The BGS Lexicon of Named Rock Units — Result Details

Tornahaish Dark Schist And Limestone Formation

Computer Code: TDSL Preferred Map Code: SYMB
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Grey to black, thinly banded to laminated, semipelites and subsidiary pelites. Micaceous psammites noted. Thin limestone interbeds. Beds slaty to schistose. To south schistose semipelites. Prominent crystalline limestone member. Graphitic pelite generally present at base.
Definition of Lower Boundary: At top of calcareous semipelite of Cock Burn Calcareous Schist Formation.
Definition of Upper Boundary: Upper limit of pelites, thin limestones and/or calcareous beds below semipelite and micaceous psammite of the Nochty Semipelite and Limestone Formation.
Thickness: 100-150m. Possibly up to 200m west of Tornahaish.
Geographical Limits: In Upper Donside west of Tornahaish to Delnadamph and Dunandhu. Also SSE adjacent to A939 road to Mammie Hill. Includes as large hornfelsed pendants and xenoliths in east part of Glen Gairn Granite.
Parent Unit: Blair Atholl Subgroup (DABA)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  Hill of Tornahaish and lower part of Burn of Tornahaish. 
Reference Section  Allt na Ciste Burn upstream of A 939 bridge for 1km. 
Memoir of the British Geological Survey, Sheet 75, in preparation. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: