The BGS Lexicon of Named Rock Units — Result Details

Auch Gleann Psammite Formation

Computer Code: AUGL Preferred Map Code: AUGL
Status Code: Full
Age range: Cryogenian Period (AC) — Cryogenian Period (AC)
Lithological Description: Interbedded pink quartzofeldspathic psammite and grey micaceous grey psammite. Parallel bedded psammite layers 10-20cm thick develop plane parallel internal lamination defined by alternations of more micaceous and quartzofeldspathic layers at a mm scale. Similar scale but undulose bedded forms also present with rare preservation of hummocky cross stratification. Subsidiary 50-100cm-thick massive beds may have a lenticular form and may be indicative of channel or sand-wave macroforms. Semipelite to pelite comprises a very minor part of the Formation but forms in layers up to 15m thick.
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: Abrupt change to white weathering pinkish-brown quartzose psammite and quartzite of the succeeding Beinn a' Chaisteil Formation.
Thickness: >1000m.
Geographical Limits: Includes all of the Grampian Group psammite rocks which extend across the northern parts of 1:50k sheets 46W (Crianlarich) and 46E (Killin).
Parent Unit: Glen Spean Subgroup (GRGS)
Previous Name(s): Moine (-3810)
Grampian Group (Undivided) (-660)
Alternative Name(s): none recorded or not applicable
Reference Section  Allt Coralan (Glen Coralan), tributary of Auch Gleann, upstream from railway viaduct. Details will be included in Sheet Description for Sheet 46W (Crianlarich);Presently in draft BGS internal report: Leslie et al. Progress Report on Geology of the Tyndrum area, 2003. 1:50k Sheet 46W (Crianlarich). 
In preparation. BGS Sheet Description for Sheet 46W (Crianlarich) and 46E (Killin). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable