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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, F02013, doi:10.1029/2004JF000265, 2005

Fluvial and marine controls on combined subaerial and subaqueous delta progradation: Morphodynamic modeling of compound-clinoform development

John B. Swenson

Department of Geological Sciences and Large Lakes Observatory, University of Minnesota, Duluth, Duluth, Minnesota, USA
Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota, USA


Chris Paola

Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota, USA
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA


Lincoln Pratson

Earth and Ocean Sciences, Duke University, Durham, North Carolina, USA


Vaughan R. Voller

Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota, USA
Department of Civil Engineering, University of Minnesota, Minneapolis, Minneosta, USA


A. Brad Murray

Earth and Ocean Sciences, Duke University, Durham, North Carolina, USA


Abstract

Fluviodeltaic systems commonly display a compound-clinoform geometry that consists of a subaerial/subaqueous delta couplet. The extent of subaqueous delta development varies significantly and, in modern systems, is a function of fluvial input and basin hydrodynamics. We present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics, respectively. We couple fluvial and shallow marine sediment dynamics via the surf zone, which we collapse to a shock condition and treat as a moving boundary. With steady sediment supply and sea level and simple basin geometry, our model naturally develops prograding deltas with compound-clinoform geometries. The subaerial delta grows via fluvial aggradation and shoreface progradation, whereas the subaqueous delta expands through foreset progradation, with only minor topset aggradation. The interplay of fluvial input with the wave/current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and, by extension, the compound-clinoform geometry. Increasing the frequency or magnitude of coastal storms, decreasing flood frequency or discharge, and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development. Our model, which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations, can explain many of the first-order morphologic features of natural delta systems, including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation.

Received 14 November 2004; accepted 28 March 2005; published 10 June 2005.

Keywords: clinoform; subaqueous delta; morphodynamic modeling.

Index Terms: 3020 Marine Geology and Geophysics: Littoral processes; 3022 Marine Geology and Geophysics: Marine sediments: processes and transport; 3225 Mathematical Geophysics: Numerical approximations and analysis (4260); 4219 Oceanography: General: Continental shelf and slope processes (3002); 4558 Oceanography: Physical: Sediment transport (1862).

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Citation: Swenson, J. B., C. Paola, L. Pratson, V. R. Voller, and A. B. Murray (2005), Fluvial and marine controls on combined subaerial and subaqueous delta progradation: Morphodynamic modeling of compound-clinoform development, J. Geophys. Res., 110, F02013, doi:10.1029/2004JF000265.