The BGS Lexicon of Named Rock Units — Result Details

Glascarnoch Psammite Formation

Computer Code: GLPS Preferred Map Code: SYMB
Status Code: Full
Age range: Tonian Period (AT) — Tonian Period (AT)
Lithological Description: Siliceous to micaceous psammite with subsidiary pelite beds. In lower part: thick beds (0.3 - 2 m) with coarsening upwards cycles with cm thick pelitic beds. In higher part: coarsening upwards units of rhythmically interbedded psammitic (siliceous and locally quarzitic) and pelitic beds, with water escape structures and slump folds.
Definition of Lower Boundary: Conformably upon the Altnaharra Psammite Formation (ALPS) - commonly with gradational boundary with the Glen Achall Psammite and Semipelite Member.
Definition of Upper Boundary: Conformably overlain by the Vaich Pelite Formation (VAPE). Boundary with Vaich Pelite Formation is normally sharp incoming of thick-bedded semipelite beds.
Thickness: c. 4000-5000 m (estimate); thinning to the west.
Geographical Limits: NW Highlands: Central Ross-shire to Sutherland. Extended southward towards the Strathconan Fault.
Parent Unit: Morar Group (MORR)
Previous Name(s): Lower Psammite [Obsolete Name and Code: Use GLPS] (-4677)
Lower Quartzite [Obsolete Name and Code: Use GLPS] (-1562)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Northern shore section along Loch Glascarnoch [NH 286 748 - NH 321 724]. 
Reference Section  Reference section: shore section along Loch Fannich [NH 264 657 - NH 253 648]. 
Reference Section  Reference section: southern slopes of Beinn Dearg [NH 26 80 - NH 28 81]. 
Reference(s):
Krabbendam, M, Strachan, R A, Leslie, A G, Goodenough, K M and Bonsor, H C. 2011. The internal structure of the Moine Nappe Complex and the stratigraphy of the Morar Group in the Fannichs-Beinn Dearg area, NW Highlands. Scottish Journal of Geology, 47, 1-20. 
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. 
Bonsor, H, Strachan, R, Prave, A and Krabbendam, M. 2012. Sedimentology of the early Neoproterozoic Morar Group in northern Scotland: implications for basin models and tectonic setting. Journal of the Geological Society of London 169, 53-65. 
Shepherd, J. 1970. The structure and metamorphism of the Carn Chuinneag area, Ross-shire. (University of Edinburgh.: unpublished PhD thesis.) 
Wilson, D. 1975. Structure and metamorphism of the Ben Wyvis District, Ross-shire. (University of Edinburgh: Unpublished PhD thesis.) 
Bonsor, H C, Strachan, R A, Prave, A and Krabbendam, M. 2010. Fluvial braidplain to shallow marine transition in the early Neoproterozoic Morar Group, Fannich Mountains, northern Scotland. Precambrian Research 183, 791-804. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S083 S093 S093