Upland Landscapes and Landforms of the Southern Uplands

Abstract

The Southern Uplands form a tract of rolling, dissected tableland, underlain by steeply dipping sedimentary and metasedimentary rocks of Ordovician and Silurian age, into which several granitic plutons were intruded during the Devonian. The landscape is one of selective glacial erosion, but the effects of successive Pleistocene glaciations are muted: deep glacial troughs and cirques are largely restricted to the Galloway Hills in the southwest and the Tweedsmuir Hills in the centre of the region. Moraines are mainly limited to those deposited by Loch Lomond Stadial glaciers in the same areas, but meltwater channels are widespread and outwash terraces deposited during retreat of the last ice sheet flank the floodplains of both trunk and tributary rivers. Frost-weathered regolith covers summits and plateaux, suggesting that these were occupied by cold-based glacier ice during the last glacial cycle. Lateglacial solifluction of regolith and till has produced smooth valley-side slopes and contributed to the accumulation of periglacial valley fills; active solifluction is represented by lobes and ploughing boulders on some of the highest ground. Rock-slope failures occur mainly in clusters and exhibit a variety of forms conditioned by the underlying geological structure and lithology. There is evidence that settlement expansion and associated land-use impacts have caused gullying of hillslopes during the Late Holocene, resulting in the deposition of alluvial fans and debris cones, and transient floodplain aggradation due to increased sediment supply to rivers.