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Geosource>Volunteer 01: /* Skiddaw Lava Member (SKDL), Carboniferous, Midland Valley of Scotland */

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Skiddaw Lava Member (SKDL), Carboniferous, Midland Valley of Scotland

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==Skiddaw Lava Member [http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=SKDL (SKDL)], Fintry-Touch Block, Carboniferous, Midland Valley of Scotland ==
Skiddaw Lava Member is part of the [[Clyde Plateau Volcanic Formation]].
=== Name ===
Previously named the Skiddaw Group (Francis et al., 1970)<ref name="Francis70">Francis, E H, Forsyth, I H, Read, W A, and Armstrong, M. 1970. The geology of the Stirling district. ''Memoir of the Geological Survey of Great Britain'', Sheet 39 (Scotland)</ref>.

=== Lithology ===
The Skiddaw Lava Member consists predominantly of plagioclase-macrophyric basalt (‘Markle’ type) and composite lavas with some plagioclase-microphyric basalt (‘Jedburgh’ type). In the east of the outcrop (NS 6572 9122) the member comprises coarse olivine basalt at the base, above which the sequence comprises: a plagioclase-macrophyric basalt lava, a composite lava composed of massive, rounded bodies mostly of plagioclase-macrophyric basalt, but also including near the centre of the lava some transitional plagioclase-microphyric to olivine-microphyric basalts, in a matrix of ‘slaggy’, highly vesicular microporphyritic basalt; and a massive, transitional plagioclase-microphyric to plagioclase-macrophyric basalt with traces of columnar jointing.

=== Stratotype ===
The type area is in the northern and western Fintry Hills, and the north-western Gargunnock Hills, north-east of Glasgow (NS 6304 8712 to NS 6577 9122) (Francis et al., 1970)<ref name="Francis70"></ref>. A reference section is at Slackgun, north-western Gargunnock Hills (NS 6572 9122) where a section 34 m thick (apparently the full thickness at this locality) was given by Francis et al. (1970)<ref name="Francis70"></ref>.

=== Lower and upper boundaries ===
The basal basalt lava of the member unconformably overlies sedimentary rocks, including sandstone, siltstone and mudstone of the [[Clyde Sandstone Formation]], of the [[Inverclyde Group]].

The Skiddaw Lava Member is overlain unconformably by the [[Slackgun Volcaniclastic Member]]. The lithological change is from transitional plagioclase-macrophyric to plagioclase-microphyric basalt lava or composite basalt lava to a dull red bole reflecting prolonged weathering of the lavas.

=== Thickness ===
Between 0 and 37 m.

=== Distribution and regional correlation ===
The member is restricted to the northern Fintry–Touch Block (Francis et al., 1970)<ref name="Francis70"></ref> and specifically to the northern and western Fintry Hills and to the north-western Gargunnock Hills, north-east of Glasgow. These rocks crop out from below Double Craigs (NS 6304 8712) north-north-west towards Skiddaw (NS 622 891) and then north-east, to the north-west side of Lees Hill (NS 6577 9122).

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

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

Skiddaw Lava Member - Revision history

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Geosource>Volunteer 01: /* Skiddaw Lava Member (SKDL), Carboniferous, Midland Valley of Scotland */