A stratigraphic framework for the early Neoproterozoic successions of the Northern Highlands of Scotland.

Krabbendam, M.. 2021 A stratigraphic framework for the early Neoproterozoic successions of the Northern Highlands of Scotland. Nottingham, UK, British Geological Survey, 85pp. (OR/21/072) (Unpublished)

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Abstract/Summary

This report sets out a revised stratigraphic framework for the for the late Mesoproterozoic and early Neoproterozoic successions of the Northern Highlands of Scotland. The late Mesoproterozoic comprises the Stoer Group that, despite its small outcrop, is well exposed and studied. No major changes as to subdivision are proposed for this group. The classic subdivision of Torridonian and Moine Supergroup for the early Neoproterozoic sedimentary rocks of the Northern Highlands of Scotland has become incompatible with new datasets (detrital zircon dates, radiometric dating of metamorphic and igneous events, sedimentological studies) and is now stratigraphically invalic. Supergroup status for the Moine is not warranted, since there is no stratigraphic continuity (as previously thought) between the Morar and Glenfinnan groups. Instead, the successions are grouped into two new Supergroups: an older Wester Ross Supergroup and a younger Loch Ness Supergroup. This subdivision is now compatible with the broad subdivisions in the wider North Atlantic region. The Wester Ross Supergroup includes the Sleat, Torridon and Morar groups, and likely the Iona, Tarskavaig (Skye), and Sand Voe, Yell Sound and Westing (Shetland) groups. These units were deposited between c. 1000-950 Ma, sourced from the Grenville orogen and deposited in a broad foreland-basin setting. Some Wester Ross Supergroup units (and equivalents in Greenland and Svalbard) have been affected by c. 950-910 Ma Renlandian metamorphic and igneous events, and deposition must thus predate this orogeny. The Loch Ness Supergroup includes the Glenfinnan and Loch Eil groups, as well as the Badenoch Group in the Grampian Highlands. Contacts between the Glenfinnan and Morar groups are sheared everywhere and there is no evidence for stratigraphic continuity. The Loch Ness Supergroup was deposited between c. 900 and 870 Ma and is at least partly associated with an extensional tectonic event. The Wester Ross Supergroup and the Loch Ness Supergroup, together with the late (<720 Ma) Neoproterozoic Dalradian Supergroup, can be correlated with the three major Megasequences recognised in the wider Neoproterozoic Northern Atlantic setting, each recording major tectonic events in the Laurentian sector of Rodinia. The late Mesoproterozoic Stoer Group remains distinct. All early Neoproterozoic Formation and Members across the Northern Highlands have been critically assessed and the terminology has been rationalised.

Item Type:	Publication - Report
Funders/Sponsors:	British Geological Survey
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed.
Date made live:	10 Jan 2022 10:06 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/531717

Item Type:

Publication - Report

Funders/Sponsors:

British Geological Survey

Additional Information. Not used in RCUK Gateway to Research.:

This item has been internally reviewed, but not externally peer-reviewed.

Date made live:

10 Jan 2022 10:06 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/531717