STATHER : MILLEPORE OOLITE NEAR SOUTH CAVE. 
399 
about by the action of springs and the erosion of the valley of the 
Drewton Beck. There is likewise the possibility of the rocks being 
affected still earlier by a small strike fault. 
(2) A later displacement of the sheet of Millepore Oolite above the 
Glacial rubble at the top of the section, which must apparently be 
attributed to some kind of Glacial action. 
As to the mode of this Glacial action, no conclusion can at present 
be reached. The absence of boulder clay and the predominance of 
local detritus in the gravelly drift tell against the supposition that the 
transport is the result of the direct impact of the great Eastern Ice- 
sheet. It has, however, long been postulated that when the estuary of 
the Humber was blocked by this ice-sheet — of which the boulder clay 
at North Ferriby is beUeved to mark the moraine — the low ground west 
of the Yorkshire Wolds must have been occupied by a lake, to which 
the name " Lake Humber " has been applied.* There are several 
features in the South Cave section which suggest that the shore of this 
old lake may at one time have been situated in this quarter. If so, the 
displacement of the hmestone may have been due to the winter freezing 
of the shallow waters and the shifting of portions of the rock-floor 
when the ice broke up, and was driven inshore in the summer. 
It is to be noted that the curious mass of rubble-drift at Sancton, f 
which has some features in common with the South Cave drifts — notably 
the presence of a clay-streak — occurs nearly at the same level — about 
170 feet above sea-level. Also that the mammahferous Glacial gravel 
at Mill Hill, EUoughton, described by Lamplugh and Sheppard, occurs 
at about 115 feet above sea-level. 
Since the above paper was read to the Society, Prof. Kendall has 
kindly sent me the following valuable notes relating to the lacustrine 
deposits of the Vale of York : — 
" The alluvial plain of the Lower Ouse, Aire and Trent, extending 
from the Escrick moraine down to the latitude of Bantry, and 
from the Magnesian Limestone outcrop in the West to the Jurassic 
escarpment of the East Riding of Yorkshire and North Lincolnshire, 
is mainly constituted of warp clays, long recognised as of lacustrine 
origin. They attain a thickness of 200 feet at Barnby Dun. 
* Carvill Lewis, Extra Morainic Lakes, Geol. Mag., dec. III., 
Vol. IV., pp. 515 to 517. Kendall, Glacier Lakes in the Cleveland 
Hills, Quart. Journ. Geol. Soc, Vol. LVIII. p. 567. 
t Trans. Hull. Geol. Soc, 1894, Vol. IL, p. 10. 
2d 
