IX.— The Drummuck Group, Girvan; A Stratigraphical Revision, with Descriptions of New Fossils from the Lower Part of the Group

Abstract

I. INTRODUCTION. The Drummuck Group as defined in this paper falls entirely within the one-inch Geological Map, Scotland, Sheet 14. It forms part of the succession in the Craighead-Glenshalloch inlier. This elongate, anticlinal inlier—which comprises all the Ordovician and Silurian beds north of the Girvan valley—consists of three main blocks:—(1) Craighead Hill; (2) Drummuck and Quarrel Hill; and (3) a less well-defined north-eastern block, entirely (Lapworth, 1882, Pl. XXIV) or partly (Geological one-inch Map, Scotland, Sheet 14) divided by faulting from the Drummuck and Quarrel Hill block. II. TABLE OF STRATA IN THE CRAIGHEAD-GLENSHALLOCH INLIER. The following table embodies the findings of previous authors (Lapworth 1882, Peach and Horne 1899, Jones 1928, etc.) and also additions proposed in the present revisory paper:— III. NOTES ON PREVIOUS RESEARCH. An early contribution to the reading of this succession was that by Murchison who distinguished an ascending series consisting of (1) lavas, (2) Craighead Limestone, (3) sandstone and conglomerate of Mulloch Hill, and (4) Drummuck shales (1851, pp. 143-146). Hugh Miller, while deferring to Murchison, was not quite sure that the Drummuck beds succeeded those of Mulloch Hill (1858, Everyman Edition, p. 299). The age and stratigraphical order of the beds were not settled until Archibald Geikie wrote a substantially correct summary interpretation (1869, pp. 8-10). It remained, however, for Lapworth, as part of his paper “The Girvan Succession,” to publish, in full detail, what is still the definitive account of the inlier (1882, pp. 614-621). In this paper, which is illustrated with This 250-word extract was created in the absence of an abstract In conclusion I wish to thank all who have helped me with advice or in the field. Professor E. B. Bailey and Dr. John Weir supervised the work while it was in progress, read the typescript of the paper, and made many suggestions. I also received assistance in identifying certain of the fossils from Mr. B. B. Bancroft and Mr. J. Shirley. Through the kindness of Dr. W. D. Lang, Miss Muir-Wood, Dr. H. Dighton Thomas, and Mr. T. H. Withers I received material from the South Kensington Museum for comparison with a number of the new Girvan species. In mapping and collecting I had the help at different times of Mr. J. L. Begg, Rev. J. M. Ewing, Mr. G. T. Smith, and others, to all of whom I am very grateful. Most of the field-work was done while the writer was in receipt of a Research Scholarship under the Carnegie Trust for the Universities of Scotland. My thanks are due to the Carnegie Trustees for this, and also for a grant towards the cost of illustrating the paper. I am further indebted to the Senate of Glasgow University for their award of a Strang Steel Scholarship, for the current session, during which the work has been completed. Mr. D. M. Filshill made the photographs for Plates VII and VIII.