--> Abstract: Simulating Alluvial Architecture in Three-Dimensions: Effects of Avulsion and Tectonism on the Spatial Distribution of Alluvial Channel-Belt Deposits, by S. D. Mackey and J. S. Bridge; #90987 (1993).

Datapages, Inc.Print this page

MACKEY, SCUDDER D., and JOHN S. BRIDGE, State University of New York, Binghamton, NY

ABSTRACT: Simulating Alluvial Architecture in Three-Dimensions: Effects of Avulsion and Tectonism on the Spatial Distribution of Alluvial Channel-Belt Deposits

A three-dimensional model of alluvial stratigraphy has been developed to simulate the spatial distribution, proportion, and connectedness

of coarse-grained channel belt deposits in alluvial strata as a function of channel-belt width, floodplain width, bankfull channel depth, channel-belt and overbank sedimentation rates, avulsion location and period, compaction, and tectonism (tilting and faulting). The location and timing of avulsions are controlled by flood magnitude and local floodplain slope relative to valley slope. Local floodplain slopes change in response to the pattern of floodplain deposition, compaction, and tectonism. The diverted channel belt follows the location ofmaximum floodplain slope. Tectonic effects on alluvial architecture are directly related to changes between rates-a floodplain deposition and tectonic deformation. Channel belts become concentrated near downthrown areas of the floodplain and may xhibit offlap away from these areas in response to changes in the location of preferred avulsion points and combined effects of tectonism and alluvial ridge development. Simulations indicate the existence of an avulsion sequence where points of avulsion migrate up-valley with a progressive decrease in avulsion period. A coarsening upwards sequence results from increasing proportion and connectedness due to decreasing avulsion period. These simulations demonstrate that apparent dimensions, proportion, and connectedness of channel-belt deposits can vary dramatically as a function of cross-section orientation and location.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.