Yol. 54.] THE COEALLIAN KOCKS OF FPWARE. 601 



40. Oa the Corallian Eocks of Upwaee (Cambs). By C. B. Wedd, 

 Esq., B.A. (Communicated by J. E. Maee, Esq., M.A., F.E.S., 

 E.G.S. Eead June 22nd, 1898.) 



As any small addition to our knowledge of this interesting district 

 may be acceptable, and as I have lately spent much time at Upware 

 and had access to sources of information too seldom available in the 

 district, it seemed advisable to put on record such new facts as have 

 come to light. The IJpware rocks have been so often described by 

 different geologists, to all of whom I am under some obligation, 

 that it is perhaps unnecessary for me to do more than express my 

 especial indebtedness to the important work of Messrs. Blake & 

 Hudleston on the Corallian Eocks of England,^ to that of Prof. 

 Bonney,^ to that of the late Mr. T. Eoberts,^ and to the maps and 

 memoirs of the Geological Survey relating to Upware.* 



The Avell-known Corallian ridge of Upware is 3 miles long, as 

 mapped by the officers of the Geological Survey, and less than a mile 

 wide in the widest part, and is nearly surrounded by fen. There 

 have long been two principal exposures of the rock : one, the 

 Northern Quarry, in oolitic rock ; the other, the Southern Quarry, 

 in ' Eag ' and oolite. Part of the intervening area on the western 

 jQiank of the ridge is covered with Gault and Lower Greensand (see 

 sketch-map, p. 612). Except a few ditch-sections in the lane 

 between the two quarries, there have been till lately no other 

 exposures of importance. The relation of the oolite of the Northern 

 Quarry to the Eag of the other was long a matter of uncertainty. 

 The Northern oolite was at first considered the higher, owing 

 to the slight northerly dip in both quarries. Messrs. Blake & 

 Hudleston placed it below the Eag for palaeontological reasons. 

 Mr. Eoberts mentioned that the Eag showed signs of oolite beneath 

 it, in which the characteristic sea-urchins of the Northern Quarry 

 occurred, and that this oolite came up towards the south. In the 

 Geological Survey Memoir of the district (1891) it was stated that 

 oolite underlay the Eag in the Southern Quarry. 



As now seen, by far the greater part of the rock of the Southern 

 Quarry is oolite or pisolite. This quarry is about 190 yards long. 

 At the southern end, where the surface is about 5 feet lower than 

 at the middle of the digging, the lowest beds are seen, a rather 

 rubbly yellowish-white rock, consisting of a soft calcareous, marly- 

 looking matrix, full of oolite- or rather pisolite-grains. It is 

 exposed in the southern end for about 5 J feet downwards from the 

 surface, and is much less fossiliferous than the higher beds of oolite. 

 In this quarry the dip is northerly, and for the most part at a small 

 angle. In the eastern bank, which is overgrown with grass, the 



1 Quart. Journ. Geol. Soc. vol. xxxiii (1877) pp. 260-404. 

 ^ ' Cambridgeshire Geology,' 1875. 



^ ' Jurassic Eocks of Cambridge,' Sedgwick Prize Essay for 1886 (1892). 

 * More especially the tables of fossils published in the Memoirs on the 

 Jurassic Eocks of Yorkshire (1892) and the Jurassic Eocks of Britain (1895). 

 Q.J.G. S. No. 216. 2u 



