| Computer Code: |
GRLA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Arundian Substage (CJ)
— Asbian Substage (CR) |
| Lithological Description: |
Plagioclase-microphyric basaltic to hawaiitic lava (Jedburgh type) with a few flows of plagioclase-macrophyric basaltic to hawaiitic lava (Markle type). At the base of the member in the Kilbirnie Hills thin beds of purple nodular tuff with intercalated fine-grained red marls are developed locally, for example east and south east of Bradshaw [NS 24 53]. A single flow of more-mafic olivine-pyroxene-macrophyric basalt (ankaramite) occurs within the member on the north slope of Castle Hill at Largs [NS 220 589]. |
| Definition of Lower Boundary: |
Underlain by the more-mafic olivine-microphyric basalts (Dalmeny type) of the Largs Lava Member. |
| Definition of Upper Boundary: |
Overlain by the non-porphyritic mugearites and olivine-free plagioclase-macrophyric hawaiites and basaltic hawaiites (Markle type) of the Strathgryfe Lava Member. |
| Thickness: |
Up to 110 m. |
| Geographical Limits: |
Restricted to the Renfrewshire Hills and Kilbirnie Hills. Crops out extensively along the top of scarp slope east of Noddsdale Water from Largs [NS 215 590] north to the Murishiel Fault, name derived from exposures in the valley of the Greeto Water [NS 228 598]. To the south of Largs the Greeto Lava Members forms a scarp feature at the top of the hills behind Largs and Fairlie [NS 21 55]. The scarp extends south-south-east on the east side of the Caaf Water valley [NS 23 53]. An outlier caps Kaim Hill [NS 22 53] to the west of the Caaf Water valley. |
| Parent Unit: |
Clyde Plateau Volcanic Formation (CPV)
|
| Previous Name(s): |
Greeto Lavas [Obsolete Name and Code: Use GRLA]
(-4688)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Well exposed in the valleys of the Greeto and Gogo waters, close to their confluence. |
| Reference(s): |
| Monro, S K. 1999. Geology of the Irvine District. Memoir of the British Geological Survey, Sheet 22W and part of 21E (Scotland). |
| Richey, J E. 1928. The north Ayrshire sequence of Calciferous Sandstone volcanic rocks. Transactions of the Geological Society of Glasgow. 18. pp 247-255. |
| Paterson, I B, Hall, I H S and Stephenson, D. 1990. Geology of the Greenock district: Memoir for 1:50000 geological sheet 30W and part of sheet 29E (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. |
| Johnstone, G S. 1965. The volcanic rocks of the Misty Law-Knockside Hills district, Renfrewshire. Bulletin of the Geological Survey of Great Britain. No. 22. pp 53-64. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S022
S030
|
