South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea.

Ali, Sajid, Hathorne, Ed C. , Frank, Martin , Gebregiorgis, Daniel, Stattegger, Karl, Stumpf, Roland, Kutterolf, Steffen , Johnson, Joel E. and Giosan, Liviu (2015) South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea. Open Access Geochemistry, Geophysics, Geosystems, 16 (2). pp. 505-521. DOI 10.1002/2014GC005586.

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The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with
glacial-interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments
draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope
compositions of the detrital clay-size fraction and clay mineral assemblages obtained from sediment core
NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the
past 60 kyr. Over this time interval eNd values changed little, generally oscillating between 27.3 and 25.3
and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further
northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly
during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely
source region is the Irrawaddy river catchment including the Indo-Burman Ranges with a possible minor
contribution from the Andaman Islands. High smectite/(illite1chlorite) ratios (up to 14), as well as low
87Sr/86Sr ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger
South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite-poor intervals
exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon,
which may have been linked to short-term northern Atlantic climate variability on millennial time

Document Type: Article
Additional Information: WOS:000351619100009
Keywords: South Asian Monsoon, radiogenic isotopes, detrital sediment fraction, clay minerals, Andaman Sea, Late Quaternary
Research affiliation: Kiel University
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2014GC005586
ISSN: 1525-2027
Date Deposited: 16 Apr 2015 08:52
Last Modified: 24 Sep 2019 00:05

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