The Carboniferous Limestone of West Cumberland. 125 



Quarry in Northumberland revealed such striking resemblances of 

 bedding, fauna, and general appearance to the First Limestone of 

 "West Cumberland as to force the conclusion that they are one and 

 the same bed. The fauna of the smaller limestones below the 

 Great to the Scar Limestone is not distinctive enough to be readily 

 correlated, but black chert is common in beds of both areas and 

 zaphrentids are noticeable corals. The Scar Limestone, which is 

 one of the thicker limestones of the Alston Moor area, and lies 

 about 250 feet below the Great Limestone, has a rich fauna ^ that is 

 comparable with that of a massive bed near the top of the Fourth 

 Limestone, Lonsdaleia duplicata alstonensis S. Smith being typical 

 in both Alston Moor and West Cumberland. 



Saccammina carteri Brady occurs in three of the beds of the 

 Fourth Limestone ; the lowest of these beds is here correlated with 

 the Tyne Bottom Limestone, wherein is the lowest known occurrence 

 of Saccammina in the Alston area. Similar faunas obtain. 



The Algal Band with Girvanella sp. occurring at the base of the 

 " Rough Beds " of the Fourth Limestone marks the next common 

 horizon, it being correlated with the Girvanella Band of Garwood, 

 which has been found by him in the lowest Yoredale limestone of the 

 Roman Fell area.^ 



The limestones below present no striking similarities until the 

 lower portion of the Fifth Limestone and the upper portion of the 

 Melmerby Scar limestone are reached, where identical faunas present 

 themselves.^ These beds are marked by an abundance of the Di 

 corals, Dibunophylliim 6 and D. Vaughan, Koninckophyllum 

 Vaughan, Carcinophyllum 6 Vaughan, with a maximum of 

 CyatJiophyllum murchisoni Edw. & Haime. Lonsdaleia duplicata 

 w,ehnerbiensis S. Smith is typical in both areas and found at no other 

 level. The lower portion of the Melmerby Scar limestone can be 

 correlated with the Sixth and Seventh Limestones of our area.* 



The foregoing correlation suggests : — 



(1 ) That the Carboniferous sea already in possession of the South- 

 West and North-West Provinces converted our district into a lagoon 

 area during Upper Seminula times and slightly before submersion 

 of the Alston area. 



(2) That with the beginning of Dj times the rate of depression in 

 the Alston district was quicker than in West Cumberland, which was 

 farther removed from the source of detrital matter or else partially 

 cut off from it by a land barrier. The detrital deposits kept pace 

 with the rate of submersion and were much thicker towards the 

 north-east, and when for some reason the deposition of detrital 

 matter temporarily ceased it allowed a deposit of limestone to be 



1 Dr. Stanley Smith has given {Q.J.G.S., voL Ixxi, 1916, p. 242) the 

 characteristic fauna of the Scar Limestone. 



2 Garwood's North-West Province paper, p. 482. 

 » Dr. S. Smith, op. cit., pp. 242-3. 



* Cf. Garwood's North-West Province paper, pp. 481, 539. 



