Into the deep:A coarse-grained carbonate turbidite valley and canyon in ultra-deep carbonate setting

• Published in: Marine Geology
• Main Authors: Mulder, T., Gillet, H., Hanquiez, V., Reijmer, J.J.G., Droxler, A.W., Recouvreur, A., Fabregas, N., Cavailhes, T., Fauquembergue, K., Blank, D.G., Guiastrennec, L., Seibert, C., Bashah, S., Bujan, S., Ducassou, E., Principaud, M., Conesa, G., Le Goff, J., Ragusa, J., Busson, J., Borgomano, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Long Island; North Atlantic
• Online Access: https://research.vu.nl/en/publications/cf2c76cc-fab4-429d-aadc-97c811b20181; https://doi.org/10.1016/j.margeo.2018.11.003; https://hdl.handle.net/1871.1/cf2c76cc-fab4-429d-aadc-97c811b20181; https://research.vu.nl/ws/files/118673632/Into_the_deep_A_coarsegrained_carbonate_turbidite_valley_and_canyon_in_ultradeep_carbonate_setting.pdf; http://www.scopus.com/inward/record.url?scp=85057473542&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=85057473542&partnerID=8YFLogxK; http://www.sciencedirect.com/science/article/pii/S0025322718302032

New high-resolution multibeam mapping images detail the southern part of Exuma Sound (Southeastern Bahamas), and its unchartered transition area to the deep abyssal plain of the Western North Atlantic, bounded by the Bahama Escarpment extending between San Salvador Island and Samana Cay. The transition area is locally referred to as Exuma Plateau. The newly established map reveals the detailed and complex morphology of a giant valley draining a long-lived carbonate platform from its upper slope down to the abyssal plain. This giant valley extends parallel to the slope of Long Island, Conception Island, and Rum Cay. It starts with a perched system flowing on top of a lower Cretaceous drowned main carbonate platform. The valley shows low sinuosity and is characterized by several bends and flow constrictions related to the presence of the small relict isolated platforms that kept alive longer than the main platform before drowning and merging tributaries. Turbidite levees on either side of the valley witness the pathway of multiple gravity flows, generated by upper slope over steepening around Exuma Sound through carbonate offbank transport, some of them locally >15°, and resulting slumping. In addition, additional periplatform sediments are transported to the main valley through numerous secondary slope gullies and several kilometre-long tributaries, draining the upper slopes of cays and islands surrounding Exuma Plateau. Some of them form knickpoints indicating surincision of the main Exuma Valley which is consistent with an important lateral supply of the main Exuma Valley. Prior to reaching the abyssal plain, the main valley abruptly evolves into a deep canyon, 5 km in width at its origin and as much as 10 km wide when it meets the abyssal plain, through two major knickpoints named “chutes” with outsized height exceeding several hundred of meters in height. Both chutes are associated with plunge pools, as deep as 200-m. In the deepest pools, the flows generate a hydraulic jump and resulting sediment ...