The BGS Lexicon of Named Rock Units — Result Details

Knowehead Lava Member

Computer Code: KNLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Knowehead Lava Member consists of a broad range of petrographic types, including plagioclase-macrophyric trachybasalt (hawaiite of 'Markle' type), olivine-clinopyroxene-plagioclase-macrophyric basalt ('Dunsapie' type), microporphyritic trachybasalt (hawaiite), basaltic trachyandesite (mugearite), and a rhyolite lava of restricted lateral extent. Numerous intercalations of coarse tuff and the slaggy tongue-like character of some of the lavas, led Craig (1980) to suggest that at least some of the lavas are close to their eruptive source, although no vents have been identified.
Definition of Lower Boundary: The Knowehead Lava Member is fault bounded and the lower boundary is not seen.
Definition of Upper Boundary: The Knowehead Lava Member is fault bounded and the upper boundary is not seen.
Thickness: Greater than 50 m
Geographical Limits: The member is restricted to the southern side of the Campsie Fells, north of Glasgow. It crops out on the south side of the Campsie Fault, in lower ground below the escarpment, bounded by the Campsie Fault to the north, and another west-north-west-trending fault to the south. The outcrop was thought by Craig (1980) to extend farther west, but correlation in that area with the similar Cochno Lava Member of the Kilpatrick Hills succession (Hall et al., 1998) is uncertain.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Knowehead Lavas (-3502)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  South side of the central Campsie Fells, north of Glasgow Forsyth et al, 1996, after Craig, 1980 
Reference Section  The member is best exposed in the Fin Glen Burn. Craig, 1980 
Reference(s):
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). 
Forsyth, I H, Hall, I H S and McMillan, A A. 1996. Geology of the Aidrie district. Memoir of the British Geological Survey, Sheet 31W (Scotland). 
Craig, P.M. 1980 The Volcanic Geology of the Campsie Fells area, Stirlingshire. Unpublished PhD thesis, University of Lancaster. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S031 S030