Abstract

Drs E. G. Freshney, S. McCourt & E. B. Selwood write: The key to the undoubtedly complex structures of the south-west England region lies in a full understanding of the stratigraphic sequences, which are only now being resolved. Unfortunately Hobson & Sanderson's interpretation (1975 this Journal131, 337–52) is based on stratigraphy which is not soundly conceived.

Their proposition that there are major recumbent folds in the Boscastle area, while almost certainly true in principle, is nonetheless erroneous in the case of the folds actually described. A considerable part of the evidence for the folding is based on a misinterpretation of the stratigraphy, which is summarized in Table 1 (details of the geological evidence are given in Supplementary Publication No. SUP 18015 (9 pages), deposited with the British Library at Boston Spa, Yorkshire, U.K. and The Geological Society library). The fold reconstructions of Hobson & Sanderson depend on the equation of the Barras Nose Formation and the Trambley Cove Formation, but the strong stratigraphical and palaeontological evidence that these are separate and distinct formations indicates that the reconstruction is untenable. The acquisition of consistent data on fold facing and sense of overturning in rocks below the Crackington Formation is very difficult, owing to the paucity of reliable sedimentary structures and the intense dismemberment of the folds. Thus any attempt using such data to construct folds which do not agree with fairly reliable stratigraphical evidence must be regarded with caution.

Hobson & Sanderson's structural synthesis (1975 fig. 9) indicates major

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