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The BGS Lexicon of Named Rock Units — Result Details

Carbeth Lava Member

Computer Code: CBTL Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: Mainly plagioclase-macrophyric basalts (Markle type). There are also some plagioclase-microphyric basalts (Jedburgh type) and olivine-clinopyroxene-plagioclase-macrophyric basalts (Dunsapie type) as well as some mugearites near the base.
Definition of Lower Boundary: The Carbeth Lava Member overlies the plagioclase-microphyric basalts (Jedburgh type) of the Auchineden Lava Member.
Definition of Upper Boundary: The Carbeth Lava Member is unconformably overlain by the Greenside Volcaniclastic Member. West of Loch Humphrey [NS 455 760] the member is reduced to one lava flow which is preserved only in isolated patches below the volcaniclastic sedimentary rocks.
Thickness: 0-150 m, thins out to south-west partly due to erosion; thins to c. 80 m in north-east.
Geographical Limits: The Carbeth Lava Member is geographically widespread in the Kilpatrick Hills, north-west of Glasgow, stretching from Strath Blane [NS 560 790] in the north-east to Brown Hill [NS 445 764] in the south-west. The lavas are well exposed around Carbeth and in the Birny Hills.
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): Carbeth Lavas (-3907)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  The Carbeth Lava Member was encountered in the Loch Humphrey Borehole beneath the Greenside Volcaniclastic Member and above the Auchineden Lava Member. It is here 20 m thick and consists of Markle-type lavas with some Jedburgh type and some thin bands of tuff. A geological description of the log is available in BGS borehole records. 
Type Area  The lavas are well exposed around Carbeth [NS 527 796] and form prominent scarp features around the Birny Hills [NS 495 770]. Hall et al., 1998. 
Reference(s):
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