Abstract

Professor T. N. George said that Dr. Blundell's discoveries and inferences were of major importance in transforming concepts of British stratigraphy in radical ways. The reconstruction of a deep basin of sediments in the southern Irish Sea was perhaps not wholly unsuspected in view of the earlier geophysical evidence in Cardigan Bay, and of the stratigraphical evidence in the Mochras borehole; but it would scarcely have been guessed that such enormous thicknesses as he envisaged would be preserved in the comparatively narrow trench between Wales and Ireland.

A central feature was the ancient delineation of a present-day topography, going back at least to Hercynian times. The geomorphic contrasts revealed by the inferred Mesozoic and Cainozoic thicknesses were a direct reflection of the persistence of a built-in tectonic frame that had dominated tectonic growth until the present day. The geomorphic development of much of western Britain correspondingly demanded re-assessment and amplification.

Several particular points arose from Dr. Blundell's exposition. It would be recalled that in Dinantian times the Leinster massif was progressively overstepped from the south, and similar fluctuating overstep was to be seen in Pembrokeshire. In a former reconstruction it was suggested that a northward embayment of Dinantian rocks occupied the floor of the channel between. It now appeared that the embayment might extend well into the southern Irish Sea and into Cardigan Bay to form a thick pile analogous to the Dinantian sequence in southern Pembrokeshire and in southernmost Ireland, with perhaps thick Upper Carboniferous rocks overlying. There would

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