The BGS Lexicon of Named Rock Units — Result Details
Meall Dubh Graphitic Schist Formation
| Computer Code: | MEDS | Preferred Map Code: | MeDG |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ) | ||
| Lithological Description: | Graphitic pelite with semipelite ribs, containing porphyroblasts of kyanite (up to 100mm), biotite, garnet and rare staurolite and albite. | ||
| Definition of Lower Boundary: | Gradational boundary with the Meall Dubh Limestone Formation with admixture of graphitic and calc-schists is poorly exposed. | ||
| Definition of Upper Boundary: | Graphitic kyanite-bearing semipelite merges with 1m of transitional muscovitic, rusty-weathering quartzite with graphitic seams which forms the base of the Meall Dubh Quartzite Formation. This transitional quartzite is possibly equivalent to the Beinn a'Ghlo Transition of Smith, R A and Harris, A L (1976). | ||
| Thickness: | 0 - 50m in Sheet 55W; much tectonic thinning compared with Beinn a' Ghlo Graphitic Schist/Ballachulish Slate. | ||
| Geographical Limits: | Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically as far west as Allt na Moine Buidhe [NN 708 612] and as far east as Allt Kynachan [NN 7790 5725]. Not present east of the Loch Tay Fault, where its place is taken by the Beinn a'Ghlo Graphitic Schist Formation; some of the 'Banvie Burn Series' may be equivalent. | ||
| Parent Unit: | Ballachulish Subgroup (DABH) | ||
| Previous Name(s): | Ballachulish Slate [Obsolete Name and Code: Use MEDS, DASL]
(*559)
Beinn A'Ghlo Graphitic Schist [Obsolete Name and Code: Use MEDS] (*922) Meall Dubh Graphitic Schist [Obsolete Name and Code: Use MEDS] (-4788) |
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| Alternative Name(s): | Beinn A'Ghlo Graphitic Schist [Obsolete: use MEDS] Ballachulish Slate [Obsolete: use MEDS, DASL] |
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| Stratotypes: | |||
| Type Section | Crag on north side of road through Strath Fionan, c.1km west-north-west of Braes of Foss. | ||
| Reference(s): | |||
| Smith, R A and Harris, A L, 1976. The Ballachulish rocks of the Blair Atholl district. Scottish Journal of Geology, Vol.12, 153-157. | |||
| 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. | |||
| Treagus, J E. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| S055 | |||