THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. VIII. 



No. X.— OCTOBER, 1881. 



L — On the Discovert of Coal-measures under New Eed Sand- 

 stone, AND on the so-called Permian Rocks of St. Helens, 

 Lancashire. 



By A. Steahan, M.A., F.G.S. ; 

 of H.M. Geological Survey. 



DUEING the last few years the Coal-measures have been reached 

 through the overlying New Eed Sandstone in three collieries, 

 and in three bore-holes, in that part of South Lancashire which lies 

 between the St, Helens and Wigan Coal-fields and the Eiver Mersey. 

 The results were in some degree unforeseen, as the Trias was thinner 

 than might have been expected, while it seems likely that the 

 Permian formation is altogether absent. 



In the eastern part of this district, the Permian rocks, proved in 

 the shaft at Edge Green, and identified by Mr. Binney,^ overlie the 

 Coal-measures, and, the Lower Mottled Sandstone being absent, 

 are succeeded by the Pebble Beds of the Bunter. To the westward 

 they are overlapped by the Pebble Beds, which then rest on the Coal- 

 measures ; but proceeding in the same direction, the Lower Mottled 

 Sandstone comes in, appearing first at Ashton, and extending thence 

 all along the southern boundary of the Coal-field. The Permian 

 rocks, after having been overlapped for a distance of about five miles, 

 were believed to reappear from beneath the Trias at St. Helens 

 Junction, the evidence of this consisting in the identification by Mr. 

 Binney of a bed of shale, 30 feet thick, and an underlying soft sand- 

 stone about 90 feet thick, as Permian Marl and Lower Permian 

 Sandstone respectively. The marl was met with in a well, but the 

 sandstone is exposed in a quarry. It is " altogether undistinguish- 

 able " from the Lower Mottled Sandstone, as stated by Prof Hull. 



On the strength of this appearance of supposed Permian rocks 

 from under the Trias, it was believed that this formation was pre- 

 sent under a large part of the Triassic area, and with a boundary 

 approximately coinciding with that of the Trias, but that, owing to 

 the unconformity of the two formations, the Permian was over- 

 lapped at intervals, so as not to appear at the surface at all. 



From this interpretation of the country, it would have been 

 expected that on sinking through the Trias towards the south, a 

 more perfect development of the Permian would be found than 



^ Mem. Lit. and Phil. Soc. Trans, of Manchester, vol. xii. 



DECADE II. — VOL. VIII. — NO. X. 28 



