Himalayan erosion and Ganga-Brahmaputra sediment delivery recorded in the Bengal Fan from IODP Expedition 354

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Author(s): France-Lanord, Christian; Galy, Albert; Huyghe, Pascale; Yoshida, Kohki; Spiess, Volkhard
Author Affiliation(s): Primary:
Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre-Les-Nancy, France
University Joseph Fourier Grenoble, France
Shinshu University, Japan
University of Bremen, Germany
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: IODP Expedition 354 in the Bengal fan [1] generated a comprehensive record of Himalayan erosion over the Neogene and Quaternary. It documents the interplay between Himalayan tectonic and the monsoon. The Bengal fan is predominantly composed of detrital sediments originating from Himalayan rivers, and transported to the N. Bengal shelf. They supply turbidity currents able to spread sediments overs 3000 km. Turbiditic record at a given site being discontinuous, Expedition 354 drilled seven sites along a 320 km E-W transect at 8°N allowing the restitution of an almost complete record of Himalayan erosion at the scale of the Neogene. In spite of the transect extension, a long absence of deposition is observed between 0.6 to 1.2 Ma indicating that turbiditic depocenter was derived more to the West for ca. 600 kyr. Bengal fan sediments have close mineralogical, geochemical and isotopic analogy with sediments of the modern Ganga-Brahmaputra rivers. Altogether they reveal mineralogical sorting associated to turbiditic transports that compares well with that of rivers in the floodplain and delta. Major and trace element geochemistry and clay compositions reveal relatively even and weak conditions of weathering throughout the 20-Ma record. Most variations are controlled by the origin of eroded sources ie. the proportions of sediments derived from Himalaya and Transhimalaya. Source tracers such as Sr-Nd isotopic compositions, and detrital carbonate compositions show organised variations with time. They also imply for some periods compositions with very high proportion of sediment derived from the Transhimalaya suggesting that the Ganga and Brahmaputra sediment delivery to the fan can be decoupled at some periods. Long term source variations imply that exposure to erosion of the different Himalayan formations has evolved as a result of the evolution of the thrusting structures. Data suggest that (1) a component derived from Transhimalayan formation was present even during Lower Miocene, (2) the Tethys Himalaya exposure to erosion was higher during Miocene than during Pliocene and Pleistocene, and (3) that the exhumation of the Lesser Himalaya was initiated around 8 Ma. France-Lanord, C., Spiess, V., Klaus, A., Schwenk, T., Expedition 354 Scientists. (2016). http://doi.org/10.14379/iodp.proc.354.2016
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Asia; Bay of Bengal; Bengal Fan; Brahmaputra River; Cores; Expedition 354; Ganges River; Himalayas; Indian Ocean; International Ocean Discovery Program; Marine sediments; Sediments
Coordinates: N080023 N080026 E0884432 E0855058
Record ID: 2019061762
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