A. J. Jukes- Br oivne — Loiver Carboniferous in Devon. 353 



II. — The Lower Cakboniferous Problem in Devonshire. 



By A. J. Jukes-Browne, B.A., F.G.S. 



'HAT represents the Carboaiferous Limestone in Devonshire, 

 is a question that has often been asked, but has never yet 

 been answered in a satisfactory manner. The question has recently 

 been nai'rowed by the identification of the Coddon Hill Beds and 

 the Posidonomya liirestones with the shales, cherts, and limestones 

 which overlie the mass of the Carboniferous Limestone in South 

 Wales,^ and with the Pendleside Beds which occupy a similar 

 position in Staffordshire, Derbyshire, and South Yorkshire.^ Dr. W. 

 Hind considers these beds to be more intimately connected with the 

 Upper than with the Lower Carboniferous Series, and in any case 

 the homotaxial equivalent of the main mass of the Carboniferous 

 Limestone must be sought for below them. 



If the upward succession from the Pilton Beds be continuous and 

 unbroken — and there is good reason to believe that it is so near 

 Barnstaple and again near Bampton — the question has now been 

 narrowed down into small limits ; for the whole Lower Carboniferous 

 Series must in that case be represented either solely by the narrow 

 band of dark shales (Fremington Beds) which intervenes between 

 the Pilton Beds and the chert beds of Coddon Hill, or else by 

 these shales together with a certain portion of the Pilton Beds. 

 Further research may reveal a purely Carboniferous fauna in the 

 higher part of the latter, but hitherto no such exclusively 

 Carboniferous assemblage has been found in them, and the problem, 

 so far as North Devon is concerned, remains as much of a puzzle 

 as ever. 



Hitherto, however, the problem has always been attacked by 

 comparing the succession in North Devon with that of areas further 

 north, and endeavouring to find equivalents for the limestones and 

 shales of the Lower Carboniferous Series which have so great 

 a development over both England and Ireland. In other words, it 

 has been tacitly assumed that this series must not only be repre- 

 sented in Devon, but that the thickness of its representative must 

 be comparable to that of the more northern facies, whether that of 

 the Bristol area, or of South Wales, or of the south of Ireland. 

 This assumption involves the further supposition that the 

 Carboniferous sea continued to be as deep or even deeper to the 

 southward than it was along the latitude of South Wales and South 

 Ireland, so as to allow of the deposition of a similar thickness of 

 sediment. 



These assumptions may have hindered the solution of the problem, 

 and it has occurred to me that it might be profitable to approach the 

 question from the south ; for if the representative of the Lower 

 Carboniferous Series on the southern side of the great Culm- 



1 See Summary Prog. Geol. Survey for 1900, p. 87. 



2 By Dr. Wheelton Hind in Geol. Mag., Dec. V, Vol. I, p. 392 (1904). 



DECADE v.— VOL. II. — NO. VIII. 23 



