The BGS Lexicon of Named Rock Units — Result Details

Fereneze Lava Member

Computer Code: FZLA Preferred Map Code: notEntered
Status Code: Full
Age range: Arundian Substage (CJ) — Asbian Substage (CR)
Lithological Description: Mainly plagioclase-macrophyric basalts (Markle type) and olivine-clinopyroxene-plagioclase basalts (Dunsapie type). Several flows of mugearite are present, two were encountered in a borehole at Crummock Park, Bieth and three in in Loanhead Quarry [NS 365 555] where a discontinuous bed of tuff is also seen. These flows are 15 m, 8 m and over 10 m thick and are separated by boles up to 50 cm thick, they are amygdaloidal with much hydrothermal alteration giving a range of secondary minerals such as calcite, prehnite, analcime, thomsonite, natrolite, bowlingite and heulandite. The quarry is well known for copper mineralisation with native copper, malachite and cuprite recorded. Some flows of plagioclase-microphyric basalt or hawaiite (Jedburgh type) and olivine-microphyric basalt (Dalmeny type) are present in the Fereneze Hills.
Definition of Lower Boundary: The Markle- and Dunsapie-type basalts of the Fereneze Lava Member appears to cut or overlap most of the underlying Dalmeny- and Dunsapie-type lavas of the Sergeantlaw Lava Member in the area of the Fereneze Hills.
Definition of Upper Boundary: In the west of the Beith-Barrhead Hills, Bog Hall [NS 362 540] to Newton of Belltrees [NS 372 582], the Fereneze Lava Member is overlain by the olivine basalts of the Beith Lava Member. The upper boundary of the unit is not seen in the eastern Beith-Barrhead Hills.
Thickness: Max thickness >120 m.
Geographical Limits: In the Beith - Barrhead lava block, on the north-west limb of the Beith Anticline, to the west of Barcraigs Reservoir [NS 384 570], the member forms good scarp and dip slope topography. In the east (on the south-east limb of the Beith Anticline), the unit underlies the Fereneze Hills between Capellie Farm [NS 465 583] and the top of Boylestone Quarry [NS 495 597].
Parent Unit: Clyde Plateau Volcanic Formation (CPV)
Previous Name(s): 'Fereneze Lavas' (-2195)
Alternative Name(s): none recorded or not applicable
Type Area  The best exposure of the Fereneze Lava Member is on the north-west limb of the Beith Anticline, to the west of Barcraigs Reservior [NS 384 570]. Monro 1999 
Reference Section  Crummock Park Borehole (Beith) penetrated 120 m of the Fereneze Lava Member, Monro 1999. A detailed geological log (NS35SE/1) is available in BGS borehole records. 
Richey, J E, Anderson, E M, and Macgregor, A G. 1930.The geology of north Ayreshire. Memoir of the Geological Survey of Great Britain. 
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). 
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:
S022 S022 S030 S030