Carbonate slope morphology revealing sediment transfer from bank-to-slope (Little Bahama Bank,Bahamas) |
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| Institution: | 1. Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, 1790 AB Den Burg, the Netherlands;2. Institut de Ciències del Mar, ICM-CSIC. Pg. Marítim de la Barceloneta 37-49,E-408003 Barcelona, Spain;1. 6D avenue Général de Gaulle, 05100 Briançon, France;2. Université de Lorraine, Faculté des Sciences et Technologies, Département des Géosciences, UMR 7359 GéoRessources, BP 70239, 54506 Vandoeuvre-lès-Nancy, France;3. Task Geoscience Ltd., Aberdeen, UK;4. 7 Chemin Charrière Blanche, 69130 Ecully, France;1. Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713, USA;2. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, 2275 Speedway C9000, Austin, Texas 78712, USA;3. School of Earth and Environment, University of Leeds, Leeds, West Yorkshire LS2 9JT,UK;4. Ocean College, Zhejiang University, Hangzhou, Zhejiang Province 310058, People''s Republic of China;5. Department of Physical & Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C1A4, Canada;1. IGAG-CNR, UOS Sapienza, Piazzale A. Moro, 5, 00185 Rome, Italy;2. Dip. Scienze della Terra, Sapienza Università di Roma, Piazzale A. Moro, 5, 00185 Rome, Italy;3. ISAC-CNR, Via Fosso del Cavaliere, 100, 00133 Rome, Italy;1. Departamento de Estratigrafía y Paleontología, Universidad de Granada, 18002 Granada, Spain;2. College of Science and Engineering, James Cook University, PO Box 6811, Cairns, QLD 4870, Australia;3. Geocoastal Group, School of Geosciences, The University of Sydney, NSW 2006, Australia;4. School of Geosciences, The University of Edinburgh, Edinburgh EH9 3FE, UK;5. Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee, NSW 2232, Australia;1. Department of Earth Sciences, University of Oregon, Eugene, OR 97403, USA;2. Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 15784 Athens, Greece;3. Department of Earth Science and Engineering, Imperial College London, SW7 2AZ, United Kingdom |
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| Abstract: | New high-quality multibeam and high-resolution seismic data reveal new observations on sediment transfer and distribution and margin morphometrics in the uppermost slope of Northeastern Little Bahama Bank between 20 and 300 m water depth. The echofacies/backscatter facies show an alongslope sediment distribution forming successive strips. The upper part of the uppermost slope corresponds to the alternation of several submerged coral terraces and escarpments that could be related to Late Quaternary sea-level variations. The terraces could either be related to periods of stagnating sea-level or slow-down in sea-level change and therefore increased erosion by waves, or periods of accelerated sea-level rise since the Last Glacial Maximum. Terraces could therefore be related to coral construction and drowing. The medium part corresponds to the marginal escarpment, a steep cemented area. The lower part of the uppermost slope shows a discontinuous Holocene sediment wedge with varying thickness between 0 and 35 m. It is separated from the upper part by a zone of well-cemented seafloor associated with the marginal escarpment. Passing cold fronts result in sediment export caused by density cascading. The associated sediment fall-out and convective sedimentation can generate density currents that form this wedge and eventually flow through linear structures on the upper slope. The survey reveals the presence of recently active channels that extend over the entire uppermost slope and interrupt the wedge. The channels connect shallow tidal channels to submarine valleys connected to the proximal part of canyons. They directly feed the canyons with platform-derived sediment forming low-density turbidity currents and could supply the deepest part of the system with coarse-grained sediment directly exported from the carbonate platform. |
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