The Carboniferous Limestone (Avonian) Succession of a portion of the North Crop of the South Wales Coalfield

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Abstract
The Avonian rocks in the area described form a narrow belt of country on the north-western border of the South Wales Coalfield, extending for a distance of some 30 miles from Kidwelly on the west to Penwyllt (Tawe Valley) on the east (figs. 1 & 2, facing p. 40). The Limestone has a predominantly southward and south-eastward dip, and the outcrop is rarely more than half a mile wide, except at a few localities in the Black Mountains where the dip is low. The outcrop is the continuation across Carmarthen Bay of the Limestone of North Pembrokeshire, and the succession presents greater resemblances to the rocks of that area than to the nearer Limestone outcrop of Gower. The North Crop of the South Wales Coalfield is the only extensive area in South Wales in which the Avonian rocks have not been zonally described. The South Crop has in part been described by Dr. F. Dixey & Dr. T. F. Sibly (1917, p. 111); the Gower area by Mr. E. E. L. Dixon & the late Dr. A. Vaughan (1911, p. 477); and the Pembrokeshire area by the Officers of the Geological Survey (1914, p. 126 & 1921, p. 64), Mr. Dixon's recent account of South Pembrokeshire being a brilliant example of the application of Vaughan's zones. The present communication is an attempt to fill, in part, the hiatus in our knowledge of the Avonian of the South-Western Province, by describing in terms of Vaughan's zones a portion of the Limestone