Contribution of clay mineralogy of Bengal Fan deposits at 8°N for understanding of Himalayan provenance and environmental conditions

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http://meetingorganizer.copernicus.org/EGU2016/EGU2016-15798.pdf
Author(s): Huyghe, Pascale; France-Lanord, Christian
Integrated Ocean Drilling Program, Expedition 354 Scientists
Author Affiliation(s): Primary:
University of Grenoble, Institut des Sciences de la Terre, Grenoble, France
Other:
University of Lorraine, France
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: The IODP 354 expedition (February-March 2015) focused on the middle part of the Bengal Fan (8°N). Seven sites were drilled along a 320 km-long transect and provided good recovery and excellent data to study both provenance of the material from the Himalayan Orogeny and paleoceanography linked to the Asian monsoon. Neogene sediments consist of an alternation of rapidly deposited, silty to muddy turbidites (10-100 cm/kyr) forming levees of channels intercalated with minor slowly deposited hemipelagic clays (1-2 cm/kyr), which may be found over the whole investigated area. Thick interlevee sand sheet units also occur between channel levees. The turbiditic sand, silt and clay have mineralogical signatures very similar to those of the modern Ganges and Brahmaputra Rivers and are therefore relevant for reconstructing time series of erosion, weathering, and changes in Himalayan sources regions. Hemipelagic calcareous clays may provide additional information on environmental conditions throughout the Himalayan basin. Preliminary shipboard XRD analysis revealed that the clayey assemblages of sediments are relatively constant through the Neogene. Turbidite clay assemblages are dominated by detrital illite and chlorite as observed in the modern Himalayan rivers, suggesting that erosion conditions were relatively steady over the last 25 Ma. Hemipelagic clay assemblages vary from 1) identical to the illite-chlorite rich clays of turbidites, characteristic for Himalayan rivers, to 2) smectite rich assemblages enriched in iron and depleted in potassium, representing either more extreme sorting of the same material or input from another source. Further detailed investigation using decomposition of X-Ray diffraction (XRD) patterns reveals much more complex clay assemblages, especially great quantities of mixed-layers, the quantity and mineralogy of which varies and differs in the three depositional units as determined by turbidites levees, hemipelagic clayey beds and interlevees sandy sheets. Specific surface-area measurements of clay material (BET) analysis is in progress and should help determine the mineralogical reactions leading to these complex assemblages. [Copyright Author(s) 2016. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Asia; Bengal Fan; Cenozoic; Clay mineralogy; Cores; East Pacific; Expedition 345; Hess Deep; Himalayas; Indian Ocean; Integrated Ocean Drilling Program; Marine sediments; Neogene; North Pacific; Northeast Pacific; Pacific Ocean; Paleo-oceanography; Provenance; Sediments; Tertiary
Coordinates: N021508 N021520 W1013234 W1013252
Record ID: 2019072100
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from European Geosciences Union, Munich, Germany