Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142
Excess Thorium-230 (230Thxs) as a constant flux tracer is an essential tool for paleoceanographic studies, but its limitations for flux normalization are still a matter of debate. In regions of rapid sediment accumulation, it has been an open question if 230Thxs-normalized fluxes are biased by parti...
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ftdatacite:10.1594/pangaea.753876 2023-05-15T18:25:32+02:00 Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 Kretschmer, Sven Geibert, Walter Rutgers van der Loeff, Michiel M Mollenhauer, Gesine 2010 application/zip https://dx.doi.org/10.1594/pangaea.753876 https://doi.pangaea.de/10.1594/PANGAEA.753876 en eng PANGAEA - Data Publisher for Earth & Environmental Science https://dx.doi.org/10.1016/j.epsl.2010.03.021 Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY Giant box corer Gravity corer Kiel type M6/6 ANT-VIII/3 Meteor 1986 Polarstern Center for Marine Environmental Sciences MARUM Marine Geochemistry @ AWI AWI_MarGeoChem article Supplementary Collection of Datasets Collection 2010 ftdatacite https://doi.org/10.1594/pangaea.753876 https://doi.org/10.1016/j.epsl.2010.03.021 2022-02-09T12:04:35Z Excess Thorium-230 (230Thxs) as a constant flux tracer is an essential tool for paleoceanographic studies, but its limitations for flux normalization are still a matter of debate. In regions of rapid sediment accumulation, it has been an open question if 230Thxs-normalized fluxes are biased by particle sorting effects during sediment redistribution. In order to study the sorting effect of sediment transport on 230Thxs, we analyzed the specific activity of 230Thxs in different particle size classes of carbonate-rich sediments from the South East Atlantic, and of opal-rich sediments from the Atlantic sector of the Southern Ocean. At both sites, we compare the 230Thxs distribution in neighboring high vs. low accumulation settings. Two grain-size fractionation methods are explored.We find that the 230Thxs distribution is strongly grain size dependent, and 50-90% of the total 230Thxs inventory is concentrated in fine material smaller than 10 µm, which is preferentially deposited at the high accumulation sites. This leads to an overestimation of the focusing factor Psi, and consequently to an underestimation of the vertical flux rate at such sites. The distribution of authigenic uranium indicates that fine organic-rich material has also been re-deposited from lateral sources. If the particle sorting effect is considered in the flux calculations, it reduces the estimated extent of sediment focusing. In order to assess the maximum effect of particle sorting on Psi, we present an extreme scenario, in which we assume a lateral sediment supply of only fine material (< 10 µm). In this case, the focusing factor of the opal-rich core would be reduced from Psi = 5.9 to Psi = 3.2. In a more likely scenario, allowing silt-sized material to be transported, Psi is reduced from 5.9 to 5.0 if particle sorting is taken into consideration. The bias introduced by particle sorting is most important for strongly focused sediments.Comparing 230Thxs-normalized mass fluxes biased by sorting effects with uncorrected mass fluxes, we suggest that 230Thxs-normalization is still a valid tool to correct for lateral sediment redistribution. However, differences in focusing factors between core locations have to be evaluated carefully, taking the grain size distributions into consideration. Article in Journal/Newspaper Southern Ocean DataCite Metadata Store (German National Library of Science and Technology) Psi ENVELOPE(-63.000,-63.000,-64.300,-64.300) Southern Ocean Sven ENVELOPE(-60.200,-60.200,-63.733,-63.733) |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
Giant box corer Gravity corer Kiel type M6/6 ANT-VIII/3 Meteor 1986 Polarstern Center for Marine Environmental Sciences MARUM Marine Geochemistry @ AWI AWI_MarGeoChem |
spellingShingle |
Giant box corer Gravity corer Kiel type M6/6 ANT-VIII/3 Meteor 1986 Polarstern Center for Marine Environmental Sciences MARUM Marine Geochemistry @ AWI AWI_MarGeoChem Kretschmer, Sven Geibert, Walter Rutgers van der Loeff, Michiel M Mollenhauer, Gesine Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
topic_facet |
