SAFL faculty, staff, and students
Tuesday, November 7, 2017 - 3:30pm

Elisabeth Steel, Post-doctoral Researcher, St. Anthony Falls Laboratory

Hyperpycnal currents are turbidity currents generated by plunging of sediment-laden rivers at the fluvial-marine interface, and they allow for cross-shelf transport of suspended sand beyond the high-energy coastline. River-derived hyperpycnal currents and turbidity currents initiated in relatively shallow water that travel into deeper and colder water commonly contain interstitial fluid that is less dense than the surrounding ambient water. These currents are initially ground-hugging due to high suspended sediment concentrations. However, as sediment settles from suspension, bulk current density may become less dense than the surrounding ambient water, at which point the current becomes buoyant and rises from the basin floor. This process of buoyancy reversal, or lofting, affects both the internal architecture of turbidites and their overall morphology. Here, we present results from field studies of Holocene fans on the continental shelf of Southern California and Jurassic hyperpycnites in the Neuquén Basin of Argentina, in combination with three-dimensional flume experiments, to demonstrate the ways in which lofted-current turbidites differ from classic turbidite models.