The BGS Lexicon of Named Rock Units — Result Details

Black Mount Lava Member

Computer Code: BMLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Black Mount Lava Member consists predominantly of plagioclase-microphyric basalt lavas (of 'Jedburgh' type) with subordinate basaltic-trachyandesite (mugearite) lavas. The microporphyritic basalt lavas are variably albitised, slaggy, vesicular, and platy jointed and are locally transitional to a partly plagioclase-macrophyric lithology.
Definition of Lower Boundary: The basal plagioclase-microphyric basalt of the Black Mount Lava Member is apparently conformable or disconformable on plagioclase-macrophyric basalt lava of the Gargunnock Hills Lava Member.
Definition of Upper Boundary: The Black Mount Member is overlain by plagioclase-macrophyric basalt lava (of 'Markle' type) of the Touch House Lava Member. The lithological transition is from plagioclase-microphyric to plagioclase-macrophyric basalt.
Thickness: More than 24 m
Geographical Limits: The member is restricted to the eastern Touch Hills, north-east of Glasgow. These rocks crop out from the west side of Black Mount [NS 7391 9175] to near Seton in the north-east [NS 7600 9327] and Garter Wood in the east [NS 7652 9189].
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Black Mount Group (-68)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  In the eastern Touch Hills, north-east of Glasgow Francis et al, 1970 
Reference Section  The south side of Touch Burn gorge, north-east Touch 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