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The global export of organic carbon (OC) is intimately linked to the total flux of terrestrial sediment to the ocean, with the continental margins receiving ~ 90% of the sediment generated by erosion on land. Recent studies suggest that a substantial amount of particulate OC (POC) might escape from the shelf and be exported to the continental slope-deep sea sector, although the mechanisms and magnitude of such deep sea POC transfer remain unknown. Here we investigate hyperpycnal flow-associated total suspended matter (TSM) collected from water depths of ~ 3000 m, near the bottom of sea floor, in the Gaoping Submarine Canyon (GSC) off southwestern Taiwan. Elemental (C, N), isotopic (δ 13 C, δ 15 N) and biomarker compositions of TSM were investigated to understand its biogeochemical characteristics. A two end-member δ 13 C mixing model indicates that deep sea TSM contains ~ 90% terrigenous OC, while a similar mixing model using δ 15 N reveals a lower proportion (~ 58%). Organic biomarkers of TSM suggest contributions from a mixture of resuspended, continental-margin derived marine organic matter (OM MAR ) and terrigenous sources, revealing that terrestrial OC likely mixes with nitrogen-rich marine material during rapid transport. This study documents that rapid transfer of terrigenous organic matter (OM TERR ) into the deeper regions of GSC occurred within a week of typhoon Morakot, likely through hyperpycnal injection of sediment-laden, warm freshwater from southern Taiwan. Evidence from this typhoon Morakot-induced hyperpycnal plume event in Taiwan demonstrates that extreme storm events provide an efficient way to export terrigenous OC without oxidation to hitherto unknown water depths of deep sea in the Oceania region.

article i nfo Results of clay mineralogy in 140 samples collected in major rivers and lakes in southwestern Taiwan and on the seafloor off Taiwan in the northeastern South China Sea (SCS), combined with clay mineral records of the Pearl River drainage basin, rivers in Luzon, and the South China shelf and slope, are used to semi- quantitatively evaluate the detrital fine-grained sediment contribution of Taiwan to the northern SCS. The clay mineral assemblage of the Taiwan-sourced sediments consists dominantly of illite (average 56%) and chlorite (41%), with very scarce kaolinite and smectite. Their respective distribution from the rivers and lakes to the seafloor off Taiwan does not show obvious basin-wide differences. Linear correlations of illite chemistry index with illite crystallinity and of illite crystallinity with kaolinite (%) present two end-members of provenances, the Pearl River and Taiwan, for the South China shelf and slope. Assuming that kaolinite in the northern SCS is provided completely from the Pearl River, the contribution of Taiwan in clay minerals is evaluated as 29% to the South China shelf and 23% to the South China slope, respectively. Accordingly, the contribution of the Pearl River to the South China shelf and slope is 52% and 31%, respectively. The Luzon Arc accounts for the rest of clay mineral components for the northern SCS mainly by providing smectite. The Bashi Strait-crossed branches of the southward deep North Pacific Deep Water and the northward surface Kuroshio Current in the western Pacific may transport Taiwan-sourced suspended sediments westwards to the northern SCS.

Three sediment cores near the spreading axis in the Andaman backarc basin (ABB) were studied for bulk and clay mineralogy, major, trace and rare earth element (REE) geochemistry in bulk and three selective leaches, to identify sediment sources to this region and to decipher probable hydrothermal contribution. REE and other geochemical data suggest a strong influence of the Irrawaddy River as a major continental source to the ABB sediments. Low carbonate content in the sediments is due to dilution by higher detrital input as well as reduced foraminiferal carbonate contribution because of low sea surface salinity. The contribution from local volcanic sources was identified from the presence of volcanic glass in the sand-sized sediment fraction; higher smectite content in the clay fraction and the trace element data. Mn concentrations in the upper 12 cm are well above those found in pelagic carbonate-free sediments. Mn distribution pattern and oxide nature suggest a hydrothermal source. Other discriminants such as Eu anomaly and Y/Ho ratio also suggest the role of hydrothermal activity. In addition, the association of Mo with Pb, Zn and Cu in the HCl-insoluble residue suggests the presence of sulfidic material probably of hydrothermal origin.