The BGS Lexicon of Named Rock Units — Result Details

Poll A' Mhuilt Member

Computer Code: TASP Preferred Map Code: TASP
Status Code: Full
Age range: Stenian Period (AI) — Stenian Period (AI)
Lithological Description: Red to black mudstone. Lower half is interbedded, with thin beds of siltstone, fine sandstone and rare limestone. Upper half is entirely massive mudstone.
Definition of Lower Boundary: Conformably overlies the Stac Fada Member (TASF). Marked by incoming of first red mudstone. Locally directly overlying the Lewisian Gneiss (L) on palaeo-highs (e.g. Enard Bay).
Definition of Upper Boundary: Conformably overlain by the Meall Dearg Formation (TAD). Incoming of red sandstone, with erosive base.
Thickness: 100 m (maximum - thins south of Stoer).
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): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Coastal section (tidal!) c. 800 m west of Stoer Village, just west of 'Stac Fada' headland; 300 m east of Rubh' a' Mhill Dheirg 
Reference Section  Coast section at Camas a' Bhothain, Enard Bay. 
Reference(s):
Gracie, A.J. and Stewart, A.D., 1967. Torridonian sediments at Enard Bay, Ross-shire. Scottish Journal of Geology, 3: 181-194. 
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. 
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. 
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:
S107