Sediment concentrations,flow conditions,and downstream evolution of two turbidity currents,Monterey Canyon,USA |
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| Institution: | 1. University of Bremen, MARUM – Center for Marine Environmental Sciences and Faculty of Geosciences, Klagenfurter Straße 4, D-28359 Bremen, Germany;2. División Geologia y Geofísica Marina, Departamento Oceanografía, Servicio de Hidrografía Naval, Montes de Oca 2124, C1270ABV Buenos Aires, Argentina;1. Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, UK;2. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, UK;3. Department of Geosciences, National Taiwan University, Roosevelt Road, Taipei, Taiwan;4. Department of Oceanography, National Sun Yat-sen University, Kaohsiung, Taiwan;5. Earth System Science, University of California, Irvine, CA, United States;1. Department of Oceanography, National Sun Yat-sen University, Kaohsiung 80424, Taiwan ROC;2. Department of Geosciences, University of Bremen, PO Box 330440, D-28334 Bremen, Germany;3. Department of Marine Environment, National Sun Yat-sen University, Kaohsiung 80424, Taiwan ROC;4. Institute of Earth Sciences, Academia Sinica, Taipei, 11529, Taiwan ROC |
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| Abstract: | The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in the submarine environment has attracted the attention of researchers from different disciplines. Yet not only are field measurements of oceanic turbidity currents a rare achievement, but also the data that have been collected consist mostly of velocity records with very limited or no suspended sediment concentration or grain size distribution data. This work focuses on two turbidity currents measured in Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, primarily controlled by the source of the gravity flows and their interaction with bed material, play a significant role in shaping the characteristics of the turbidity currents as they travel down the canyon. Before the flows reach their normal or quasi-steady state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through a preliminary adjustment stage where they are subject to capacity-driven deposition, and release heavy material in excess. Flows composed of fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm that flow patterns differ between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology. |
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| Keywords: | Turbidity currents Sediment transport Grain size Monterey canyon |
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