Synopsis
The stratigraphy of the upper Brigantian (Lower Limestone Group and upper Calciferous Sandstone Measures) of the south-west margin of the Central Coalfield, of North and Central Ayrshire and of the Douglas Coalfield and Muirkirk Syncline is reviewed. The prolonged basal overlap of the upper Brigantian on to an upland area is seen to have been complicated by both gradual and intermittent tectonic activity. Sequences have thus been affected by a number of disconformities of varying extent and magnitude. A new correlation between Ayrshire and the Paisley district is proposed. The Dockra, Broadstone and Upper and Lower Old Mill Limestones of Ayrshire correlate respectively with the Hurlet, Blackbyre, Hollybush and Dykebar Limestones of Paisley. The major complication is associated with the supra-Dockra (Hurlet) disconformity which caused the Dockra Limestone to be exhumed over a wide area in Ayrshire. In the subsequent overlap of this surface the Blackhall Limestone transgression failed to reach North Ayrshire. The Hosie Limestones A–D of Ayrshire correlate with the Main to Top Hosie Limestones of Paisley. The disconformity at the Hosie Fireclay (Lillie's Shale Coal) position has caused the local erosion of Hosie Limestone B (Mid Hosie) and perhaps also of Hosie Limestone A (Main Hosie).