Orroland Member

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Orroland Member (ORR), Carboniferous, Midland Valley of Scotland[edit]

Orroland Member is part of the Ballagan Formation

Name[edit]

Previously known as the Orroland Limestone Beds by Craig and Nairn (1956)[1], the Orroland Group by Deegan (1973)[2], and the Orroland Formation by Lintern and Floyd (2000)[3]. The status is here changed to a member.

Lithology[edit]

Conglomerates, conglomeratic sandstones, sandstones, red siltstones, ‘marls’ and pedogenic dolostones (‘cornstones’).

Stratotype[edit]

The type section is the coastal section from Port Mary to Castle Muir (NX 7445 4537 to 7980 4720) where the sequence comprises (base upwards) of about 90.m of conglomerates and sandstones; 18 m of conglomeratic sandstones, siltstones, ‘marls’ and dolostones; 25.m of conglomeratic sandstones, and silty and sandy ‘marls’ with dolostone nodules; about 10 m of calcareous sandstones, mudstones, ‘marls’ and impure marine limestones; about 9.m of burrowed marine sandstone; 28 m of conglomeratic sandstones and ‘marls’ with dolostone nodules; and 90–100.m of conglomeratic sandstones and sandstones (Deegan, 1973[2]; see also Lintern and Floyd, 2000, p. 85[3]).

Lower and upper boundaries[edit]

The base of the member is faulted against the sandstones and conglomerates of the Wall Hill Member (Figure.10, Column 1).

The top of the member is faulted against the conglomeratic sandstone and thin interbeds of calcareous mudstone and siltstone of the Rascarrel Member (Fell Sandstone Formation).

Thickness[edit]

About 280 m.

Distribution and regional correlation[edit]

Coastal section from Port Mary (NX 7445 4537) to Castle Muir (NX 7980 4720), south-west Scotland (Solway Firth).

Age[edit]

Chadian.

References[edit]

  1. Craig, G Y, and Nairn, A E M.1956.The Lower Carboniferous outliers of the Colvend and Rerrick shores, Kirkcudbrightshire.Geological Magazine, Vol. 93, 249–256.
  2. 2.0 2.1 Deegan, C E.1973.Tectonic control of sedimentation at the margin of a Carboniferous depositional basin in Kirkcud-brightshire.Scottish Journal of Geology, Vol. 9, 1–28.
  3. 3.0 3.1 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)