Rheological Characteristics of Rappahannock Estuary Muds, Southeastern Virginia, U.S.A.

  1. S.-D. Nio,
  2. R. T. E. Shüttenhelm and
  3. Tj. C. E. Van Weering
  1. Richard W. Faas

Published Online: 29 JUN 2009

DOI: 10.1002/9781444303759.ch35

Holocene Marine Sedimentation in the North Sea Basin

Holocene Marine Sedimentation in the North Sea Basin

How to Cite

Faas, R. W. (1981) Rheological Characteristics of Rappahannock Estuary Muds, Southeastern Virginia, U.S.A., in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch35

Author Information

  1. Department of Geology, Lafayette College, Easton, Pennsylvania 18042, USA

Publication History

  1. Published Online: 29 JUN 2009
  2. Published Print: 23 DEC 1981

ISBN Information

Print ISBN: 9780632008582

Online ISBN: 9781444303759

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Keywords:

  • ‘turbidity maximum’;
  • pseudoplastic behaviour (shear rate thinning);
  • dilatant behaviour (shear rate thickening);
  • rheological properties of sediments;
  • viscosity ‘notch’ development

Summary

Samples of naturally occurring fluid mud were taken from the upper, middle, and lower reaches of the Rappahannock Estuary, a relatively straight, funnel-shaped, partially mixed coastal plain estuary, possessing a well-developed ‘turbidity maximum’. Samples were analysed to determine their viscosity characteristics using a conventional rotational viscometer. Analyses were made aboard ship immediately after retrieval and were followed by laboratory analyses to determine the effects of settling times on viscosity behaviour. Fluid mud samples exhibited various forms of non-Newtonian behaviour, varying from pseudoplastic to dilatant, depending upon shear rates and stresses, and position within the estuary relative to salt content.

Viscosity of sediments in the upper freshwater portion of the estuary is less than that of sediments from the lower, more saline portion. Pseudoplastic behaviour (shear rate thinning) is exhibited by all samples with dilatant behaviour (shear rate thickening) occurring through intermediate shear rates in a 20 mile segment of the middle estuary. Viscosity variations, including thixotropic effects, are believed to influence sediment transport throughout the estuary and maintain the ‘turbidity maximum’ in the middle estuary.