The Bengal Fan record of Himalayan erosion from Miocene to Present from IODP Expedition 354

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Author(s): France-Lanord, Christian; Galy, Albert; Spiess, Volkhard; Klaus, Adam
Author Affiliation(s): Primary:
Centre de Recherches Pétrographiques et Géochimiques-Université Lorraine, Vandoeuvre les Nancy, France
University of Bremen, Germany
Texas A&M University, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During IODP Expedition 354, an E-W transect of seven holes was drilled in the Bengal fan. It is located at 8°N, in the middle fan, approximately 1500 km south of the Ganga-Brahmaputra delta. The fan is dominated by detrital sediments supplied by Himalayan rivers, and transported through the delta and shelf canyon, supplying turbidity currents loaded with a wide spectrum of grain sizes. Overall, the transect allows the restitution of a complete record of Himalayan erosion at the scale of the Neogene and documents the interplay between the monsoon and Himalayan tectonic. Analyses of detrital sediments reveal close mineralogical and geochemical similitude with modern river sediments derived from the Himalaya. Major and trace element geochemistry show relatively stable compositions throughout the Neogene. They reveal a very weak regime of chemical weathering, lower than present, and with no significant variation through time. This clearly differs from the distal fan record (Leg 116 at 1°S) where from ∼7 to 1 Ma, weathered and smectite rich sediments are predominant. It implies that the distal fan record does not reflect an evolution of the source erosion. Rather, it is controlled by a change in sediment transport and sorting within the fan. Low weathering of the sediments at 8°N indicates that erosion is driven by physical processes and transport rapid enough to prevent evolution of particles. In the modern Himalaya, low weathering is achieved primarily by landslides and rapid transfer through the floodplain, i.e. limited recycling of sediment deposited in the floodplain. Both processes are favoured by the seasonality and the intensity of the monsoon. Isotopic compositions of silicates and carbonate document the geological formations exposed to erosion. They imply that exposure to erosion of the different Himalayan formations has evolved as a result of the evolution of the thrusting structures.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Bay of Bengal; Bengal Fan; Cenozoic; Cores; Expedition 354; Indian Ocean; International Ocean Discovery Program; Leg 116; Marine sediments; Miocene; Neogene; Ocean Drilling Program; Quaternary; Sediments; Tertiary
Coordinates: S010116 S005547 E0812404 E0812324
N080023 N080026 E0884432 E0855058
Record ID: 2017051754
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