| Computer Code: |
OVLA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Asbian Substage (CR) |
| Lithological Description: |
The Overton Lava Member consists of at least one plagioclase-macrophyric basalt lava (of 'Markle' type) overlying a basaltic-trachyandesite lava (mugearite). Several lavas, including trachybasalt, may be present and the best exposures are in the faulted River Carron section, to the north-west of Nicholswalls [NS 764 843] and in the Overton Burn, east of Overton [NS 772 834]. No source for the lavas has been identified. |
| Definition of Lower Boundary: |
The basal basaltic-trachyandesite (mugearite) lava of the member is conformable or disconformable in the north on the trachybasalt lavas of the undivided lower north and south Campsie lavas (Campsie Lava Member). Elsewhere the base is not seen. |
| Definition of Upper Boundary: |
The Overton Lava Member in the east is overlain conformably or disconformably by the undivided upper north and south Campsie lavas (Campsie Lava Member), and in the north, the member is overlain specifically by the upper north Campsie lavas. The transition is from plagioclase-macrophyric basalt lava to plagioclase-microphyric trachybasalt and some basalt lavas (basalt to hawaiite of 'Jedburgh' type) with scoriaceous agglomerates and tuffs. |
| Thickness: |
35 m |
| Geographical Limits: |
The member is restricted to the Campsie Block and specifically to the eastern part of the Kilsyth Hills, north-east of Glasgow. |
| Parent Unit: |
Clyde Plateau Volcanic Formation (CPV)
|
| Previous Name(s): |
Overton Lavas [Obsolete Name and Code: Use OVLA]
(-4240)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
Overton Burn, east of Overton, eastern Kilsyth HIlls, north-east of Glasgow. Craig, 1980. |
| Type Area |
Eastern 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 Airdrie 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 Unpublished PhD thesis, University of Lancaster. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S031
|
