The BGS Lexicon of Named Rock Units — Result Details

Laird's Loup Lava Member

Computer Code: LDLL Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Laird's Loup Lava Member consists of plagioclase-macrophyric trachybasalt lavas (of 'Markle' type). At least six lavas are well exposed in the Laird's Loup area of the Garrel Burn [NS 703 804], where the section is 50 m thick. The base of the member is not exposed in this section, but the topmost lava is. Individual lavas range in thickness from 6 to 15 m, though some are variable in thickness. The lavas are massive, and there is a lack of significant tuff between the lavas, suggesting that the flows are relatively distal The lavas are variably altered and some are characterised by their ophitic texture. No specific source vent has been identified for the lavas although the vent at Craigdouffie, is a possible source (Craig, 1980), since the neck of the vent is infilled with breccia of similar material and exposures of the member near to the vent show proximal-facies characteristics.
Definition of Lower Boundary: The basal trachybasalt of the Laird's Loup Lava Member appears to be either conformable or disconformable on the underlying microporphyritic basalt lava of the Drumnessie Lava Member.
Definition of Upper Boundary: At the western end of its outcrop, the Laird's Loup Lava Member is overlain by the Campsie Lava Member. The lithological change is to mostly plagioclase-microphyric basalt or trachybasalt (basalt to hawaiite of 'Jedburgh' type). At the eastern end of its outcrop, the member is overlain by the Tappetknowe Lava Member, the lithological change being to microporphyritic basaltic-trachyandesite (mugearite) and trachybasalt (hawaiite) lavas and rare plagioclase-macrophyric trachybasalt (hawaiite) lavas (of 'Markle' type).
Thickness: 65 m
Geographical Limits: The member is restricted to the southern part of the Campsie Block (Forsyth et al, 1996) and specifically to the southern side of the central Kilsyth Hills, north-east of Glasgow. These rocks crop out along the escarpment on the southern side of the Kilsyth Hills, north of Kilsyth, from the southern flank of Laird's HiIl [NS 6920 7974], eastwards to Green Bank [NS 7224 8068]. A further small area of outcrop in the Craigdouffie Burn ([NS 7424 8088] to [NS 7437 8073]) is tentatively correlated with the member.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Laird's Loup Lavas (-2894)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Laird's Loup area of the Garrel Burn, south-central Kilsyth Hills, north-east of Glasgow Craig, 1980 
Type Area  South-central Kilsyth Hills, north-east of Glasgow Forsyth et al, 1996, after Craig, 1980 
Reference(s):
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