The BGS Lexicon of Named Rock Units — Result Details

Stac Fada Member

Computer Code: TASF Preferred Map Code: TASF
Status Code: Full
Age range: Stenian Period (AI) — Mesoproterozoic Era (AX)
Lithological Description: Mainly greenish to buff sandstone with abundant dark green glassy mafic fragments(shards); these fragments have abundant vesicles. 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: 10-15 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; 300 m east of Rubh' a; Mhill Dheirg 
Reference Section  Coast section at Camas a' Bhothain, Enard Bay, 
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.) 
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. 
Lawson, D.E., 1972. Torridonian volcanic sediments. Scottish Journal of Geology, 8: 345-362. 
Young, G.M., 2002. Stratigraphy and geochemistry of volcanic mass flows in the Stac Fada Member of the Stoer Group, Torridonian, NW Scotland. Transactions of the Royal Society of Edinburgh, Earth Sciences, 93: 1-16. 
Sanders, I.S. and Johnston, J.D., 1989. The Torridonian Stac Fada Member: an extrusion of fluidized peperite? Transactions of the Royal Society of Edinburgh, Earth Sciences, 80: 1-4. 
Amor, K., Hesselbo, S.P., Porcelli, D., Thackrey, S. and Parnell, J., 2008. A Precambrian proximal ejecta blanket from Scotland. Geology, 36: 303-306. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S101 S107 S091