14 V. C. DA VIES ON THE UPPER CARBONIFEROUS 



The thickness of this series of sandstones is very great; it has been 

 estimated by Mr. Hull* at 1500 feet ; and possibly it reaches that 

 thickness ; but it is difficult to define the uppermost limit of the group, 

 as it appears to graduate into the overlying Bunter, as may be seen 

 by following the ravine Shellbrook upwards towards the S.E. 



These sandstones have recently been bored through near the village 

 of Whittington, two miles N.E. of Oswestry, and six miles south of 

 the Dee-side section. The boring, after leaving the drift, passed 

 through bright red soft sandstone belonging to the " New Red," and 

 entered these dark sandstones, which proved to be 620 feet thick. 

 They there consist of coarse- and fine-grained dark red and brown 

 sandstones, occasionally streaked with white ; and near their base there 

 is a bed of white rock 2 feet thick. With the exception of a thin 

 bed containing a few fragments of darker rock, there are no con- 

 glomerates or brecciated beds ; at this point these upper sandstones 

 rest immediately upon the lower portion of the red marls of group 

 3, the Ifton Coal-measures and the upper portion of the red marls 

 being absent. At Croeswylan, two miles south of this boring, these 

 upper sandstones have thinned out to about 70 feet in thickness, and 

 they rest upon the red marls. AtLlynclys, two miles to the south of 

 Croeswylan, they rest immediately upon the Carboniferous Limestone 

 and Millstone Grit. At Alberbury, seven miles S.E. of Llynclys, they 

 cover the calcareous conglomerate for which that place is celebrated. 

 I have been careful to trace these upper sandstones in their pro- 

 gress southwards, because of their bearing upon the inferences to be 

 drawn presently as to their true stratigraphical position. 



In the year 1859 I describedf the coal-seams at the top of group 3, 

 section 11, as ordinary Coal-measures, and I argued from them for an 

 extension of the Coal-measures eastward ; for I should here observe 

 that in the maps of the Geological Survey the boundary between the 

 Coal-measures and the Permian crosses the horizontal section at 

 point A (PL I. B). In 1869 Mr. HullJ, in speaking of the red marls, 

 group 3, as seen at Newbridge and at Hafod-y-bwch Colliery, de- 

 scribes them as Upper Coal-measures, and he begins the Permian at 

 the base of the dark sandstone of the Dee, group 4, section 11. 



Subsequently to the publication of my paperf in 1859 I observed 

 from time to time the unconform ability of groups 2 and 3 to the un- 

 derlying Coal-measures — an unconformability amounting sometimes 

 to between 700 and 800 feet; I noticed also the identity of the red 

 marls of group 3 with those mapped as Permian at Plassau, N.E. 

 of Puabon, and elsewhere. On reading the description by the late 

 SirP.I.Murchison and Prof. Harkness§ of the Permian strata of the 

 N.W. of England, I was struck with the similarity of the plant- 

 remains of the shales in group 3 of their section No. 3, to those 

 found at Ifton, section 11 in the same group, as well as with the re- 



* Triassic and Permian Kocks of the Midland Counties, p. 22. 

 t "On the Eastern Boundary of the North Wales Coal-field," Proceedings 

 ©f the Geologists' Association, vol. i. p. 14. 



| The Triassic and Permian rocks of the Midland Counties, p. 22. 

 § Quart. Journ. Geol. Soc. vol. xx. p. 144. 



