| Computer Code: |
MBLA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Tonian Period (AT)
— Tonian Period (AT) |
| Lithological Description: |
Coarse pelitic gneiss, garnetiferous, locally migmatitic, with gneissose semipelite and psammite. Quartzite occurs locally. Calcsilicate bands are common within psammite. |
| Definition of Lower Boundary: |
Overlies the Resipol Striped Formation (RESI) south of Moidart. Further north: either the base is cut by the Sgurr beag Thrust, or overlies conformably the Reidh Psammite (REP), or occurs directly unconformably (sheared) on Lewisianoid crystalline basement. |
| Definition of Upper Boundary: |
Overlain by the Beinn An Tuim Striped Formation (BTU), likely conformable, or directly by Loch Eil Group (LEIL). |
| Thickness: |
Highly variable, possibly up to 2-3 km. |
| Geographical Limits: |
Northern Highlands: Loch Sunart to Dornoch Firth. Restricted to the Sgurr Beag Nappe. |
| Parent Unit: |
Glenfinnan Group (GLEN)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| Roberts, A M, Strachan, R A, Harris, A L, Barr, D and Holdsworth, R E, 1987. The Sgurr Beag Nappe: A reassessment of the stratigraphy and structure of the Northern Highland Moine. Geological Society of America Bulletin, Vol.98, 497-506. |
| Strachan, R A, May, F and Barr, D, 1988. The Glenfinnan and Loch Eil Divisions of the Moine Assemblage. 32-45 IIV Winchester, J A (editor). Later Proterozoic stratigraphy of the Northern Atlantic regions (Glasgow and London: Blackie). |
| Krabbendam, M. 2021. A stratigraphic framework for the early Neoproterozoic successions of the Northern Highlands of Scotland. UK Stratigraphic Framework Series. British Geological Survey Open Report, OR/21/072. 86pp. |
| Tanner, P W G. 1971. The Sgurr Beag Slide - a major tectonic break within the Moinian of the Western Highlands of Scotland. Quarterly Journal of the Geological Society, Vol. 126, 435-463. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S092
S061
S062
|
