122 J. E. Marr — The Skiddaw Slates. 



V. — Notes on the Skiddaw Slates. 

 By J. E. Marr, M.A., F.E.S., Sec.G.S. 



THE Woodwardian Museum has for many years contained a fine 

 series of Skiddaw Slate fossils. In 1890 this was increased by 

 the addition of many specimens obtained by the members of Prof. 

 Hughes' Long Vacation party, and immediately afterwards the 

 University acquired, by donation, the valuable collection of the late 

 Mr. Kinsey Dover. Prof. Nicholson has also presented a large 

 number of Graptolites. When time permits, I hope to be able to 

 describe our unrivalled collection of Skiddaw Slate fossils ; mean- 

 while, a few notes on the distribution of these organisms will throw 

 such light ou the development of the Skiddaw Slates as is required 

 for the elucidation of the detailed structure of the district, a task 

 which Mr. Harker and I shall attempt to perform ere long. 



For a considerable period the Skiddaw Slates were unhesitatingly 

 correlated with the Arenig rocks of North Wales. The late Mr. 

 Clifton Ward was the first to return to the opinion, long ago formed 

 by Sedgwick, that representatives of much older deposits might occur 

 amongst these slates. In the volume of this Magazine for 1879 ' he 

 remarks : " The physical evidence inclines one to believe that the 

 Skiddaw Slates include the Arenig Slates, the Arenig Grit, the 

 Tremadoc Slates, and the Lingula Flags." Mi\ Ward drew up his 

 subdivisions almost entirely on physical evidence, and, indeed, 

 treated (as was customary at the time) the evidence yielded by the 

 Graptolites as of little practical utility. A study of these Graptolites 

 shows that he was quite correct in his view that the slates were not 

 entirely formed during Arenig times, but the actual divisions which 

 he proposed, as shown in the map and sections accompanying his 

 paper and in the explanations thereof, do not stand the pal^onto- 

 logical test. 



The term " Skiddaw Slates " has been used for all sedimentary 

 and contemporaneous volcanic deposits of the Lake District and 

 neighbourhood which lie below the great volcanic group known as 

 the Borrowdale Series, and in that sense it will be used in this 

 paper, though no attempt will be here made to discuss the character 

 of the junction between the two groups at diiferent places. 



Although the general use of the term has been as above, never- 

 theless other deposits, which are undoubtedly of very diff"erent age, 

 have been at times included in the Skiddaw Slates, as, for instance, 

 the Drygill Shales, described by Prof. Nicholson and myself in this 

 Magazine.^ 



The main outcrop of the Skiddaw Slates lies north of the mass of 

 volcanic rocks constituting the central hills of Cumbria, and, owing 

 to the existence of an anticlinal fold, separates those volcanic rocks 

 from their equivalents in the Caldbeck Fells and the comparatively 

 low country north of Bassenthwaite Lake. This outcrop appears to 

 be continuous (though in one place covered by the Carboniferous con- 



1 Geol. Mag. 1879, Dec. II. Vol. VI. p. 124. 



2 Geol. Mag. 1887, Dec. III. Vol. IV. p. 339. 



