Final published version
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A Multi-Proxy Approach to Unravel Late Pleistocene Sediment Flux and Bottom Water Conditions in the Western South Atlantic Ocean
AU - Mathias, G.L.
AU - Roud, S.C.
AU - Chiessi, C.M.
AU - Campos, M.C.
AU - Dias, B.B.
AU - Santos, T.P.
AU - Albuquerque, A.L.S.
AU - Toledo, F.A.L.
AU - Costa, K.B.
AU - Maher, B.A.
PY - 2021/4/30
Y1 - 2021/4/30
N2 - Magnetic signals in deep-sea sediments have the potential to unravel past continental environmental changes, via changes in primary terrigenous magnetic supply, but also record past marine environmental conditions, via in situ formation of secondary magnetic minerals, particularly when complemented by independent proxies. By combining environmagnetic, geochemical, and siliciclastic grain size data, we investigated marine sediment core GL-1090 (24.92°S, 42.51°W, 2,225 m water depth) aiming to unravel changes in terrigenous sediment input and bottom water conditions during the last ∼184 ka at the western South Atlantic middepth. The Al/Si, Fe/κ and siliciclastic grain size data show that terrigenous sediments at this core location derived from the Plata River (southeastern South America). This material was transported northwards by the Brazilian Coastal Current and their delivery to our core site was modulated by sea-level oscillations. Periods of low sea-level were characterized by the input of coarser and more abundant terrigenous sediments. Environmagnetic parameters indicate significant downcore variations in the magnetic domain state, which we interpret as changes in the content of biogenic magnetite following glacial-interglacial cycles. Coeval negative excursions in magnetic grain size and benthic δ13C suggests that concentrations of single domain magnetite (possibly magnetotactic bacterial magnetite) vary in response to middepth water ventilation. We suggest that reduced ventilation in the middepth western South Atlantic bottom waters during peak glaciations triggered a decrease in the production of biogenic magnetite. Peak glaciations were, in turn, linked with increases in the residence time of North Atlantic Deep Water (or its glacial counterpart).
AB - Magnetic signals in deep-sea sediments have the potential to unravel past continental environmental changes, via changes in primary terrigenous magnetic supply, but also record past marine environmental conditions, via in situ formation of secondary magnetic minerals, particularly when complemented by independent proxies. By combining environmagnetic, geochemical, and siliciclastic grain size data, we investigated marine sediment core GL-1090 (24.92°S, 42.51°W, 2,225 m water depth) aiming to unravel changes in terrigenous sediment input and bottom water conditions during the last ∼184 ka at the western South Atlantic middepth. The Al/Si, Fe/κ and siliciclastic grain size data show that terrigenous sediments at this core location derived from the Plata River (southeastern South America). This material was transported northwards by the Brazilian Coastal Current and their delivery to our core site was modulated by sea-level oscillations. Periods of low sea-level were characterized by the input of coarser and more abundant terrigenous sediments. Environmagnetic parameters indicate significant downcore variations in the magnetic domain state, which we interpret as changes in the content of biogenic magnetite following glacial-interglacial cycles. Coeval negative excursions in magnetic grain size and benthic δ13C suggests that concentrations of single domain magnetite (possibly magnetotactic bacterial magnetite) vary in response to middepth water ventilation. We suggest that reduced ventilation in the middepth western South Atlantic bottom waters during peak glaciations triggered a decrease in the production of biogenic magnetite. Peak glaciations were, in turn, linked with increases in the residence time of North Atlantic Deep Water (or its glacial counterpart).
KW - biogenic magnetite
KW - environmental magnetism
KW - paleoceanography
KW - paleoclimatology
KW - western south Atlantic
KW - bottom water
KW - grain size
KW - magnetite
KW - marine sediment
KW - North Atlantic Deep Water
KW - Pleistocene
KW - residence time
KW - sea level change
KW - sediment core
KW - Atlantic Ocean
KW - Atlantic Ocean (North)
KW - Atlantic Ocean (South)
KW - Bacteria (microorganisms)
U2 - 10.1029/2020PA004058
DO - 10.1029/2020PA004058
M3 - Journal article
VL - 36
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
IS - 4
M1 - e2020PA004058
ER -