Glaciogenic rocks of the Neoproterozoic Smalfjord and Mortensnes formations, Vestertana Group, E. Finnmark, Norway

The Vestertana Group in East Finnmark, North Norway, contains two Neoproterozoic glaciogenic sequences, the Smalfjord and Mortensnes formations, preserved on the northern edge of Baltica. The former comprises up to 420 m of aeolian, fluvioglacial and glaciomarine sediments and terrestrial diamictite...

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Bibliographic Details
Published in:Geological Society, London, Memoirs
Main Authors: Rice, Alexander Hugh N., Edwards, Marc B., Hansen, Tor A., Arnaud, Emmanuelle, Halverson, Galen Pippa
Other Authors: School of Earth and Environmental Sciences
Format: Article in Journal/Newspaper
Language:English
Published: 2012
Subjects:
Mortensnes
Norway
Smalfjord
Tanafjorden
Vestertana
Finnmark
North Norway
Online Access:http://hdl.handle.net/2440/74256
https://doi.org/10.1144/M36.57
Description
Summary:The Vestertana Group in East Finnmark, North Norway, contains two Neoproterozoic glaciogenic sequences, the Smalfjord and Mortensnes formations, preserved on the northern edge of Baltica. The former comprises up to 420 m of aeolian, fluvioglacial and glaciomarine sediments and terrestrial diamictite. The latter consists of up to 50 m of predominantly diamictite. The Smalfjord Formation (Fm.) is underlain by dolostones (Grasdalen Fm., Tanafjorden Group), only locally preserved due to the sub-Smalfjord Fm. unconformity, which cuts down-section through a c. 2.5 km dominantly clastic sequence to rest on Baltic Shield gneisses. The two glaciogenic successions are separated by c. 350 m of mostly clastic sediments (Nyborg Fm.), with thin dolostones at the base and towards the top. The latter are generally absent due to the sub-Mortensnes Fm. unconformity, which also cuts down southwards through the Nyborg and Smalfjord formations to the Baltic Shield. No robust isotopic age constraints are available for the succession. δ13C data, together with cap dolostone characteristics, offer paradigmic correlations with other areas (Smalfjord ≡ Marinoan; Mortensnes ≡ Gaskiers). A limited Ediacaran fauna, including Aspidella, give only broad age constraints. Palaeomagnetic data are ambiguous; some suggest Baltica lay at equatorial (15°S) to mid-latitudes (50°S) for the period 750–550 Ma, respectively, while other interpretations place it at either 30°N or S at c. 550 Ma. A. Hugh N. Rice, Marc B. Edwards, Tor A. Hansen, Emmanuelle Arnaud and Galen P. Halverson

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