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

By
A. Hugh N. Rice
A. Hugh N. Rice
Vienna University, Structural Processes Group, Department of Geodynamics and Sedimentology, Althanstrasse 14, 1090 Vienna, Austria, Europe
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Marc B. Edwards
Marc B. Edwards
5430 Dumfries Drive, Houston, Texas, USA
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Tor A. Hansen
Tor A. Hansen
Talisman Energy Norge AS, Verven 4, PO Box 649, Stavanger, Norway
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Emmanuelle Arnaud
Emmanuelle Arnaud
Department of Land Resource Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Galen P. Halverson
Galen P. Halverson
Department of Geology & Geophysics, School of Earth & Environmental Sciences, University of Adelaide, North Terrace, Adelaide, SA 5005, AustraliaPresent address: Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec, H3A 2A7, Canada
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Published:
January 01, 2011

Abstract

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.

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Contents

Geological Society, London, Memoirs

The Geological Record of Neoproterozoic Glaciations

Emmanuelle Arnaud
Emmanuelle Arnaud
University of Guelph, Canada
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Galen P. Halverson
Galen P. Halverson
McGill University, Canada
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Graham Shields-Zhou
Graham Shields-Zhou
University College London, UK
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Geological Society of London
Volume
36
ISBN electronic:
9781862394117
Publication date:
January 01, 2011

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