The Far Northwest: Sutherland, Assynt and Coigach

Citation

Bradwell T & Ballantyne C (2021) The Far Northwest: Sutherland, Assynt and Coigach. In: Ballantyne C & Gordon J (eds.) Landscapes and Landforms of Scotland. 1 ed. World Geomorphological Landscaper. Cham, Zug, CH: Springer Nature, pp. 233-250. https://doi.org/10.1007/978-3-030-71246-4_12

Abstract
The far northwest of mainland Scotland is renowned for its scenery, structural complexity and geodiversity, and is designated as a UNESCO Global Geopark. The region is bisected by the Moine Thrust Zone (MTZ) , west of which a foreland of undeformed Archaean gneiss supports inselbergs of Neoproterozoic and Palaeozoic rocks, and east of which are thrust-stacked, deformed metasedimentary rocks of the Neoproterozoic Moine Supergroup. The MTZ forms a north–south belt within which rocks were extensively thrust and folded during the Caledonian Orogeny. Successive Pleistocene glaciations have resulted in an array of erosional landforms: troughs, rock basins, cirques, glacially steepened inselbergs, extensive areas of knock-and-lochan terrain and clusters of glacial megagrooves. During the last and earlier ice-sheet glaciations, the region sourced northwestward-flowing ice feeding the Minch Ice Stream, which extended far across the adjacent shelf, but by ~15 ka the last ice sheet had retreated to its mountain heartland. The Loch Lomond Stade (~12.9 to 11.7 ka) witnessed reoccupation of the main mountain axis by a substantial (~350 km2) icefield, and cirque glaciers formed on peripheral mountains; the extent of the former is mainly delimited by multiple recessional moraines, the latter by end-moraine belts. Lateglacial and Holocene landforms include outwash or delta terraces at fjord heads, sea stacks, beaches backed by sand dunes, rock-slope failures, relict talus accumulations, and active periglacial and aeolian features on high ground. Karst terrain developed on dolostones comprises sinkholes, resurgences and extensive cave networks formed by water-table lowering due to Middle and Late Pleistocene valley deepening.

Keywords
Stable foreland; Moine Thrust Zone; Inselbergs; Glacial troughs; Cirques; Knock-and-lochan topography; Glacial megagrooves; Glacial landsystems; Hummocky recessional moraines; Coastal landforms; Landslides; Periglacial features; Karst; Caves

People

Dr Tom Bradwell

Senior Lecturer, Biological and Environmental Sciences