| Computer Code: |
GAPS |
Preferred Map Code: |
SYMB |
| Status Code: |
Full |
| Age range: |
Proterozoic Eon (AP)
— Proterozoic Eon (AP) |
| Lithological Description: |
[Obsolete: use REP]
Buff to pale brown and pink, flaggy, siliceous and feldspathic psammite with micaceous partings, some heavy mineral bands and numerous streaky lenticles displaying quartzofeldspathic segregations. |
| Definition of Lower Boundary: |
Located at the Sgurr Beag Thrust Plane, which is commonly interdigitated with Lewisianoid tectonic slices. This formation is structurely the lowest Moine group unit in the Sgurr Beag Nappe. |
| Definition of Upper Boundary: |
Defined by the western edge of the Ben Wyvis Pelite Formation, with the appearance of predominantly pelitic rocks to the east. The boundary has probably been significantly tectonically modified. |
| Thickness: |
Not recorded. |
| Geographical Limits: |
Forms a thin, nearly continuous belt running south-west to north-east from Loch Luichart (NH383602) to Loch Coire (NH525762). South and west of Loch Luichart, it is repeated in a series of folds and thrusts; e.g.Sgurr Beag Thrust, extending to the west at Loch Bhad Ghaineamhaich (NH323590), where it terminates against the Strathconon Fault. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Ben Wyvis Psammite [Obsolete Name and Code: Use GAPS]
(-274)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Beinn a' Ghuilbein, 3.2 km north-east of Garve. |
| Reference(s): |
| Wilson, D. 1975. Structure and metamorphism of the Ben Wyvis District, Ross-shire. (University of Edinburgh: Unpublished PhD thesis.) |
| Grant, C J. 1989. The kinematics and tectonic significance of ductile shear zones within the Northern Highland Moine. (University of Liverpool: unpublished PhD thesis.) |
| Holdsworth, R E, Strachan, R A and Harris, A L, 1994. Precambrian rocks in northern Scotland east of the Moine Thrust: The Moine Supergroup in Gibbons, W and Harris, A L (editors). A revised correlation of Precambrian rocks in the British Isles. Special Report of the Geological Society, No.22. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S093
S093
S093
|
