Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge
Recently, the use of “extinction ages” of excesses in U-series isotopes (230Thxs, 231Paxs) has been proposed for the setting of benchmark ages of up to ~350 and ~150 ka, respectively, in late Quaternary marine records from the Arctic Ocean. However, the use of such U-series-based chronostratigraphic...
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ftunivquebec:oai:archipel.uqam.ca:15444 2023-07-16T03:55:31+02:00 Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge Purcell, Karl Hillaire-Marcel, Claude de Vernal, Anne Ghaleb, Bassam Stein, Ruediger 2022 application/pdf http://archipel.uqam.ca/15444/1/pii/S0025322722000731 en eng http://archipel.uqam.ca/15444/ https://doi.org/10.1016/j.margeo.2022.106802 doi.org/10.1016/j.margeo.2022.106802 http://archipel.uqam.ca/15444/1/pii/S0025322722000731 Purcell, Karl; Hillaire-Marcel, Claude; de Vernal, Anne; Ghaleb, Bassam et Stein, Ruediger (2022). « Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge ». Marine Geology, 448, p. 106802. Arctique géologie sediments Quaternaire Article de revue scientifique PeerReviewed 2022 ftunivquebec https://doi.org/10.1016/j.margeo.2022.106802 2023-06-24T23:22:54Z Recently, the use of “extinction ages” of excesses in U-series isotopes (230Thxs, 231Paxs) has been proposed for the setting of benchmark ages of up to ~350 and ~150 ka, respectively, in late Quaternary marine records from the Arctic Ocean. However, the use of such U-series-based chronostratigraphic approaches has some limitations. These limitations are illustrated by U-series measurements in a cored sequence from the southern Lomonosov Ridge (PS2757). In this core, the final measurable excess in 230Th (230Thxs), strictly linked to the sedimentary flux of this isotope from the overlying water column (230Thxs-marine), is observed at a depth of ~590 cm downcore. An “extinction age” of ~230 ka can be estimated for the residual 230Thxs at this depth. It approximately matches the Marine Isotope Stage 7/8 transition. Below this transition, strong redox gradients constrained by a layer enriched in organic carbon resulted in a late-diagenetic relocation of uranium leached from detrital minerals in the over- and underlying oxidized layers. This uranium relocation resulted in large amplitude radioactive disequilibria within a core section otherwise characterized by near secular equilibria between inventories of 238U series isotopes, implying an age greater than the “230Thxs-marine extinction age” for the whole section. In the overlying part of the core, the 230Thxs distribution correlates with other 230Thxs-documented sequences from the Central Arctic Ocean. 230Thxs can be thus used for stratigraphic correlations between the relatively low sedimentation rate marine sequences of this basin, over the last two or three glacial cycles, but special attention to potential diagenetic effects is recommended. Moreover, as for a given 230Thxs-marine flux at the seafloor, initial 230Thxs-values are broadly inversely-proportional to the sedimentation rate, the resulting estimates of 230Thxs “extinction age” vary accordingly. This variability restricts the chronostratigraphic use of 230Thxs to sequences with relatively low ... Text Arctic Arctic Arctic Ocean Arctique* Lomonosov Ridge UQAM - Université du Québec à Montréal: archipel Arctic Arctic Ocean Marine Geology 448 106802 |
institution |
Open Polar |
collection |
UQAM - Université du Québec à Montréal: archipel |
op_collection_id |
ftunivquebec |
language |
English |
topic |
Arctique géologie sediments Quaternaire |
spellingShingle |
Arctique géologie sediments Quaternaire Purcell, Karl Hillaire-Marcel, Claude de Vernal, Anne Ghaleb, Bassam Stein, Ruediger Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
topic_facet |
Arctique géologie sediments Quaternaire |
description |
Recently, the use of “extinction ages” of excesses in U-series isotopes (230Thxs, 231Paxs) has been proposed for the setting of benchmark ages of up to ~350 and ~150 ka, respectively, in late Quaternary marine records from the Arctic Ocean. However, the use of such U-series-based chronostratigraphic approaches has some limitations. These limitations are illustrated by U-series measurements in a cored sequence from the southern Lomonosov Ridge (PS2757). In this core, the final measurable excess in 230Th (230Thxs), strictly linked to the sedimentary flux of this isotope from the overlying water column (230Thxs-marine), is observed at a depth of ~590 cm downcore. An “extinction age” of ~230 ka can be estimated for the residual 230Thxs at this depth. It approximately matches the Marine Isotope Stage 7/8 transition. Below this transition, strong redox gradients constrained by a layer enriched in organic carbon resulted in a late-diagenetic relocation of uranium leached from detrital minerals in the over- and underlying oxidized layers. This uranium relocation resulted in large amplitude radioactive disequilibria within a core section otherwise characterized by near secular equilibria between inventories of 238U series isotopes, implying an age greater than the “230Thxs-marine extinction age” for the whole section. In the overlying part of the core, the 230Thxs distribution correlates with other 230Thxs-documented sequences from the Central Arctic Ocean. 230Thxs can be thus used for stratigraphic correlations between the relatively low sedimentation rate marine sequences of this basin, over the last two or three glacial cycles, but special attention to potential diagenetic effects is recommended. Moreover, as for a given 230Thxs-marine flux at the seafloor, initial 230Thxs-values are broadly inversely-proportional to the sedimentation rate, the resulting estimates of 230Thxs “extinction age” vary accordingly. This variability restricts the chronostratigraphic use of 230Thxs to sequences with relatively low ... |
format |
Text |
author |
Purcell, Karl Hillaire-Marcel, Claude de Vernal, Anne Ghaleb, Bassam Stein, Ruediger |
author_facet |
Purcell, Karl Hillaire-Marcel, Claude de Vernal, Anne Ghaleb, Bassam Stein, Ruediger |
author_sort |
Purcell, Karl |
title |
Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
title_short |
Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
title_full |
Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
title_fullStr |
Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
title_full_unstemmed |
Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge |
title_sort |
potential and limitation of 230th-excess as a chronostratigraphic tool for late quaternary arctic ocean sediment studies: an example from the southern lomonosov ridge |
publishDate |
2022 |
url |
http://archipel.uqam.ca/15444/1/pii/S0025322722000731 |
geographic |
Arctic Arctic Ocean |
geographic_facet |
Arctic Arctic Ocean |
genre |
Arctic Arctic Arctic Ocean Arctique* Lomonosov Ridge |
genre_facet |
Arctic Arctic Arctic Ocean Arctique* Lomonosov Ridge |
op_relation |
http://archipel.uqam.ca/15444/ https://doi.org/10.1016/j.margeo.2022.106802 doi.org/10.1016/j.margeo.2022.106802 http://archipel.uqam.ca/15444/1/pii/S0025322722000731 Purcell, Karl; Hillaire-Marcel, Claude; de Vernal, Anne; Ghaleb, Bassam et Stein, Ruediger (2022). « Potential and limitation of 230Th-excess as a chronostratigraphic tool for late Quaternary Arctic Ocean sediment studies: An example from the Southern Lomonosov Ridge ». Marine Geology, 448, p. 106802. |
op_doi |
https://doi.org/10.1016/j.margeo.2022.106802 |
container_title |
Marine Geology |
container_volume |
448 |
container_start_page |
106802 |
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1771541751877599232 |