New Evidence of Glacial Abrasion of the Late Proterozoic Unconformity around Varangerfjorden, Northern Norway

  1. Wladyslaw Altermann3 and
  2. Patricia L. Corcoran4
  1. K. Laajoki1,2

Published Online: 12 MAR 2009

DOI: 10.1002/9781444304312.ch19

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

How to Cite

Laajoki, K. (2002) New Evidence of Glacial Abrasion of the Late Proterozoic Unconformity around Varangerfjorden, Northern Norway, in Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems (eds W. Altermann and P. L. Corcoran), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304312.ch19

Editor Information

  1. 3

    Institut für Allgemeine und Angewandte Geologie, Ludwig-Maximilians-Universität München, Luisenstrasse 37, D-80333 Munich, Germany

  2. 4

    Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada

Author Information

  1. 1

    Mineralogical–Geological Museum, University of Oslo, Sars'gate 1, 0562 Oslo, Norway

  2. 2

    Department of Geology, University of Oulu, Box 3000, 90401 Oulu, Finland

Publication History

  1. Published Online: 12 MAR 2009
  2. Published Print: 18 FEB 2002

ISBN Information

Print ISBN: 9780632064151

Online ISBN: 9781444304312

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Keywords:

  • glacial abrasion of late proterozoic unconformity around Varangerfjorden, northern Norway;
  • geological setting and regional stratigraphy;
  • late proterozoic Smalfjord formation of Vestertana group;
  • Varangerfjorden unconformity;
  • Varangerfjorden unconformity (VFU) - best exposed and main target study;
  • facies under Varangerfjorden unconformity;
  • Ruossoaivi (Ruosso'aivi), southern Vieranjarga;
  • glacial versus non-glacial abrasion of Bigganjargga surface;
  • new striation and small groove observations;
  • Bjørlykke's glacial palaeovalley model for Varangerfjorden unconformity confirming subglacial origin of Bigganjargga surface

Summary

The regional angular unconformity that separates the late Proterozoic (Riphean–Vendian) Vadsø and Tanafjorden groups from the overlying Varangerian (late Vendian) glacigenic rocks (the Smalfjord, Nyborg and Mortensnes formations) of the Vestertana Group can be mapped on both sides of south-western Varangerfjorden. New observations of late Proterozoic glacial striations and small grooves were made at Handelsneset, Skjåholmen and Vieranjarga, 5–20 km east of Bigganjargga. The striations and grooves, in addition to the fact that the classical Bigganjargga surface is not a plane, but part of a wider striated trough, support glacial abrasion of the Varangerfjorden unconformity and the Bigganjargga surface being an essential part of it. Indicator stone observations support transport from the present south-east to north-west. At palaeotopographically higher parts of Vieranjarga, the subglacially abraded unconformity was destroyed in part by syn-Smalfjord in situ brecciation attributed to periglacial frost shattering. A large part of the unconformity at East Vieranjarga and Skjåholmen was incised by intra-Smalfjord (interglacial) erosion, which went several metres down to the underlying Vadsø Group basement. Diagenetic processes modified the classical Bigganjargga surface. There are no features on the unconformity that permit differentiation between late Proterozoic glacial abrasion processes and those of Palaeozoic or later ice ages. Special care is needed to distinguish glacigenic soft-sediment striations and small grooves from those inscribed in hard rock. The former mark the presence of a hiatus or disconformity within a stratigraphic sequence and may be produced subglacially or by floating ice, whereas the latter indicate, in most cases, a marked angular unconformity, of which the Bigganjargga surface is a classical example, or a non-conformity.