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Tertiary Fumaroles on the Island of Raasay, Inverness-shire

Published online by Cambridge University Press:  01 May 2009

R. C. Selley
R. C. Selley
Affiliation:
Dept. of Geology, Imperial College, London, S.W.7.
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Abstract

Three large pipes of brecciated Torridonian sediments set in matrices of calcite and calcareous mudstone occur on the island of Raasay. Previous work has shown that these structures may be due to explosive fumarole activity during the Tertiary volcanic episode. A recent study of the Torridonian stratigraphic succession has made it possible to demonstrate that there was considerable variation in the amount of vertical collapse of the local country rock caused by the explosions. In one vent local fracturing and brecciation took place with no downward movement; in another it is possible to show that Torridonian boulders tumbled at least 350 metres down into the throat of the fumarole. The amount of vertical collapse increases from vent to vent southwards towards the Cuillins volcanic centre.

These vents are of particular interest for two reasons. Though clearly of volcanic origin they contain no volcanic material. Secondly, the carbonate matrix of analogous structures is generally believed to be due to the hydrothermal solution of underlying limestone beds. The latter are absent in these examples and the carbonate material seems to be solely of volcanic origin.

Type
Articles
Information
Geological Magazine , Volume 103 , Issue 6 , December 1966 , pp. 558 - 564
Copyright
Copyright © Cambridge University Press 1966

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References

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