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Morphology, Mechanisms, and Processes for the Formation of a Non-Bifurcating Fluvial-Deltaic Channel Prograding into Grapevine Reservoir, Texas

Gary D. Tomanka
The University of Texas at Arlington

Non-bifurcating channels in modern reservoirs, tie channels, and the Mississippi River Bird-Foot Delta share a common morphology that is likely due to an underlying common mechanism. The Denton Creek Delta in Grapevine Reservoir located in Denton County, Texas is one such delta. Data analysis indicates that the Denton Creek Delta has prograded into Grapevine Reservoir for 56 years, adhering to the buried pre-impoundment channel without alteration. The hydrodynamic mechanism that controls this adherence is that of a turbulent jet. The properties of the turbulent jet create a dynamic two-phase process, whereby prodelta clays and rare mouth bar sands are eroded while the jet contemporaneously builds sandy levees. A mouth-ward tapering channel acts to focus and intensify the jet at less cohesive clays that overlie the preexisting channel. A conceptual model is presented comprising basinward tapered levees, the action of the turbulent jet, and rapidly rising basin levels, which account for the self-sustained progradation of the delta without bifurcation, and result in a distinctive delta morphology.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013