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): | Lochaber (Transition) Subgroup [Obsolete Name and Code: Use DALO]
(-3976)
Eilde, Binnein and Glen Coe Quartzites [Obsolete Name and Code: Use DALO] (-2738) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | On both shores of Loch Leven and east of Kinlochleven. | ||
| Reference(s): | |||
| 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.) | |||
| 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). | |||
| 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. | |||
| 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 | |||