The BGS Lexicon of Named Rock Units — Result Details

Portsoy Limestone Formation

Computer Code: PTSL Preferred Map Code: PtsL
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Interbedded units of semipelite with graphitic pelite, beds of crystalline metalimestone, quartzite and minor dolomite. Distinctive kyanite after andalusite in graphitic pelite of basal Sandy Pots Limestone Member. Some pebbly quartzite and psammite.
Definition of Lower Boundary: First limestone bed above Castle Point Pelite Formation.
Definition of Upper Boundary: Not seen at type section: upper part cut out by Portsoy basic intrusion and Portsoy Shear Zone. Screens and rafts of semipelite and metalimestone in basic body.
Thickness: Probably c.200m+, but much disrupted by Portsoy basic intrusion and movement along Portsoy Shear Zone.
Geographical Limits: Coast section in western part of Portsoy [NJ 584 665-586 662], together with isolated inliers and xenoliths in Portsoy basic intrusion. Some equivalent strata may have been included within the Castle Point Formation in the poorly exposed ground in the south of Sheet 96W and the north of Sheet 86W.
Parent Unit: Easdale Subgroup (DBED)
Previous Name(s): Upper Part Of Portsoy Group (-472)
Portsoy Group [Obsolete Name And Code: See CAPT And PTSL] (DBPB)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Coastal section from Sandy Pots to Mara Vista (house in Marine Terrace, Portsoy). 
Reference(s):
Stephenson, D and Gould, D , 1995. British Regional Geology: the Grampian Highlands (4th edition). (London: HMSO for the British Geological Survey), 67-68. 
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. 
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:
S096