Siliciclastic Braided-Alluvial Sediments Intercalated within Continental Flood Basalts in the Early to Middle Proterozoic Mount Isa Inlier, Australia

  1. M. Marzo and
  2. C. Puigdefábregas
  1. K. A. Eriksson1 and
  2. E. L. Simpson2

Published Online: 14 APR 2009

DOI: 10.1002/9781444303995.ch30

Alluvial Sedimentation

Alluvial Sedimentation

How to Cite

Eriksson, K. A. and Simpson, E. L. (1993) Siliciclastic Braided-Alluvial Sediments Intercalated within Continental Flood Basalts in the Early to Middle Proterozoic Mount Isa Inlier, Australia, in Alluvial Sedimentation (eds M. Marzo and C. Puigdefábregas), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303995.ch30

Editor Information

  1. Barcelona, Spain

Author Information

  1. 1

    Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

  2. 2

    Department of Physical Sciences, Kutztown University, Kutztown, PA 19530, USA

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 16 SEP 1993

ISBN Information

Print ISBN: 9780632035458

Online ISBN: 9781444303995

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Keywords:

  • Lena conglomerate contains mainly felsic volcanic, red granite;
  • Magnetite concentrations -density segregation of particles within grainflows;
  • Reactivation surfaces are common within cross-bed sets;
  • volcanism, sedimentation and tectonics;
  • Siliciclastic sedimentary units intercalated within the Eastern Creek Volcanics

Summary

The Eastern Creek Volcanics in the Mount Isa Inlier are up to 7 km thick and consist of two successions of subaerial basalts (5.5 km and 0.7 km thick) separated by a siliciclastic unit (up to 750 m thick). Predominantly tabular, siliciclastic units from 1 to 40 m thick are present in the upper half of the lowermost basaltic succession and throughout the uppermost basaltic succession. Siliciclastic debris was derived exclusively from the east from a provenance terrain consisting of quartz arenites, felsic volcanics and granites. With the exception of local aeolian facies, the siliciclastic units are exclusively of braided-alluvial origin. Facies analysis has identified two interacting alluvial systems: a relatively high-gradient and coarse-grained, transverse system that supplied siliciclastic debris from eastern highlands, and a lower-gradient and finer-grained, longitudinal or trunk system that reworked sediment down a south-to-north palaeoslope. Areal persistence of most siliciclastic units in the trunk system is attributed to continuous lateral switching of shallow, braided rivers. Lateral switching was promoted by slow subsidence attributed to cooling and thermal contraction of the volcanics. Siliciclastic units define prolonged hiatuses in volcanism; this interpretation is supported by the presence of a calcrete unit at the top of a basalt flow and below a siliciclastic unit.