Are remnants of an Ocean-Continent-Transition Zone preserved at the Highland Border in Scotland?
The geological significance of the boundary between the Midland Valley and the Highlands of Scotland, known traditionally as the Highland Border, has been a source of controversy and debate since the beginning of the last century. The ‘Highland Line’ is one of Scotland’s most iconic and readily visible landscape features, linked intimately with the Highland Boundary Fault Zone. That structure separates Dalradian metamorphic rocks of Neoproterozoic to Lower Palaeozoic age in the NW from Silurian-Devonian sedimentary rocks to the SE. The Dalradian rocks have been affected by early Ordovician (Arenig-Llanvirn) Grampian orogenesis, whereas only mid-Devonian (Emsian) Acadian and late-Carboniferous deformation affects the rocks of the Midland Valley. Geoff Tanner has now revived debate on the significance of the Highland Border with a number of published papers, most recently in the Journal of the Geological Society, London1,2,3,4. The Highland Border zone is generally less than a kilometre
