The Morphological and Stratigraphical Effects of Base-Level Change: a Review of Experimental Studies

  1. Michael D. Blum4,
  2. Susan B. Marriott5 and
  3. Suzanne F. Leclair6
  1. Frank G. Ethridge1,
  2. Dru Germanoski2,
  3. Stanley A. Schumm1 and
  4. Lesli J. Wood3

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304350.ch13

Fluvial Sedimentology VII

Fluvial Sedimentology VII

How to Cite

Ethridge, F. G., Germanoski, D., Schumm, S. A. and Wood, L. J. (2009) The Morphological and Stratigraphical Effects of Base-Level Change: a Review of Experimental Studies, in Fluvial Sedimentology VII (eds M. D. Blum, S. B. Marriott and S. F. Leclair), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304350.ch13

Editor Information

  1. 4

    Baton Rouge, Louisiana, USA

  2. 5

    School of Geography and Environmental Management, University of the West of England, Bristol BS16 1QY, UK

  3. 6

    Department of Earth and Environmental Sciences, Tulane University, Dimwiddie Hall, New Orleans, LA 70118, USA

Author Information

  1. 1

    Department of Earth Resources, Colorado State University, Fort Collins, CO, 80523, USA

  2. 2

    Department of Geology and Environmental Geosciences Lafayette College, Easton, PA 18042, USA

  3. 3

    Bureau of Economic Geology, The University of Texas at Austin, University Station, Box X, Austin, TX 78713-8924, USA

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 15 FEB 2005

Book Series:

  1. Special Publication Number 35 of the International Association of Sedimentologists

Book Series Editors:

  1. Ian Jarvis

Series Editor Information

  1. School of Earth Sciences and Geography, Centre for Earth and Environmental Science Research, Kingston University, Penrhyn Road, Kingston-upon-Thames KT1 2EE, UK

ISBN Information

Print ISBN: 9781405126519

Online ISBN: 9781444304350

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Keywords:

  • experimental and numerical modelling;
  • morphological and stratigraphical effects of base-level change - a review of experimental studies;
  • Colorado State University (CSU);
  • concept of base level - basic to geological, geomorphological and engineering thought;
  • base level - ‘The theoretical limit or lowest level toward which erosion of Earth's surface constantly progresses’;
  • valley networks;
  • falling base level;
  • effects of rates of base-level change;
  • comparison rising and falling base level

Summary

Results obtained during 20 yr of experimental research at Colorado State University (CSU) provide partial answers to questions posed by the conveners of this symposium on the response of near-coastal fluvial systems to sea-level change. These questions do not have easy answers because response will be variable depending upon system size, magnitude of base-level change and initial condition. Most flume experiments were designed to observe the effects of base-level change on the evolution of channel and valley networks, and they provide general conclusions regarding the effects of base-level change. Base-level change at a river's terminus has a geographically limited influence on a drainage system and that influence is usually confined to the coastal plain. Small base-level change is commonly accommodated by changes in channel sinuosity, roughness and width. Larger base-level changes, such as lowering of base level below a major topographic break, results in down cutting and the formation of one or more upslope valleys or valley networks. Channels commonly adjust rapidly to base-level change especially at the point of change. Base-level fall usually has a more dramatic effect on channels and valleys than does base-level rise. Incision resulting from a base-level fall concentrates energy in a narrow, deep valley that extends rapidly up valley. Aggradation from base-level rise, however, is restricted spatially by the position of the static backwater profile and the effect is over the entire valley width.

Colorado State University experiments designed specifically to test the sequence stratigraphical paradigm reveal how variable and complex the morphological and sedimentological response on a continental shelf and slope can be depending on initial conditions and rates and magnitudes of base-level change. Shelf valleys formed only when base level dropped below a significant break in slope. Because the growth of these valleys occurred by headward erosion there was usually a lag time when no source-to-sink, cross-shelf bypass valley existed. During this time only fine-grained sediments were delivered to the deep-water offshore environment. This process may explain the muddy nature of early lowstand deposits in many deep-water basins around the world. Once a source-to-sink bypass valley developed, sediment from the hinterland drainage basin could be transported to form a coarse-grained lowstand fan. Experimental results suggest that late lowstand and early transgressive times are periods when the greatest volumes of coarse-grained sediment are transported to the downstream portions of the fluvial system. As base-level rise continued a lowstand wedge formed within the main bypass valley. When base-level rise accelerated and the shoreline moved onto the shelf, the transgressive systems tract within the bypass valley consisted of backstepping deltaic and marine deposits. Valley fills varied significantly between shelf bypass valleys and abandoned shelf break valleys. Valley cross-sections are modified during base-level rise by mass wasting and slumping of valley walls both in the flume experiments and in natural settings. Results of recent experiments at the University of Minnesota and Utrecht reveal many similarities and a few differences with CSU experiments. Furthermore, they add scaling factors that allow development of quantitative analogue experiments of real-world systems.