The BGS Lexicon of Named Rock Units — Result Details

Laird's Hill Lava Member

Computer Code: LDHL Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Laird's Hill Lava Member consists of only one or two lavas. In the stream sections to the north and west of Corrie Reservoir [NS 674 791] it is represented by a single lava of plagioclase-macrophyric basalt (of 'Markle' type). Farther north-east, it consists of a similar flow, underlain by a basaltic-trachyandesite (mugearite) lava. The source of the lavas is uncertain.
Definition of Lower Boundary: The basal plagioclase-macrophyric basalt, or locally basaltic-trachyandesite (mugearite), of the member is conformable or disconformable in the south on the underlying microporphyritic trachybasalt lava of the lower south Campsie lavas (Campsie Lava Member), and in the north, on the undivided microporphyritic trachybasalt lavas of the lower north and south Campsie lavas (Campsie Lava Member).
Definition of Upper Boundary: The Laird's Hill Lava Member is overlain in the north by the undivided upper north and south Campsie lavas (Campsie Lava Member) and the lithological change is to microporphyritic trachybasalt. However, in the south, the upper north and south Campsie lavas are absent due to erosion prior to deposition of the Lower Lecket Hill Lava Member and the Laird's Hill Lava Member is overlain unconformably by basaltic-trachyandesite of the Lower Lecket Hill Lava Member. Locally also, in the south, the Laird's Hill Lava Member is itself absent, presumably due to erosion prior to deposition of the Lower Lecket Hill Lava Member.
Thickness: 20 m
Geographical Limits: The member is restricted to the Campsie Block (Forsyth et al, 1996) and specifically to the central part of the Kilsyth Hills, north-east of Glasgow. These rocks crop out in two main area. One, on the northern side of the Campsie Fault extends eastwards from the east flank of Brown HiIl [NS 6670 7913] (not identifiable as separate lithologies on 50k sheet 31W). It is locally absent on the south-west flank of Laird's HIll (between [NS 6844 7964] and [NS 6938 7996], but re-appears on the south-east, east and north flanks of Laird's HIll [NS 6957 8018] (difficult to delineate as separate lithologies on 50k sheet 31W and 10k sheets NS67NE and NS68SE). The second area of outcrop extends from the north flank of Barrel HIll [NS 7042 8158] westwards as far as the Burnhouse Burn on the south-east side of Meikle Bin [NS 6746 8194].
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Laird's Hill Lavas (-3517)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Central Kilsyth Hills, north-east of Glasgow, in particular near the summit of Laird's Hill [NS 696 801]. Forsyth et al., 1996, after Craig, 1980 
Reference Section  Birken Burn, central Kilsyth Hills, north-east of Glasgow. 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