Investigation of sediment emplacement in the Cretaceous Panther Tongue, Star Point Formation, east central Utah, shows that resedimentation via density flows was the main sedimentation process within the delta front subenvironment. The stream mouth bar (SMB) served as an effective, temporary storage site in front of the active distributary channel. Sands were deposited during periods of low discharge in the distributary channel, and were then redistributed to the delta front during major river-flooding events. These river-flooding events destabilized the SMB and triggered density flows (surge-like turbidity currents) which spread out in a seaward direction, depositing fan-shaped sheets of sand and silt in the delta front. Marine storms played a secondary role in redistributing the sands to the delta front.
Data from detailed field study led to analysis of depositional processes and the interpretation of hydrodynamic processes. In the SMB, predominantly structureless beds with locally faint lamina, and large scale soft sediment deformation, including large-scale flame structures, are evidence for rapid deposition and liquefaction. In the delta front, most beds are sharp-based, and show waning flow attributes, interpreted as the result of resedimentation processes. A few beds reveal waxing then waning energy, implying isolated deposits from hyperpycnal flows. Burrowed to bioturbated siltstones occur interbedded with the sharp-based sandstone beds, and are interpreted as deposits of hypopycnal processes, which occurred during fair weather conditions as sand was actively being stored in the SMB. I propose that river-dominated deltas are characterized by two temporally distinct stages of deposition – one is when sediment is stored in the SMB, and a second in which sediment is remobilized to the delta front.
|Advisor:||Kamola, Diane L.|
|Commitee:||Ludvigson, Gregory A., Walker, J. Douglas|
|School:||University of Kansas|
|School Location:||United States -- Kansas|
|Source:||MAI 51/04M(E), Masters Abstracts International|
|Subjects:||Geology, Sedimentary Geology|
|Keywords:||Depositional mechanisms, Land-based storms, Panther tongue, Redeposition, Stream mouth bar, Upper cretaceous|
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