Pre-Quaternary landscape evolution in the Scottish Highlands

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Abstract
The development of the relief of the Scottish Highlands is traced over the last 400 Ma. Evidence from Late Palaeozoic and Mesozoic sediments and near-surface volcanic and igneous rocks shows that post-Devonian erosion of basement has been < 1–2 km and that the main morphotectonic units of the Highlands were already established by the end of the Palaeozoic. During the Mesozoic, the Highlands experienced several major erosional cycles, beginning with uplift, reactivation of relief and stripping of cover rocks, followed by progressive reduction of relief through etchplanation and culminating in extensive marine transgressions in the Late Triassic, Late Jurassic and Late Cretaceous. In the Early Tertiary major uplift affected the Highlands, with downwarping and block movements along basin margins, but levels of uplift and denudation around the Tertiary igneous centres cannot be extrapolated to other areas. Buchan and Caithness remained relatively stable and Mesozoic relief elements were maintained during gradual surface lowering. Earth movements of lesser magnitude continued episodically until at least the end of the Tertiary. After 50 Ma the Highland terrain evolved by dynamic etching, with deep weathering of varied geology under warm to temperate humid environments leading to a progressive differentiation of relief, with formation of basins, valleys, scarps and inselbergs often closely adjusted to lithostructural controls.