IODP Expedition 354 to the Bengal Fan; a Neogene record of Himalayan erosion; implications on the carbon cycle

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Author(s): France-Lanord, Christian; Spiess, Volkhard; Galy, Albert; Galy, Valier; Huyghe, Pascale; Klaus, Adam
International Ocean Discovery Program, Expedition 354 Scientists, College Station, TX
Author Affiliation(s): Primary:
Université de Lorraine, Vandoeuvre-les-Nancy, France
University of Bremen, Germany
Woods Hole Oceanographic Institution, United States
Université Joseph Fourier, France
Texas A&M University, United States
Volume Title: European Geosciences Union general assembly 2016
Source: Geophysical Research Abstracts, Vol.18; European Geosciences Union general assembly 2016, Vienna, Austria, April 17-22, 2016. Publisher: Copernicus GmbH on behalf of the European Geosciences Union (EGU), Katlenburg-Lindau, Germany. ISSN: 1029-7006
Note: In English
Summary: Bengal Fan Expedition 354 drilled an E-W transect in the middle fan at 8 N to investigate interactions between the growth of the Himalaya, the development of the Indian monsoon, and processes affecting the carbon cycle. A comprehensive record of turbiditic deposition between the Late Oligocene and Holocene was drilled over a seven sites E-W transect at 8 N. Shipboard results reveal that the chemical and mineralogical compositions of turbiditic sediments cored across the transect are relatively stable throughout the Neogene. By comparison to modern river sediment compositions (Lupker et al. ref), they reveal a weak intensity of chemical weathering without marked variation through time. Clay assemblages are dominated by illite and chlorite with minor proportions of newly formed clays. This differs from the distal fan record (Leg 116) where the Late Miocene and Pliocene turbidites show high weathering signatures and smectite rich clay assemblage. This difference implies that the distal fan record does not reflect to an evolution of the source erosion. Rather it is controlled by a change in sediment transport within the fan. Shipboard estimates of organic carbon loading and behavior resemble observations made in the modern Ganga-Brahmaputra river sediments, suggesting efficient terrestrial organic carbon burial in the Bengal Fan [1]. Preliminary observations support the idea that Himalayan erosion has consumed atmospheric CO2 through the burial of organic carbon, more than by silicate weathering. The main evolution observed in Expedition 354 record is the content of detrital carbonate that is persistent through the Neogene but appears to show a consistent decreasing trend from 8-10% during the Miocene to 3-6% during the Pleistocene and Pliocene. Also, a prominent feature of Miocene silt and sand beds is the higher abundance of plant fragments compared to younger sediments. Together these observations reveal changes in the sediment sources and erosion conditions of the hinterland during the Miocene and Pliocene. Among hypotheses, the Miocene Himalaya may have exposed more Tethyan limestone rich formations than during Pliocene to modern time. Alternatively, carbonate preservation during erosion may reflect lower water/sediment ratio, which would imply weaker weathering condition during Miocene. Expedition 354 cores will allow to estimate the overall impact of Himalayan erosion on the carbon cycle by coupling growth rate of the fan, erosion rate and chemical composition of the sediment. Preliminary observations support the idea that Himalayan erosion has consumed atmospheric CO2 through the burial of organic carbon, more than by silicate weathering. Ref: [Copyright Author(s) 2016. CC Attribution 3.0 License:]
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Asia; Bay of Bengal; Bengal Fan; Carbon; Carbon cycle; Carbonates; Cenozoic; Clay minerals; Cores; Depositional environment; Erosion; Expedition 354; Geochemical cycle; Himalayas; Indian Ocean; International Ocean Discovery Program; Lithofacies; Lithostratigraphy; Organic carbon; Quaternary; Sheet silicates; Silicates; Submarine fans; Tertiary; Turbidite; Weathering
Coordinates: N080023 N080026 E0884432 E0855058
Record ID: 2019065097
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from European Geosciences Union, Munich, Germany