Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629
High-resolution records of opal, carbonate, and terrigenous fluxes have been obtained from a high-sedimentation rate core (MD84-527: 43°50'S; 51°19'E; 3269 m) by normalization to 230Th. This method estimates paleofluxes to the seafloor on a point-by-point basis and distinguishes changes in...
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ftdatacite:10.1594/pangaea.730380 2023-05-15T18:26:02+02:00 Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 Francois, Roger Bacon, Michael P Altabet, Mark A Labeyrie, Laurent D 1993 application/zip https://dx.doi.org/10.1594/pangaea.730380 https://doi.pangaea.de/10.1594/PANGAEA.730380 en eng PANGAEA - Data Publisher for Earth & Environmental Science https://dx.doi.org/10.1029/93pa00784 Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY Piston corer MD38 Marion Dufresne 1972 Silicon Cycling in the World Ocean SINOPS Supplementary Collection of Datasets Collection article 1993 ftdatacite https://doi.org/10.1594/pangaea.730380 https://doi.org/10.1029/93pa00784 2022-02-08T16:24:46Z High-resolution records of opal, carbonate, and terrigenous fluxes have been obtained from a high-sedimentation rate core (MD84-527: 43°50'S; 51°19'E; 3269 m) by normalization to 230Th. This method estimates paleofluxes to the seafloor on a point-by-point basis and distinguishes changes in sediment accumulation due to variations in vertical rain rates from those due to changes in syndepositional sediment redistribution by bottom currents. We also measured sediment delta15N to evaluate the changes in nitrate utilization in the overlying surface waters associated with paleoflux variations. Our results show that opal accumulation rates on the seafloor during the Holocene and stage 3, based on 14C dating, were respectively tenfold and fivefold higher than the vertical rain rates, At this particular location, changes in opal accumulation on the seafloor appear to be mainly controlled by sediment redistribution by bottom currents rather than variations in opal fluxes from the overlying water column. Correction for syndepositional sediment redistribution and the improved time resolution that can be achieved by normalization to 230Th disclose important variations in opal rain rates. We found relatively high but variable opal paleoflux during stage 3, with two maxima centered at 36 and 30 kyr B.P., low opal paleoflux during stage 2 and deglaciation and a pronounced maximum during the early Holocene, We interpret this record as reflecting variations in opal production rates associated with climate-induced latitudinal migration of the southern ocean frontal system. Sediments deposited during periods of high opal paleoflux also have high authigenic U concentrations, suggesting more reducing conditions in the sediment, and high Pa-231/Th-230 ratios, suggesting increased scavenging from the water column. Sediment delta15N is circa 1.5 per mil higher during isotopic stage 2 and deglaciation. The low opal rain rates recorded during that period appear to have been associated with increased nitrate depletion. This suggests that opal paleofluxes do not simply reflect latitudinal migration of the frontal system but also changes in the structure of the upper water column. Increased stratification during isotopic stage 2 and deglaciation could have been produced by a meltwater lid, leading to lower nitrate supply rates to surface waters. Article in Journal/Newspaper Southern Ocean DataCite Metadata Store (German National Library of Science and Technology) Indian Southern Ocean |
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DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
Piston corer MD38 Marion Dufresne 1972 Silicon Cycling in the World Ocean SINOPS |
spellingShingle |
Piston corer MD38 Marion Dufresne 1972 Silicon Cycling in the World Ocean SINOPS Francois, Roger Bacon, Michael P Altabet, Mark A Labeyrie, Laurent D Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
topic_facet |
Piston corer MD38 Marion Dufresne 1972 Silicon Cycling in the World Ocean SINOPS |
description |
High-resolution records of opal, carbonate, and terrigenous fluxes have been obtained from a high-sedimentation rate core (MD84-527: 43°50'S; 51°19'E; 3269 m) by normalization to 230Th. This method estimates paleofluxes to the seafloor on a point-by-point basis and distinguishes changes in sediment accumulation due to variations in vertical rain rates from those due to changes in syndepositional sediment redistribution by bottom currents. We also measured sediment delta15N to evaluate the changes in nitrate utilization in the overlying surface waters associated with paleoflux variations. Our results show that opal accumulation rates on the seafloor during the Holocene and stage 3, based on 14C dating, were respectively tenfold and fivefold higher than the vertical rain rates, At this particular location, changes in opal accumulation on the seafloor appear to be mainly controlled by sediment redistribution by bottom currents rather than variations in opal fluxes from the overlying water column. Correction for syndepositional sediment redistribution and the improved time resolution that can be achieved by normalization to 230Th disclose important variations in opal rain rates. We found relatively high but variable opal paleoflux during stage 3, with two maxima centered at 36 and 30 kyr B.P., low opal paleoflux during stage 2 and deglaciation and a pronounced maximum during the early Holocene, We interpret this record as reflecting variations in opal production rates associated with climate-induced latitudinal migration of the southern ocean frontal system. Sediments deposited during periods of high opal paleoflux also have high authigenic U concentrations, suggesting more reducing conditions in the sediment, and high Pa-231/Th-230 ratios, suggesting increased scavenging from the water column. Sediment delta15N is circa 1.5 per mil higher during isotopic stage 2 and deglaciation. The low opal rain rates recorded during that period appear to have been associated with increased nitrate depletion. This suggests that opal paleofluxes do not simply reflect latitudinal migration of the frontal system but also changes in the structure of the upper water column. Increased stratification during isotopic stage 2 and deglaciation could have been produced by a meltwater lid, leading to lower nitrate supply rates to surface waters. |
format |
Article in Journal/Newspaper |
author |
Francois, Roger Bacon, Michael P Altabet, Mark A Labeyrie, Laurent D |
author_facet |
Francois, Roger Bacon, Michael P Altabet, Mark A Labeyrie, Laurent D |
author_sort |
Francois, Roger |
title |
Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
title_short |
Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
title_full |
Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
title_fullStr |
Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
title_full_unstemmed |
Sedimentology and Th, Pa, U, and N isotopic composition of core MD84-527, supplement to: Francois, Roger; Bacon, Michael P; Altabet, Mark A; Labeyrie, Laurent D (1993): Glacial/interglacial changes in sediment rain rate in the SW Indian sector of subantarctic waters as recorded by 230Th, 231Pa, U and d15N. Paleoceanography, 8(5), 611-629 |
title_sort |
sedimentology and th, pa, u, and n isotopic composition of core md84-527, supplement to: francois, roger; bacon, michael p; altabet, mark a; labeyrie, laurent d (1993): glacial/interglacial changes in sediment rain rate in the sw indian sector of subantarctic waters as recorded by 230th, 231pa, u and d15n. paleoceanography, 8(5), 611-629 |
publisher |
PANGAEA - Data Publisher for Earth & Environmental Science |
publishDate |
1993 |
url |
https://dx.doi.org/10.1594/pangaea.730380 https://doi.pangaea.de/10.1594/PANGAEA.730380 |
geographic |
Indian Southern Ocean |
geographic_facet |
Indian Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://dx.doi.org/10.1029/93pa00784 |
op_rights |
Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1594/pangaea.730380 https://doi.org/10.1029/93pa00784 |
_version_ |
1766207835509620736 |