Present Channel Stability and Late Quaternary Valley Deposits in Northern Mississippi

  1. J. D. Collinson and
  2. J. Lewin
  1. E. H. Grissinger and
  2. J. B. Murphey

Published Online: 29 APR 2009

DOI: 10.1002/9781444303773.ch19

Modern and Ancient Fluvial Systems

Modern and Ancient Fluvial Systems

How to Cite

Grissinger, E. H. and Murphey, J. B. (1983) Present Channel Stability and Late Quaternary Valley Deposits in Northern Mississippi, in Modern and Ancient Fluvial Systems (eds J. D. Collinson and J. Lewin), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303773.ch19

Author Information

  1. U.S. Department of Agriculture, Agricultural Research Service, USDA Sedimentation Laboratory, P.O. Box 1157, Oxford, Mississippi 38655, USA

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 7 FEB 1983

ISBN Information

Print ISBN: 9780632009978

Online ISBN: 9781444303773

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Keywords:

  • present channel stability and late Quaternary valley deposits in northern Mississippi;
  • Yazoo-Little Thallahatchie catchment;
  • lithologic units;
  • Early Holocene depositional sequence;
  • palaeoclimatic controls;
  • channel stability and morphology

Summary

Seven lithologic units have been identified in the Holocene valley-fill deposits of the loess region of northern Mississippi. These units are (1) post-settlement alluvium, (2) meander-belt alluvium, (3) channel fill, (4) massive silt, (5) bog-type materials, (6) unconsolidated grey silt and (7) channel lag deposits. In addition, several pre-Holocene deposits have been sampled, but at this time are poorly defined.

The chronology and relative lithologies of these units from the loess region are consistent with the valley-fill deposits over most of northern Mississippi. This valley-fill sequence is comparable with sequences for other sections of the United States and is coherent with the Holocene palaeoclimatic conditions.

The individual lithologic units and their sequences influence present-day channel bed and bank failure mechanics. Failure of the post-settlement and meander-belt alluvium results primarily from gravity stress accentuated by tension crack development. Failure of the massive silt also results from gravity stress but the failure mechanism for this unit is controlled by its distinctive polygonal structure. Exposure of the easily erodible unconsolidated bog-type and channel lag deposits in a bank toe position typically increases rates of failure due to gravity stress. The interactions of these lithologic controls of failure mechanics with channel realignment and entrenchment during historic times has produced the present-day channel morphology. The degree of entrenchment is, in turn, related to the presence or absence of pre-Holocene consolidated sandstones.