Beith Lava Member

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Beith Lava Member (BELA), Beith-Barrhead Hills, Carboniferous, Midland Valley of Scotland[edit]

The Beith Lava Member is part of the Clyde Plateau Volcanic Formation.

Name[edit]

The Beith Lava Member was previously known as the ‘Beith Lavas’ (Paterson et al. 1990[1]; Monro 1999[2]), and the ‘Upper Group’ (Richey et al. 1930)[3].

Lithology[edit]

The formation comprises olivine-microphyric basalt (‘Dalmeny’ type). Red boles are common between flows and interbedded chocolate-coloured ‘marls’ are present. Evidence from outcrop and the Crummock Park borehole (NS 3503 5392) suggests large parts of the flows are extensively altered and decomposed. South of Roebank Glen (NS 353 554) a flow of plagioclase-macrophyric basalt (‘Markle’ type) crops out within the member.

Stratotype[edit]

The Beith Lava Member crops out in its type area on lower slopes at the south-west limit of the Beith–Barrhead Hills between (NS 35 54) and (NS 36 57) (see Monro, 1999)[2]. A reference section is the Crummock Park Borehole (see above) which penetrates the lowest 50 m of the Beith Lava Member, but no detailed geological log is available (see Monro, 1999)[2].

Lower and upper boundaries[edit]

The member is underlain by the ‘Markle’ and ‘Dunsapie’ type basalts of the Fereneze Lava Member.

The member is overlain by volcaniclastic sedimentary rocks of the Kirkwood Formation (Strathclyde Group) wherever the top of the member crops out.

Thickness[edit]

About 90 m.

Distribution and regional correlation[edit]

The member occurs to the west and south-west of the Beith–Barrhead Hills, on the north-west limb of the Beith Anticline, but is faulted out on the south-eastern limb. The unit underlies the town of Beith (NS 35 54) and extends north-east until it is faulted out against the Paisley Ruck Fault just north of East Gavin (NS 389 599).

Age[edit]

Mid Visean (Arundian to Asbian).

References[edit]

  1. Paterson, I B, Hall, I H S, and Stephenson, D. 1990. Geology of the Greenock district. Memoir of the British Geological Survey, Sheet 30W part 29E (Scotland)
  2. 2.0 2.1 2.2 Monro, S K. 1999. Geology of the Irvine district. Memoir of the British Geological Survey, Sheet 22W, part 21E (Scotland)
  3. Richey, J E, Anderson, E M, and MacGregor, A G. 1930. The geology of north Ayrshire. Memoir of the Geological Survey of Great Britain, Sheet 22 (Scotland)