| Computer Code: |
TC |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Tonian Period (AT)
— Tonian Period (AT) |
| Lithological Description: |
Dominated by red sandstone: coarse in Applecross Formation; fine-medium in Aultbea Formation. Thick-bedded, cross-bedded and commonly contorted. Subordinate pebble conglomerate and thin grey siltstones. Planar and cross-bedding are common, with co-sets typically 0.5-1 m thick, locally up to 3-6 m. Soft-sediment deformation is common and ubiquitous in the Aultbea Formation. The higher Cailleach Head Formation comprises thinly bedded mudstones and siltstones in coarsening upwards cycles. |
| Definition of Lower Boundary: |
Upon Kinloch Formation (TBK) (Sleat Group - TB) via minor unconformity: elsewhere with angular unconformity upon Stoer group (TA) or Lewisian Gneiss (L). |
| Definition of Upper Boundary: |
Not exposed, eroded. Unconformably overlain by Cambrian Ardvreck Group quartz arenite (ARDV). |
| Thickness: |
c. 4000-6000 m. |
| Geographical Limits: |
Northwest Highlands, from Cape Wrath to Rhum. Locally within Moine Thrust Zone (Assynt culmination and Kishorn Nappe). |
| Parent Unit: |
Wester Ross Supergroup (WROS)
|
| Previous Name(s): |
Torridon Sandstone [Obsolete Name and Code: Use TC]
(-3073)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Loch Torridon, Highland Region. |
| 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. |
| Krabbendam, M, Bonsor, H, Horstwood, M S, and Rivers, T. 2017. Tracking the evolution of the Grenvillian foreland basin: Constraints from sedimentology and detrital zircon and rutile in the Sleat and Torridon groups, Scotland. Precambrian Research, Vol. 295, 67-89. |
| Bird, A, Cutts, K, Strachan, R, Thirlwall, M F, and Hand, M. 2018. First evidence of Renlandian (c. 950-940 Ma) orogeny in mainland Scotland: Implications for the status of the Moine Supergroup and circum-North Atlantic correlations. Precambrian Research 305, 283-294. |
| Nicholson, P G. 1993. A basin reappraisal of the Proterozoic Torridon Group, northwest Scotland. 183-202 in Tectonic Controls and Signatures in Sedimentary Successions. Frostick, L, and Steel, R (eds). Special Publication of the International Association of Sedimentologists, 20. |
| Owen, G. 1995. Soft-sediment deformation in upper Proterozoic Torridonian sandstones (Applecross Formation) at Torridon, northwest Scotland. Journal of Sedimentary Research, Vol. 65, 495-504. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S114
S071
S071
S107
S108
S081
S082
S092
S092
S101
S101
S081
S102
S113
S070
S060
S091
|
