| Computer Code: |
CBRL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Asbian Substage (CR) |
| Lithological Description: |
The Carron Bridge Lava Member consists predominantly of plagioclase-macrophyric trachybasalt lavas ('basaltic hawaiite' to hawaiite of 'Markle' type). Many of the lavas are relatively thick, some being in excess of 15 m. All of the lavas are massive, relatively altered, and in the Carron Bridge and Faughlin areas, have particularly high concentrations of plagioclase phenocrysts which tend to be elongate, up to 6 mm in length, and aligned in the presumed direction of flow. In addition, fairly large pseudomorphed olivine phenocrysts are also present, but are less common than the plagioclase phenocrysts. Craig (1980) regarded these lavas as having distal-facies characterisitics. There is no indication of the source of the lavas. |
| Definition of Lower Boundary: |
The base has not been seen but is likely to be unconformable on sedimentary rocks of the Inverclyde Group. |
| Definition of Upper Boundary: |
In the section of the River Carron, below the bridge [NS 748 838], and in the Faughlin area to the south [NS 735 827], the Carron Bridge Lava Member is overlain, apparently conformably, or disconformably, by the Faughlin Lava Member. The lithological change is to tuff and agglomerate and basaltic-trachyandesite (mugearite). However, in the Carron River section above the bridge, and on its southern bank, the Faughlin Lava Member is absent, and the Carron Bridge Lava Member is overlain, disconformably or unconformably, by the Campsie Lava Member. |
| Thickness: |
More than 50 m, base not seen. |
| Geographical Limits: |
The member is restricted to the eastern part of the Campsie Block and specifically to the eastern Kilsyth Hills, north-east of Glasgow. |
| Parent Unit: |
Clyde Plateau Volcanic Formation (CPV)
|
| Previous Name(s): |
Carron Bridge Lavas [Obsolete Name and Code: Use CBRL]
(-3906)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
In the eastern Kilsyth Hills, north-east of Glasgow. Forsyth et al., 1996, after Craig, 1980. |
| Reference Section |
River Carron, above and below the bridge, north-west Kilsyth Hills, north-east of Glasgow. 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 Unpublished PhD thesis, University of Lancaster.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 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S031
|
