Vol. 53-. GLACIO-MARINE DRIFT OF THE YALE OF CLWYD.
345
St. Asaph road, north-west of Parc-y-Meirch, 220 feet above O.D., a
stream has cut into the drift, over which it falls for a few feet as
a waterfall, and here is disclosed a well-stratified sandy deposit.
My observations generally go to show that the drift here described
represents a shore sloping up gradually from the lowland of the Vale
of Clwyd, until it is backed up at a greater angle against the lime-
stone-cliffs forming the west side of the Vale.
(2) Glacial Sands and Gravels, east side of the
Vale of Clwyd.
The country between Rhyddlan and Diserth is mostly covered
with red sand, evidently derived from the Trias, which is the bottom
rock of the Vale. 1
South-east of Diserth Castle, near Prestatyn Branch Eailway, is a
striking grass-covered mound of sand and gravel (No. 5 in the Map),' 2
W
Esker south-east of Diserth Castle.
A
I bou
bro^
Large Limestone -Boulders
the structure of which may be investigated where it is broken into
by the excavations for gravel. The axis of this mound has a
north-easterly trend, and it forms a spur from the hill on which it
lies. Orographically it resembles an Irish esker. The excavation
shows that the bedding of the sand and gravel largely follows the
external form, the flank, where exposed, being covered with a
layer of Boulder Clay, as illustrated in the above diagram. In the
1 Between Abergele and Rhyddlan the Glacial beds are masked by post-
Glacial deposits, but borings seem to show that Boulder Clay and Sands alternate.
There are good sections of the Marine Drift on the river-bank at R-hyddlan, and
these have been described by Prof. M C K. Hughes, ' Geol. of the Vale of Clwyd,'
Proc. Chester Soc. Nat. Sci. 1884, no. 3. See also remarks on Drift in ' Trias of
the Yale of Clwyd,' Proc. Liverp. Geol. Soc, Session 1890-91, vol. vi.pt. iii.p. 285.
2 See ' Geology of Rhyl, Abergele, and Colwyn ' (p. 32 & map), by Aubrey
Strahan, Mem. Geol.