The BGS Lexicon of Named Rock Units — Result Details

Ballachulish Subgroup

Computer Code: DABH Preferred Map Code: Bchu
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Basal limestone, succeeded upward by graphitic pelite; this in turn overlain by persistent quartzite, which is overlain by striped semipelite with thin limestone units.
Definition of Lower Boundary: At top of the Lochaber Subgroup: in most areas there is a prominent limestone at the base of the Ballachulish Subgroup: also pelites become markedly graphitic at boundary.
Definition of Upper Boundary: At base of Blair Atholl Subgroup: generally at the transition from banded semipelite and limestone to more graphitic pelite with limestone beds.
Thickness: c.500-1100m (but locally tectonically thinned to 100m)
Geographical Limits: Islay; Appin to Lochaber; also a thin strip from near Loch Errochty to the Moray Firth coast at Sandend Bay (between Cullen and Portsoy). Also occurs in Ireland extensively in Co. Donegal.
Parent Unit: Appin Group (APP)
Previous Name(s): Blair Atholl Series (-835)
Ballachulish Group (-1473)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Strath of Appin and Island of Shuna, east shore of Loch Linnhe. Litherland, 1980. 
Type Area  Ballachulish, Argyll. 
Type Section  (Local). Traverse running south across Strath Fionan, commencing c.1km westsouthwest of Lochan Beoil. Line B-B' on Figure 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. 
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). 
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. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). 
Smith, R A and Harris, A L, 1976. The Ballachulish rocks of the Blair Atholl district. Scottish Journal of Geology, Vol.12, 153-157. 
Litherland, M, 1980. The stratigraphy of the Dalradian rocks around Loch Creran, Argyll. Scottish Journal of Geology, Vol.16, 105-123. 
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, 1934. West Highland tectonics, Loch Leven to Glen Roy. Quarterly Journal of the Geological Society of London, 90, 462. 
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. 
Bailey, E B, 1910. Recumbent folds in the schists of the Scottish Highlands. Quarterly Journal of the Geological Society of London. 66, 592. 
Harris, A L and Pitcher, W S, 1975. The Dalradian Supergroup. "In" Harris, A L, Shackleton, R M, Watson, J, Downie, C, Harland, W B and Moorbath, S. A correlation of the Precambrian rocks in the British Isles. Geological Society Special Report, No.6. p.52-75. Scottish Academic Press, Edinburgh. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S019 S027 S044 S045 S053 S055 S055 S064 S065 S065 S075 S075 S085 S086 S096 S045 S062 S063 S063 S096 S054 S054 S046 S053