Craigdouffie Lava Member

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Craigdouffie Lava Member (CDLA), Campsie Block, Carboniferous, Midland Valley of Scotland[edit]

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

Name[edit]

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

Lithology[edit]

The Craigdouffie Lava Member consists of a sequence of at least four lavas, comprising alternating plagioclase-macrophyric basalt or trachybasalt (basalt to hawaiite of ‘Markle’ type) and aphyric basaltic-trachyandesite (mugearite), all with proximal-facies characteristics (Craig, 1980)[2].

Stratotype[edit]

The type area is the south-eastern Kilsyth Hills, north-east of Glasgow (NS 7442 8070 to NS 7479 8078) (Forsyth et al., 1996)[1]. The only reference section is Craigdouffie Burn, south-eastern Kilsyth Hills (NS 7484 8074 to NS 7438 8072) where at least four lavas, at least 15 m thick in total, are seen at the top of the member (Craig, 1980[2]; Forsyth et al., 1996[1]).

Lower and upper boundaries[edit]

The base of the Craigdouffie Lava Member is faulted and unseen. It is overlain by poorly exposed volcaniclastic sedimentary rocks of the Kirkwood Formation of the Strathclyde Group. The lithological change is from basalt or trachybasalt to tuffaceous mudstone and tuff, but the nature of the contact is not known.

Thickness[edit]

More than 15 m, base not seen.

Distribution and regional correlation[edit]

The member is restricted to a small area adjacent to the south side of the Campsie Fault and adjacent to the north-east side of the Tak-ma-doon Fault (Craig, 1980)[2], in the south-eastern Kilsyth Hills, north-east of Glasgow. These rocks crop out east-north-east of Drumnessie, mainly in the Craigdouffie Burn (NS 7448 8072 to NS 7484 8074) and on its northern side to (NS 7479 8078). The source is probably an undetected vent in the immediate vicinity (Craig, 1980)[2].

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. 2.0 2.1 2.2 2.3 Craig, P M. 1980. The volcanic geology of the Campsie Fells area, Stirlingshire. Unpublished PhD Thesis, University of Lancaster