The Upper Brigantian (Lower Carboniferous) of Central Strathclyde

Abstract

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).

The Upper Brigantian (Lower Carboniferous) of Central Strathclyde: reply

“…I am happy to accept Wilson's view that the H o w w o o d area (33-35) lay close to the margin of the Dykebar transgression but I do not think that this precludes an extension of the Dykebar Limestone into N o r t h Ayrshire (Whyte 1981, fig. 3).…”

“…It was not m y intention to provide a detailed account of the complex history of correlations within the area and thus m y references to Hinxman et al (1921) and Lumsden (1967) to which Wilson draws attention were intended to acknowledge descriptive sources rather than the correlations which had previously been set out (Whyte 1981, …”

Scottish Carboniferous fresh-water limestones in their regional setting

“…The Lower Limestone Formation (Smith et al, this volume) consists of a number of cycles of Yoredale facies in which marine conditions are well developed. Though volcanic activity persisted in the Bathgate Hills and in West Fife and though the Clyde Plateau Volcanic Formation still provided a partial barrier between the Central and Ayrshire Basins (Whyte 1981), deposition within the group was more uniform than previously (Goodlet 1957;Browne et al 1985).…”

“…Towards the top of the Strathclyde Group the Clyde Plateau Volcanic Formation became increasingly overstepped and the palaeogeography of Lake Cadell began to break down. Though marine conditions extended far into the Midland Valley on a number of occasions (Whyte 1981;Wilson 1989) some fresh-water carbonates, including the East Kirkton Limestone, were also deposited (see Sections 2.3 and 2.4).…”

“…A very localised development of lacustrine oncoids and stromatolites occurs in the Lower Limestone Formation of Ayrshire at South Hourat. This development is associated with the supra-Dockra disconformity (Whyte 1981) and rests on the eroded surface of the Dockra Limestone. The oncoids and stromatolites grow on and round fragments of the marine limestone.…”