THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE V. VOL. III. 



No. XI. — NOVEMBEK, 1906. 



I. — On the Stratigraphtoal Kelations of the Dufton Shales 

 AND Keislet Limestone of the Cross Fell Inlier. 



By J. E. Mark, Sc.D., F.K.S. 



A'OTWITHSTANDING all that has been written concerning the 

 i\ Keislfj Limestone, its exact relations with the older Dufton 

 Shales have never been clearly ascertained. I accordingly devoted 

 a few days of the Easter vacation to the study of these relations 

 in company with Messrs. W. G. Fearn sides, R. H. Eastall, and 

 T. 0. Bosworth, whose help I gratefully acknowledge. 



For many years the Dufton and Keisley groups were referred to 

 the ' Coniston Limestone,' and no attempt was made to separate them, 

 although it was clear that the great differences existing between 

 them required explanation. In a paper by the late Professor 

 Nicholson and myself " On the Cross Fell Inlier " ^ we remarked of 

 the Keisley Limestone, " the occurrence of some forms which have 

 not been found nearer than the Chair of Kildare may indicate that 

 we have here a fossil zone which is not represented by fossiliferous 

 beds in the central pai"t of the Lake District." 



In a paper on "The Coniston Limestone Series " ^ I divided this 

 series into three groups, namely, the Ashgill Group at the top, the 

 Sleddale Group in the centre, and the Roman Fell Group at the base, 

 placing the Keisley Limestone in the central and the Staurocephalus 

 Limestone in the upper group. Furthermore, I stated (p. 101) that 

 if the suggestion that the representative of the Keisley Limestone 

 occurs at the top of the ordinary Sleddale Limestone in the main 

 part of the Lake District be correct, "a further division of the 

 Applethwaite Group may be made into a lower stage characterized by 

 the ordinary Applethwaite fauna, and an upper stage characterized 

 by the fauna of Keisley and the Chair of Kildare." This Applethwaite 

 Group, it should be stated, is the upper division of the Sleddale 

 Group. 



1 Quart. Joum. Geol. Soc, toI. xlvii, p. 511. 



2 Geol. Mag., Dec. Ill, Vol. IX, p. 97. 



DBCADE V. yOL. III. — NO. XI. 31 



