Mr. C. Lapworth on the Moffat Series. 73 



narrow bands of black carbonaceous and Graptolitic shales, which, 

 from their especial abundance in the neighbourhood of the town of 

 Moffat, Dumfriesshire, are known to geologists as the Moffat Shales 

 or Moffat Series. 



The most perfect section of the black shales visible within the 

 Moffat area is exhibited in the cliffs of the gorge of Dobb's Linn, at 

 the head of Moffatdale. It was shown by the author that they are here 

 disposed in a broken and partially inverted anticlinal, which throws 

 off on both sides the basal beds of the surrounding non-fossiliferous 

 greywackes. They are distinctly arranged in three successive groups 

 or divisions. Each of these divisions is distinguished by special 

 lithological characteristics, and possesses a distinct fauna. To the 

 lower and middle divisions a few fossils are common ; but between 

 the middle and upper divisions the palaeontological break is com- 

 plete. These divisions, again, are naturally subdivided into several 

 zones, each characterized by special species or groups of species. 



A larger exposure of the same deposits occurs at Craigmichan, a 

 few miles to the south-west, where the beds of the lower division 

 are shown to a much greater depth than at Dobb's Linn. In these 

 two localities the general succession of the Graptolitic shales is as 

 follows : — 



feet. 

 (c) Birlihill { fl \ TJ x>- i 1 mi f Grey and purple flagstones, with 



V ' Shales, or < 6 > U PP er BirMn11 \ lines of black and white shale . 70 to 80 

 Upper ' / \ T Ti- 1 1 -n j Black pvritcus shales, with seams 



Moffat. { (a) L ° Wer ElrMnU 1 of brightly coloured clays 60 to 70 



(b) Hartfell 1 , -n , - .,. 



1 ) Shales,ov (5) Upper Hartfell { Pa f le ^ °* / reen ^-fossili- 



TWrni I- ierous mudstones 45 



TVI" 1 W t ( a ) Lower Hartfell Black hard slaty shales and flags 40 to 50 

 (a) GlenkibbS [ Yellow and grey shales and flags, 



' I 



8hales,or | J non-fossiliferous, with a few 

 Lower f 1 bands of soft black Graptolitic 

 Moffat. I shales 150 



With the aid afforded by these sections, the thorough investigation 

 of the ten subparallel black shale-bands of the Moffat area is ren- 

 dered a matter of ease and certainty. Of these, the four bands 

 lying to the south-west of Saint Mary's Loch are the most con- 

 tinuous. They were described in detail by the author ; and it was 

 shown that in each the only strata apparent are indisputably those 

 of the type sections of Dobb's Linn and Craigmichan, with which 

 they agree zone for zone in sequence and in all their characters, 

 mineralogical and zoological. Here, also, the beds are arranged in 

 greatly elongated anticlinal foims, the axes of which are, as a rule, 

 inverted. In any single transverse section, the succession of the 

 beds on the opposite sides of the median line of the band is identical ; 

 and the highest zone of the black shales everywhere passes up con- 

 formably into the basal bed of the surrounding greywackes. The 

 varying width of the band is dependent simply upon the var} T ing 

 elevation of the crown of the anticlinal. Where the band is of least 

 diameter, only the highest beds of the Birkhill shales rise from 

 below the greywackes. As the band expands, the underlying zones 



