The BGS Lexicon of Named Rock Units — Result Details

Inverlair Psammite Formation

Computer Code: INVL Preferred Map Code: IN
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Feldspathic and siliceous psammite and feldspathic quartzite with interbedded layers of semipelite. Minor micaceous psammite locally.
Definition of Lower Boundary: Transitional boundary, the lower boundary placed where thicker and laterally more extensive psammites become dominant and the semipelites of the underlying Clachaig Semipelite and Psammite Formation become scarce.
Definition of Upper Boundary: Transitional contact where psammites and quartzites are replaced by semipelite-dominated succession of the overlying Appin Group.
Thickness: 0 to 900m
Geographical Limits: Southern part of the Central Highlands of Scotland bounded to the NW by Glen Roy and the uppermost Spey Valley, to the south by Glen Spean and extending east to Ardverikie Forest and the River Pattack [NN 54 86].
Parent Unit: Glen Spean Subgroup (GRGS)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Inverlair Gorge of the River Spean, either side of the Fersit road bridge. 
Reference(s):
Winchester, J A and Glover, BW, 1988. The Grampian Group, in Winchester, J A [ed.]. Late Proterozoic stratigraphy of the northern Atlantic regions. Blackie, Glasgow, 146-161. 
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]. 
British Geological Survey, 1995. Glen Roy, Scotland sheet 63W. Solid Geology 1:50000 (Keyworth, Nottingham, British Geological Survey). 
Glover, B W and Winchester, J A, 1989. The Grampian Group, a major Late Proterozoic clastic sequence in the Central Highlands of Scotland. Journal of the Geological Society, London. Vol.146, 85-96. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S063 S063