Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N
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...
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AGU (American Geophysical Union)
1993
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Online Access: | https://oceanrep.geomar.de/id/eprint/45882/ https://oceanrep.geomar.de/id/eprint/45882/1/Francois2.pdf https://doi.org/10.1029/93PA00784 |
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ftoceanrep:oai:oceanrep.geomar.de:45882 2023-05-15T18:25:54+02:00 Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N Francois, Roger Bacon, Michael P. Altabet, Mark A. Labeyrie, Laurent D. 1993 text https://oceanrep.geomar.de/id/eprint/45882/ https://oceanrep.geomar.de/id/eprint/45882/1/Francois2.pdf https://doi.org/10.1029/93PA00784 en eng AGU (American Geophysical Union) https://oceanrep.geomar.de/id/eprint/45882/1/Francois2.pdf Francois, R., Bacon, M. P., Altabet, M. A. and Labeyrie, L. D. (1993) Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N. Paleoceanography, 8 (5). pp. 611-629. DOI 10.1029/93PA00784 <https://doi.org/10.1029/93PA00784>. doi:10.1029/93PA00784 info:eu-repo/semantics/restrictedAccess Article PeerReviewed 1993 ftoceanrep https://doi.org/10.1029/93PA00784 2023-04-07T15:43:54Z 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 δ15N 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 δ15N 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 ... Article in Journal/Newspaper Southern Ocean OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Indian Southern Ocean Paleoceanography 8 5 611 629 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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ftoceanrep |
language |
English |
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 δ15N 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 δ15N 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 ... |
format |
Article in Journal/Newspaper |
author |
Francois, Roger Bacon, Michael P. Altabet, Mark A. Labeyrie, Laurent D. |
spellingShingle |
Francois, Roger Bacon, Michael P. Altabet, Mark A. Labeyrie, Laurent D. Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
author_facet |
Francois, Roger Bacon, Michael P. Altabet, Mark A. Labeyrie, Laurent D. |
author_sort |
Francois, Roger |
title |
Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
title_short |
Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
title_full |
Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
title_fullStr |
Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
title_full_unstemmed |
Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N |
title_sort |
glacial/interglacial changes in sediment rain rate in the sw indian sector of subantarctic waters as recorded by 230th, 231pa, u, and δ15n |
publisher |
AGU (American Geophysical Union) |
publishDate |
1993 |
url |
https://oceanrep.geomar.de/id/eprint/45882/ https://oceanrep.geomar.de/id/eprint/45882/1/Francois2.pdf https://doi.org/10.1029/93PA00784 |
geographic |
Indian Southern Ocean |
geographic_facet |
Indian Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://oceanrep.geomar.de/id/eprint/45882/1/Francois2.pdf Francois, R., Bacon, M. P., Altabet, M. A. and Labeyrie, L. D. (1993) Glacial/interglacial changes in sediment rain rate in the SW Indian Sector of subantarctic Waters as recorded by 230Th, 231Pa, U, and δ15N. Paleoceanography, 8 (5). pp. 611-629. DOI 10.1029/93PA00784 <https://doi.org/10.1029/93PA00784>. doi:10.1029/93PA00784 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1029/93PA00784 |
container_title |
Paleoceanography |
container_volume |
8 |
container_issue |
5 |
container_start_page |
611 |
op_container_end_page |
629 |
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1766207619727360000 |