On the Occurrence of Tremadoc Shales in the Tortworth Inlier (Gloucestershire)

Abstract

I. Introduction The presence in South Gloucestershire of rocks older than the Old Red Sandstone was made known more than a century ago by the researches of W. Buckland and W. D. Conybeare (1824, p. 216) and T. Weaver (1824). Murchison included them in his Silurian system (1839, pp. 447–9, 454–62, and map separately issued), utilizing, in addition to his own observations, notes and sketches made by the Rev. George Cooke, Rector of Tortworth at that time. The area was mapped by D. Williams, J. Phillips, A. C. Ramsay, and H. W. Bristow of the Geological Survey during the directorship of De la Beche, and the information was published in 1845 (Geological Survey 1-inch Map, Sheet 35). Bristow revised this part of the sheet in 1865, and further information was added to the map in 1866. John Phillips (1848, pp. 190–8 & pl. i) gives a good account of the Palæozoic inlier, and H. B. Woodward includes a shorter and less accurate description of the beds in his memoir on the Bristol coalfield (1876, pp. 9–11 & pl. i). Within recent years, S. H. Reynolds, partly in collaboration with C. Lloyd Morgan and F. R. C. Reed, has written a series of papers dealing with the geology, petrology, and palæontology of the southern part of the outcrop, and has summarized the results in his ‘Geological Excursion Handbook for the Bristol District’ (1912 & 1921, pp. 200–9). Nothing, however, has been published about the northern part (that is, the country north