Abstract

Dr J. K. Ingham said the Silurian succession at Girvan is no less complex than the underlying Ordovician and the authors are to be commended for rationalizing some of the problems affecting the lithostratigraphy and local correlation. In doing so, a large number of new formational names have been created and yet the very useful major group names, introduced by Lapworth, have not been retained (Mulloch Hill Group, Saugh Hill Group, etc.). Although the new interpretation would affect slightly the meaning of some of these terms, minimum adaptation would still make them useable. They correspond broadly to groups of formations which the authors have shown are both lithostratigraphically and biostratigraphically of a cyclical nature. What do the authors feel about the possible retention of these terms? Secondly, what Dr Ingham regarded as a singly dominantly argillaceous formation, with a calcarenite member developed locally, has been given three separate formational names in the three known areas, the Woodland Formation/Tralorg Formation/Glenwells Shale unit. How do the authors justify this treatment?

The Authors thanked Dr Ingham for his kind remarks. They themselves regretted the large number of formational names, but the stratigraphy of the area is not simple, consisting as it does of thick deposits representing perhaps twenty million years of the Silurian. Lapworth's names have been conserved where possible, though many have been synonymized; new names are only proposed to meet particular needs, as explained for each case in the main text. They had not used Lapworth's group names for two reasons;

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