Late Caledonian (Scandian) and Proto-Variscan (Acadian) orogenic events in Scotland

The later tectonic phases of the Caledonian Orogeny reflect the collision of Baltica and Laurentia. The result was the Scandian event in Silurian times, and the oblique docking of Eastern Avalonia with Scotland, generating deformation and metamorphism in the Southern Uplands. The exhumation of the Caledonide Orogen was then accompanied by sinistral transtensional faulting and emplacement of granitoid plutons. The Iapetus Ocean was finally closed, and subduction activity had migrated south to the Rheic Ocean by early Devonian times. Continental rifting and deposition of the Lower Old Red Sandstone fluvial-lacustrine succession, accompanied by basaltic-andesitic volcanism, occurred across Scotland. Deposition commenced in the late Silurian and continued through to Emsian times, when it was interrupted by the short-lived, northward-directed Acadian event. The resultant deformation and folding, a product of sinistral transpression, were focussed along the major pre-existing faults and shear zones.