the effects of later faulting make precise estimates of thickness difficult. It is subdivided into seven formations. History The earliest event recorded in the terrane is the intrusion of the protoliths to the Scourian gneisses at about 3.0–2.7 Ga. Blocks within the Lewisian complex were then juxtaposed by Inverian and Laxfordian deformation from about 2.4–1.7 Ga. At about 1200 Ma, the terrane was affected by extensional tectonics causing rifting and the deposition of the thick coarse clastic sequence of the Torridonian. This was interrupted by a tilting event of unknown origin that caused a hiatus of about 200 Ma, followed by further deposition. At the start of the Cambrian, there was a marine transgression and deposition of shallow marine sandstone and carbonates continuing into the Ordovician. In the Silurian the terrane became involved in the Caledonian continental collision, with the Highland Terrane being thrust over this segment of the Laurentian foreland. References Geology of Scotland Terranes Archean Proterozoic