68 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 20, 



Coleorton in Leicestershire, and on the Permian Rocks further south 

 at "Warwick, — the whole of the Bunter Sandstone having consequently 

 thinned out. 



B. Keuper. — "We now proceed to trace the range of the Keuper, 

 under its two principal subdivisions — the Lower Keuper Sandstone, 

 and Red Marl. The former of these is frequently introduced by a 

 band of hard calcareous breccia, with laminated red shales, which 

 is succeeded by evenly bedded ripple-marked sandstones and marls 

 (called " Waterstones" by Mr. Ormerod*). In Cheshire and Lan- 

 cashire, the Lower Keuper Sandstone reaches a thickness of 450 

 feet, forming the scarped ranges of the Runcorn, Delamere, and 

 Peckforton Hills. These beds have been traced on the maps of the 

 Geological Survey over the western and central counties ; and, as a 

 general rule, they are found to decrease in thickness in proportion 

 as they approach the South-eastern counties. Around the skirts of the 

 Leicestershire Coal-field this subdivision has a general thickness of 

 200 feet; and over the centre and the eastern side it rests immediately 

 on the Coal-measures, without the intervention of the Bunter Sand- 

 stone. The district around "Warwick is that along which it becomes 

 most rapidily attenuated, and where it is on the point of being 

 ultimately concealed by the Red Marl. As in the ease of the 

 Leicestershire Coal-field, the Lower Keuper Sandstone is here the 

 most ancient member of the Trias, and I am informed by Mr. 

 Howell, of the Geological Survey, that its thickness may be esti- 

 mated at not more than 150 feet. 



Comparing, then, the thickness of this subformation where it is 

 visible for the last time towards the south-east with that which it 

 assumes in "West Cheshire, we find that it has decreased by two- 

 thirds in its extension from the one locality to the other ; the hori- 

 zontal distance being 85 miles. Now, if this decrease continues in 

 the same proportion, the whole subformation ought to disappear 

 several miles N.W. of Oxford f (Plate IY. figs. 2, 3, 4). 



C. Bed Marl. — The thickness of the Red Marl in Cheshire has 

 been much under- estimated. From considerations connected with 

 the depths of the salt-beds, Mr. Ormerod estimates it at more than 

 700 feet % ; but I feel sure he will allow that these data can scarcely 

 afford even an approximate computation, as we are still uncertain 

 of the nature of the beds which underlie the salt-rocks, and of the 

 position of those through which the shafts have been sunk at 

 Northwich. 



A very perfect section along the banks of a brook (without a 

 name in the Ordnance Map), three miles south of Malpas, although it 

 does not extend nearly to the top of the formation, shows the Red 

 Marl to be of much greater thickness than it is generally considered. 

 The beds, consisting of fine laminated red and grey shales, may be 



* Quart. Journ. Geol. Soc. vol. iv. 



t Maps of the Geol. Survey, 53 N.W.— 63 S.W. 



{ Quart. Journ. Geol. Soc. vol. iv. p. 288. For local descriptions of the 

 Triassic Rocks of Cheshire and Lancashire, see the Memoirs of Messrs. Binney, 

 Ormerod, J. Cunningham, and R. Rawlinson in the Journal of the Geological 

 Society. 



