The Highland Border Complex, Scotland: a paradox resolved

A previously inexplicable difference between the Highland Border Complex, Scotland, and its correlative in Ireland, the Clew Bay Complex, is that rocks of Caradoc-Ashgill age occur only in the former. We reject evidence from supposed chitinozoa for this dichotomy: no sedimentary rocks of proven age younger than Arenig occur in the Highland Border Complex. Consequentially, the stratigraphy must be totally recast, and the 'exotic terrane model' replaced by one in which a largely autochthonous Highland Border Complex in stratigraphical continuity with the Dalradian (Grampian terrane), was overridden by the Highland Border ophiolite (Midland Valley terrane). Tectonic models for SE Laurentia are thereby considerably simplified.