A re-examination of the Tintagel high strain zone and the Padstow facing confrontation, Cornwall

Pamplin, Christopher Francis (1988) A re-examination of the Tintagel high strain zone and the Padstow facing confrontation, Cornwall. University of Southampton, Doctoral Thesis.

Abstract

Recent conflicts in the interpretation of the structure of north Cornwall has resulted in the need for a re-examination of the well exposed coastal sections. Detailed mapping combined with the extensive application of shear criteria has allowed the relative importance of the fold and thrust solutions to be assessed. This work has shown that D1, characterised by the development of large fold nappes, was diachronous across Cornwall. The Padstow Facing Confrontation is confirmed as a zone of interference between two early fold nappes of opposed transport. The High Strain Zone around Tintagel, characterised by intense northwards shear, is reassigned to D2. Petrographic and microstructural analysis demonstrates that early ductile shear became confined to discrete thrust planes which dismembered the earlier fold nappes. Petrographic, illite crystallinity and fluid inclusion analysis shows that peak metamorphism (M2) was synchronous with D2 in the High Strain Zone and overprints a syn-D1 metamorphic event (M1). However, M2 is absent in the Padstow Facing Confrontation. A model for the structural evolution of north Cornwall is developed. This involves compression and inversion of the Trevone and Culm Basins and the ejection of sediments in large fold nappes. The High Strain is interpreted as a later out-of-sequence thrust system generated in response to continued compression. (DX86457)

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