of D^. The highest beds 

 seen are thinly-bedded, dark-grey and blue, cherty limestones, 

 about 30 feet thick, exposed in Dale Quarry. The underlying 

 series, which is free from chert, comprises limestones of varying 

 lithological character. Light-grej' or white limestones, oolitic in 

 parts and forming massive beds, predominate ; but dark-grey or 

 black limestones, with occasional shaly partings, occur at more than 

 one level. The best section is afforded by Stoneycroft Quarry, 

 immediately adjacent to the Middlepeak Quarries. 



(B) Sections in the South-Western Part of the Area. 



In the south-western part of the area, extensive and readily- 

 accessible sections of D., are very few in number.^ 



^ Mr. Arnold-Bern rose cousiders the lava of this section to be the lower lava 

 of the Matlock area ; see Quart. Journ. Geol. Soc. vol. Ixiii (1907) p. 258. 

 If we regard the horizon of this lava as the base of D2, the Gratton-Dale section 

 agrees with the sequence in the Matlock district, where, as Mr. 0. B. Wedd 

 informs me, the lower lava represents approximately the base of D.,. 



- ' Summary of Progress of the Geological Survey for 1904' 1905, pp. 8 & 9. 



^ Dove Dale and its immediate neighbourhood afford excellent sections ; but 

 the stratigraphy of the district is not easy of interpretation, and a profitable 

 description of the sections would require much more careful investigation of 

 the ground than I have had ti)ue to make. 



