The BGS Lexicon of Named Rock Units — Result Details

Cnoc An Fhithich Banded Semipelite Formation

Computer Code: CAFS Preferred Map Code: CnFS
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Banded alternation of rusty-weathering semipelite with 5 - 10cm beds of psammite in equal proportions; however 25% of upper part of formation consists of white, quartz-rich psammite alternating with dark, biotitic, graded pelite.
Definition of Lower Boundary: Transitional, with interbanding of calcareous semipelite with thin grey limestone beds marks junction with upper limestone of Blair Atholl Dark Limestone and Dark Schist Formation.
Definition of Upper Boundary: Sharp boundary with buff limestone of Drumchastle Pale Limestone Formation at type locality; elsewhere taken at base of calc-muscovite-biotite pelite lithology transitional to Drumchastle Pale Limestone Formation.
Thickness: 0 - 150m in Sheet 55W; probably tectonically attenuated.
Geographical Limits: From east side of Errochty Synform at Errochty Water [NN 7245 6480] discontinuously to near Braes of Foss [NN 7465 5590]. East of the Loch Tay Fault and north of the Killiecrankie Slide, it occurs from Allt Bhaic [NN 840 640] and on the eastern slopes of Glen Tilt [NN 886 680 - 898 713 and NN 912 714 - 942 745].
Parent Unit: Blair Atholl Subgroup (DABA)
Previous Name(s): Banded Series within Pale Group of Blair Atholl Series [Obsolete Name and Code: Use CAFS] (-3896)
Banded Group within Blair Atholl Subgroup [Obsolete Name and Code: Use CAFS] (-103)
Banded Schist within Blair Atholl Subgroup [Obsolete Name and Code: Use CAFS] (-104)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  300m north of Allt Leathan, on eastern slopes of Cnoc an Fhithich. 
Reference(s):
Treagus, J E. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). 
Bailey, E B, 1925. Perthshire tectonics: Loch Tummel, Blair Atholl and Glen Shee. Transactions of the Royal Society of Edinburgh, Vol.53, 671-698. 
Barrow, G, Grant Wilson, J S and Cunningham Craig, E H, 1905. The geology of the country around Blair Atholl, Pitlochry and Aberfeldy. Memoir of the British Geological Survey, Scotland (Sheet 55). 
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. 
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. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055 S055 S064