The BGS Lexicon of Named Rock Units — Result Details

An Stac Semipelite and Psammite Formation

Computer Code: ANST Preferred Map Code: AS
Status Code: Full
Age range: Tonian Period (AT) — Tonian Period (AT)
Lithological Description: Striped association of semipelite, psammite and siliceous psammite with subordinate quartzite and calc-silicate rock, variably gneissose.
Definition of Lower Boundary: Base marked by interbanded garnetiferous quartzite and predominantly semipelite above psammites of the Creag an Loin Psammite Formation.
Definition of Upper Boundary: Invariably marked by a narrow zone of ductile shear overlain by gneissose feldspathic psammites of the Creag Liath Psammite Formation.
Thickness: 600-700 metres.
Geographical Limits: Central Highlands of Scotland. Newtonmore - Glen Banchor - Kincraig areas.
Parent Unit: Glen Banchor Subgroup (GLBA)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Summit area of An Stac. 
Reference Section  Immediately north of Creag an Loin - basal part of unit. 
Reference(s):
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S063 S064 S074