Iona Group

Stratigraphic range: 1000–950 Ma
Type| Group
Unit of| Wester Ross Supergroup
Thickness| ~700 m
Lithology
Primary| metasandstone
Other| metasiltstone, semipelite, mylonite, conglomerate
Location
Region| Inner Hebrides
Country| Scotland
Type section
Named for| Iona

The Iona Group is a sequence of metamorphosed Neoproterozoic sedimentary rocks that outcrop along the east coast of the island of Iona within the Inner Hebrides of Scotland. The name was given to this sequence by Stewart in 1969, keeping it distinct from the Torridonian, which it resembles. Since c. 2021, it has been assigned to the Wester Ross Supergroup.[1]

Three divisions are recognised; i) interbedded metasandstones and metasiltstones, ii) slaty semipelites and iii) conglomerates, the clasts of which are largely metamorphic in origin. The rock strata are steeply inclined to vertical.[2][3]

## References

[edit]

1. ^ Krabbendam, M.; Strachan, R.; Prave, T. (2022). "A new stratigraphic framework for the early Neoproterozoic successions of Scotland". Journal of the Geological Society. 179. doi:10.1144/jgs2021-054. hdl:10023/24155.
2. ^ "Ross of Mull". Geological maps portal. British Geological Survey. Retrieved 1 March 2020.
3. ^ "Iona Group". The BGS Lexicon of Named Rock Units. British Geological Survey. Retrieved 7 July 2021.

*[c.]: circa