﻿56 MB. T. r. SIBLT ON THE FAUNAL SUCCESSION IN THE [Feb. I908, 



(i) The Waterhouses section. 



At Waterhouses, the quarries on each side of the valley, together 

 with small railway-cuttings on the south side, give an excellent series 

 of exposures. On account of the discontinuity of the exposure and 

 the variable dip of the beds, I have not been able to estimate the 

 vertical extent of the section ; but it is certain that the series 

 exposed includes a very large part of D.,. The limestones are of 

 varied character, including some thinly-bedded dark-grey bands^ 

 with black shale-partings, but there is no considerable development 

 of chert in any part of the section. 



(ii) The Manifold Valley. 



In the Manifold Yalley, a few miles north of Waterhouses^ 

 cuttings on the light railway between Grindon and Ecton Stations 

 expose a much-folded and faulted series of thinly-bedded, dark- 

 grey or blue limestones with strong chert. These beds belong 

 to D.,. The cherty series evidently attains a great thickness, but 

 no estimation is possible. 



The foregoing notes illustrate the fact that considerable varia- 

 tions in the lithological character of the limestones composing the 

 Lonsdalia-suhzoue occur, in passing from point to point in the 

 area. Undoubtedly, the most striking feature is the variable 

 development of cherty limestones. The greatest measurable de- 

 velopment of the chertj^ series is found in the typical section, in 

 the eastern part of the area, in which practically the whole of D.^ 

 consists of stronglj'-cherty limestones. It is quite possible, however, 

 that in the Manifold Valley, in the south-western part of the area^ 

 the cherty limestones attain as great a thickness. Outside these 

 two localities of maximum development, the cherty series generally 

 plays a much less important part in D,,. In the eastern part of the 

 area, where the nature of the exposures enables us to estimate the 

 vertical extent of the cherty series with some approach to accuracy^ 

 it is found that the decrease in the downward extent of the chert 

 is more pronounced in a southerly direction from the typical section 

 than in a northerly direction. 



It is a noteworth}^ fact that, whatever its vertical extent, the 

 chert-facies, once firmly established, usually persists 

 to the top of the Carboniferous Limestone without con- 

 siderable interruption. Further, an abundant development of chert, 

 though sometimes found in massive light-coloured limestones, is in 

 most cases confined either to thinly-bedded blue limestones, or to 

 thinly-bedded dark-grey or black limestones of compact texture. I 

 do not know of any instance in which the peculiar compact black 

 limestones, such as those of the Ashford ' Black-Marble Quarry V are 

 developed without an abundant accompaniment of chert. 



^ The black limestones of Ashford, well-known as being used for ornamental 

 purposes, occur in D3, but limestones of precisely-similar lithological character 

 are developed in D^, in the typical section and elsewhere. 



