The BGS Lexicon of Named Rock Units — Result Details

Sargeantlaw Lava Member

Computer Code: SLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: Olivine-microphyric basalts (Dalmeny type) and olivine-clinopyroxene-plagioclase-macrophyric basalt (Dunsapie type). In the closure of the Beith anticline the basal flow of the member is a distinctive clinopyroxene-olivine-macrophyric basalt (ankaramite or Craiglockhart type). In Boylestone Quarry [2495 6597] hydrothermal veins and cavities contain a wide variety of minerals including calcite, analcime, prehnite, heulandite, bowlingite, thompsonite and natrolite. Native copper, cuprite and malachite are also found.
Definition of Lower Boundary: The Sergeantlaw Lava Member overlies the plagioclase-macrophyric basalts (Markle type) of the Gleniffer Lava Member. South of Wester Gavin [2380 6589] the mafic basalts of the Sergeantlaw Lava Member appear to rest upon volcaniclastic sediments and it is possible that in this area the underlying Glenliffer Lava Member has been overlapped. To the north of Harelaw Reservoir [2485 6590] the Sergeantlaw Lava Member appears to cut out or overlap most of the Gleniffer Lava Member.
Definition of Upper Boundary: Resting upon the Sergeantlaw Lava Member and forming a broad dip slope outcrop south of Muirdykes [2395 6591] are the plagioclase-macrophyric basalts (Markle type) and olivine-clinopyroxene-plagioclase basalts (Dunsapie type) of the Fereneze Lava Member.
Thickness: none recorded or not applicable
Geographical Limits: The Sergeantlaw Lava Member crops out in the Beith - Barrhead Hills, to the north and south of Barcraigs Reservoir [239 657]. It is well seen between Townhead of Threepwood [239 655] and Gillies Hill [238 654], and forms scarp features around Walls Hill [2412 6589]. It is also present in the area between Sergeant Law [2455 6596] and Greenfieldmuir [2456 6583] and in the Lochliboside Hills [2450 6575].
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): 'Sargeantlaw Lavas' (-3681)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  The Sergeantlaw Lava Member is well seen in the area between Townhead of Threepwood and Gillies Hill. Monro 1999 
Type Area  Outcrop on SE limb of Beith Anticline, from Sergeant Law to Greenfieldmuir 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). 
Monro, S K. 1999. Geology of the Irvine District. Memoir of the British Geological Survey, Sheet 22W and part of 21E (Scotland). 
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). 
Richey, J E, Anderson, E M, and Macgregor, A G. 1930.The geology of north Ayreshire. Memoir of the Geological Survey of Great Britain. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S022 S022 S030 S030