The BGS Lexicon of Named Rock Units — Result Details

Holehead Lava Member

Computer Code: HHLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Holehead Lava Member consists mainly of plagioclase-macrophyric basalts and trachybasalts (basalts to hawaiites of 'Markle' type), characterised by the presence of variable amounts of generally relatively small plagioclase macrophenocrysts. In addition, one lava of transitional trachybasalt to mugearite composition is exposed in the middle of lava sequence. The flows tend to be relatively thin with slaggy tops and locally rubbly bases. The lavas were thought by Craig (1980) to have been derived from the Waterhead Centre ('Waterhead Central Volcanic Complex').
Definition of Lower Boundary: The basal plagioclase-macrophyric basalt, and or trachybasalt (hawaiite), is conformable or disconformable on basaltic-trachyandesite (mugearite) of the Fin Glen Lava Member.
Definition of Upper Boundary: The Holehead Lava Member occupies summit areas across its outcrop and the top of the member has been eroded.
Thickness: More than 100 m, top eroded
Geographical Limits: The member is restricted to the Campsie Block and has a limited geographical extent in the Central Campsie Fells, north of Glasgow.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Holehead Lavas (-2237)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Central Campsie Fells, north of Glasgow Forsyth et al, 1996, after Craig, 1980 
Reference Section  Aldesssan Burn, central Campsie Fells, north of Glasgow 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). 
Craig, P.M. 1980 The Volcanic Geology of the Campsie Fells area, Stirlingshire. Unpublished PhD thesis, University of Lancaster. 
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S031 S030