Acadian tectonics of Wales during Avalonia/Laurentia Convergence

Abstract

Acadian (Late Caledonian) structures in Wales record the inversion and strong deformation of the Welsh Basin during docking of the Eastern Avalonia microcontinent with Laurasia in Late Silurian to Mid Devonian time. A basement‐involved deformation model is developed in which deep faults and buried granites or horsts controlled the main arcuate trends of Welsh structure. A south southeast directed shortening across the basin is implied by the variation in amount and sense of transection of folds by cleavage around the major arcs. This shortening induced sinistral transpression and clockwise transection across northeast or north northeast trending folds but more orthogonal shortening and zero or vaak anticlockwise transection across east northeast or east trending folds. The south southeast shortening direction parallels mineral lineations in north Wales. It is an estimate of the Avalonia/Laurentia convergence vector but is about 35° anticlockwise of that derived by Soper et al. [1987] from northwest England. Displacement partitioning within the convergence zone may explain this discrepancy.