Southern Uplands Fault

One of the major geological features of Scotland, the Southern Uplands Fault stretches from the northern tip of the Rhins of Galloway, in the west, across the mouth of Loch Ryan, trending east northeast to the south of Ballantrae eventually reaching Dunbar on the coast of East Lothian. It marks the southern boundary of the Midland Valley, the rift valley which runs across the centre of the country, comprising primarily sedimentary rocks of Devonian and Carboniferous age, deposited in desert and shallow marine conditions. To the south are older Silurian and Ordovician sediments deposited in a deep ocean environment. The Southern Uplands Fault, together with the complementary Highland Boundary Fault located approximately 60 miles (100 km) to the north, permitted the Midland Valley to descend as a major rift or graben by as much as 4000m (13,123 feet).

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