| Computer Code: |
TCDF |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Tonian Period (AT)
— Tonian Period (AT) |
| Lithological Description: |
Predominantly coarse-grained sandstone, with subordinate granular sandstone and basal breccia; breccias and granular sandstones occur at the base of the member, on or near the underlying Lewisian Gneiss; the coarse sandstones gradually become medium-grained towards the top of the member. |
| Definition of Lower Boundary: |
NM 3720 9366. Unconformable contact with Lewisian Gneiss. |
| Definition of Upper Boundary: |
NM 3730 9366. Highly variable gradational and/or interdigitating transition into overlying Laimhrig Shale Member, which may occur over several tens of metres of stratigraphical thickness, eg NM 3695 9905. |
| Thickness: |
35m-70m in type locality (highly variable elsewhere). |
| Geographical Limits: |
Isle of Rhum, Fiachanis. |
| Parent Unit: |
Diabaig Formation (TCD)
|
| Previous Name(s): |
Basal Grit (Millstone Grit) [Obsolete Name and Code: Use TCDF]
(-3075)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Isle of Rhum, Fiachanis [NM 374 939 - NM 375 939]. |
| Reference(s): |
| Emeleus, C H. 1997. Geology of Rum and the adjacent islands. Memoir (sheet) of the Geological Survey of Great Britain (Scotland) (60). (The Stationery Office for the British Geological Survey.) 171pp. |
| Stewart, A D. 2002. The later Proterozoic Torridonian rocks of Scotland: their sedimentology, geochemistry and origin. Geological Society Memoir. Vol. 24. (The Geological Society.) |
| 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. |
| Black, G P, and Welsh, W, 1961. The Torridonian succession of the Isle of Rhum. Geological Magazine, Vol. 98, 265-276. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
S060
|
