The BGS Lexicon of Named Rock Units — Result Details

Aultbea Formation

Computer Code: TCAU Preferred Map Code: notEntered
Status Code: Full
Age range: Tonian Period (AT) — Tonian Period (AT)
Lithological Description: Fine-medium grained, pale red sandstone, thick-bedded (2-5 m); some coarser grained and rarely pebbly sandstone occur locally. Cross bedding in large (1-4 m) cosets, but virtually all beds are contorted.
Definition of Lower Boundary: Conformable upon Applecross Formation (TCA), with gradational boundary, with incoming of consistent fine-medium grained sandstone.
Definition of Upper Boundary: Conformably overlain by Cailleach Head Formation (TCC). The lower contact is only exposed on Gruinard Island - not re-analysed since the Second World War due to anthrax contamination.
Thickness: c. 2000-3000 m (estimate: the unit is nowhere exposed in one single section).
Geographical Limits: Northwest Highlands, from Enard Bay to Rum.
Parent Unit: Torridon Group (TC)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Coastal section, SW side of Gruinard Bay, Aultbea peninsula [NG 880 976 - NG 900 955]. 
Reference(s):
Stewart, A D. 2002. The later Proterozoic Torridonian rocks of Scotland: their sedimentology, geochemistry and origin. Geological Society Memoir. Vol. 24. (The Geological Society.) 
Rainbird, R.H., Hamilton, M.A. and Young, G.M., 2001. Detrital zircon geochronology and provenance of the Torridonian, NW Scotland. Journal of the Geological Society of London, 158: 15-27. 
Krabbendam, M. 2021. A stratigraphic framework for the early Neoproterozoic successions of the Northern Highlands of Scotland. UK Stratigraphic Framework Series. British Geological Survey Open Report, OR/21/072. 86pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S071 S081 S082 S092 S101 S060 S091