High-Level Glacial Gravels, Gloppa, Cyrn-y-bwch, near Oswestry

Abstract

The Gloppa (spelt ‘Glopa’ on the Ordnance map) is a small farm, about two miles north-east of Oswestry, situate on the eastern slope of the ridge of Carboniferous rocks (Millstone Grit) which forms the western boundary of the Northern Shropshire and Cheshire Plain, and upon this and adjacent farms the gravels and sands are spread out. The main mass is comprised in a ridge of eskers about 1000 yards long, and appears to rest immediately upon the Millstone Grit, the beds of which formation crop out directly to the westward, and dip here about 20° to 25° E. and S.E., the average slope of the hill being about 10°. The portion of the deposit worked out forms but a small part of the whole, although about 33,000 tons of material have now been extracted. A pit was opened here in the year 1888 for the purpose of getting sand for the filter-beds on the Oswestry works of the Liverpool Vyrnwy Waterworks, and since that date I have had it under observation; it is not now being worked. The deposit ranges here from about 900 to 1160 feet above sea-level, but the main mass is from 1000 to 1150 feet, the sandpit worked being 1070 to 1130 feet. The highest point at which I have found marine shells in the drift is 1120 feet; the other recorded instances of such drift at similar heights in Great Britain being Moel Tryfaen (1330 to 1360 feet), Prestwich's Patch, Macclesfield (1150 feet); and in