Geology of the Ayr district

This account of the geology of the Ayr district, in the south-west of the Midland Valley of Scotland, covers the area from around Monkton in the north, to Dailly in the south. The description of the bedrock geology includes field observations recorded up to 2002, together with earlier published and unpublished work on the area. The Quaternary section updates field records and reviews earlier published work. The district covers the growing town and administrative centre of Ayr and its neighbour Prestwick, extending south into rural farmland and scenic hill country. Farther south is the market town of Maybole and the former coalfield around Dailly. It also covers some dramatic coastal scenery and sweeping bays, with tourist attractions stretching from the golf courses south of Troon, past the ruined castles of Greenan and Dunure, to Culzean Castle overlooking Culzean Bay and onto Maidens and Turnberry. The bulk of the rocks are sedimentary and Palaeozoic in age, with a succession extending from Ordovician to early Permian, punctuated by several volcanic and intrusive igneous episodes. In Mid Ordovician times, about 470 Ma ago, the district lay close to the southern edge of the Laurentian continent. Oceanic crust was thrust up when a volcanic arc collided with the microcontinental segment that formed the Midland Valley Terrane as it docked against Laurentia. Upper Ordovician to lower Silurian sediments were deposited in a forearc basin on the southern margin of this terrane and were deformed as the Southern Uplands accretionary prism was pushed up from the south during the Caledonian Orogeny. The Lanark Group was later deposited, in Siluro-Devonian times, in a sequence of sandstones and conglomerates lain down in a semi-arid environment, prior to the Early Devonian calc-alkaline magmatic event which produced shallow intrusions and eruptions of predominantly basaltic andesite. By Mid Devonian times the Lanark Group had been weakly deformed and uplifted as a far-field effect of the late stage Acadian deformation event.