Morphology and Quaternary Sedimentation of the Mozambique Fan and Environs, Southwestern Indian Ocean

  1. Dorrik A. V. Stow
  1. Venkatarathnam Kolla,
  2. John A. Kostecki,
  3. Lawrence Henderson and
  4. Lillian Hess

Published Online: 29 APR 2009

DOI: 10.1002/9781444304473.ch36

Deep-Water Turbidite Systems

Deep-Water Turbidite Systems

How to Cite

Kolla, V., Kostecki, J. A., Henderson, L. and Hess, L. (1991) Morphology and Quaternary Sedimentation of the Mozambique Fan and Environs, Southwestern Indian Ocean, in Deep-Water Turbidite Systems (ed D. A. V. Stow), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304473.ch36

Editor Information

  1. Department of Geology, University of Southampton, UK

Author Information

  1. Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964, USA

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:

  • Quaternary sediments of Mozambique Fan;
  • Coriolis force;
  • Antarctic Bottom Water;
  • middle fan, having distributary channels;
  • hemipelagic sediments

Summary

Most of the Quaternary sediments of the Mozambique Fan have been derived from Africa-Madagascar and deposited by turbidity currents in Pleistocene time. Currents caused by movement of the Antarctic Bottom Water also played a significant role in reworking and redepositing sediments along the marginal areas of the fan. The inner or upper Mozambique Fan is characterized by a single, leveed valley. Due to the effects of the Coriolis force, the natural levees to the east of the valley (left, looking downstream) are higher and contain more terrigenous sediments than those to the west of the valley. The sea floor to the west of the valley returns regular hyperbolic echoes as seen on 3.5 kHz echograms, whereas to the east of the valley, the sea floor is relatively smooth. The sediments on the valley floor are coarse-grained (with median grain up to 2 mm) and poorly sorted, and occur often as massive turbidites, interbedded with hemipelagic sediments. Away from the valley, both to the east and the west, the terrigenous sediments are relatively fine-grained and have been deposited as overbank turbidite sequences. We estimate the maximum velocities of the channelized turbidity currents in the upper fan to have been 8–32 ms−1. The middle fan has several distributary channels with no levees and has a relatively flat sea floor, characterized by lack of acoustic penetration. Thick, sheet-like, turbidite sand beds, deposited primarily by unchannelized turbidity currents, characterize the middle fan. The middle fan grades, towards the margins, into the outer (lower) fan which is relatively free of channels, has good acoustic penetration and contains hemipelagic and pelagic sediments, and thin, fine-sand turbidite and/or contourite beds. A wide zone of sediment waves, formed from the reworking of the turbidity current-fed sediments by the Antarctic Bottom Water, forms part of the outer fan.