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Indian Monsoonal Variations During the Past 80 Kyr Recorded in NGHP‐02 Hole 19B, Western Bay of Bengal: Implications From Chemical and Mineral Properties

2018; Wiley; Volume: 20; Issue: 1 Linguagem: Inglês

10.1029/2018gc007772

1525-2027

Yuki Ota, Hodaka Kawahata, Junichiro Kuroda, Asuka Yamaguchi, Atsushi Suzuki, Daisuke Araoka, Ayako Abe‐Ouchi, Yasuhiro Yamada, Akira Ijiri, Toshiya Kanamatsu, Masataka Kinoshita, Kyaw Moe, Weiren Lin, Saneatsu Saito, Yoshinori Sanada, Yohei Hamada, Yasuyuki Nakamura, Yuichi Shinmoto, Hung‐Yu Wu, Naokazu Ahagon, Kan Aoike, Koichi Iijima, Hideaki Machiyama, Maria Luisa Tejada, Keita Umetsu, Yoichi Usui, Yuzuru Yamamoto, Shuro Yoshikawa, F.J. Jiménez-Espejo, Satoru Haraguchi, Nobuharu Komai, Hisami Suga, Natsue Abe, Lallan P. Gupta, Takehiro Hirose, Yuka Masaki, Shun Nomura, Takamitsu Sugihara, Wataru Tanikawa, Yusuke Kubo, Lena Maeda, Sean Toczko,

earthquake and tectonic studies

Abstract Detailed reconstruction of Indian summer monsoons is necessary to better understand the late Quaternary climate history of the Bay of Bengal and Indian peninsula. We established a chronostratigraphy for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BP and examined major and trace element compositions and clay mineral components of the sediments. Higher δ 18 O values, lower TiO 2 contents, and weaker weathering in the sediment source area during marine isotope stages (MIS) 2 and 4 compared to MIS 1, 3, and 5 are explained by increased Indian summer monsoonal precipitation and river discharge around the western Bay of Bengal. Clay mineral and chemical components indicate a felsic sediment source, suggesting the Precambrian gneissic complex of the eastern Indian peninsula as the dominant sediment source at this site since 80 kyr. Trace element ratios (Cr/Th, Th/Sc, Th/Co, La/Cr, and Eu/Eu*) indicate increased sediment contributions from mafic rocks during MIS 2 and 4. We interpret these results as reflecting the changing influences of the eastern and western branches of the Indian summer monsoon and a greater decrease in rainfall in the eastern and northeastern parts of the Indian peninsula than in the western part during MIS 2 and 4.