--> Abstract: External Morphology Versus Internal Facies Architecture of Deltas Challenge Tripartite Classification Scheme, by M. Royhan Gani and Janok P. Bhattacharya; #90039 (2005)
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External Morphology Versus Internal Facies Architecture of Deltas Challenge Tripartite Classification Scheme

M. Royhan Gani and Janok P. Bhattacharya
U. of Texas at Dallas, Richardson, TX

The tripartite classification of deltas into Previous HitwaveNext Hit-, tide- and fluvial-dominated end members was largely based on compilations about the plan-view morphology of modern deltas. The modern Brazos, Baram/Trusan, and Burdekin deltas show smooth-fronted plan view shapes indicating Previous HitwaveNext Hit-dominated end members, but detailed internal facies analysis suggests dominance of river and tidal processes. Likewise, sandstone-isolith shape of delta lobes within the Cretaceous Wall Creek Member of the Frontier Formation in Wyoming suggest Previous HitwaveNext Hit-dominance, but the internal facies architecture shows a dominance of river-flood splays and channels with significant local tidal and Previous HitwaveNext Hit reworking. Although the tripartite classification continues to be used as a framework for understanding deltas, it is clear that the end-member Previous HittypesTop are not mutually exclusive in terms of delta building processes and facies. The plan-view morphology of any given modern delta reflects dominant surficial process but may not necessarily reflect the short-lived constructional processes of river floods that dominate the internal facies architecture. Plan-view morphology can also evolve from one end-member type to another during the lifetime of a single delta (e.g. Mekong delta). Therefore, it may be misleading to infer a specific internal facies distribution with its consequent control on reservoir quality based on plan-view morphology alone.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005