PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. II. 1836. No. 45. 



Feb. 24. — William John Prescott, Esq., of Threadneedle- street, 

 and Thomas CoUett, Esq., of the Inner Temple, were elected Fellov/s 

 of this Society. 



A paper was first read, entitled " Observations on a Patch of red 

 and variegated Marls, containing Fossil Shells, at Collyhurst, near 

 Manchester," by J. Leigh, Esq., and E. W. Binney, Esq., and com- 

 municated by Roderick Impey Murchison, Esq., F.G.S. 



Manchester stands on a slightly elevated platform of upper new 

 red sandstone ; but the country to the north-west, north, and east of 

 the town rises to a considerable height, and is traversed by the valleys 

 of the Irwell, the Irk, and the Medlock, which furnish the only natural 

 sections of the district. The formations exhibited in these valleys, and 

 supposed to extend under Manchester, are, first and lowest, the car- 

 boniferous group J secondly, the lower red sandstone and marls j 

 thirdly, the magnesian limestone ; fourthly, the lower red marl ; 

 fifthly, the upper red sandstone ; sixthly, the upper red marl ; and 

 seventhly, the superficial detritus. 



The principal object of the authors being to describe the upper red 

 marl, they notice briefly the characters of the other deposits. 



The accumulations of superficial detritus are sometimes thirty feet 

 thick, capping nearly all the high ground, and extending over the val- 

 leys. In the lower part they consist of water-worn fragments of gra- 

 nite, greenstone, porphyry, claystone, mountain limestone, and coal 

 measures, imbedded in sand ; and in the upper, of stiff" blue clay, 

 containing partially rounded fragments of the same rocks but of 

 greater size. Portions of the lower red sandstone and marl are some- 

 times found, but none of the magnesian limestone. Blocks of granite, 

 weighing two or three tons, occur on the summit of some of the hills 

 which surround the Irwell and the Irk. 



The lower red sandstone, the magnesian limestone, and lower red 

 marl are exposed at Worsley Mills and at Stockport, dipping conform- 

 ably with the coal measures ; but at the latter locality they are stated 

 to be overlaid unconformably by the upper new red sandstone. 



The immediate vicinity of Manchester consists of upper new red 

 sandstone, occupying the cavity formed by a flexure in the underlying 



VOL. II. 2 c 



