104 J. E. Marr — The Coniston Limestone Series. 



Further details concerning tlie beds of this area will be found in the 

 paper by Professor Nicholson and myself which has been alluded to 

 previously. 



The beds of the Sedbergh District are generally comparable 

 with those of the Cross Fell inlier, i.e. the Sleddale Group assumes 

 the facies of the Dufton Shales more closely than that of the region, 

 around Windermere and Coniston. The Calcareous Shales of Sally 

 Beck south of Eavenstonedale are closely comparable with the 

 Dufton Shales of Cross Fell. The Stain-ocephalus Limestone has 

 not yet been detected in these regions, though the Ashgill Shales 

 are developed in force ; indeed the characteristic Brachiopod of these 

 shales — Strophomena sihiriana, Dav. — is figured in Mr. Davidson's 

 Monograph from specimens obtained at Fairy Gill. In the centre of 

 the Ashgill Shales a very calcareous grit is found (cf. Marr and 

 Nicholson, Q.J.G.S. vol. xliv. p. 700), as seen at Backside Beck.^ 



The rocks of the Settle district have been referred to by me in 

 a paper published in this Magazine (Dec. III. Yol. IV. p. 35). The 

 Applethwaite Group has the facies of the Dufton Shales, though a 

 band of ashes is interstratified with the calcareous shales. The 

 Staurocephalus Limestone has not been detected, though the Ashgill 

 Shales are seen in the stream south of Wharfe, for I have found 

 fossils of this age in the beds numbered "4. Blue, flaggy Brachiopod 

 shales," in the paper referred to. Though the relationship of the 

 Coniston Limestone Series to the representatives of the Stockdale 

 Shales is perfectly clear in this neighbourhood, the true relations 

 of the former to the Ingleton Green Slates is by no means clear. 

 We have seen that in the central part of the Lake District the 

 Coniston Limestone rests sometimes on the Skiddaw Slates, and not 

 on the Borrodale rocks. Now the only reason why the Ingleton 

 Green Slates have been referred to the Borrodale Series is because 

 they are made up of volcanic detritus, and are immediately succeeded 

 by the Coniston Limestone Series. As the latter fact does not prove 

 their age, we can only point to the occurrence of volcanic detritus 

 as a proof of the correctness of the correlation. The lithological 

 resemblances, however, are very slight, and the volcanic detritus 

 may be derived from rocks of any age. I am inclined to think 

 that these Ingleton Green Slates may be older than any other beds 

 hitherto recorded from the English Lake District, for there are 

 grave difficulties in the way of correlating them with the Borrodale 

 Volcanic Series. 



* Since ■writing the above I have received the Survey Memoir of Quarter- Sheet 

 97 N.W. The contemporaneous volcanic series of Backside Beck and Wandale 

 occurs at a higher horizon than that of any of the contemporaneous lavas hitherto 

 detected in other parts of the district, with the possible exception of that running 

 from_ Kentmere to Shap, and separating the Stile End Limestone from the Apple- 

 thwaite Beds. It seems to occur high up in the Sleddale Group, and it wilf be 

 remembered that contemporaneous volcanic ashes are found at the very summit of 

 this group in the Coniston area. Mr. Strahan records the occurrence of a grit in 

 the Ashgill Shales on a position corresponding to that of the above-mentioned 

 calcareous grit, both in Taiths Gill and Birk's Field Gill. 



The thickness of the Ashgill Shales recorded in Fairy Gill is exceptional. 



