| 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 [Obsolete Name and Code: Use DNLA]
(-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): |
| Forsyth, I H, Hall, I H S and McMillan, A A. 1996. Geology of the Airdrie district. Memoir of the British Geological Survey, Sheet 31W (Scotland). |
| Dean, M T, Browne, M A E, Waters, C N and Powell, J H. 2011. A lithostratigraphical framework for the Carboniferous successions of northern Great Britain (onshore). British Geological Survey Research Report, RR/10/007. 165pp. |
| 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
|
