Powillimount Sandstone Member

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Powillimount Sandstone Member (POSD), Carboniferous, Midland Valley of Scotland[edit]

Powillimount Sandstone Member is part of the Border Group


Originally named the Powillimount Beds and Thirlstane Sandstone by Craig (1956), and the Powillimount Sandstone Formation by Lintern and Floyd (2000)[1].


See Craig (1956)[2] and Deegan (1970)[3]. Interbedded bioturbated sandstone, sandy limestone (with some oncolite beds), and sparsely fossiliferous mudstone. There is subsidiary siltstone and a trace of coal.


The type section is the coast between Powillimount Bay (NX 9880 5610) and Thirl Stane (NX 9925 5690) with about 160 m of sandstone, limestone, and mudstone. The top 25 m of the member comprise the thick-bedded Thirlstane Sandstone Beds (Lintern and Floyd, 2000[1]).

Lower and upper boundaries[edit]

The base is gradational and taken where mainly interbedded medium- to coarse-grained sandstone and subsidiary conglomerate of the Gillfoot Sandstone Member gives way to mainly interbedded bioturbated sandstone, sandy limestone and mudstone of the Powillimount Sandstone Member (Figure 10, Column 2).

The top of the member is taken at the top of the Thirlstane Sandstone, which lies conformably beneath the interbedded marine limestone, mudstone and subsidiary siltstone, with thick cross-bedded, bioturbated, medium-grained sandstone of the Arbigland Limestone Member, Tyne Limestone Formation.


Some 135 m

Distribution and regional correlation[edit]

Powillimount shore, Southerness, Kirkcudbrightshire, south-western Scotland (Southern Uplands).


Arundian to Holkerian.


  1. 1.0 1.1 Lintern, B C, and Floyd, J D.2000.Geology of the Kirkcudbright–Dalbeattie district.Memoir of the British Geological Survey, Sheets 5W and 5E, part 6W (Scotland)
  2. Craig, G Y.1956.The Lower Carboniferous outlier of Kirkbean, Kirkcudbrightshire.Transactions of the Geological Society of Glasgow. Vol. 22, 113–122
  3. Deegan, C E.1970.The petrology and sedimentology of the Lower Carboniferous rocks between White Port and Kirkbean, Kirkcudbrightshire. Unpublished PhD thesis, University of Wales, Aberystwyth