^^^- 55-] "^^^ CPvATEM DISTRICT OF TOEKSHIRE. 339 



brachiopoda, lamellibranchs, crinoids, corals, etc., many fairly 

 perfect.' ^ The crystalline nature of the limestone and the frequent 

 abundance of fossils in a beautiful state of preservation is, so far as 

 I know, a characteristic of knoll-structure not only in the Craven 

 district, but elsewhere, and it has been justly pointed out to me 

 i)hat, if the knolls were formed owing to marked earth-movements, 

 the perfection of the fossils is somewhat remarkable. The fossils, 

 however, are distributed in a very sporadic manner ; we often find 

 great masses of white crystalline limestone crowded with organisms, 

 while at other times similar limestones are apparently unfossili- 

 ferous. This holds good of all areas in which I have examined 

 knoll-structures. Sometimes a knoll is fossiliferous throughout, at 

 others unfossiliferous, while we often find parts of one knoll crowded 

 with fossils, and other parts of the same knoll yielding none. Now, I 

 shall endeavour to show that the knolls were formed where there was 

 relief from pressure, and as the result of this relief the crystalline 

 structure was developed, and the fossils were either destroyed, or, if 

 not destroyed, did not undergo distortion. 



The Settle knolls ^ occur immediately south of the Middle Craven 

 Fault, and are seen as a series of eminences between Settle, on 

 the west, and the head of the Stockdale Yalley on the east, where 

 the Millstone Grit abuts against the Scar Limestone north of the 

 faalt ; but a similar set of knolls is found against the fault in the 

 Malham Valley. These knolls, like those of Cracoe, are arranged 

 with a general linear trend, in this case parallel with the fault, though 

 they also occur in somewhat irregular groups. The structures ex- 

 hibited by them are similar to those seen at Cracoe, and no further 

 description of them is necessary at this point. A view of the knolls, 

 with the fault-escarpment in the background, is reproduced in 

 PI. XXIV, facing this page. 



I will now adduce various kinds of evidence in favour of the 

 formation of knolls as the result of marked earth-movements and 

 rock-folding. 



T have already described in detail the production of a structure 

 analogous to knoll-structure, and indeed, in my opinion, one which 

 is knoll-structure on an almost microscopic scale, in a thin limestone 

 interbedded with shale in the left anticline of Draughton Quarry 

 (p. 337). From a structure of this size all gradations may be traced 

 to the large knolls which sometimes rise to a height of 400 feet, and 

 in the case of the smaller knolls there is naturally more opportunity 

 of studying the characters than when viewing large knolls which 

 .frequently only exhibit superficial exposures, or, at best, sections 

 through portions of the knoll. Study of the smaller knolls shows 

 that they often vary in detail, but the general plan is the same ; 



1 Eep. Brit. Assoc. 1889 (N'castle-on-Tyne) p. 602. 



^ It is due to Mr. Tiddeman that I should state here that Ihe Craroe and 

 Downham knolls are the only knolls that I have examined which Mr. Tiddeman, 

 to my knowledge, has accepted as his ' reef-knolls.' I do not know whether he 

 would admit the Settle structures as such, though I endeavour to show that 

 they are similar to those observed in the neighbourhood of Cracoe. 



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