Structure of the Southern Uplands of Scotland

Abstract

Summary In the Moffat Shale lithology of the Southern Uplands, the primary Caledonian structure consists of thrusting at a low angle to the bedding. Thrusting was associated with minor and large scale folding and northwesterly rotation of beds and thrust planes. Wrench faulting is considered as the final major Caledonian event. All these structural phases were caused by similar principal stress orientations. The primary thrusting is best studied in the Moffat Shale inliers where stratigraphical control is excellent. It is possible that these beds overlie a major plane of décollement. Thrusting is less conspicuous in the overlying greywacke sequence where the beds are more competent, and the stratigraphy is less well defined. Otherwise, the Caledonide structural evolution of the greywacke is essentially the same as that in the underlying pelagic sequence. Consequently it is suggested that nearly all the Caledonian structures of the Southern Uplands can be broadly explained by a common but evolving stress system.