﻿Yol. 64.] CARBONIFEROUS LIMESTONE OF THE MIDLAND AREA. 81 



Series, and the Millstone Grits were all at the maximum thickness, 

 and thinned away eastwards, westwards, and southwards. 



It was difficult to compare the Derbyshire and Bristol Carboni- 

 ferous areas because, although in each there was a complete 

 conformable Carboniferous succession, yet the question remained, 

 what was happening in the South-Western Province? — where the 

 succession was 



Coal-Measures, 



Millstone Grit = Ci/cdhaxojiia-'Beds, fide Sibly, 



while the several thousand feet of detrital matter, represented by 

 the Pendleside Series and Millstone Grits, were being laid down in 

 the Derbyshire area ; the Coal-Measures of Bristol being, if anything, 

 higher than the Lower Coal-Measures of Staff'ordshire. 



Mr. C. B. Wedd congratulated the Author on the completion of 

 another piece of careful Carboniferous zoning, and concurred with 

 the results obtained, so far as they affected that part of the district 

 with which he was familiar. It was satisfactory that the Author 

 had been able to determine the relationship to the rest of the 

 limestone of the puzzling brachiopod-beds of Park Hill and other 

 places on the west side. The Author had referred to the litho- 

 logical changes that took place between the west and east sides, 

 particularly in the greater development of cherty limestone at the 

 top on the west side. The matter needed further research in its 

 relation to faunal distribution. 



The speaker pointed out an apparently great thickening of the D^ 

 subzone in the north-west of the region, as compared with the south- 

 east — where that subzone was only about 200 feet thick, as defined 

 by the incoming of the Cyathaa^onia-fsiunsL above and by the horizon 

 of the lower lava of Matlock below. Just above that lava the D, 

 coral-fauna was usually abundant, while he had not found it lower. 



The Author had mentioned two local unconformities at the 

 junction of the limestone with the overlying shales. One of these 

 at Darley Dale showed an anticlinal dome of limestone dissected by 

 quarrying operations. If stripped of the shale above, the dome 

 would have a knoll-like aspect. On the north and east sides these 

 shales, nearly horizontal, overstepped the denuded edge of the cherty 

 limestone (there normally about 50 feet thick) on to the white 

 limestone below. 



Mr. J. A. Douglas commented on the extreme thickness of the 

 I)ihunoj)hyUu7n-Zone in the Midland District, as being interesting 

 in connexion with some recent work that he had been doing on the 

 Carboniferous Limestone in the West of Ireland (Co. Clare). The 

 general succession there was : — 



Thickness in feet. 



Upper Limestone 1900 



J f unstratified 750 



i stratified 450 



Lower Limestone-Shales 150 



Total 3250 



Q. J. G. S. No. 253. =^ « 



