57 research outputs found
THE LAST GLACIAL-INTERGLACIAL TRANSITION IN THE SOUTH CHINA SEA RECORDED BY STABLE ISOTOPE OF BENTHIC AND PLANCTONIC FORAMINIFERA
Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system
Author Posting. © Nature Publishing Group, 2007. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 450 (2007): 407-410, doi:10.1038/nature06273.Continental erosion controls atmospheric carbon dioxide levels on geological timescales
through silicate weathering, riverine transport and subsequent burial of organic carbon
in oceanic sediments. The efficiency of organic carbon deposition in sedimentary basins
is however limited by the organic carbon load capacity of the sediments and organic
carbon oxidation in continental margins. At the global scale, previous studies have
suggested that about 70 per cent of riverine organic carbon is returned to the
atmosphere, such as in the Amazon basin. Here we present a comprehensive organic
carbon budget for the Himalayan erosional system, including source rocks, river
sediments and marine sediments buried in the Bengal fan. We show that organic carbon
export is controlled by sediment properties, and that oxidative loss is negligible during
transport and deposition to the ocean. Our results indicate that 70 to 85 per cent of the
organic carbon is recent organic matter captured during transport, which serves as a
net sink for atmospheric carbon dioxide. The amount of organic carbon deposited in the
Bengal basin represents about 10 to 20 per cent of the total terrestrial organic carbon
buried in oceanic sediments. High erosion rates in the Himalayas generate high
sedimentation rates and low oxygen availability in the Bay of Bengal that sustain the
observed extreme organic carbon burial efficiency. Active orogenic systems generate
enhanced physical erosion and the resulting organic carbon burial buffers atmospheric
carbon dioxide levels, thereby exerting a negative feedback on climate over geological
timescales
Hemipelagic Sediment Accumulation Rates in the South China Sea Related to Late Quaternary Sea-Level Changes
Sediments of 13 piston cores from opposite continental slopes of the South China Sea, off southern China and Sabah (northern Borneo), were analyzed by sedimentological methods and dated by oxygen isotope stratigraphy. Sediments mostly consist of hemipelagic clay with 20% carbonate off Sabah and 40% off China. We calculated terrigenous and carbonate accumulation rates for up to 11 time-slices from the Holocene to oxygen-isotope stage 6. Terrigenous accumulation rates generally increase with water depth and reach a maximum at the middle slope off Sabah and at the lower continental slope off China. During glacial and interglacial times this distribution pattern did not markedly change, despite an increase of accumulation rates for glacial periods by a factor of 2 to 5 compared to interglacial periods. Rates are negatively correlated with positions of sea level, which controls the partition of fluviatile terrigenous material for deposition on shelf, slope, and abyssal plain. Carbonate accumulation rates are higher off China by a factor of 2 compared to Sabah, probably indicating higher calcareous plankton productivity
Side-scan sonar surveying on the continental shelf off Sierra Leone
Along the Sierra Leone continental shelf edge, bedded rocks, presumably mostly calcareous sandstone, calcarenites and siltstones form exposures up to 10 km long in water depths ranging from 80 to 110 m. These outcrops are found in a 6 km broad zone along the shelf edge; landward they get covered by recent shelf sands. Their apparent strike direction parallds the shelf edge indicating nearly horizontal bedding which locally is interrupted by faulting. On the middle shelf, a terrace is well developed at a water depth of 56 m. Ripples, megaripples, pockmarks 1-5 m in diameter, and canyon-heads form other significant features of the shelf
Stratigraphische Untersuchungen an Sedimentkernen des ibero-marokkanischen Kontinentalrandes
Sedimenttransport durch tropische Wirbelströme im submarinen Delta des Ganges-Brahmaputra/Bangladesh
Acoustic characterisation of shallow marine sediments of the Bengal Shelf from high-resolution Parasound echosounder data and sediment cores
Architecture of the Bengal Sediment Fan - New insights from high resolution seismic and hydroacoustic surveying during R/V Sonne cruise SO125
Architecture of the Bengal Fan - New Insights from High Resolution Seismic and Hydroacoustic Surveying During R/V Sonne Cruise SO 125
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