Indian summer monsoon and winter hydrographic variations over past millennia resolved by clay sedimentation

Reconstruction of century‐scale Indian monsoon and winter hydrography is made from an AMS‐dated core located in the unique region of the southeast Arabian Sea which lies in the pathways of the low‐salinity Bay of Bengal Waters, advecting during winter northeast monsoon (NEM). Based upon clay mineral...

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Published in:Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2010-09, Vol.11 (9), p.n/a
Main Authors: Chauhan, Onkar S., Dayal, A. M., Basavaiah, Nathani, Kader, U. Syed Abdul
Format: Article
Language:English
Subjects:
Bay of Bengal Waters
Clay
clay sedimentation
Climate change
Continental margins
Earth
Fluctuations
Geobiology
Hydrography
Indian summer monsoon
Kaolinite
Monsoons
Oceanography
Paleoclimate science
Paleontology
southeast Arabian Sea
Summer
suspended load
Winter
winter hydrography
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Summary:Reconstruction of century‐scale Indian monsoon and winter hydrography is made from an AMS‐dated core located in the unique region of the southeast Arabian Sea which lies in the pathways of the low‐salinity Bay of Bengal Waters, advecting during winter northeast monsoon (NEM). Based upon clay mineral analyses in seawaters, we identify chlorite and kaolinite as specific clays supplied by the Bay of Bengal Waters and local fluvial flux (by the southwest monsoon (SWM) precipitation from the Peninsular India), respectively, along the southwest continental margin of India. An evaluation of clay flux and δ18O in G. ruber portrays century‐scale weaker SWM precipitation events during ∼450–650 yr, ∼1000 yr, and 1800–2200 cal yr BP. Kaolinite wt % and flux were found to be low during all these events, though chlorite had a persistent or enhanced flux. From the enhanced flux of chlorite and reduced kaolinite/chlorite ratio, during weaker phases of SWM, we deduce a stronger NEM (winter hydrography), implying an inverse coupling between the summer and the winter monsoon.
ISSN:1525-2027
1525-2027
DOI:10.1029/2010GC003067