The BGS Lexicon of Named Rock Units — Result Details

Greeto Lava Member

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 110m.
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 (-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). 
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. 
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 & Stephenson, D. 1990. Geology of the Greenock district: Memoir for 1:50000 geological sheet 30W and part of sheet 29E (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S022 S030