The Geology of the Country between Llanelidan and Bryneglwys

Abstract

The district here described lies partly in southern Denbighshire and partly in north-eastern Merionethshire. It covers an area of about twenty square miles, and includes the upper part of the Vale of Clwyd, and the upland region on the south of it. The parishes of Derwen, Grwyddelwern, Llanelidan, a large part of Bryneglwys and part of Llansantfraid-Grlyn-Dyfrdwy are included in the area. A close geological and geographical relationship exists between the present district and the main mass of the Denbighshire Moors on the north-west. The region consists of a more or less flat-topped upland which has been dissected by numerous valleys. The average height of the land is 1000 feet, but to north, west, and south it descends below 600 feet O.D. Towards the east the area is connected by a ridge extending from Moel Traan to Mynydd-Cricor, averaging 1000 feet in height. The district here described thus forms a more or less rectangular tract of relatively high land surrounded on three sides by low-lying valleys. The grain of the country runs from south-west to north-east, and is thus of Caledonian trend. A system of parallel valleys, most of which carry streams, separates the ridges. Less well-marked valleys also cut the upland in a west to east direction, intersecting the former at angles of about 60°. Where the two valley-systems meet, rather flat and swampy ground is usual. On the north the uplands descend steeply to the upper part of the Vale of the Clwyd. The river Clywd follows this