Contained (Reflected) Turbidity Currents from the Middle Ordovician Cloridorme Formation, Quebec, Canada: An Alternative to the Antidune Hypothesis

  1. Dorrik A. V. Stow
  1. Kevin T. Pickering1 and
  2. Richard N. Hiscott2

Published Online: 29 APR 2009

DOI: 10.1002/9781444304473.ch6

Deep-Water Turbidite Systems

Deep-Water Turbidite Systems

How to Cite

Pickering, K. T. and Hiscott, R. N. (1991) Contained (Reflected) Turbidity Currents from the Middle Ordovician Cloridorme Formation, Quebec, Canada: An Alternative to the Antidune Hypothesis, in Deep-Water Turbidite Systems (ed D. A. V. Stow), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304473.ch6

Editor Information

  1. Department of Geology, University of Southampton, UK

Author Information

  1. 1

    Department of Geology, University of London, Goldsmiths' College, Rachel McMillan Building, Creek Road, London SE8 3BU, UK

  2. 2

    Earth Sciences Department, Memorial University of Newfoundland, St John's, Newfoundland A1B 3X5, Canada

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 11 NOV 1991

ISBN Information

Print ISBN: 9780632032624

Online ISBN: 9781444304473

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Keywords:

  • Cloridorme formation, syn-orogenic flysch succession;
  • cross-stratification;
  • Middle Ordovician Cloridorme formation;
  • thick-bedded calcareous wackes (TCW);
  • upstream-inclined laminae;
  • basin-plain deposits, in Miocene Marnoso-arenacea formation

Summary

The parautochthonous Cloridorme Formation is a syn-orogenic flysch succession that was deposited in an elongate foredeep basin as mainly lower middle-fan, outer-fan, and basin-floor deposits. The basin-floor deposits (about 1.5 km thick) are confined to members β1, β2 and γ1, and are characterized by graded, thick (1–10 m) mud-rich calcareous greywacke beds previously interpreted as deposits of concentrated, muddy, unidirectional turbidity currents that locally generated backset (antidune) lamination in internally stratified flows.

The dominant flow directions were from east to west, but west to east transport also occurred, as seen in the orientation of ripples, climbing ripples, flutes, consistently overturned flames, and grain imbrication. We believe that the flows that deposited these thick calcareous greywacke beds reversed by roughly 180° one or more times during deposition of the lower sandy part of the beds. Flow reversals are consistent with the sharp grain-size breaks and mud partings within sandy divisions. Measurement of grain fabric relative to stratification in the most celebrated ‘antidune’ bedforms indicates flow from west to east; thus, the bedforms were produced by west-to-east migration of megaripples, not by the upcurrent migration of antidunes.

The thick muddy beds were deposited by large-volume, muddy flows that were deflected and reflected from the side slopes and internal topographic highs of a confined basin floor, much like the ‘Contessa’ and similar beds of the Italian Apennines. Large quantities of suspended mud were ponded above the irregular basin floor and settled to produce the thick silty mudstone caps seen on each bed. Because of their mode of emplacement, we propose that these beds be called contained turbidites.