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A Caradoc Failed-Rift within the Ordovician Marginal Basin of Wales

Published online by Cambridge University Press:  01 May 2009

S. D. G. Campbell ,
M. F. Howells ,
M. Smith  and
A. J. Reedman
S. D. G. Campbell
Affiliation:
British Geological Survey (NERC), Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY
M. F. Howells
Affiliation:
British Geological Survey (NERC), Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY
M. Smith
Affiliation:
British Geological Survey (NERC), Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY
A. J. Reedman
Affiliation:
British Geological Survey (NERC), Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY
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Abstract

The dolerite and basalt intrusions within the Lower Palaeozoic sequence of northwest Wales are largely restricted to the outcrop of Ordovician strata. Their distribution and close association with known volcano-tectonic structures were controlled by a tectonic framework of deep-seated fractures. In central and northern Snowdonia, volcanism during Caradoc times was related to the evolution of a fracture-controlled trough. An increase in the extensional stress across the trough with time is reflected in the progressive increase in basaltic magma movement during the volcanic cycle. The trough represents an attempted rift in the lithospheric plate, which failed to create an ocean basin and was subsequently aborted.

Type
Articles
Information
Geological Magazine , Volume 125 , Issue 3 , May 1988 , pp. 257 - 266
Copyright
Copyright © Cambridge University Press 1988

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