The BGS Lexicon of Named Rock Units — Result Details

Sgorr Mhor Sandstone Member

Computer Code: TCSM Preferred Map Code: notEntered
Status Code: Full
Age range: Tonian Period (AT) — Tonian Period (AT)
Lithological Description: Fine- to medium-grained sandstones without "exotic" pebbles, thick-bedded. Abundant cross-bedding and convolute, soft-sediment deformation structures. Detrital heavy minerals of silt to fine-grained sand grade common.
Definition of Lower Boundary: Base: (eg NM 3769 9147 or NG 3360 0247) : marked by the disappearance of 'exotic' pebbles characteristic of the Applecross Formation.
Definition of Upper Boundary: Top: not seen (nor defined) on Rhum.
Thickness: Minimum thickness (from NM 3698 9106 to NM 3659 9172) of 175m. (Stratigraphical top is nowhere visible; in the type locality the stratigraphical base and top are not visible).
Geographical Limits: Inner Hebrides: Rum.
Parent Unit: Aultbea Formation (TCAU)
Previous Name(s): Guirdil Arkose [Obsolete Name and Code: Use TCAS, TCSM] (-3074)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Type Area - Isle of Rhum, Sgor Mhor: Guirdial Bay to Camas na h-Atha [NG 315 011 to NM 301 996]. 
Reference(s):
Emeleus, C H. 1997. Geology of Rum and the adjacent islands. Memoir (sheet) of the Geological Survey of Great Britain (Scotland) (60). (The Stationery Office for the British Geological Survey.) 171pp. 
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. 
Black, G P and Welsh, W, 1961. The Torridonian succession of the Isle of Rhum. Geological Magazine, Vol.98, 265-276. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S060