The Carboniferous Limestone Series in the West of the Vale of Glamorgan

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Abstract
I. Introduction and Historical Notes The deposits that are present over the greater part of the Vale of Glamorgan consist of a more or less thick covering of Mesozoic (Triassic, Rhætic, and Lower Liassic) rocks through which extensive inliers of Upper Palæozoic strata emerge. The latter are chiefly of Avonian age, and constitute fragments of the southern arc bounding the syncline of the South Wales coalfield. The present paper is concerned with those Lower Carboniferous inliers, lying to the west of the River Ddawan, that form the tracts of down county in the neighbourhood of Porthcawl, Bridgend, and St. Bride's Major, and which are a continuation of the series of folds comprising the Cardiff-Cowbridge anticline (see fig. 1). The area lies wholly within the 1-inch (New Series) Geological Survey map no. 261–2, and was described by the officers of the Survey in the memoir (‘The Country around Bridgend,’ 1904, p. 13) accompanying that map. It is the purpose of this paper to supplement the information contained in the memoir with an account of the zonal sequence and of the structures elucidated by the application of the stratigraphical details obtained. It will be obvious that the work is based to a very great degree upon the publications of the Geological Survey; my indebtedness to them is considerable, especially as regards the construction of the map. Apart from the information contained in the Survey Memoir, which almost entirely relates to the lithology, a brief note by Sibly (1920, p. 90) is the