TERRAPUB Geochemical Journal
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Geochemical Journal, Vol. 53 (No. 2), pp. e1-e7, 2019
doi:10.2343/geochemj.2.0552

EXPRESS LETTER

Mekong River discharge and the East Asian monsoon recorded by a coral geochemical record from Con Dao Island, Vietnam

Tung Thanh Phan,1 Atsuko Yamazaki,1,2,6 Hong-Wei Chiang,3 Chuan-Chou Shen,3,4 Lam Dinh Doan5 and Tsuyoshi Watanabe1,6*

1Faculty of Science, Hokkaido University, N10W8 Kita-ku, Sapporo 060-0810, Japan
2Faculty of Science, Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan
3High-Precision Mass Spectrometry and Environment Change Laboratory, Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan R.O.C.
4Research Center for Future Earth, National Taiwan University, Taipei 10617, Taiwan R.O.C.
5Department of Sedimentary Geology, Institute of Geological Sciences, Vietnam Academy of Science and Technology, Hanoi 100000, Viet Nam
6KIKAI Institute for Coral Reef Sciences, Shiomichi 1508, Kikai-town, Kagoshima 891-6151, Japan

(Received August 14, 2018; Accepted November 23, 2018; Online published February 8, 2019)

Abstract: The offshore flow of the Mekong River is strongly governed by the East Asian monsoon (EAM). Monthly-resolved skeletal carbonate Sr/Ca, Ba/Ca and oxygen isotope (δ18Oc) data from 1980 to 2005 of a Porites coral from Con Dao Island, ∼90 km from the Mekong River mouth, were analyzed for capturing the past flood events and the signal of East Asian winter monsoon. Ba/Ca time series is characterized with intra-annual double peaks, the first large one in March during the dry season and relative small one in August during the wet season. The low values of seawater δ18O (δ18Osw), deduced from both the Sr/Ca ratio and δ18Oc, in the wet season resulted from precipitation and/or freshwater input from the Mekong River. The difference in the seasonal characteristics of Ba/Ca and δ18Osw between flood and no-flood years could be attributed to the seasonal reversal of the regional ocean current derived from the EAM.
Key words: coral skeleton, Ba/Ca, oxygen isotope, Con Dao Island, Mekong River


*Corresponding author E-mail: nabe@sci.hokudai.ac.jp


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