The last glacial cycle documented on the Lower Bengal Fan; chronological and paleoclimate implications

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Author(s): Weber, Michael E.; Dekens, Petra; Reilly, Brendan; Lantzsch, Hendrik; Selkin, Peter A.; Das, Supriyo K.; Williams, Trevor; Martos, Yasmina M.; Adhikari, Rishi R.; Gyawali, Babu R.; Jia Guodong; Fox, Lyndsey R.; Ge Junyi; Manoj, M. C.; Savian, Jairo F.; Meynadier, Laure; Spiess, Volkhard; France-Lanord, Christian; Klaus, Adam
Author Affiliation(s): Primary:
University of Bonn, Steinmann Institute, Bonn, Germany
Other:
San Francisco State University, United States
Oregon State University, United States
University of Bremen, Germany
University of Washington-Tacoma, United States
Presidency University, India
Lamont Doherty Earth Observatory, United States
NERC British Antarctic Survey, United Kingdom
Tohoku University, Japan
Tongji University, China
Natural History Museum, United Kingdom
Chinese Academy of Sciences, China
National Centre for Antarctic & Ocean Research, India
Institute of Astronomy, Geophysics and Atmospheric Sciences, Brazil
Institut de Physique du Globe, France
Centre de Recherches Pétrographiques et Géochimiques, France
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: IODP Expedition 354 set out in February to March 2015 to drill seven sites along an east west oriented core transect of 320 km length at 8°N in the Bengal Fan (France-Lanord et al., 2015). Sediments show complex intercalation of turbiditic and hemipelagic deposits, documenting the interaction of fan evolution and paleoceanographic history. Hemipelagic sequences represent a several meter thick top layer of Late Quaternary sediment. Deposits are either rich in biogenic opal/clay or in carbonate. We studied physical, optical, geochemical, grain-size, and stable isotopic properties of this top layer to establish a time frame, estimate sedimentary properties, and assess the development of the region during the last glacial cycle. For this purpose, we sampled Site U1452C-1H continuously for the uppermost 480 cm in 2-cm increments. Preliminary results indicate the Toba Ash 1 (74 ka) is a distinct time marker in most physical property data sets. Records of wet-bulk density as well as color reflectance b* (the red-green component) and L* (the lightness) show a dominant precession cyclicity. Hence, we are able to provide an insolation-tuned chronology for the last 200 ka (MIS1-7). These records agree well with δ18O records retrieved from Chinese caves. An independent age model is derived from records of relative paleointensity (RPI), including the assessment of the Laschamp Event (∼40 ka), and on RPI tuning to global templates. We will compare both chronologies and evaluate their chronological and paleoclimatic implications. We will also present preliminary grain-size and paleoceanographic proxy data (sea-surface temperature, sea-surface salinity, and Mg/Ca) as well as color endmember modeling to reconstruct ice volume, marine biological productivity, nutrient supply, and deep-water circulation. The sedimentologic, oceanographic and climatic conditions are linked to changes in monsoonal strength and terrestrial input, which will also be studied using sedimentary proxies to reconstruct chemical weathering, sediment sources, and transport time. Our work addresses primary cruise objectives--linking monsoon variability, regional and global climate, and Bay of Bengal sediment deposition.
Year of Publication: 2016
Key Words: 24 Surficial Geology, Quaternary Geology
Record ID: 2017039637
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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