Cochno Lava Member

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Cochno Lava Member (CCLA), Kilpatrick Hills, Carboniferous, Midland Valley of Scotland[edit]

The Conch Lava Member is part of the Clyde Plateau Volcanic Formation.

Name[edit]

Previously named the Cochno Lavas (Hall et al., 1998)[1].

Lithology[edit]

The Cochno Lava Member includes a wide range of lava types but is characterised by mafic varieties, particularly near the base. These include olivine-microphyric basalts (‘Dalmeny’ type), olivine-clinopyroxene-macrophyric basalts (‘Craiglockhart’ type) and olivine-clinopyroxene-plagioclase-macrophyric basalts (‘Dunsapie’ type). Localised plagioclase-macrophyric basalts (‘Markle’ type) and plagioclase-microphyric basalts (‘Jedburgh’ type) occur around Bowling (NS 445 738).

Stratotype[edit]

The Cochno Lava Member crops out in its type area between Cochno Loch (NS 500 760) and Craigton (NS 520 770).

Lower and upper boundaries[edit]

The Cochno Lava Member overlies the Greenside Volcaniclastic Member and represents the recommencement of lava extrusion after a major break in activity. It is overlain by the Mugdock Lava Member.

Thickness[edit]

Between 100 and 250 m thick in the Kilpatrick Hills region. The member thins towards the north-east of the region, but is thicker adjacent to the Campsie Fault (Hall et al., 1998[1], table 5).

Distribution and regional correlation[edit]

The Cochno Lava Member stretches north-east from Bowling (NS 450 738) in the south-west of the Kilpatrick Hills to the south of Clachan of Campsie (NN 610 790) where the lavas are correlated with the Knowehead Lava Member of the Western Campsie Fells area. Associated vents are located at Burnside (NS 474 741), Black Loch (NS 500 765), and Craigton (NS 525 770).

Age[edit]

Mid Visean (Arundian to Asbian).

References[edit]

  1. 1.0 1.1 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)