The role of discharge variability in determining alluvial stratigraphy

Nicholas, Andrew P.; Sambrook Smith, Gregory H.; Amsler, Mario L.; Ashworth, Philip J.; Best, James L.; Hardy, Richard J.; Lane, Stuart N.; Orfeo, Oscar; Parsons, Daniel R.; Reesink, Arnold J.H.; Sandbach, Steven D.; Simpson, Christopher J.; Szupiany, Ricardo N.

Abstract

We illustrate the potential for using physics-based modeling to link alluvial stratigraphy to large river morphology and dynamics. Model simulations, validated using ground penetrating radar data from the Río Paraná, Argentina, demonstrate a strong relationship between bar-scale set thickness and channel depth, which applies across a wide range of river patterns and bar types. We show that hydrologic regime, indexed by discharge variability and flood duration, exerts a first-order influence on morphodynamics and hence bar set thickness, and that planform morphology alone may be a misleading variable for interpreting deposits. Indeed, our results illustrate that rivers evolving under contrasting hydrologic regimes may have very similar morphology, yet be characterized by marked differences in stratigraphy. This realization represents an important limitation on the application of established theory that links river topography to alluvial deposits, and highlights the need to obtain field evidence of discharge variability when developing paleoenvironmental reconstructions. Model simulations demonstrate the potential for deriving such evidence using metrics of paleocurrent variance.

Citation

Nicholas, A. P., Sambrook Smith, G. H., Amsler, M. L., Ashworth, P. J., Best, J. L., Hardy, R. J., Lane, S. N., Orfeo, O., Parsons, D. R., Reesink, A. J., Sandbach, S. D., Simpson, C. J., & Szupiany, R. N. (2016). The role of discharge variability in determining alluvial stratigraphy. Geology, 44(1), 3-6. https://doi.org/10.1130/G37215.1

• Journal Article Type: Article
• Acceptance Date: Oct 12, 2015
• Online Publication Date: Nov 11, 2015
• Publication Date: 2016-01
• Deposit Date: Dec 20, 2016
• Publicly Available Date: Dec 20, 2016
• Journal: Geology
• Print ISSN: 0091-7613
• Publisher: Geological Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 44
• Issue: 1
• Pages: 3-6
• DOI: https://doi.org/10.1130/G37215.1
• Keywords: Alluvial stratigraphy, River morphology, Dynamics, Río Paraná, Argentina, Discharge variability
• Public URL: https://hull-repository.worktribe.com/output/446421
• Publisher URL: http://geology.gsapubs.org/content/44/1/3
• Additional Information: Copy of article first published in: Geology, 2015, v.44, issue 1.
• Contract Date: Dec 20, 2016