332 Wilniorc : The Limcs/oiic Kno/is of C^ raven. 



The following types of knolls may be recog"nised : — 



(rt) Those in the g^iey or bhiish-while limestone. Sonic of these 

 are well-beddcd and very fos.silifcrous ; some are obscurely 

 bedded ; some are not apparently very fossiliferoiis. 



[b) Those in the dark limestones with niimeroiis shales ; these knolls 



are lower and more rounded. 



(c) Scar-knolls ; truncated folds weathered into semi-rounded and 



more or less detached masses. These vary from small crags 

 through large peninsular masses to long' scar-like ridges. 

 These ma)- be in the wliite or dark limestones. Sometimes a 

 scar-knoll has been detached from llie main mass of limestone 

 by weathering. 



There are gradations of ev-ery degree connecting these 

 types. 



Examples of all these types of knolls occur on one well- 

 defined horizon. They may all be seen striking- parallel with 

 the Pendleside shales containing" Posidononivd becJicri, Posi- 

 dotiiella Icevis^ Avicnlopecten papyraceiis, and immediately- 

 succeeded by these shales. The succession may be seen at 

 Cracoe and Thorpe, Stockdale, Newsholme, Broughton and 

 Thornton, Downham, Slaidburn. 



The knolls are most conspicuous on the margins of the 

 district. They are seen close to the faults at Threshfield, Mal- 

 ham, Attermire, Stockdale, and Bell Busk. Against the grit 

 ridges on the southern side they are well developed at Thorpe 

 and Cracoe, Broughton and Thornton, and near Downham. 



It is noteworthy that knoll-like masses are seen north of the 

 Grassington branch of the Craven faults, at Craven moor, and 

 near Dibble's Bridge. Here the massive white limestones come 

 up with a much greater dip than is usual north of the faults. 



The whole district is much folded. There are w'ell-defined 

 folds with N. E.-S.W. axes intersected by less conspicuous folds 

 parallel to the main Pennine axis. The interference of these 

 fold-systems seems to have directly produced some of the knolls. 

 Folding is seen everywhere, in both the dark and the white 

 limestones ; though the well-bedded dark limestones naturally 

 show it best. Minor faults are common, and some of the knolls 

 appear to be due in part of faulting. 



The more massive knolls of while limestone appear to be 

 due to irregular aggregations of submarine debris. Folding 

 has ridged up these massive limestones, and weathering has 

 intensified the difference between these and the commoner 

 knolls of the district. The smaller knolls are due to folding 

 and subsequent weathering. 



Naturalist, 



