The BGS Lexicon of Named Rock Units — Result Details

Balnakiel Formation

Computer Code: BNK Preferred Map Code: notEntered
Status Code: Full
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Alternations of dark grey dolostones and dolomitic limestones and lighter grey bioclastic limestones.
Definition of Lower Boundary: Conformably overlies the Sangomore Formation.
Definition of Upper Boundary: Conformably overlain by the Croisaphuill Formation.
Thickness: About 140 m thick, although estimated at over 300 m thick by some authors.
Geographical Limits: The Durness Group forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye. The Balnakiel Formation does not occur in Assynt or Skye and appears to be limited to the more northern parts of the outcrop of the Durness Group.
Parent Unit: Durness Group (DNG)
Previous Name(s): BALNAKIEL GROUP
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  South coast of Balnakeil Bay, Durness area, north coast of Scotland. 
Reference Section  Inland outcrops on the west side of Loch Croispol, south of Balnakeil Bay. 
Reference(s):
Peach, B N, Horne, J, Gunn, W, Clough, C T and Hinxman, L W. 1907. The geological structure of the North-West Highlands of Scotland. Memoirs of the Geological Survey of Great Britain. 
Lapworth, C. 1883. The secret of the Highlands. Geolgical Magazine, Decade 2, Vol. 10, 120-128, 193-199, 337-344. 
Johnston, G S and Mykura, W. 1989. British regional geology: the Northern Highlands (4th edition) (London: HMSO for the British Geological Survey.) 
Park, E G, Stewart, A D and Wright, D T. 2002. The Hebredean Terrane. 45-80 in the Geology of Scotland. Trewin, N H (Editor). (The Geological Society, London.) 
Phemister, J. 1948. British Regional Geology: Scotland: the Northern Highlands (2nd edition) (Edinburgh: HSMO for the Geological Survey and Museum.) 
Prigmore, J K and Rushton, A W A. 1999. Scotland: Cambrian and Ordovician of the Hebridean Terrane. 295-315 in British Cambrian to Ordovician Stratigraphy. Rushton, A W A, Owen, A W, Owens, R M and Prigmore, J K (editors). Geological Conservation Review Series. (Joint Nature Conservation Committee.) 
Wright, D T and Knight, I. 1995. A revised chronostratigraphy for the lower Durness Group. Scottish Journal of Geology, Vol. 31, 11-22. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S114