STATHER : NOTES UN THE DRIFTS OF THE HUMBER GAP. 219 
The Lower Clay appears to be a westward prolongation of one 
of the lower divisions seen on the coast. Its texture, boulders (see 
above), and associated laminated clays, suggest the basement series 
of Dimlington and Bridlington, but the deposit has not yet yielded 
Arctic shells, nor is its colour that of the basement clay of the coast 
sections. But as the shells have been shown to occur in the base- 
ment clay merely as derived " pebbles," their absence in this section 
may be no more than a local accident ; and also as the colour of the 
boulder clays, and especially of the basement clay varies according 
to the material of which it is composed, neither of these differences 
is of much importance. 
At the eastern end of the Hed Cliff section, it might appear at 
Hrst sight that there was a continuous series of laminated and sandy 
beds from the bottom to the top of the section, but a closer examina- 
tion seems to sliow% as already described, that between the Laminated 
Clay and the High Level Warp and Sandy Series, there is a well- 
marked line of erosion (figs. 4, 5 and 6). Indeed the latter series 
makes an unconformable overlap upon the glacial deposits below, 
since it rests, as mentioned above, first on the Laminated Clay, then 
on the Lower Boulder Clay a little further to the west, and further 
still in that direction on the Upper Boulder Clay. 
The curious intermediate bed at the base of the High Level 
Warps, seems to be due to the breaking up of the top of the laminated 
clay, perhaps when in a frozen condition, and the rolling of the frag- 
ments into pebble-like form. 
As for the age of the High Level Warps this must for the present 
remain uncertain. They are clearly newer than the Upper Clay (5), 
but are older than the Gravel capping the section (3), which the 
Officers of the Survey regard as the extension of the Brough and 
Ellerker Gravels, supposed to be of glacial age. This would imply 
that the Warps themselves are not newer than late glacial times, but 
as has been pointed out "there is probably in the Vale of York a 
succession of stratified warp deposits dating from the close of glacial 
conditions to the present time. 
* Survey Memoir. — The Geology of the Country North east of York and 
South of Malton. 
