Ib'i Geological Society, 



development of a ribboned structure due to movement, while the 

 matrix in other varieties has become crystalline, as though under 

 relief from pressure. The limestone is squeezed into the softer 

 .shale-bands, and a thin limestone-seam which occurs in one of the 

 principal shale-beds is frequently repeated by faulting - , and in one 

 case is heaped up by repetition to form a miniature knoll, which 

 possesses many of the characters of the larger knolls. 



The prominent features of the knolls are the crystalline character 

 of the limestone, the horizontality of bedding in the interior of the 

 knolls, the general parallelism of the bedding of the exterior to the 

 contour of the knolls, and the obscurity of the bedding. Fpssils, 

 when present, are usually very perfectly preserved and undistorted ; 

 breccias are frequently found in the shales bordering the knolls and, 

 Jiiuch less commonly, in the limestone of a knoll itself. Evidence of 

 movement in the knolls is seen in the lenticular character of the 

 beds of limestone, in visible folded structures, the termination of 

 lenticular beds in hooks against a divisional plane, and in the shales 

 by the presence of a structure undistinguishable from cleavage. 

 Dolomitized and silicified limestones are frequently associated with 

 the knolls, and the perfection of the quartz-crystals in certain 

 examples of the latter variety of rock suggests crystallization during 

 relief of pressure. The breccias belong to three main types : — 

 (T) Fragments of limestone in a matrix of similar material ; 

 (2) large nodules of black limestone enwrapped in shales: (3) various 

 limestone-fragments in a tine calcareous paste. Examples of each 

 type are described, and each is explained as resulting from some form 

 of earth-movement. Breccias of similar types are found to be pro- 

 duced out of grit-fragments, and in places the grits are found to be 

 piled together by faulting so as to produce knolls, which somewhat 

 resemble those in the limestone. . • 



A comparison of the deposits in both sides of the faults enables 

 the author to suggest the following correlation of the beds : — 

 South Side. North Side. 



Millstone Grit. Millstone Grit. 



Bowland Shales. Shales above Upper Scar Limestone. 



Pendlesicle Limestone. Upper Scar Limestone. 



Shales with limestone. Yoredale Shales with limestone. 



Clitheroe Limestone. Lower Scar Limestone. 



The disparity in thickness of the limestone on the two sides will 

 not be so marked, if the explanation of knolls given in the paper be 

 correct. Dealing with the nature of the movements, the writer 

 argues that the Middle Craven Fault is an overthrust from the north, 

 and that the Limestone Series has undergone differential movements 

 with respect to the hard Lower Palaeozoic rocks beneath and the 

 massive Millstone Grit above. The limestones have been squeezed- 

 out from under the synclines, and they have accumulated under the 

 anticlines where the pressure was relieved. In conclusion, a number 

 of examples of knolls are cited from other localities which show 

 similar features, such as the limestones of Keisley, Millom, and 

 near Dalton-in-Furness, some of the Devonian limestones near 

 Torquay, the Leptan,a-limestone of Dalecarlia, and the Devonian 

 limestone of Koneprus in Bohemia. 



