F. Dixey — The Coal-measures of Clapton, Somerset. 313 



The Carboniferous Limestone forms a ridge which extends east- 

 wards from Clevedon to beyond Clapton in Gordano. On the northern 

 flank of this ridge lie two separate outliers of Coal-measures. 

 In the east, around Clapton in Gordano, the Coal-measures cover 

 a considerable area and constitute the Clapton Coal-field, but in 

 the west their outcrop forms only a narrow discontinuous strip 

 which extends as far as Clevedon. 



A glance at the Geological Survey map l of this district shows that 

 the relation between the Lower and Upper Carboniferous is an 

 abnormal one. In the neighbourhood of Clapton in Gordano, the 

 southern boundary of the Coal-measures transgresses the outcrops of 

 the Carboniferous Limestone, the Lower Limestone Shales, and the 

 Old Red Sandstone, and the Coal-measures enclose several small 

 patches of Carboniferous Limestone. Moreover, whereas the Lower 

 Carboniferous and older strata possess a variable but persistent 

 southern dip, the Coal-measures dip to the north and north-west. 



In the Geological Survey memoir on East Somerset and the 

 Bristol Coal-fields, 2 the Coal-measures of the Clapton area are assigned 

 mainly to the Pennant Grit or Middle Series of the Bristol and 

 Somerset Coal-fields. The only reference made to the anomalous 

 relation of the Coal-measures and the Carboniferous Limestone is 

 contained in the following passage 3 : " Around Clapton in Gordano 

 are several patches of Carboniferous Limestone occurring in the 

 midst of Coal-measures, positions which it seems difficult to 

 account for." 



Professor C. Lloyd Morgan maintained 4 that the small isolated 

 masses of Carboniferous Limestone are the remnants of a sheet of 

 Carboniferous Limestone which was carried down over the Coal- 

 measures by a "flat-lying fault ". 



Dr. A. Vaughan, however, in his paper on the Carboniferous 

 Limestone of the Bristol area, 5 wrote as follows: "I am strongly 

 inclined to believe that there is, in this region, evidence of post- 

 Tournaisian upheaval and denudation, and that the area was not again 

 submerged until the Coal-measures were laid down in a narrow 

 inlet, bounded on the west by the Clevedon-Portishead ridge and on 

 the south by the western part of the Clevedon-Failand ridge. Within 

 this inlet, the masses of Carboniferous Limestone in the Clapton 

 district stood up as small islands." 



My own observations in this district confirm the unconformable 

 relation of the Coal-measures to the Lower Carboniferous and the 

 Old Red Sandstone. It is evident that, in Carboniferous times, the 

 district suffered not only considerable folding, but also much faulting, 

 as shown by the relative position of the ' islands ' and main outcrop 

 of the Carboniferous Limestone. 



1 Sheet 19 (Old Series), Somersetshire. 



2 Geology of East Somerset and the Bristol Coalfields (Mem. Geol. Surv.), 

 1876, p. 45. 



3 Ibid., p. 42. 



4 "Geology of the Avon Basin (Portbury and Clapton Districts) " : Proc. 

 Bristol Nat. Soc, N.S., vol. v, 1885-8, p. 44. 



6 " Paleeontological Sequence in the Bristol area " : Q.J.G.S., vol. lxi, 1905, 

 p. 232. 



