Age of cleavage in the Skiddaw Slates in relation to the Skiddaw aureole

Abstract

A recent hypothesis concerning the age of orogenic deformation of the Skiddaw Slates in the English Lake District has proposed that the main slaty cleavage (S1) and superimposed subhorizontal crenulation-cleavage (S2) are of intra-Ordovician age. A study of the fabric of the aureole of the (end-Silurian) Skiddaw granite shows that the granite was emplaced towards the end of the D1 deformation phase, but before the formation of S2. These structures are therefore of broadly end-Silurian age, and evidence of an intra-Ordovician orogeny in this area is lacking.