374 PROCEEDINGS COTTESWOLD CLUB 1912 



The bed of coarse gravel (No. VI.), in which at a depth 

 of about 12 feet the water-level was reached and further 

 excavation was prevented, is composed mainly of well-rounded 

 pebbles of quartzite and other rocks usually found associated 

 with the Bunter Drift near the Severn in this district. 

 The only Jurassic fragment found in this bed is a much water- 

 worn piece of the shell of a Gryphc^a arciiata. In a trial- 

 boring made some time previous to my visit, it was ascertained 

 that a thin bed of coarse sand intervened between the gravel 

 and the underlying Lower Lias rock. 



Many of the irregular shaped masses in No. III. consist 

 of Oolitic debris ; others are fine quartzose sand and a few 

 are clay. An angular boulder of the latter found at 9 feet 

 from the surface measured 4 feet in length and 10 inches in 

 thickness. 



That the enclosed masses are really isolated and not 

 sections of beds of lenticular shape I ascertained by examin- 

 ing several of them in trenches cut at right angles to one 

 another. 



Widely different conditions are indicated by the coarse 

 and fine sediments, but they may have been deposited within 

 a short period from shifting currents flowing into a lake or 

 estuary receiving alternately the characteristic debris trans- 

 ported into the area from the Severn, Teme, Avon, and 

 Leadon Valleys towards the close of the Glacial Epoch. The 

 conversion of the area into a lake by a barrier that may never 

 have been sufficiently high to dam the torrents completely 

 would provide favourable conditions for the conveyance of ice- 

 floes detached from the shore of a lake or the banks of a 

 river during seasonal or other changes of climate. On melting, 

 the floes would release their burdens of detritus, and some 

 portions still in a frozen state would sink down to the soft 

 sand and clay, pressing the surface into wavy lines or becom- 

 ing completely embedded. The breaking up of other masses 

 on sinking would account for the production of irregular 

 seams. 



It is not improbable that in times more recent than the 

 Glacial Epoch frozen masses of gravel and sand were carried 



