The BGS Lexicon of Named Rock Units — Result Details

Tarnash Phyllite And Limestone Formation

Computer Code: TNPL Preferred Map Code: TnPL
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Semipelite, commonly thinly bedded, with white to pale grey metacarbonate and green-grey calc-silicate rocks. Prominent white limestone (Linkbrae Limestone Member) near base well developed on coast. Dolomitic metalimestone developed in lower part in Tarnash area. Less calcareous in the Grange area (River Isla).
Definition of Lower Boundary: At upper limit of quartzite of the Corryhabbie Quartzite Formation, where present. Otherwise at lowest appearance of white limestone or muscovite-rich semipelite above Mortlach Graphitic Schist Formation.
Definition of Upper Boundary: Rapid gradation from calcareous semipelite and limestone to graphitic pelite/semipelite and dark-grey limestone of Fordyce Limestone Formation.
Thickness: 240m from Deskford ORS outlier to Sandend Bay; c.400m in Grange area; c.250m in Tarnash area.
Geographical Limits: Extends southsouthwest from coast section in eastern half of Sandend Bay [NJ 559 664], to Stripeside [466 518], and south of the River Isla around the Herricks and Birken Burns [NJ 45 48]. Farther southwest, equivalent unit is termed the Ailnack Phyllite and Limestone Formation.
Parent Unit: Ballachulish Subgroup (DABH)
Previous Name(s): Sandend Formation [Obsolete Name And Code: See SNDL, TNPL And FORD] (DASG)
Middle Part Of Sandend Group (-3525)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Lower part of Burn of Tarnash and Birken Burn. 
Partial Type Section  Burn of Paithnick, 400m west of Gordonstown Farm. 
Partial Type Section  (Linkbrae Limestone Member). Disused, flooded quarry in middle of beach, Sandend Bay. 
Reference(s):
Stephenson, D, et al. 1993. Stratigraphy and correlation of the Dalradian rocks of the East Grampian Project area. British Geological Survey Technical Report WA/93/91. 
Harris, A L, Haselock, P J, Kennedy, M J and Mendum, J R, 1994. The Dalradian Supergroup in Scotland, Shetland and Ireland. 33-53 in Gibbons, W E and Harris, A L (editors). A revised correlation of Precambrian rocks in the British Isles. Special Report of the Geological Society, London, No.22. 
Stephenson, D and Gould, D , 1995. British Regional Geology: the Grampian Highlands (4th edition). (London: HMSO for the British Geological Survey), 67-68. 
Read, H H, 1923. Geology of the country around Banff, Huntly and Turriff, Lower Banffshire and north-west Aberdeenshire. Memoir of the Geological Survey, Scotland Sheets 86 and 96 (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S086 S096