Cockermouth Volcanic Formation

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Cockermouth Volcanic Formation (CKML), Carboniferous, Midland Valley of Scotland[edit]

Cockermouth Volcanic Member is part of the Ravenstonedale Group

Name[edit]

Originally named the Cockermouth Lavas (Eastwood, 1928[1]). See also Millward in Stephenson et al. (2003)[2]; Macdonald and Walker (1985)[3].

Lithology[edit]

Basalt, olivine-phyric and andesite, tholeiitic. Up to four sheets of massive to intensely amygdaloidal and scoriaceous rock, dark blue-grey to grey. Interpreted to be lavas. No intercalated pyroclastic or sedimentary rocks are present.

Stratotype[edit]

The partial type section is Gill Beck, immediately south of Blindcrake, about 4.5 km north-east of Cockermouth, Cumbria (NY 149 341 to 149 344) where a sequence of at least four tholeiitic olivine-phyric basalt lavas about 67 m thick can be seen, though the base and top of the succession is not exposed (see Millward in Stephenson et al., 2003,pp. 116–120[2]). A reference section is Bothel Craggs Quarry, on the west side of the A591 road, about 1.5 km south-south-east of Bothel, Cumbria (NY 186 371) where apparently one, sparsely amygdaloidal tholeiitic andesite about 4.m thick is seen, though the base and top of the succession are not exposed (see Millward in Stephenson et al., 2003,pp. 120–122[2]).

Lower and upper boundaries[edit]

In north Cumbria the base is conformable on the conglomerates and sandstones of the Marsett Formation, and the top lies beneath bedded mudstone, limestone and sandstone at the base of the Great Scar Limestone Group (specifically beneath a conglomerate developed locally at the base of the Frizington Limestone Formation) (Figure.14, Column 2).

Thickness[edit]

Some 105 m in the Cockermouth area; 67 m thick in the type section.

Distribution and regional correlation[edit]

Northern margin of the Lake District Lower Palaeozoic massif, from just west of Cockermouth to Bothel. Intrusions of dolerite and deposits of lapilli-tuff on Little Mell Fell, in the Appleby district, may include intrusive equivalents to the Cockermouth Volcanic Formation (Macdonald and Walker, 1985[3]).

Age[edit]

Courceyan.

References[edit]

  1. Eastwood, T.1928.The Cockermouth Lavas, Cumberland.–.a Carboniferous volcanic episode.15–22 in Summary of progress of the Geological Survey of Great Britain and the Museum of Practical Geology for the year 1927, Pt. 2. (London: His Majesty’s Stationary Office.)
  2. 2.0 2.1 2.2 Stephenson, D, Loughlin, S C, Millward, D, Waters, C N, and Williamson, I T.2003.Carboniferous and Permian Igneous Rocks of Great Britain North of the Variscan Front.Geological Conservation Review Series, No. 27. (Peterborough: Joint Nature Conservation Committee.)
  3. 3.0 3.1 MacDonald, R, and Walker, B H.1985.Geochemistry and tectonic significance of the Lower Carboniferous Cockermouth lavas, Cumbria.Proceedings of the Yorkshire Geological Society, Vol. 45, 141–146.