The BGS Lexicon of Named Rock Units — Result Details

Mauchline Volcanic Formation

Computer Code: MVL Preferred Map Code: MVL
Status Code: Full
Age range: Cisuralian Epoch (PLC) — Cisuralian Epoch (PLC)
Lithological Description: Basic lavas with intercalated tuff, tuff breccia, agglomerate, sandstone and mudstone. The lavas are mainly olivine-microphyric and olivine-clinopyroxene-microphyric basalt with some nepheline basanities, analcime basanities and olivine nephelinities (Eyles et al., 1949). Most lava flows appear to be altered and colour varies between grey and purplish-red (Williamson, 2003).
Definition of Lower Boundary: The basal strata, commonly tuff or sandstone, are between 3-88m thick and conformably overlie reddened sedimentary rocks of the Upper Coal Measures but with no marked discordance (Williamson, 2003). The boundary is taken at the lowest occurrence of either bright red sandstone with some wind-rounded grains or a sedimentory rock containing lava fragments. Lithologies in the basal strata are varied and can include siltstone, sandstone, mudstone, marly tuff and marl (Mykura, 1967).
Definition of Upper Boundary: Tuff and basalt lava of the Mauchline Volcanic Formation are interbedded with conglomerate of lava clasts and red sandstone towards the top of the Formation and overlain conformably by the Mauchline Sandstone Formation. The boundary is picked in borehole core at the top of the uppermost occurrence of conglomeratic sandstone with many large pebbles and blocks, up to 25cm [10 inches], of vesicular and non-vesicular basalt in a sandstone matrix and is considered by Mykura [1965] to be diachronous.
Thickness: The rocks of the Mauchline Volcanic Formation crop out around the Mauchline Basin with thicknesses known from boreholes; between 98m and 180m [300 to 550 feet] along the western and southwestern margins of the basin, generally greater than 197m [600 feet] in the east and northeast. The maximum thickness recovered is 252m [770 feet] in the Redcraig Borehole towards the northern margin of the basin.
Geographical Limits: The Mauchline Volcanic Formation is present only within the Permian Mauchline Basin, in the vicinity of Mauchline, Ochiltree and Tarbolton in Ayrshire, southwest Scotland.
Parent Unit: Stewartry Group (STEW)
Previous Name(s): Mauchline Volcanic Beds [Obsolete Name And Code: Use MVL] (MVB)
Alternative Name(s): none recorded or not applicable
Partial Type Section  Exposure of the upper part and upper boundary of the Mauchline Volcanic Formation in the cliffs of the River Ayr near Howford Bridge immediately west of the old [A76] road. Williamson, 2003. 
Type Section  The Redcraig Borehole [NS 42 NE/15] penetrated and cored the entire thickness of the Mauchline Volcanic Formation at depths from 313m to 565m below start of drilling. Mykura, 1967. A detailed log of the borehole core and selected samples are held at BGS Edinburgh. The 43 samples and are described as lava, dolerite and basalt. Other core materials might be held by the Coal Authority. 
Eyles, V A, Simpson, J B and Macgregor, M C. 1949. Geology of Central Ayrshire. Memoir of the Geological Survey of Scotland, British Geological Survey, Sheet 14 (Scotland). 
Jin, Y, Wardlaw, B R, Glenister, B F and Kotlyar, G V. 1997. Permian chronostratigraphic subdivisions. Episodes, Vol.20, 10-15. 
Wagner, R H. 1983. A lower Rotliegend flora from Ayrshire. Scottish Journal of Geology, Vol.19, 135-155. 
Mykura, W. 1967. The Upper Carboniferous rocks of south-west Ayrshire. Bulletin of the Geological Survey of Great Britain, Vol.26, 23-98. 
Mykura, W. 1965. The age of the New Red Sandstone of south-west Scotland. Scottish Journal of Geology, Vol.1, 9-18. 
Williamson, I T. 2003. Howford Bridge, east Ayreshire. 166-169 in Stephenson, D, Loughlin, S C, Millward, D, Waters, C N and Williamson, I T, Carboniferous and Permian rocks of Great Britain north of the Variscan Front. Geological Conservation Review Series, No. 27, Joint Nature Conservation Committee, Peterborough. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S014 S014 S022 S022