﻿Vol. 66.] LIMESTONE SOUTH OP THE CKAVEN FAULT. 565 



Series is here very thin, for the grits come on in the dam side a 

 little farther up. 1 



In the impure limestone bed above the concretionary shales occur, 

 among other fossils, Productus aff. pustulosis, Sjyirifer bisulcatus, 

 Bhipidomella michelini, and a species of Lithostrotion (? m'coyanum). 

 A crushed Caninia or Campophyllum is also present, but it is not 

 possible to identify it from the material that I have seen. 



The distance from the point at the entrance to the Gill, where the 

 highest limestone probably occurs, to the turn-over of the beds is 

 1800 feet. The average dip may be taken at about 12° to 14° : 

 hence the thickness of the beds may be approximately 400 feet. 

 Measured in the opposite direction, the thickness does not seem 

 quite so great, perhaps about 300 feet. It is not, however, easy 

 to determine where to locate the centre of the anticline, and 

 how much precisely to allow for diminishing dip as the middle is 

 approached. 



Some General Notes. 



The change in lithology. — There is a marked change in the 

 lithology of beds on or near the same horizon, as they are traced 

 laterally. From Troller's Gill, through Appletreewick, to near 

 Burnsall, most of the strata are distinctly well-bedded and fine- 

 grained, with a tendency towards coarser beading in the upper strata 

 as we get nearer to Burnsall. The comparatively coarse crinoidal 

 limestone of the upper beds of Appletreewick gradually gives place 

 to mixed crinoidal and shell breccias towards Elbolton and Swinden. 

 Here the coarseness of the bedding and the difficulty of determining 

 the dip is accompanied by the profusion of loosely cemented shells 

 which makes these knolls so excellent a collecting-ground. 



' As the beds are followed westwards, the finer- grained lower white 

 and grey limestones of Appletreewick become well-bedded bluish- 

 black limestones at Burnsall. Farther west, beyond the knoll 

 region, the whole of the beds are of this character, with the excep- 

 tion of a comparatively limited, but variable bed of crinoidal and 

 shell breccia, such as is seen at Crag Laithe and Fogger. This 

 occurs near the top of the limestone massif, and seems to be homo- 

 taxial with the muddy crinoidal limestone of the Thornton and 

 Broughton region, and with the famous crinoidal limestone of 

 Clitheroe. 



The remarkable change in the lithology of the upper beds is well 

 seen, as one traces them from the comparatively thin shell-and- 

 crinoid beds in the upper part of the Ilylstone Eailway Quarry, to 

 the richly fossiliferous beds of Elbolton, the richness of which in 

 fossils (and also the apparent thickness) is somewhat augmented, 

 as I believe, by folding. Midway between these extremes, at 

 Skelterton Knoll, near Cracoe, the upper crinoidal and shell breccias 

 occur at the top of beds which are, for the most part, composed of 



1 See Wheelton Hind & J. A. Howe, Quart. Journ. Geol. Soc. vol. lvii 

 (1901) p. 363. 



