The BGS Lexicon of Named Rock Units — Result Details

Mortlach Graphitic Schist Formation

Computer Code: MOGS Preferred Map Code: SYMB
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Semipelitic and pelitic schist, commonly graphitic, with calc-silicate lenses and metalimestone in lowermost part.
Definition of Lower Boundary: At the top of the Pitlurg Formation where interbedded thin limestones, calc-silicate beds and semipelites and psammites pass up into either graphitic schist or massive limestone.
Definition of Upper Boundary: At the base of the Corriehabbie Quartzite Formation where the schists pass up into flaggy psammites, phyllites and quartzite.
Thickness: c. 970m, including any thickening due to folding in the type section; thinned and thickened considerably by deformation elsewhere.
Geographical Limits: From the coast at Sandend, SW through the Keith and Dufftown area into Glen Rinnes, thence continuing into Glenlivet, to the Bridge of Avon area west of Tomintoul and then in the Allnack Gorge, running SE into Glen Avon.
Parent Unit: Ballachulish Subgroup (DABH)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Stream section in Corriehabbie Burn and its upper tributaries. 
Reference Section  Stream section in Dullan Water at the Mortlach Distillery, Dufftown. 
Reference Section  Stream section in Burn of Tervie, Glenlivet between Braushie Cree and Mains of Morinsh. 
Reference(s):
Memoir of the British Geological Survey, Sheet 75, in preparation. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S086 S096