Enterkin Mudstone Formation
Enterkin Mudstone Formation is part of the Clackmannan Group
The formation consists dominantly of purple-grey mudstone and siltstone with interbedded sandstone.
This mixed shelf carbonate and deltaic (‘Yoredale’) facies unit formed in a marine–intertidal environment. The mudstones contain a marine fauna.
The type section is in the Enterkin Burn (NS 8706 0526) where up to 15 m of interbedded red-brown and purple mudstone and siltstone, and purplish red sandstone and seatearth are exposed (McMillan, 2002; Simpson and Richey, 1936, table 3).
Lower and upper boundaries
The base of the formation is unconformable on the mainly sandstone-dominated turbidites of the Ordovician Glenlee Formation, Leadhills Supergroup.
The top of the formation is conformable with the base of the Scottish Lower Coal Measures Formation (Figure 6, Column 6) comprising sandstones, siltstones and mudstones, with seatearths.
Distribution and regional correlation
The formation is restricted to the Thornhill Basin. The mudstones contain a fauna, that suggests possible correlation with the Clackmannan Group (undivided) Visean strata of the Sanquhar Basin.
Age and biostratigraphical characterisation
Visean to Namurian (Brigantian to early Pendleian). The mudstones contain a brachiopod, bivalve and nautiloid fauna, which may be of similar age to the fauna of the Closeburn Limestone Formation.
- McMillan, A A.2002.Geology of the New Galloway and Thornhill district.Memoir of the British Geological Survey, Sheets 9E and 9W (Scotland).
- Simpson, J B, and Richey, J E.1936.The geology of the Sanquhar coalfield and adjacent basin of Thornhill.Memoir of the Geological Survey of Great Britain, Sheets part 9 and 15 (Scotland)