The BGS Lexicon of Named Rock Units — Result Details

Monadhliath Semipelite Formation

Computer Code: MNSP Preferred Map Code: M
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Interbedded thin micaceous psammites and semipelites with subordinate feldspathic and siliceous psammite and quartzite. Quartzite is more common in the basal part of the formation.
Definition of Lower Boundary: Overlies Glen Doe Psammite and Loch Laggan Psammite Formations. Marked by gradual increase in semipelite beds in top of psammite formations.
Definition of Upper Boundary: With increase in micaceous psammite and feldspathic psammite passes up transitionally into Carn Leac Psammite Formation (Foyers District - Haselock et al, 1982. Sheet 73E) and the Auchivarie Psammite Formation (Glen Roy district - Key et al, 1997. Sheet 63W). See May and Highton (1997).
Thickness: Up to 2km in type area, west of the Corrieyairack Pass.
Geographical Limits: Central and south-western Monadhliath Highlands, Loch Killin to Fort Augustus district.
Parent Unit: Corrieyairack Subgroup (GRCO)
Previous Name(s): Tarff Banded Formation (TARF)
Ardair Semipelite Formation (ARDR)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  River Tarff - basal contact tectonic, upper contact not exposed. 
Type Area  Ovoid area ca. 10km x 2.5km, south and east of Loch Killin [in core of large F2 fold], upper and lower contacts intact. 
Reference(s):
British Geological Survey, 1993. Invermoriston, Scotland. Sheet 73W. Solid Geology, 1:50 000 (Keyworth, Nottingham: British Geological Survey). 
British Geological Survey, 1996. Foyers Scotland Sheet 73E. Solid geology 1:50000 [Keyworth, Nottingham, British Geological Survey]. 
May, F and Highton, A J, 1997. Geology of the Invermoriston district. Memoir of the British Geological Survey, sheet 73W [Scotland]. 
British Geological Survey, 1995. Glen Roy, Scotland sheet 63W. Solid Geology 1:50000 (Keyworth, Nottingham, British Geological Survey). 
Key, R M, Clark, G C, May, F, Phillips, E R, Chacksfield, B C and Peacock, J D, 1997. Geology of the Glen Roy district. Memoir of the British Geological Survey, Sheet 63W [Scotland]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S073 S073