The BGS Lexicon of Named Rock Units — Result Details

Tullochroisk Semipelite Formation

Computer Code: TULS Preferred Map Code: TulS
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Lower part - rusty weathering pyritic semipelite with psammitic beds, non-graphitic; Upper part - semipelite, moderately graphitic, with biotite porphyroblasts.
Definition of Lower Boundary: Sharp contact with pale limestone of Strath Fionan Pale Limestone Formation.
Definition of Upper Boundary: Sharp boundary with graphitic limestone at base of Blair Atholl Dark Limestone and Dark Schist Formation.
Thickness: 0 - 200m in Sheet 55W; probably some tectonic thinning.
Geographical Limits: Intermittently from closure of Errochty Synform [NN 713 670] to the south bank of Allt Kynachan [NN 7778 5722]. Not present east of the Loch Tay Fault, where its place is taken by the upper part of the Monzie Limestone and Schist Formation.
Parent Unit: Ballachulish Subgroup (DABH)
Previous Name(s): Monzie Limestone And Schist Formation (-4323)
Strath Fionan Dark Schist And Limestone Formation (-1242)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Upper part of formation - 700m southeast of south end of Lochan an Daim; along line of traverse C-C' (Fig.4 of Treagus, in press). 
Partial Type Section  Lower part of formation - Section in the stream, 700m southeast of south end of Lochan an Daim; close to C-C' (Fig.4 of Treagus, J E. 2001). 
Reference(s):
Bailey, E B, 1925. Perthshire tectonics: Loch Tummel, Blair Atholl and Glen Shee. Transactions of the Royal Society of Edinburgh, Vol.53, 671-698. 
Bailey, E B and McCallien, W J, 1937. Perthshire tectonics: Schiehallion to Glen Lyon. Transactions of the Royal Society of Edinburgh, Vol.59, 79-117. 
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. 
Smith, R A and Harris, A L, 1976. The Ballachulish rocks of the Blair Atholl district. Scottish Journal of Geology, Vol.12, 153-157. 
Stephenson, D and Gould, D , 1995. British Regional Geology: the Grampian Highlands (4th edition). (London: HMSO for the British Geological Survey), 67-68. 
Treagus, J E and King, G, 1978. A complete Lower Dalradian succession in the Schiehallion district, central Perthshire. Scottish Journal of Geology, Vol.14, 157-166. 
Treagus, J E. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055