Difference between revisions of "Sandy Craig Formation"

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Sandy Craig Formation, (SCB)Carboniferous, Midland Valley of Scotland[edit]

The Sandy Craig Formation is part of the Strathclyde Group in the Fife area.

Name[edit]

From Sandy Craig, east Fife. The unit was originally described by Forsyth and Chisholm (1977)[1] and given formation status by Browne (1986)[2].

Lithology[edit]

The Sandy Craig Formation is characterised by mudstone and siltstone with a minor percentage of algal rich oil shale. Thin beds of non-marine limestone and dolostone are also developed, some of which contain oncolites and stromatolites. The Burdiehouse Limestone of the Lothians is represented in central Fife by at least three beds of limestone (Geikie, 1900, p.46)[3]. Multicoloured, mainly fine- to medium-grained sandstone is subordinate to the argillaceous rocks, but thick, upward-fining, multi-storey sandstones are locally developed. Greenish grey clayrock and calcareous mudstone occur, as do thin beds of coal and ironstone. Nodular beds of pedogenic limestone and dolomite (‘cornstone’) are also present. The formation is distinguished from its neighbours by the relative rarity of marine beds, and by the local presence of cornstones.

Genetic interpretation[edit]

The pattern of sedimentation within the formation is of upward-coarsening deltaic cycles, with thinner upward-fining fluvial units erosively capping them, and rare marine incursions.

Stratotype[edit]

Partial type sections in the Sandy Craig Formation occur at Pittenweem Harbour (NO 5518 0236 to NO 5452 0238), nearby at Sandy Craig (NO 5453 0215 to NO 5419 0226) and from 203 to 700 m depth in the Kilconquhar Bore 79/1 (BGS Registration Number NO40SE/26) (NO 4845 0305) near Elie.

Lower and upper boundaries[edit]

The conformable base of the Sandy Craig Formation lies in a transitional sequence and is taken at the top of the St Andrews Castle Marine Band (SCMB) above the mudstone and siltstone of the Pittenweem Formation (Figure 6, Column 4C).

The top of the formation is now drawn at the base of the West Braes Marine Band (WBMB) (Browne, 1986, fig. 2)[2], marking the base of the Pathhead Formation.

Thickness[edit]

The maximum thickness of the formation as now defined is about 670 m in east Fife (Browne, 1986, fig. 2)[2].

Distribution and regional correlation[edit]

Fife.

Age and biostratigraphical characterisation[edit]

Visean (Asbian). Marine faunas are very rare, and are usually restricted, consisting in some cases only of the brachiopod Lingula. The bivalve Curvirimula dominates the abundant, but restricted, nonmarine faunas.

References[edit]

  1. Forsyth, I H, and Chisholm, J I. 1977. The geology of east Fife. Memoir of the Geological Survey of Great Britain, Sheets 41 part 49 (Scotland)
  2. 2.0 2.1 2.2 Browne, M A E. 1986. The classification of the Lower Carboniferous in Fife and Lothian. Scottish Journal of Geology, Vol. 22, 422-425
  3. Geikie, A. 1900. The geology of central and western Fife and Kinross. Memoirs of the Geological Survey, Scotland.