Faughlin Lava Member

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Faughlin Lava Member (FGHL), Campsie Block, Carboniferous, Midland Valley of Scotland[edit]

Faughlin Lava Member is part of the Clyde Plateau Volcanic Formation.

Name[edit]

Previously named the Faughlin Lavas (Forsyth et al., 1996)[1].

Lithology[edit]

The Faughlin Lava Member, which is poorly exposed, consists predominantly of microphyric trachybasalt and basaltic-trachyandesite lava (hawaiite to mugearite). A single plagioclase-macrophyric trachybasalt (hawaiite of ‘Markle’ type) is also present and tuff and agglomerate are present at the base of the member in the small stream due south of the bridge over the River Carron (NS 748 838).

Stratotype[edit]

The type area is in the north-eastern Kilsyth Hills, north-east of Glasgow (NS 7334 8238 to NS 7783 8401) (Forsyth et al., 1996)[1]. A reference section is an unnamed tributary of the River Carron, north-east Kilsyth Hills (NS 7479 8376 to NS 7486 8365) (Craig, 1980)[2]. This shows the base of the member.

Lower and upper boundaries[edit]

The lower boundary of the Faughlin Lava Member is conformable or disconformable on the underlying Carron Bridge Lava Member, and is marked by a tuff overlying trachybasalt in the small stream due south of the bridge over the River Carron (NS 748 838).

The Faughlin Lava Member is overlain by the Campsie Lava Member. The lithological change is to mostly plagioclase-microphyric basalt and trachybasalt (‘Jedburgh’ type).

Thickness[edit]

Some 35 m.

Distribution and regional correlation[edit]

The member is restricted to the eastern part of the Campsie Block (Forsyth et al., 1996)[1], specifically to two small areas of the north-eastern Kilsyth Hills, north-east of Glasgow. The rocks crop out in a small area south and east of the Faughlin Reservoir, from Faughlin Burn (NS 7336 8242) to the east of Carron Bridge (NS 7484 8378), and in a separate area between Langhill (NS 7698 8426) and the west bank of the River Carron (NS 7783 8401). The source of this member is probably local.

Age[edit]

Mid Visean (Arundian to Asbian).

References[edit]

  1. 1.0 1.1 1.2 Forsyth, I H, Hall, I H S, and McMillan, A A. 1996. Geology of the Airdrie district. Memoir of the British Geological Survey, Sheet 31W (Scotland).
  2. Craig, P M. 1980. The volcanic geology of the Campsie Fells area, Stirlingshire. Unpublished PhD Thesis, University of Lancaster.