Redistribution of multi-phase particulate organic carbon in a marine shelf and canyon system during an exceptional river flood: Effects of Typhoon Morakot on the Gaoping River–Canyon system - Archive ouverte HAL
Article Dans Une Revue Marine Geology Année : 2015

Redistribution of multi-phase particulate organic carbon in a marine shelf and canyon system during an exceptional river flood: Effects of Typhoon Morakot on the Gaoping River–Canyon system

Résumé

Volumetrically, turbidity currents are the prime suppliers of sediment to the deep sea, and conveyors of organic carbon from the terrestrial biosphere and submarine shelf into marine depositional basins. They result from com- plex processes of erosion, transport and deposition that can be difficult to study in detail. Here we present data from the Gaoping submarine canyon system, off SW Taiwan, which was perturbed in 2009 by the addition of flood deposits following Typhoon Morakot and sampled by gravity coring less than 2 months after the event. We use the different origins of organic carbon, distinguished by their carbon and nitrogen concentrations and δ13 C and δ15 N isotopic composition, to compare and contrast standard and extreme sedimentological conditions. Using well-constrained end-members, the results were de-convolved into inputs of metamorphic and sedimen- tary fossil organic carbon eroded within the Gaoping River basin, terrestrial non-fossil carbon and marine organic matter. In the upper Gaoping Canyon, sedimentation is dominated by the highly-localised hyperpycnal input of river washload and submarine sediment slumps, each associated with extensive flooding following Typhoon Morakot, whilst the shelf experienced deposition and reworking of hemi-pelagic marine sediments. A terrestrial signal is also found in the core-top of a fine-grained shelf sample over 20 km from the Gaoping Canyon, in a re- gion normally dominated by marine carbon deposition, showing that Morakot was an unusually large flood event. Conversely, sediment from just above the canyon thalweg contains 0.23 wt.% depth-averaged marine or- ganic carbon (37% of the TOC content) implying that terrestrial OC-dominated turbidites are tightly constrained within the canyon. Hyperpycnal processes can lead to the rapid and efficient transport of both terrestrial and sub- marine sediments to more permanent burial locations.

Domaines

Géochimie

Dates et versions

hal-03800760 , version 1 (06-10-2022)

Identifiants

Citer

Robert Sparkes, In-Tian Lin, Niels Hovius, Albert Galy, James Liu, et al.. Redistribution of multi-phase particulate organic carbon in a marine shelf and canyon system during an exceptional river flood: Effects of Typhoon Morakot on the Gaoping River–Canyon system. Marine Geology, 2015, 363, pp.191-201. ⟨10.1016/j.margeo.2015.02.013⟩. ⟨hal-03800760⟩
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