402 A. Sfrahan — Lower Keuper Sandstone. 



in the Upper Mottled Sandstone by colour, cannot therefore be 

 considered of much value. 



Nor again can the appearances of erosion at the base of the Lower 

 Keuper Sandstone be accepted as evidence of the unconformity 

 between the Bunter and Keuper. Not only are these appearances 

 reproduced at the base of every bed of conglomeratic sandstone in 

 the Lower Keuper, but they are equally strong at the base of the 

 Pebble Beds in the Bunter (Triassic Memoir, pp. 35, 36, etc.), while 

 they occur also in the Upper Mottled Sandstone itself. The Frodsham 

 Beds, and soft partings in the Lower Keuper Sandstone, are exactly 

 similar to the Upper and Lower Mottled Sandstones of the Bunter, 

 and the conglomerate beds of the two subdivisions are so alike as 

 to have been wrongly identified in some cases in the first survey of 

 the district. There is therefore a striking similarity between the 

 various horizons at which signs of erosion appear, and there is no 

 evidence in this district that the erosion was greater at the base 

 of the Lower Keuper Sandstone than at any one of the other 

 horizons. These phenomena are not evidences of unconformity, but 

 like the current bedding by which the whole of the Lower Keuper 

 and Bunter are traversed, indicate the action of currents varying in 

 strength and possibly in direction, an increase of strength causing 

 sand already deposited to be partially removed, and coarser sediment 

 to be laid down in its place. 



It has been already stated that the Lower Keuper Sandstone has 

 approximately the same geographical distribution as the Bunter. 

 From what has been said of the neighbourhood of Nottingham, it 

 will have been seen that the Lower Keuper Sandstone is on the 

 point of thinning out, though the Waterstones are well developed. 

 The same fact is observable in proceeding southwards from Cheshire 

 to those districts, where the Bunter thins out as described by Prof. 

 Hull, and though it is not possible to give the exact range of the 

 Lower Keuper Sandstone, until the separation of the Waterstones 

 has been completely carried out, yet it may now be stated that over 

 a large area, where Lower Keuper Sandstone is represented on the 

 maps, the Waterstones only are present, without any equivalent of 

 the Basement Beds of Cheshire. In the event of the sharp division 

 of the Waterstones from the Basement Beds being found to hold 

 good over the whole area, and taking into consideration the strong 

 lithological resemblance of the Lower Keuper Sandstone to the 

 Bunter, and the similarity of its distribution, it will have to be 

 reconsidered whether the break at the base of the Lower Keuper 

 Sandstone has not been greatly overestimated, and whether the base 

 of the Waterstones does not constitute a more important strati- 

 graphical horizon in the Trias. 



The fossil evidence, so far as it goes, points to an association of 

 the Keuper Basement Beds with the Waterstones, for the Clieiro- 

 therium footprints are equally well known in both, but this evidence, 

 depending, as it does, on a want of knowledge of the fossil contents 

 of the Bunter, is of a purely negative character. Leaving for the 

 present the difficult question of the correlation of these beds with 



