The BGS Lexicon of Named Rock Units — Result Details

Skiddaw Lava Member

Computer Code: SKDL Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Skiddaw Lava Member consists predominantly of plagioclase-macrophyric basalt (of 'Markle' type) and composite lavas with some plagioclase-microphyric basalt (of 'Jedburgh' type). In the east of the outcrop [NS 6572 9122], the member includes a composite lava composed of massive, rounded bodies mostly of macroporphyritic basalt, but also includng near the centre of the lava some transitional plagioclase-microphyric to olivine-microphyric basalts, in a matrix of slaggy, highly vesicular microporphyritic basalt.
Definition of Lower Boundary: The basal basalt of the member unconformably overlies sedimentary rocks, including sandstone, siltstone and mudstone of the Clyde Sandstone Formation, of the Inverclyde Group.
Definition of Upper Boundary: 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 below.
Thickness: 0-37 m
Geographical Limits: The member is restricted 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].
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Slackgun, north-western Gargunnock Hills, north-east of Glasgow Francis et al, 1970 
Type Area  In the northern and western Fintry Hills, and in the north-western Gargunnock Hills, north-east of Glasgow Francis et al, 1970 
Reference(s):
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S039