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Paleoclimatic and diagenetic history of the Late Quaternary sediments in a core from the southeastern Arabian Sea: Geochemical and magnetic signals

DRS at CSIR-National Institute of Oceanography

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Title Paleoclimatic and diagenetic history of the Late Quaternary sediments in a core from the southeastern Arabian Sea: Geochemical and magnetic signals
 
Creator Rao, V.P.
Kessarkar, P.M.
Thamban, M.
Patil, S.K.
 
Subject palaeoclimate
geochemistry
magnetic properties
redox potential
 
Description Geochemical and rock-magnetic investigations were carried out on a sediment core collected from the SE Arabian Sea at 1420 m depth in oxygenated waters below the present-day oxygen minimum zone. The top 250 cm of the core sediments represent the last 35 kaBP. The delta sup(18)O values of Globigerinoides ruber are heaviest during the Last Glacial Maximum (LGM) and appear unaffected by low-saline waters transported from the Bay of Bengal by the strong northeast monsoon and West Indian coastal current. The signatures of Bolling-Allerod and Younger Dryas events are distinct in the records of magnetic susceptibility, organic carbon (OC) and delta sup(18)O. Glacial sediments show higher OC, CaCO sub(3), Ba, Mo, U and Cd, while the early-to-late Holocene sediments show increasing concentrations of OC, CaCO sub(3), Ba, Cu, Ni and Zn and decreasing concentrations of Mo, U and Cd. Productivity induced low-oxygenated bottom waters and reducing sedimentary conditions during glaciation, and productivity and oxygenated bottom waters in the Holocene are responsible for their variation. The core exhibits different stages of diagenesis at different sediment intervals. The occurrence of fine-grained, low-coercivity, ferrimagnetic mineral during glacial periods is indicative of its formation in organic-rich, anoxic sediments, which may be analogous to the diagenetic magnetic enhancement known in sapropels of the Mediterranean Sea and Japan Sea. The glacial sediments exhibiting reductive diagenesis with anoxic sedimentary environment in this core correspond to reductive diagenesis and intermittent bioturbation (oxygenation) reported in another core in the vicinity. This suggests that the poorly oxygenated bottom water conditions during glacial times should not be generalized, but are influenced locally by productivity, sedimentation rates and sediment reworking
 
Date 2009-12-24T05:03:41Z
2009-12-24T05:03:41Z
2010
 
Type Journal Article
 
Identifier Journal of Oceanography, vol.66(1); 133-146
no
http://drs.nio.org/drs/handle/2264/3522
 
Language en
 
Rights An edited version of this paper was published by the Oceanographic Society of Japanr. Copyright [2009] The Oceanographic Society of Japan
 
Publisher The Oceanographic Society of Japan