Lower carboniferous volcanic vents in the West of Scotland |
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| Authors: | F Whyte |
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| Institution: | 1. Dept of Geology, The University, Dundee, Scotland
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| Abstract: | Recent studies of Lower Carboniferous volcanic vents in the Campsie and Kilpatrick Hills and at Heads of Ayr have revealed a number of common features which are discussed. The present outcrops of both vents and plugs seldom represent the diameters of the original pipes. Late-stage subsidence occurred within ring fractures which developed around the craters and pipes. The main evidence for subsidence rests on the distortions of the marginal country rocks, and also on the presence within the vents of bedded pyroclastic rocks from the volcanic cone. In some vents, blocks of country rock occur at structural levels lower than that at which they are exposed in their nearest outcrop. The attitude of cooling joints in intrusive basalts of the vents shows many of them to be sheets rather than plugs. The distinction between sedimentary and flow-banded vent pyroclastic rocks is often difficult, and the most useful indicators of a sedimentary origin are discussed. |
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