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Cambrian and early Tremadoc rocks of the Llangynog Inlier, Dyfed, South Wales

Published online by Cambridge University Press:  01 May 2009

J. C. W. Cope  and
A. W. A. Rushton
J. C. W. Cope
Affiliation:
Department of Geology, University of Wales, P.O. Box 914, Cardiff CF1 3YE, U.K.
A. W. A. Rushton
Affiliation:
British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
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Abstract

Until recently no Cambrian rocks were known in the Llangynog area. Detailed mapping has now revealed a succession of ?Lower and Upper Cambrian rocks overlain by Tremadoc rocks. The Allt y Shed Sandstones (new) rest unconformably on the Precambrian, but have yielded no diagnostic fossils and are tentatively assigned to the Comley Series. Succeeding with faulted or unconformable contact is an Upper Cambrian Merioneth Series succession which includes in ascending order: conglomerates, sandstones and siltstones with olenid trilobites and resembling the Treffgarne Bridge Beds of the Haverfordwest area; micaceous shales and siltstones referred to the Ffestiniog Flags Formation; and black mudstones with calcareous concretions and a rich olenid fauna referred to the Dolgellau Formation. Succeeding the latter with possible disconformity is a succession belonging to the lower part of the Tremadoc Series and earlier than any rocks of that series hitherto recorded from the area.

Type
Articles
Information
Geological Magazine , Volume 129 , Issue 5 , September 1992 , pp. 543 - 552
Copyright
Copyright © Cambridge University Press 1992

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