1.—Dalradian Structure and Stratigraphy of the Northern Loch Awe District, Argyllshire

Abstract

Synopsis A structural profile has been constructed for part of the Caledonian fold belt from a map of the Dalradian rocks of the Loch Awe District of Argyllshire. The profile includes the Loch Awe Syncline (Bailey 1913) and the root to the Tay Nappe (Shackleton 1958). The Loch Awe Syncline is shown to be a compound syncline of F1 age, congruent with the Tay Nappe. The F1 structures are accompanied by a penetrative deformation and modified by secondary structures. The stratigraphic succession, which includes the Upper Dalradian and part of the Middle Dalradian, has been reconstructed from the profiles and is shown to have originally been about 10 km thick. The prominent features are the development of a basin to the south-east of the present area in the Late Pre-Cambrian and the extrusion of a 2 km thick basic submarine lava pile in Lower Cambrian times. A subsequent basic submarine lava sequence was extruded in Late Lower Cambrian or Middle Cambrian time and represents the topmos lithostratigraphic group yet recorded from the Dalradian of S.W. Argyll.