454 T. M. EEADE ON THE ACTION OF LAND-ICE 



32. Evidence of the Action of Land-Ice at Gkeat Crosby, Lanca- 

 shire. By T. Mellard Eeade, Esq., C.E., E.Gr.S. (Read 

 May 13, 1885.) 



(Abridged.) 



In previous papers* I have described a deposit of rubble-debris 

 and red sand lying on the Triassic rocks and underlying the Low- 

 level Boulder-clay and sands in the neighbourhood of Liverpool, 

 which I suggested was due to the grinding and crushing action of 

 land-ice. I also pointed out that where this deposit did not occur, 

 the rocks, as is well known, are usually polished, grooved, and striated. 

 Until lately no opportunity has occurred of testing the validity of 

 this view by reference to any other than sandstone rock that such 

 land-ice may have moved over f- 



In October 1884 I described, in the ' Geological Magazine,' a 

 section of Keuper marls at Great Crosby previously unknown, and 

 since then I have made frequent observations of the upper part of the 

 marls in relation to the Low-level Boulder-clay that overlies them. 



Prom time to time as the excavations have proceeded, it became 

 clearly apparent that the upper part of the marls had been from 

 some cause or other much disturbed. There were imbedded in it 

 large angular and sometimes nearly square blocks of sandstone. 

 These were not merely pressed into the surface, but actually 

 imbedded in the marl at all angles. In the undisturbed marls are 

 well-defined bands of a harder nature, and one of these bands was 

 at one place broken up and contorted, the fragments displaced, and 

 irregularly forced into and amongst the worked-up softer marls or 

 shales (see fig. p. 455). This was very striking, as the band con- 

 tinued in an undisturbed condition towards the south-west J. 



As fresh faces were disclosed by the progress of the excavations, 

 it could be distinctly seen that in some cases the upper soft fissile 

 marls had been forced up into contortions. The thickness of the dis- 

 turbed bed was from 3 to 4 feet. 



The imbedded sandstone blocks were of two kinds : one a very fine- 

 grained grey rock slightly micaceous ; the other composed of coarsely 

 rounded grains, mostly quartzose. They are evidently sandstones 

 belonging to the Keuper series, though not found in this pit in situ. 

 Neither are they exactly like any of the Lower Keuper sandstone 

 beds found in the quarry at Little Crosby, about one mile and a half 

 to the north-west. I am of opinion that they belong to beds under- 

 lying those at the bottom of the pit, which at the north-east side 

 approach in structure the coarser of the two sandstones. 



* " Drift deposits of the N.W. of England," Quart. Journ. Geol. Soc. vol. 

 XXX. p. 27 ; and vol. xxxix. p, 122. 



t Mr. Stralian, in his Survey memoir of the ' Geology of the Country around 

 Chester,' 1882, says " There is evidence of the passage of a heavy body over the 

 ground in the crushing and drawing out of soft beds as if by pressure " (p. 29). 



X The contortion of the beds below the eroded line in the section I consider 

 to be due to earth movements. 



