Pre-Carboniferous history of the Midland Valley of Scotland

Abstract

ABSTRACTThe pre-Carboniferous Midland Valley of Scotland comprises three tectonic elements: an arc, a proximal fore-arc basin and a marginal basin. These tectonic elements have been juxtaposed by strike-slip and thrust faulting, both of which have effected a 300% reduction in the width of the orogenic belt.Rocks which span Arenig to Late Devonian or Early Carboniferous times and which are found S of the Highland Boundary fault have no clasts of certain Dalradian provenance despite substantial uplift of the Dalradian block at this time. This, combined with other evidence, suggests the Midland Valley to have been remote from this rapidly uplifting terrane. The Dalradian block, eroded down by c. 410 Ma was thrust southeastwards in Late Devonian–Early Carboniferous times. However, this thrust movement was minor, yielding little sediment, but it caused Dalradian rocks to cover the northern margin of the Midland Valley where (1) the source for part of the Old Red Sandstone rocks existed and (2) the faults along which the Midland Valley block was transported to dock against the Dalradian block are thought to be present. The existing Highland Boundary fault is therefore seen as a late Old Red Sandstone reverse fault which covered more significant older structures.