The BGS Lexicon of Named Rock Units — Result Details

Blair Atholl Dark Limestone And Dark Schist Formation

Computer Code: DLDS Preferred Map Code: BADL
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Lower part - grey to cream-weathering graphitic calcite limestone, with millimetre thick ribs of quartz; Central part - black, rusty-weathering, highly graphitic pelite; Upper part - grey graphitic limestone with quartz ribs, similar to lower part.
Definition of Lower Boundary: Sharp boundary with semipelite and graphitic pelite of Tullochroisk Semipelite Formation.
Definition of Upper Boundary: Transitional, with interbanding of calcareous semipelite with thin grey limestone beds marks junction with the Cnoc an Fhithich Banded Semipelite Formation.
Thickness: 1 - 120m in Sheet 55W; probably tectonically attenuated; appears to be thicker in Sheet 55E.
Geographical Limits: From north shore of Loch Errochty [NN 710 660] almost continuously to the Loch Tay Fault [NN 790 550 - 791 572]. East of the Loch Tay Fault and north of the Killiecrankie Slide, it occurs from Conbhar [NN 825 616] to 1km east of Forest Lodge in Glen Tilt [NN 943 743] and via Loch Moraig as far as the south end of Loch Loch [NN 988 735].
Parent Unit: Blair Atholl Subgroup (DABA)
Previous Name(s): Upper part of Strath Fionan Dark Limestone and Dark Schist Formation [Obsolete Name and Code: Use DLDS] (-3363)
Dark Group Of Blair Atholl Series (-864)
Dark Limestone and Dark Schist within Blair Atholl Subgroup [Obsolete Name and Code: Use DLDS] (-3997)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Traverse running south from Allt Leathan, 800m south of Lochan an Daim; on line C-C' (Fig 4 of Treagus, J E. 2001). 
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. 
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. 
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). 
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. 
Smith, R A and Harris, A L, 1976. The Ballachulish rocks of the Blair Atholl district. Scottish Journal of Geology, Vol.12, 153-157. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055 S055 S064