﻿Vol. 66.] LI&ESTOITE SOUTH OF THE CRAVEN EATTLT. 561 



Some notes on the origin of the knolls. — It is quite 

 evident from the accounts of the individual knolls, and from the 

 notes on the other exposures, that there is a good deal of folding, 

 with probably much faulting in this knoll region. It would 

 certainly appear, a priori, that there ought to be much disturbance. 

 The knolls occur in the folded region, south of the great fault; and 

 all the other beds, which are similarly situated with respect to the 

 fault, are sharply folded, faulted, and slickensided. The dark fine- 

 grained limestone shows the evidence of disturbance to perfection, 

 and in the following anticlinal region it may be seen over and over 

 again: — Thornton - in - Craven, Skipton, Draughton and Bolton 

 Abbey, Hetton and Eshton Moor. The beds are very sharply 

 arched over at llain Hall, and again at Skibeden, east of Skipton, 

 and there are many minor folds. 



It is, then, quite in keeping with expectation when we find 

 Swinden, Elbolton, and Stebden showing much evidence of great 

 disturbance. Dr. Marr was quite right in insisting on the fact 

 that the knoll beds are much disturbed. 1 The great knolls of 

 Elbolton and Swinden are probably homologous with the Skibeden 

 Hill in the next valley and with the rounded hills of the Rain Hall 

 region • but the great difference in the lithology of the folded beds 

 has been the cause of great difference in the way in which they 

 have weathered. I have, in an earlier paper, pointed out how 

 the beds at Downham and Chatburn have been dissected by longi- 

 tudinal and transverse streams into prominent knoll-like masses. 

 The same general results of weathering must, cceteris paribus, have 

 been produced in the district under consideration. But at Downham 

 and Chatburn the coarsely bedded limestone dips steadily to the 

 south ; here the same limestone (with the same assemblage of 

 fossils) is much more sharply folded. Hence some of the difference 

 in the aspect of the knolls. 



The coarsely-bedded limestone, especially when it is largely 

 made up of masses of shells, is very permeable, even when it is not 

 conspicuously jointed, and thus such masses resist denudation, and 

 I think it is demonstrable that the evenness of the erosion and the 

 lowering of the folded beds of the whole of the Craven Lowlands is 

 proportional to the fineness of the structure of the limestone. 



I submit that the ' quaquaversal dip ' theory as due to original 

 deposition can no longer be maintained. If, in any given hill, the 

 dips seem to be of that nature, it is due to folding and not to 

 deposition, and there would seem to be as little call for such a 

 theory to explain the sharp dips of these highly folded beds as 

 there would be to adopt it for the fine-grained foraminiferal lime- 

 stones of the neighbouring districts. 



In the whole district the general nature of the folding is the 

 same v but the lithology of the beds varies greatly ; hence the folding 

 and the subsequent denudation have produced results so markedly 

 different. 



1 Quart. Journ. Geol. Soc. vol. lv (1899) pp. 331-38. 



