| Computer Code: |
TASF |
Preferred Map Code: |
TASF |
| Status Code: |
Full |
| Age range: |
Stenian Period (AI)
— Stenian Period (AI) |
| Lithological Description: |
Mainly greenish to buff sandstone with abundant dark green glassy mafic fragments (shards); these fragments have abundant vesicles. Angular clasts of gneiss occur commonly in the lower part. Accretionary lapilli occur in top part. Locally at Stoer, base of unit contains rafts of dismembered sandstone. |
| Definition of Lower Boundary: |
Conformably contact with remainder of the Bay of Stoer Formation (TAS). |
| Definition of Upper Boundary: |
Conformably overlain by the Poll a’ Mhuilt Member (TASP). |
| Thickness: |
10 - 30 m. |
| Geographical Limits: |
Occurs on several headlands in the NW Highlands, east of the Coigach Fault, and west of the Moine Thrust |
| Parent Unit: |
Bay of Stoer Formation (TAS)
|
| Previous Name(s): |
Stac Fada Formation [Obsolete Name And Code: Use TASF]
(TAF)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Small headland, locally known as Stac Fada, 800 m west of Stoer village, Stoer peninsula [NC 033 285]. |
| Reference Section |
Coast section at Camas a' Bhothain, Enard Bay [NC 031 146]. |
| Reference(s): |
| 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. |
| Simms, M J. 2015. The Stac Fada impact ejecta deposit and the Lairg Gravity Low: evidence for a buried Precambrian impact crater in Scotland? Proceedings of the Geologists' Association, Vol. 126, 742-761. |
| Parnell, J., Mark, D., Fallick, T.E., Boyce, A. and Thackrey, S., 2011. The age of the Mesoproterozoic Stoer Group sedimentary and impact deposits, NW Scotland. Journal of the Geological Society of London, 168: 349 - 358. |
| Amor, K, Hesselbo, S P, Porcelli, D, Thackrey, S, and Parnell, J. 2008. A Precambrian proximal ejecta blanket from Scotland. Geology, 36, 303-306. |
| Stewart, A D. 2002. The later Proterozoic Torridonian rocks of Scotland: their sedimentology, geochemistry and origin. Geological Society Memoir. Vol. 24. (The Geological Society.) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S101
S107
S091
|
