Abstract

E. B. Selwood & J. M. Thomas write: Although we agree with many of the direct structural observations of Andrews et al. and can accept that opposed facing is present in north Cornwall, our objection to the confrontation model of Roberts & Sanderson (1971) basically stemmed from stratigraphic analysis. In their reaffirmation of this model Andrews et al. have correctly perceived that it is essential to maintain the presence of a D1n overfold north of the confrontation (for clarity we use the notation of Andrews et al.).

To retain a normal succession in the long limb of the overfold, they assert ‘The fact that the Jacket's Point Formation is younger than the Tredorn Slate Formation,

and that the change from one to another is gradational within thesame nappe is critical our to overall interpretation’.Not only does palaeontological evidence deny this ‘fact’, in that the Jacket’s Point Slate Formation is of Frasnian and the Tredorn Slate Formation of mid to late Famennianage, but also these formations belong to different successions. The Jacket’s Point Slates occur in an inverted conformable succession with the Polzeath Slate Formation (Upper Frasnian-Middle Famennian), whereas theTredorn Slates young into Lower Carboniferous slates (Selwood & Thomas 1986). In the cliffs north of Jacket’s Point, the flat-lying contact between the Tredorn Slates above, and the inverted Jacket’s Point Slates below, cannot be stratigraphic. We reaffirm its faulted nature and equate it with the Trekelland Thrust (Stewart 1981). It follows from the field observations of Andrews et al. south

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