Abstract

Appin (lower) and Argyll (middle) Dalradian metasediments and associated igneous rocks are described and a formal stratigraphy proposed. The deformation history has four main phases, D1 to D4. Major "nappe" structures, formed during D1 and D2, were refolded by two phases of approximately coaxial crossfolding developed during D3 and D4. Two of the major F4 cross-folds, the Connemara Antiform and Joyce's Synform, superficially dominate the structure of the area. The main penetrative fabric in the rocks, an axial planar schistosity, was developed during D2. The deformations were accompanied by metamorphism that reached its peak (in the Maumturks) between D2 and D3 (MP2). The rocks were metamorphosed in the amphibolite facies and show an increase in grade from north to south across the area. It is suggested that the prograde MP2 metamorphism, with coeval growth of staurolite and sillimanite, was partly caused by heat emanating from the complex of basic, ultrabasic and migmatitic rocks located during MP2 in the upper limb of the F1 Lissoughter Anticline, structurally above the present day outcrop in the Maumturks and now occurring mainly in south Connemara.

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