GEOLOGY 



formations, and an occasional fragment of granite or volcanic grit. 1 

 Speaking generally the massed gravels are more abundant in the north 

 than in the south, and more persistent towards the base of the sub- 

 division than near its summit. They are largely quarried for road metal 

 and gravel in Trentham Park, Cannock Chase, south of Cheadle, Longton, 

 and in many localities bordering the South Staffordshire Coalfield. 



To the west of the South Staffordshire Coalfield the sub-division is 

 situated with apparent perfect conformity between the Lower and Upper 

 Mottled Sandstone, but elsewhere in the county rests with a great discord- 

 ance on the various members of the Carboniferous rocks or on 'Permian.' 

 This unconformity can nowhere be better illustrated than by the outliers 

 at Endon and around Leek, where the nearly horizontal pebbly Bunter 

 sandstones rest on highly inclined or sharply folded Lower Carboniferous 

 rocks. 



In its course along the western margin of the South Staffordshire 

 Coalfield the outcrop is indicated by conspicuous ridges, such as Abbots 

 Castle Hill, near Trysull, and Kinver Edge. Along the eastern side of 

 the coalfield the outcrop extends in a well marked ridge from near 

 Birmingham northward to Aldridge. The greatest expanse however 

 constitutes the open undulating heather-clad moorland of Cannock Chase 

 on which the characteristic weathering into deep coombes with inter- 

 mediate rounded lobes is admirably illustrated. The same character is 

 clearly portrayed round the North Staffordshire Coalfield, where the 

 sub-formation gives rise to the picturesque woodlands of Maer, Swyn- 

 nerton Park, Trentham Park, Burnt Wood and Bishops Wood. Perhaps 

 the most interesting outcrop occurs in the Churnet valley between 

 Cheddleton and Leek, where a small patch about seven miles long has 

 been preserved in a deep pre-Triassic hollow excavated in the Lower 

 Carboniferous rocks which on all sides surround and overlook the 

 much newer formation. 



The mode and place of origin of the sandstones and shingle beds 

 have given rise to much controversy among geologists. They have 

 been regarded as the products of powerful oceanic currents ; another 

 opinion holds them to be of sub-aerial origin, brought together by 

 large rivers liable to heavy floods, or else by tumultuous torrents the effect 

 of cloudbursts. Some geologists consider the pebbles to be derived from 

 the breaking up of the conglomerates of the Old Red Sandstone ; others 

 again would derive them from Palaeozoic rocks of different ages in rapid 

 course of destruction by the ordinary agents of denudation acting during 

 the Bunter period. Again, the views as to the source of origin are 

 widely divergent : some geologists maintain that the pebbles were derived 

 from the older formations in the north of England and Scotland ; others 

 look to their source from an old rocky ridge extending between the south- 

 west of England and western France ; while others think it not improb- 

 able that much of the material might have been obtained from the older 



1 W. Molyneux, ' On the Gravel Beds of Trentham Park,' Trans. North Staff. Nat. Field Club 

 (1886) ; Geol. Mag. iv. 173 (1867). 



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