LIAS IN SHROPSHIRE AND CHESHIRE. 



23 



been detected, we find that this bowl has a length of about ten, and a breadth of three 

 to four and a half miles 1 . The greater part of this district consists of Lower Lias Shale, 

 but the overlying subdivision of the Marlstone is also apparent. 



Marlstone. — This member of the Lias is well exposed in the hill on which the church 

 of Prees is built, (see centre of wood-cut above, and Plate 29. fig. 2.) both in quarries 

 and by the sides of the roads, dipping to the north-north-east at low angles. The upper 

 beds are composed of yellowish and greenish thin-bedded sandstone, slightly micaceous, 

 and in part calcareous ; the middle, of other yellowish sandstones, some of which are 

 more calcareous ; and the lowest beds, of sandy, dark-coloured slaty marl, and shale 

 with flattened spheroids of impure blue Lias limestone, which are undistinguishable from 

 the well-known cement-stones of the Yorkshire coast. The fossils which I obtained are 

 those which best characterize the Marlstone in Worcestershire and Gloucestershire, viz. 



Avicula incequivalvis. M. C. t. 244. f. 2. Pecten cequivalvis. M. C. t. 136. f. 1. 



Gryphcea gigantea. M. C. t. 391. 



together with an Ammonite which appears to be referrible to Ammonites geometricus 

 (Phillips) of the Yorkshire Lias. 



Lower Lias. — The Lower Lias consists entirely of finely laminated shale, as proved 

 by shafts which have been sunk on Wolliston Common. In the vicinity of Burley Dam, 

 some of the beds are so hard as to have induced Lord Combermere to quarry them for 

 slating purposes, and others at the same locality being slightly bituminous have very 

 much the mineral aspect of Kimmeridge Coal 2 . At Lightwood Green, the shale was 

 found to contain nodules of ferruginous cement-stone : while at Cloverly, beneath nu- 

 merous beds of dark marly shale, occurred one thin band of hard white stone with others 

 of a blue colour. These bands have been traced by the Rev. Thomas Egerton, from 

 Moreton Wood near Cloverly Hall, to Audlem and Burley Dam. 



The natural facilities for examining the deposit are few, the surface being generally 

 covered by superficial clay and coarse gravel, sometimes to the thickness of twenty or 

 thirty yards, but its characters have been abundantly ascertained by borings for coal at 

 Heathgate, Moreton Wood, Prees Wood, Calver Hall, Burley Dam, Marchamly, Cloverly, 



1 At Moreton Wood the Lias dips westerly, thus indicating, that it is there near the eastern side of the basin ; 

 whilst at Audlem and Burley Dam, along the north-eastern and northern boundary, the strata dip south-west 

 and south, at angles varying from 5° to 7°. I am much indebted to the Rev. T. Egerton and the Rev. W. 

 Egerton for their assistance in determining the outlines of this mass of Lias, 



3 The Shale which forms the base of the upper division of the Oolitic series, occurs extensively in the coast 

 cliffs at Kimmeridge, in the Isle of Purbeck, and hence it has been termed Kimmeridge clay. Some of the beds 

 are very bituminous, and being occasionally used as fuel, are called Kimmeridge coal. The mineralogical cha- 

 racters of this formation so closely resemble coal shale, that those unacquainted with its stratigraphical position 

 and zoological contents, particularly in Oxfordshire and other interior parts of the kingdom, have frequently 

 sunk into it in search of coal ! ! See Outlines of the Geology of England and Wales, p. 177. 



c 2 



