Annales de la Société Géologique de Belgique

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Abstract

Unconformities below the Cambrian, Arenig, Ashgill and Upper Devonian can be traced from the Welsh Basin across the Midland Platform to the buried Anglian Basin and on into the Brabant area of Belgium. The widespread correlation of the resulting tripartite sequence stratigraphy in the Welsh Basin (Dyfed, Gwynedd and Powys Supergroups) reflects shared eustatic and tectonic controls. The Condroz and Ardennes areas of Belgium were dominated by earlier Caledonian events, and a pre-Caledonian depositional history that does not match the other areas.

Published borehole data are used to compare the Welsh and Anglian Caledonides on a number of criteria. In both areas the cleavage and folding front is roughly coincident with the former platform/basin facies transition, but metamorphic isograds show some departures from it. In strong contrast with Wales, Pridoli and Devonian deposition in the central part of the Anglian belt was more persistent both before and after the Acadian orogenic climax. This Devonian basin was partly controlled by a NE-trending basement structure, named the Cambridge Line, which had probably also influenced Lower Paleozoic deposition.

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