Aspects of Late Palaeoproterozoic Fluvial Style: The Uairén Formation, Roraima Supergroup, Venezuela

  1. Wladyslaw Altermann2 and
  2. Patricia L. Corcoran3
  1. D. G. F. Long

Published Online: 12 MAR 2009

DOI: 10.1002/9781444304312.ch14

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems

How to Cite

Long, D. G. F. (2002) Aspects of Late Palaeoproterozoic Fluvial Style: The Uairén Formation, Roraima Supergroup, Venezuela, 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.ch14

Editor Information

  1. 2

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

  2. 3

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

Author Information

  1. Department of Earth Sciences, Laurentian University, Sudbury, Ontario, P3E 2C6, Canada

Publication History

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

ISBN Information

Print ISBN: 9780632064151

Online ISBN: 9781444304312

SEARCH

Keywords:

  • late palaeoproterozoic fluvial style - Uairén formation, Roraima Supergroup, Venezuela;
  • Roraima Supergroup - gently dipping to flat lying, late palaeoproterozoic sandstones, siltstones and conglomerates;
  • stratigraphic distribution of strata within Uairén formation;
  • lower member of Uairén formation;
  • sedimentology of Uairén formation;
  • implications for models of pre-vegetative fluvial systems

Summary

Strata of the Uairén Formation, at the base of the Late Palaeoproterozoic Roraima Supergroup in the Gran Sabana, near Santa Elena de Uairén, Bolívar, south-eastern Venezuela, can be interpreted in terms of deposition in a variety of vegetation-free fluvial environments in a foreland basin setting. Sandstones and small to medium pebble conglomerates at the base of the formation reflect erratic deposition from high-energy (proximal) gravelly braided streams in valley-fill and valley-marginal alluvial fan settings. Arid conditions are indicated by the presence of minor diamictites of debris flow origin. Overlying predominantly sandy strata were deposited by sheet floods in a low-relief basin characterized by flashy ephemeral sandy braided fluvial systems in a terminal-fluvial setting. Temporary development of playa lakes may be indicated by thin mud drapes and fine to very fine sandstones with symmetrical ripples. Low angle truncation of laminae may reflect erosion and deposition by sheet floods. Aeolian reworking may be significant in this setting and is indicated locally by ripple cross-stratified silt-free sandstone sets between more poorly sorted sandstones. Medium to very large pebble conglomerate at the base of the upper member of the formation rests on a regionally significant erosion surface, reflecting uplift and/or a dramatic change in climatic regime. Overlying sandstones reflect deposition by sandy and gravelly sandy perennial braided fluvial systems with high width to depth ratios. Strata of the Uairén Formation are succeeded by poorly exposed lacustrine mudstones of the Cuquenán Formation, which are overlain by fluvial and aeolian deposits of the Uaimapué Formation. In Proterozoic and Phanerozoic sequences, thick sets of flat laminated sandstones are commonly interpreted in terms of beach-face deposition. This study shows that this can be incorrect and that such sequences are a common feature of pre-vegetation fluvial settings, especially in arid to semi-arid terminal fluvial systems.