The geology of the Kirkmichael area, Ayrshire

This description is of the geology of 1:10 000 Sheet NS 30 NW (Kirkmichael) which lies within 1:50 000 Geological Sheet 14W Ayr (Scotland). The area is crossed by the north-easterly trending Kerse Loch Fault (Figure 1) which separates mainly Siluro-Devonian strata to the north-west from Carboniferous strata to the south-east. The Siluro-Devonian strata comprise continental fluviatile sandstones and conglomerates, belonging to the Swanhaw Sandstone Formation, which were intruded by a suite of basic to andesitic sills and dykes in early Devonian times. The oldest Carboniferous rocks belong to the Inverclyde Group (Tournaisian to early Visean), which includes the Kinnesswood, Ballagan and Clyde Sandstone formations. They are not well exposed but represent a passage from semi-arid fluviatile sandstones through lagoonal mudstones, sandstones and limestones back into semi-arid fluviatile sandstones. These are unconformably succeeded by Visean deltaic deposits belonging to the Lawmuir Formation of the Strathclyde Group. This formation is succeeded by the Upper Visean Lower Limestone Formation and the Lower Namurian Limestone Coal Formation preserved within the core of the major Dailly Syncline. The Limestone Coal Formation contains significant coal seams which have been extensively mined. In Tertiary (Palaeocene) times minor intrusions of basaltic to microgabbroic rock were intruded as part of the Mull Dyke Swarm. The age of some of the mafic rocks is uncertain; they could be early Devonian to Palaeocene in age. Quaternary deposits, laid down after the Late Devensian Glaciation, cover most of the sedimentary rocks. The cover generally consists of lodgement till moulded below the ice into a drumlin field. Remnants of the ice around Maybole downwasted and poorly sorted hummocky glacial deposits accumulated. Glaciofluvial sand and gravel was deposited in patches near the Water of Girvan and in a belt passing through Kirkmichael. A broad belt of alluvium was deposited by the Water of Girvan and patches elsewhere occur between drumlins and hummocky glacial deposits. Most of the soils in the area are loams. Heavy loams and peaty soils are found locally in the alluvial areas near the Water of Girvan and the small lochans south-east of Maybole. Minor areas of made ground are mapped, mostly around Maybole. Patches of worked and worked and back-filled ground are even more limited.