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Welsh Basin ‘contourites’ reinterpreted as fine-grained turbidites: the Grogal Sandstones

Published online by Cambridge University Press:  01 May 2009

R. D. A. Smith  and
J. M. Anketell
R. D. A. Smith
Affiliation:
KSPEL, Shell Research, Volmerlaan 6, 2288 GD Rijswijk, The Netherlands
J. M. Anketell
Affiliation:
Department of Geology, University of Manchester, Manchester, M13 9PL, U.K.
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Abstract

Since 1976 the Lower Silurian Grogal Sandstones of the Welsh Basin have been interpreted as contourites. Here we show that they are in fact fine-grained turbidites, frequently with pale-coloured oxidized top layers which enable distinction of individual event deposits. As reported previously, palaeocurrent directions derived from ripple cross-lamination are typically at a high angle, often close to perpendicular, to those measured from sole structures. The favoured explanation is that ripples migrated under transverse internal waves generated at an intrabasinal slope to the east. Evidence for the lateral confinement of the overlying Aberystwyth Grits by such a slope provides support for this explanation.

Type
Articles
Information
Geological Magazine , Volume 129 , Issue 5 , September 1992 , pp. 609 - 614
Copyright
Copyright © Cambridge University Press 1992

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