Giant box corer Gravity corer Kiel type M6/6 ANT-VIII/3 Meteor 1986 Polarstern Center for Marine Environmental Sciences MARUM Marine Geochemistry @ AWI AWI_MarGeoChem |
description |
Excess Thorium-230 (230Thxs) as a constant flux tracer is an essential tool for paleoceanographic studies, but its limitations for flux normalization are still a matter of debate. In regions of rapid sediment accumulation, it has been an open question if 230Thxs-normalized fluxes are biased by particle sorting effects during sediment redistribution. In order to study the sorting effect of sediment transport on 230Thxs, we analyzed the specific activity of 230Thxs in different particle size classes of carbonate-rich sediments from the South East Atlantic, and of opal-rich sediments from the Atlantic sector of the Southern Ocean. At both sites, we compare the 230Thxs distribution in neighboring high vs. low accumulation settings. Two grain-size fractionation methods are explored.We find that the 230Thxs distribution is strongly grain size dependent, and 50-90% of the total 230Thxs inventory is concentrated in fine material smaller than 10 µm, which is preferentially deposited at the high accumulation sites. This leads to an overestimation of the focusing factor Psi, and consequently to an underestimation of the vertical flux rate at such sites. The distribution of authigenic uranium indicates that fine organic-rich material has also been re-deposited from lateral sources. If the particle sorting effect is considered in the flux calculations, it reduces the estimated extent of sediment focusing. In order to assess the maximum effect of particle sorting on Psi, we present an extreme scenario, in which we assume a lateral sediment supply of only fine material (< 10 µm). In this case, the focusing factor of the opal-rich core would be reduced from Psi = 5.9 to Psi = 3.2. In a more likely scenario, allowing silt-sized material to be transported, Psi is reduced from 5.9 to 5.0 if particle sorting is taken into consideration. The bias introduced by particle sorting is most important for strongly focused sediments.Comparing 230Thxs-normalized mass fluxes biased by sorting effects with uncorrected mass fluxes, we suggest that 230Thxs-normalization is still a valid tool to correct for lateral sediment redistribution. However, differences in focusing factors between core locations have to be evaluated carefully, taking the grain size distributions into consideration. |
format |
Article in Journal/Newspaper |
author |
Kretschmer, Sven Geibert, Walter Rutgers van der Loeff, Michiel M Mollenhauer, Gesine |
author_facet |
Kretschmer, Sven Geibert, Walter Rutgers van der Loeff, Michiel M Mollenhauer, Gesine |
author_sort |
Kretschmer, Sven |
title |
Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
title_short |
Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
title_full |
Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
title_fullStr |
Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
title_full_unstemmed |
Grain size effects on excess Thorium-230 of sediment cores from the Southern Ocean and the South East Atlantic, supplement to: Kretschmer, Sven; Geibert, Walter; Rutgers van der Loeff, Michiel M; Mollenhauer, Gesine (2010): Grain size effects on Th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. Earth and Planetary Science Letters, 294(1-2), 131-142 |
title_sort |
grain size effects on excess thorium-230 of sediment cores from the southern ocean and the south east atlantic, supplement to: kretschmer, sven; geibert, walter; rutgers van der loeff, michiel m; mollenhauer, gesine (2010): grain size effects on th-230 (xs) inventories in opal-rich and carbonate-rich marine sediments. earth and planetary science letters, 294(1-2), 131-142 |
publisher |
PANGAEA - Data Publisher for Earth & Environmental Science |
publishDate |
2010 |
url |
https://dx.doi.org/10.1594/pangaea.753876 https://doi.pangaea.de/10.1594/PANGAEA.753876 |
long_lat |
ENVELOPE(-63.000,-63.000,-64.300,-64.300) ENVELOPE(-60.200,-60.200,-63.733,-63.733) |
geographic |
Psi Southern Ocean Sven |
geographic_facet |
Psi Southern Ocean Sven |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://dx.doi.org/10.1016/j.epsl.2010.03.021 |
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.753876 https://doi.org/10.1016/j.epsl.2010.03.021 |
_version_ |
1766207047508951040 |