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Gleniffer Lava Member (GLLA), Beith-Barrhead Hills

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== Gleniffer Lava Member [http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=GLLA (GLLA)], Beith-Barrhead Hills, Carboniferous, Midland Valley of Scotland==

The Gleniffer Lava Member is part of the [[Clyde Plateau Volcanic Formation]].

=== Name ===
Previously known as the ‘Gleniffer Lavas’ (Hall et al., 1998<ref name="hall98">Hall, I H S, Browne, M A E, and Forsyth, I H. 1998. Geology of the Glasgow district. ''Memoir of the British Geological Survey'', Sheet 30E (Scotland)</ref>, Monro, 1999<ref name="monro99">Monro, S K. 1999. Geology of the Irvine district. ''Memoir of the British Geological Survey'', Sheet 22W, part 21E (Scotland)</ref>; Paterson et al., 1990<ref name="paterson90">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)</ref>), ‘Lower Group (a)’ (Richey et al., 1930)<ref name="richey30>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)</ref>.

=== Lithology ===
The member comprises distinctive olivine-bearing plagioclase-macrophyric basalts (‘Markle’ type). Characterised by lavas with abundant, platy phenocrysts of plagioclase up to 25 mm long and microphenocrysts of red-brown olivine. A massive flow of plagioclase-microphyric basalt (‘Jedburgh’ type) forms the base of the member at Linn Well (NS 475 605). The lavas are interbedded with volcaniclastic sedimentary rocks at the base.

=== Stratotype ===
The Gleniffer Lava Member crops out in a prominent scarp in its type area along the north side of Gleniffer Braes to Brownside Braes (NS 450 607 to NS 485 605) (see Hall et al., 1998)<ref name="hall98"/>.

=== Lower and upper boundaries ===
The Gleniffer Lava Member is underlain by the sedimentary rocks of the [[Glenburn Volcaniclastic Member]] to the north and east of Brownside Braes (NS 485 605).

The member is overlain and may be cut out or overlapped, by the mafic basalts of the [[Sergeantlaw Lava Member]] around Sergeantlaw (NS 455 597) and to the east of Middleton (NS 445 579), and to the west of Barcraigs Reservoir (NS 39 57) and Walls Hill (NS 41 59).

=== Thickness ===
The thickness is not stated.

=== Distribution and regional correlation ===
The Gleniffer Lava Member crops out in the Beith–Barrhead Hills to the east of Barcraigs Reservoir (NS 39 57) and is faulted against the [[Kirkwood Formation]] and [[Lawmuir Formation]] in the north, to the north of High Burnside (NS 42 60). It extends eastwards through Gleniffer Braes (NS 450 607) to Brownside Braes (NS 485 605). To the south the unit is faulted against the [[Upper Limestone Formation]] in Loch Libo (NS 435 556), and the [[Limestone Coal Formation]] by the Dusk Water Fault.

=== Age ===
Mid Visean (Arundian to Asbian).

== References ==

<references/>
[[Category:Carboniferous lithostratigraphical nomenclature]]

Gleniffer Lava Member - Revision history

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Geosource>Volunteer 01: /* Gleniffer Lava Member (GLLA), Beith-Barrhead Hills */