An Entrenched Thalweg Channel on the Rhone fan: Interpretation From a Seabeam and Seamarc I Survey
Published:January 01, 1991
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Suzanne O’Connell, William R. Normark, William B. F. Ryan, Neil H. Kenyon, 1991. "An Entrenched Thalweg Channel on the Rhone fan: Interpretation From a Seabeam and Seamarc I Survey", From Shoreline to Abyss: Contributions in Marine Geology in Honor of Francis Parker Shepard, Robert H. Osborne
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A recent breach in the western (right-hand, looking downcurrent) levee of the main valley on the Rhone Fan resulted in a rejunevated thalweg within the valley-floor sediment fill and formation of an incipient, sandy, depositional lobe high on the fan. The new thalweg exhibits an unusual cuspate or scalloped form in contrast with the abandoned thalweg downstream of the avulsion that exhibits the more typical meandering or sinusoidal form. The cusps have a radius of curvature that is usually about 0.25 km. Long-range (GLORIA) and high-resolution, deep-tow (SeaMARC I) side-looking sonar images provide details concerning the surface texture (through acoustic-backscatter patterns) and morphology of the relatively young entrenched channel and its surroundings. These data suggest that mass wasting, seen as small gullies on channel walls and deposits on the thalweg floor, accompanied the downcutting of the thalweg and played a major role in forming the cusp-shape morphology. The side-looking sonar images also confirm the widespread occurrence of sediment failure on the main levee areas, as suggested by previous work based on seismic-reflection profiles.
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From Shoreline to Abyss: Contributions in Marine Geology in Honor of Francis Parker Shepard
From Shoreline to Abyss: Contributions in Marine Geology in Honor of Francis Parker Shepard - Francis P. Shepard left a rich scientific legacy including more than 230 published papers and books primarily addressed to the study of submarine canyons and turbidity currents, continental shelves and associated sediments, coastal processes and sediments and marine physiography and tectonics. He is best remembered for his work on submarine canyons; however, his broad range of scientific interests and his remarkable ability to break new ground in each of these disciplines have served as a model for at least four generations of ?Shepard? students. This new work from these Shepard students addresses problems in marine geology from the global scale to the local outcrop scale. Relationships among tectonics, eustacy and both siliciclastic and carbonate sedimentation create a unifying theme. Special topics include coastal processes, shelf and slope evolution, and submarine canyon and fan systems.