Sand volcanoes in the Silurian rocks of Kirkcudbrightshire

Abstract

Introduction and Acknowledgements The purpose of this paper is to record the occurrence of a series of unusually large and strikingly well-developed fossilized sand volcanoes in the Silurian Raeberry Castle Beds of Kirkcudbrightshire. The exposure (near Gipsy Point, G.R. NX 686 437) lies within a military training area a few miles south of the town of Kirkcudbright. I thank Colonel A. E. Hay for permission to visit this Girdstringwood range. I also thank Professor G. Y. Craig for introducing me to the area, and J. Jameson for his help in the field. Description The sand volcanoes occur at a single stratigraphical level, as part of a near vertical sequence of conglomerates, sandstones, siltstones and mudstones ([Craig and Walton 1959][1], [1962][2]). They overly a complex slump bed c . 50 m thick. The matrix of this slump bed is predominantly grey siltstone and contains large (several m3) lumps of contorted sandstones and interbedded sandstones and shales. Towards the base of the slump bed at one locality, thicker, coarser-grained sandstones, with flute moulds c . 1 m in length, fill fossilized channels several metres deep. The volcanoes themselves occur in three groups over c . 100 m of excellent exposure along strike on the foreshore. Ten volcanoes were recognized, ranging from c . 1.5–3 m across, c . 0.5–1.5 m thick, with craters c . 0.5–1 m across (Pl. 1). The largest of the volcanoes has complex internal stratification. One of the smaller volcanoes immediately overlies another small, separate, volcano. Laminations extend out of the . . . [1]: #ref-2 [2]: #ref-3