THE CARBONIFEROUS SYSTKM 299 



broad syncline (see Fig. 99), while the Upper Measures are nearly 

 horizontal ; the base of the latter being a mottled clay known as 

 " calaminker " overlain by a bed of gravel or conglomerate called 

 the " Rough Rock." As this series is traced southwards the lower 

 members thin out and disappear, while the Middle Measures over- 

 step the Millstone grit so as to rest on the Old Red Sandstone, and 

 this is their position in the Forest of Wyre west of Kidderminster 

 and around Bewdley. 



In South Staffordshire there appears to be a similar break 

 between the Middle and Upper Measures, for the diminution in the 

 thickness of the Middle Group toward the south is probably in 

 part owing to an overstep on the part of the Upper Measures. 

 According to Professor Lapworth the succession south of Dudley is 

 as follows : 



Feet. 



Upper (Red sandstones and marls (Hunnington) . . 1300 



and -I Grey sandstones and marls (Halesowen) . . 800 



Trans. C.M. (Red marls and greenish sandstones . . . 800 



Middle or productive Coal-measures ...... 500 



3400 



The same succession is found in Warwickshire. 



From the preceding account of the stratigraphical arrangement 

 of the several members of the Westphalian Series in this region it 

 will be seen that they all become thinner southwards, each stage 

 passing beyond the limits of the one below farther and farther on 

 to the Midland area which was land in Avonian time Moreover, 

 it is apparent that there was some terrestrial disturbance and uplift 

 in this southern part of the region after the formation of the 

 Middle Coal-measures. 



It may also be inferred that the main rnasa of the Westphalian 

 Series above described was deposited in a trough which extended 

 from west to east across what is now the Pennine range, and that this 

 trough was continually deepened by subsidence, while in the area 

 to the south of it subsidence was interrupted by stationary epochs 

 and at one time by an uplift with consequent flexure and erosion. 



' Further, the student should note that the existing coalfields on 

 each side of the Pennine ridge still extend far below the newer 

 beds which cover their outer parts. Thus the Lancashire coalfield 

 probably passes westward below Liverpool Bay, and the Yorkshire 

 coalfield is known to extend as far as Haxey in Lincolnshire, where 

 a boring has been carried to a depth of 3185 feet passing through 

 1457 feet of Coal-measures. It is believed that the subterranean 

 extension of this coalfield reaches as far eastward as Lincoln and 

 Brigg. 



