The BGS Lexicon of Named Rock Units — Result Details

Drumnessie Lava Member

Computer Code: DNLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: The Drumnessie Lava Member consists of several lavas with intercalations, which make up to 50% of the total thickness of the member, of agglomerate and variably stratified lapilli-tuff, composed substantially of accidental and 'accessory' pyroclasts. The agglomerates include breadcrust bombs. The lavas are mostly plagioclase-, olivine-plagioclase-, and olivine-microphyric basalts (of 'Jedburgh' transitional to 'Dalmeny' types), but there is also one clinopyroxene-olivine-macrophyric basalt ('ankaramite' of 'Craiglockhart' type). The lavas exhibit proximal characteristics and several nearby necks of the South Campsie Linear Vent-swarm are plugged by basalt of similar type (e.g. near St Mirren's well [NS721 795]), and are probable sources. The BGS Tak-ma-doon borehole intersected the middle and basal lavas of this member.
Definition of Lower Boundary: The base is unconformable. In the BGS Tak-ma-doon borehole the basal lava of the Drumnessie Lava Member was seen to overlie mudstone, siltstone and nodular dolomitic limestone of the Ballagan Formation. However, 2 km to the west, in the Bachille Burn [NS 707 793], the member rests directly on sandstone and nodular limestone of the Kinnesswood Formation.
Definition of Upper Boundary: The Drumnessie Lava Member is overlain conformably or disconformably by the Laird's Loup Lava Member. The lithological change is to plagioclase-macrophyric basalt lava (of 'Markle' type).
Thickness: Up to 60 m
Geographical Limits: The member is restricted to the southern part of the Campsie Block and specifically to the southern side of the central Kilsyth Hills, north-east of Glasgow.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Drumnessie Lavas (-215)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  South-central Kilsyth Hills, north-east of Glasgow Forsyth et al, 1996, after Craig, 1980 
Reference Section  The BGS Tak-ma-doon borehole (NS78SW BJ5 [NS 7291 8053]), south-central Kilsyth Hills, north-east of Glasgow, 43 m section intersected Craig, 1980 
Reference(s):
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 Unpublished PhD thesis, University of Lancaster.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