﻿458 ME. R. H. RASTALL ON THE [Aug. 1905, 



Discussion. 



The Chairman (Mr. H. B. Woodward) remarked that the abstract 

 of the Author's paper did not sufficiently indicate the new matter 

 which he contributed ; but he had undoubtedly raised many points 

 for discussion, in connection with the evidences of local erosion and 

 of derived fossils at the base of the Dogger. 



Mr. Fox Stranoways complimented the Author upon the very 

 clear way in which he had put before the Society the relationship 

 between the Lias and the base of the Oolites in so interesting a 

 district. There were, however, a few points as to which further 

 information was required. One was in reference to the so-called 

 ' pebbles ' of the Dogger. What were they ? Some were un- 

 doubtedly worn fragments of other rocks, but they were not all so. 

 Some were phosphatic, and there were concretions of various kinds. 

 Many authors had alluded to this, but no one seemed to have given 

 a satisfactory explanation. The Author stated that the Lias was 

 denuded before the deposition of the Dogger, but if the pebbles 

 were derived from the Middle Lias, the denudation must have been 

 contemporaneous. 



The Blea-Wyke Beds were stated to be unrepresented elsewhere, 

 but there were certain beds at Castle Howard which Mr. Hudleston 

 considered to be of that age. The base of the Dogger was taken at 

 a higher horizon than by previous authors. There did not seem to 

 be sufficient reason for this ; and, as the line now proposed was in 

 the midst of a thick mass of sandstone, it would be impossible to 

 trace such a line across country. 



Mr. Hudleston said that he was naturally much interested in a 

 paper which offered a fresh description of the Blea-Wyke Beds, 

 while showing their relation to the Dogger as ordinarily developed 

 throughout North-East Yorkshire. He had always been much 

 impressed with the immense difference between the development of 

 the Dogger on the east and on the west side of the Peak Fault. It 

 was to be regretted that the Author had been unsuccessful in his 

 search for fossils in the Grey Sands which constitute the platform at 

 Blea-Wyke Point. Dr. Wright was the first to indicate the im- 

 portance of the Cephalopoda of this horizon, which he justly 

 compared with his ' Cephalopoda-Bed ' at Frocester and elsewhere in 

 the Cotteswolds ; while more recently Mr. Buckman had described 

 numerous forms of the ammonite-genera Oxynoticeras (Hudlestonia), 

 Grammoceras, etc., based upon specimens from this spot. Within the 

 space of li miles, reckoning from Blea-Wyke Point, the whole of 

 this series, comprising some 150 feet of beds, is missiDg on the 

 north-west side of the fault, and the Dogger is reduced to some 

 4 feet, with the usual pebble- or nodule-bed towards the base. 



There could be no doubt that many of these bodies were reman ie 

 forms, mainly derived from the contemporaneous erosion of the 

 Upper Lias ; and they had in many cases been partly phosphatized, 

 like the derived forms in the Cambridge Greensand. One of 

 the chief lessons to be learnt from the geology of this region was 



