| Computer Code: |
TCC |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Tonian Period (AT)
— Tonian Period (AT) |
| Lithological Description: |
Thin-bedded siltstone, mudstone and sandstone, in c. 20 - 50 m thick coarsening-up cycles. Each cycle has an erosional base covered with laminated grey siltstone with dessication cracks, followed by wave-rippled sandstone, topped by trough cross-bedded sandstone to the top. |
| Definition of Lower Boundary: |
Conformable upon Aultbea Formation (TCAU) (Contact only exposed on Gruinard Island - not re-analysed since the early 20th century due to anthrax contamination in the Second World War). |
| Definition of Upper Boundary: |
Erosional - not exposed. Unconformably overlain by Cambrian Ardvreck Group (ARDV). |
| Thickness: |
c. 630 m (minimum at type section); total possibly 1000 m. |
| Geographical Limits: |
Northwest Highlands, on Cailleach Head and Gruinard Island. |
| Parent Unit: |
Torridon Group (TC)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Caileach Head, Scoraig [NC 986 986 to NC 986 979]. |
| 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.) |
| 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: |
|
S101
|
