| Computer Code: |
CBLA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Asbian Substage (CR) |
| Lithological Description: |
The lowest exposed part of the member (80 m seen) comprises flows of olivine-microphyric basalt and plagioclase-microphyric basalt to hawaiite, with single flows of plagioclase-macrophyric basalt to hawaiite and olivine-clinopyroxene-plagioclase-macrophyric basalt. The upper part (50 m maximum) is dominantly of flows that are varients of olivine-clinopyroxene-plagioclase-macrophyric basalt, with olivine-clinopyroxene-microphyric basalt flows towards the top. Flows vary from a few metres to over 20 m in thickness. Thin intercalations of basaltic agglomerate and tuff also occur. |
| Definition of Lower Boundary: |
The succession dips gently to the south or south-east, and hence the lowest lavas occur in the north. Since the northern boundaries of the member are entirely faulted (against Limestone Coal Formation and Scottish Coal Measures Group strata), the base of the member does not crop out. |
| Definition of Upper Boundary: |
Various lavas are overlain unconformably by volcaniclastic sedimentary rocks of the Kirkwood Formation in the south-west of the outcrop, around Carmunnock, and by sandstones and mudstones of the Lawmuir Formation in the south-east, near Nerston. |
| Thickness: |
At least 130 m. |
| Geographical Limits: |
The member is restricted to and forms the whole of the Cathkin Braes Block in the south-east of Glasgow. It forms a marked, north-facing scarp extending for 7 km from south-west of Castlemilk [NS 595 582] in the west, along Cathkin Braes to Dechmont Hill [NS 657 583] in the east. The north - south width of the outcrop is just over 3 km. |
| Parent Unit: |
Clyde Plateau Volcanic Formation (CPV)
|
| Previous Name(s): |
Eaglesham Lavas [Obsolete Name and Code: Use CBLA, EMLA]
(-4637)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
The lower, microporphyritic flows of the member and the lowest flow of the upper, macroporphyritic part are well exposed along the scarp of the Cathkin Braes as a series of well-defined trap features. Forsyth et al., 1996. |
| Partial Type Section |
Several of the lowest flows of the upper, macroporphyritic part of the member, together with bedded tuffs, are (or were) exposed in Cathkin Quarry. Forsyth et al., 1996. |
| Reference(s): |
| Macgregor, M, Dinham, C H, Bailey, E B and Anderson, E M. 1925. The geology of the Glasgow district. (2nd edition) Memoir of the Geological Survey of Scotland (parts of sheets 30, 31, 22 and 23). |
| 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). |
| Hall, I H S, Browne, M A E and Forsyth, I H. 1998. Geology of the Glasgow district. Memoir of the British Geological Survey, Sheet 30E (Scotland). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S030
S031
S022
S023
|
