The BGS Lexicon of Named Rock Units — Result Details

Ardair Semipelite Formation

Computer Code: ARDR Preferred Map Code: AR
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Interbedded schistose semipelite and micaceous psammite in roughly equal proportions
Definition of Lower Boundary: Transitional with underlying micaceous psammites of the Loch Laggan Psammite Formation.Marked by increase in semipelite and thin-banded micaceous psammite content.
Definition of Upper Boundary: Sharp to transitional with thinly bedded feldspathic and micaceous psammites of the Creag Meagaidh Psammite Formation
Thickness: 770m in type area.
Geographical Limits: South-western Monadhliath Highlands, Glen Roy - Glen Banchor, and Adverikie and Ben Alder Forest areas.
Parent Unit: Corrieyairack Subgroup (GRCO)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Roadcuts on north side of A86, north of Lower Laggan Reservoir. 
Reference Section  Summit area of Creag Pitridh - upper contact. 
Type Area  South wall of Coire Ardair on Creag Meagaidh 
Reference(s):
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:
S074 S063 S063 S073