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Quaternary climate modulation of Pb isotopes in the deep Indian Ocean linked to the Himalayan chemical weathering

DRS at CSIR-National Institute of Oceanography

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Title Quaternary climate modulation of Pb isotopes in the deep Indian Ocean linked to the Himalayan chemical weathering
 
Creator Wilson, D.J.
Galy, A.
Piotrowski, A.M.
Banakar, V.K.
 
Subject GEOLOGY AND GEOPHYSICS
GEOLOGY AND GEOPHYSICS
GEOLOGY AND GEOPHYSICS
 
Description We use reductive sediment leaching to extract lead (Pb) from the authigenic fraction of marine sediments and reconstruct the Pb isotope evolution of the deep central Indian Ocean over the past 250 thousand years at ~3 kyr resolution. Temporal variations define a binary mixing line that is consistent with data from ferromanganese nodules and which records mixing between two well-defined endmembers through time. The unradiogenic endmember appears to represent a widely-distributed Pb source, from mid-ocean ridges or possibly volcanic aerosols, while the radiogenic endmember coincides with the composition of Ganges–Brahmaputra river sediments that are indicative of the Himalayan weathering inputs. Glacial–interglacial Pb isotope variations are striking and can be explained by an enhancement of Himalayan contributions by two to three times during interglacial periods, indicating that climate modulates the supply of dissolved elements to the ocean. While these changes could accurately record variations in the continental chemical weathering flux in response to warmer and wetter conditions during interglacials, the relative proportions of Pb derived from the Ganges and Brahmaputra appear to have been constant through time. This observation may point towards particulate-dissolved interactions in the estuary or pro-delta as a buffer of short timescale variability in the composition (and potentially flux) of the fluvial inputs. In addition, the changes are recorded at 3800 m water depth, and with the lack of deep water formation in the Bay of Bengal, a mechanism to transfer such a signature into the deep ocean could either be reversible scavenging of dissolved Pb inputs and/or boundary exchange on the deep sea fan. Unless the mechanism transferring the Pb isotope signature into the deep ocean was itself highly sensitive to global climate cycles, and with the absence of a precessional signal in our Pb isotope data, we suggest that the Indian climate and its influence on basin-scale chemical weathering were strongly modulated by glacial versus interglacial boundary conditions
 
Date 2015-09-08T09:26:00Z
2015-09-08T09:26:00Z
2015
 
Type Journal Article
 
Identifier Earth and Planetary Science Letters, vol.424; 2015; 256-268
http://drs.nio.org/drs/handle/2264/4783
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2015] Elsevier
 
Publisher Elsevier