| 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
|
