The BGS Lexicon of Named Rock Units — Result Details
Iona Group
Computer Code: | IONA | Preferred Map Code: | SYMB |
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Status Code: | Full | ||
Age range: | Tonian Period (AT) — Tonian Period (AT) | ||
Lithological Description: | Lower Unit: very coarse cobble-boulder conglomerate, interbedded with, and grading upwards a pebble conglomerate. Followed by a pink to grey coarse, arkosic sandstone, interbedded with thin mudstone. Upper Unit: interbedded fine-grained grey sandstone and thin dark mudstone beds with ripple laminations. | ||
Definition of Lower Boundary: | Unconformable upon Lewisian Gneiss inlier (L); unconformity locally sheared. | ||
Definition of Upper Boundary: | Not exposed - eroded. | ||
Thickness: | c. 700 m: Lower unit: c. 0-165 m; Upper Unit c. 500 m (minimum). | ||
Geographical Limits: | none recorded or not applicable | ||
Parent Unit: | Wester Ross Supergroup (WROS) | ||
Previous Name(s): | none recorded or not applicable | ||
Alternative Name(s): | Colonsay Group Torridonian [Obsolete: use T] |
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Stratotypes: | |||
Reference Section | Coastal section on NE coast of Iona [NM 292 262 - NM 295 260]. | ||
Reference(s): | |||
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. | |||
Gibbons, W and Harris, A L. 1994. A revised correlation of Precambrian rocks in the British Isles. Geological Society of London Special Report, No.22. | |||
Stewart, A D. 2002. The later Proterozoic Torridonian rocks of Scotland: their sedimentology, geochemistry and origin. Geological Society Memoir. Vol. 24. (The Geological Society.) | |||
McAteer, C A, Daly, J S, Flowerdew, M J, Whitehouse, M J, and Monaghan, N M. 2014. Sedimentary provenance, age and possible correlation of the Iona Group SW Scotland. Scottish Journal of Geology, Vol. 50, 143-158. | |||
Stewart, A D. 1962. On the Torridonian sediments of Colonsay and their relationship to the main outcrop in north-west Scotland. Geological Journal, Vol. 3, 121-156. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
S043 |