Comparison of Avulsion Cycles from Subaerial and Subaqueous Fan Experiments with Supercritical Channels
Published:January 01, 2016
Paul Hamilton, Kyle Strom, David Hoyal, 2016. "Comparison of Avulsion Cycles from Subaerial and Subaqueous Fan Experiments with Supercritical Channels", Autogenic Dynamics and Self-Organization in Sedimentary Systems, David A. Budd, Elizabeth A. Hajek, Sam J. Purkis
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A series of alluvial fan experiments was compared to a series of submarine fan experiments in order to explore the similarities and differences of autogenic supercritical avulsion cycles in the two environments. Both systems have cycles of: distributive channel formation and basinward extension, deceleration and mouth bar deposition, flow interaction with the aggrading mouth bar, propagation of the channel-to-lobe transition in the upstream direction, and flow reorganization. The channel-to-lobe transition in both alluvial fan and submarine fan experiments was located at the supercritical-to-subcritical flow transition. Channel-to-lobe transitions were also the primary locus of deposition in each case, and their aggradation in turn forced upstream accretion. The commonalities between the two environments are striking and lend evidence toward the hypothesis that supercritical vs. subcritical flow in distributary channels is a more significant distinction than subaerial vs. subaqueous environment in termsof the hydraulic and sediment transport properties.
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Autogenic Dynamics and Self-Organization in Sedimentary Systems
Autogenic dynamics and self-organization in sedimentary systems are increasingly viewed as significant and important processes that drive erosion, sediment transport, and sediment accumulation across the Earth’s surface. These internal dynamics can dramatically modulate the formation of the stratigraphic record, form biologically constructed depositional packages, affect ecological patterning in time and space, and impact aspects of geochemical sedimentation and diagenesis. The notion that autogenic processes are local phenomena of short duration and distance is now recognized as false. Understanding autogenic dynamics in sedimentary systems is thus essential for deciphering the morphodynamics of moderns sedimentary systems, accurately reconstructing Earth history, and predicting the spatial and temporal distribution of sedimentary and paleobiologic features in the stratigraphic record. The thirteen papers in this volume present exciting new ideas and research related to autogenic dynamics and self-organization in sedimentology, stratigraphy, ecology, paleobiology, sedimentary geochemistry, and diagenesis. Five papers summarize the current state of thinking about autogenic processes and products in fluvial-deltaic, eolian, and carbonate depositional systems, and in paleobiologic and geochemical contexts. A second group of papers provide perspectives derived from numerical modeling and laboratory experiments. The final section consists of field studies that explore autogenic processes and autogenically modulated stratigraphy in five case studies covering modern and ancient fluvial, deltaic, and shelf settings. This SP should stimulate further research as to how self-organization might promote a better understanding of the sedimentary record.