The BGS Lexicon of Named Rock Units — Result Details

Lochaber Subgroup

Computer Code: DALO Preferred Map Code: Loch
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Alternating units of psammite to quartzite and semipelite to pelite; in places becoming calcareous near the top of the Subgroup. Many of the finer-grained lithologies are flaggy, but in some places this may be a tectonic effect. Succession from Grampian Group into Lochaber Subgroup continuous in some areas, e.g. Schiehallion, Banffshire, but in Glen Spean there may be a tectonically modified unconformity at the base of the Leven Schist.
Definition of Lower Boundary: Generally sharp transition from underlying Grampian Group, from monotonous psammites, generally flaggy, with thin quartzite and semipelite units to better sorted psammite or quartzite and semipelite or pelite.
Definition of Upper Boundary: Incoming of more calcareous sediment, and more graphite in the pelitic and semipelitic rocks, indicating a decrease in the amount of input clastic material.
Thickness: Variable locally 1500m where untectonised (Lochaber, Banffshire); in Schiehallion district thickness reduced to about 80m, but full succession can still be recognised.
Geographical Limits: Core of Islay antiform: Appin to Ballachulish; Loch Leven to Glen Spean; Kinlochlaggan; Strath Fionan to Baddoch Burn (very attenuated); Dufftown to Banffshire coast west of Sandend; Glenlivet, Derback, Inchrory area (Valley of River Avon).
Parent Unit: Appin Group (APP)
Previous Name(s): Eilde, Binnein And Glen Coe Quartzites (-2738)
Lochaber (Transition) Subgroup (-3976)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  On both shores of Loch Leven and east of Kinlochleven. 
Reference(s):
Treagus, J E, 1974. A structural cross-section of the Moine and Dalradian rocks of the Kinlochleven area, Scotland. Journal of the Geological Society of London, Vol.130, 525-544. 
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. 
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. 
Bailey, E B and Maufe, H B, 1960. The geology of Ben Nevis and Glen Coe (Second Edition). Memoir of the Geological Survey of the United Kingdom. (Scotland, Sheet 53). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S053 S054 S055 S063 S064 S065 S085 S086 S095 S096 S045 S045 S027 S019 S055 S062 S063 S086 S096 S054 S046 S053