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Changing sedimentary environment during the late Quaternary: Sedimentological and isotopic evidence from the distal Bengal Fan

DRS at CSIR-National Institute of Oceanography

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Title Changing sedimentary environment during the late Quaternary: Sedimentological and isotopic evidence from the distal Bengal Fan
 
Creator Kessarkar, P.M.
Rao, V.P.
Ahmad, S.M.
Patil, S.K.
AnilKumar, A.
AnilBabu, G.
Chakraborty, S.
SounderRajan, R.
 
Subject pelagic sediments
pelagic sedimentation
sedimentary environments
turbidities
provenance
quaternary
neodymium isotopes
strontium isotopes
 
Description The sediments recovered from two gravity cores of the lower and distal Bengal Fan were investigated for sedimentological properties and Sr -Nd isotopes.Each core exhibits two distinct units, the lower unit 2 and upper unit 1 sediments. The unit 2 sediments are predominantly olive black/grey in colour with abundant finer silt-size fractions, low organic carbon and CaCO sub(3), quartz and mica in the coarse fraction, dominant illite and chlorite in the less than 2 Mu m fraction and uniform rock-magnetic properties. Biogenic constituents are extremely rare or restricted to the lower part of unit 2. The unit 1 sediments, on the other hand, are moderate brown/yellowish brown in colour with intermittent thin dark-coloured sediment layers. Higher clay, organic carbon, CaCO sub(3), and biogenic constituents in the coarse fraction, and enriched smectite and kaolinite in the o m fraction are typical. Magnetic susceptibility values are higher and correlate well with acid-insoluble residue content. Higher Rb, Sr, Sm and Nd concentrations, sup(87)Sr/sup(86)Sr ratios and more radiogenic epsilon Nd values are characteristic for unit 2 sediments compared to unit 1 in both the cores. The unit 2 sediments represent Pleistocene hemiturbidites, older than 13 sup(14)C kyr BP with their source from the northern Bay of Bengal (NBOB), derived from the Himalayas and transported by the Ganges -Brahmaputra (G -B)River system. Unit 1 sediments are calcareous pelagic sediments, which started depositing approx. 12 sup(14)C kyr BP, with its clastic sediments derived from the Himalayas and SE Indian/Sri Lankan margins. The change in lithofacies from unit 2 to unit 1 suggests that the sediment deposition by turbidity current activity ceased in the distal Bengal Fan at approx. 12 sup(14)C kyr BP, perhaps because of the rapid rise in sea-level during the melt water pulse 1A and Holocene.
 
Date 2008-02-22T05:30:11Z
2008-02-22T05:30:11Z
2005
 
Type Journal Article
 
Identifier Deep-sea research. Part I. Oceanographic research papers, Vol.52; 1591-1615p.
http://drs.nio.org/drs/handle/2264/937
 
Language en
 
Rights Copyright [2005]. It is tried to respect the rights of the copyright holders to the best of the knowledge. If it is brought to our notice by copyright holder that the rights are voilated then the item would be withdrawn.
 
Publisher Elsevier