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.