The BGS Lexicon of Named Rock Units — Result Details
Crom Psammite Formation
| Computer Code: | CMPS | Preferred Map Code: | SYMB |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Tonian Period (AT) — Tonian Period (AT) | ||
| Lithological Description: | Basal part: interbedded micaceous psammite and semipelite-pelite beds, with upwards increase in psammite component. Central part: gritty or pebbly arkosic psammite, with beds 0.5 - 2 m thick, with cm-scale semipelite beds. Trough cross-bedding and water escape structures common. Upper part: similar to the lower part. | ||
| Definition of Lower Boundary: | Overlies the Vach Pelite Formation, where predominantly pelitic lithologies pass into predominaintly psammitic lithologies. | ||
| Definition of Upper Boundary: | Overlain by the Diebidale Pelite Formation, where predominainlty psammitic lithologies pass into predominantly pelitic lithologies. The upper boundary is locally obscured by the Sgurr Beag Thrust, the Carn Chunneag-Inchbae Granite Gneiss, or the Old Red Sandstone unconformity. | ||
| Thickness: | c. 2500-3000 m (estimate); thinning to the east. | ||
| Geographical Limits: | NW Highlands, Central Ross-shire; southern Sutherland. | ||
| Parent Unit: | Morar Group (MORR) | ||
| Previous Name(s): | Upper Psammite [Obsolete Name and Code: Use CMPS]
(-4558)
Upper Quartzite [Obsolete Name and Code: Use CMPS] (-1447) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Reference section: Allt Crom Loch section [NH 372 830 - NH 390 830]. | ||
| Type Area | Glen Calvie: Croick to Beinn Tharsuinn. [NC 45 89 - NC 29 83]. | ||
| Reference(s): | |||
| Shepherd, J. 1970. The structure and metamorphism of the Carn Chuinneag area, Ross-shire. (University of Edinburgh.: unpublished PhD thesis.) | |||
| Holdsworth, R E, Strachan, R A and Harris, A L, 1994. Precambrian rocks in northern Scotland east of the Moine Thrust: The Moine Supergroup in Gibbons, W and Harris, A L (editors). A revised correlation of Precambrian rocks in the British Isles. Special Report of the Geological Society, No.22. | |||
| Wilson, D. 1975. Structure and metamorphism of the Ben Wyvis District, Ross-shire. (University of Edinburgh: Unpublished PhD thesis.) | |||
| 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. | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| S083 S093 S093 S093 | |||