Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps
<p>Marine sedimentary archives are well dated and often span several glacial cycles; cosmogenic <span class="inline-formula"><sup>10</sup>Be</span> concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-12-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/7/1059/2019/esurf-7-1059-2019.pdf |
| _version_ | 1828433385807151104 |
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| author | A. Mariotti P.-H. Blard J. Charreau C. Petit S. Molliex S. Molliex the ASTER Team the ASTER Team |
| author_facet | A. Mariotti P.-H. Blard J. Charreau C. Petit S. Molliex S. Molliex the ASTER Team the ASTER Team |
| author_sort | A. Mariotti |
| collection | DOAJ |
| description | <p>Marine sedimentary archives are well dated and often span several glacial
cycles; cosmogenic <span class="inline-formula"><sup>10</sup>Be</span> concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past denudation rates. However, these archives often comprise sediments much finer (<span class="inline-formula"><250</span> <span class="inline-formula">µ</span>m) than typically analyzed in <span class="inline-formula"><sup>10</sup>Be</span> studies, and few studies have measured <span class="inline-formula"><sup>10</sup>Be</span> concentrations in quartz grains smaller than 100 <span class="inline-formula">µ</span>m or assessed the impacts of mixing, grain size, and interannual variability on the <span class="inline-formula"><sup>10</sup>Be</span> concentrations of such fine-grained sediments. Here, we analyzed the in situ cosmogenic <span class="inline-formula"><sup>10</sup>Be</span> concentrations of quartz grains in the 50–100 and 100–250 <span class="inline-formula">µ</span>m size fractions of sediments from the Var basin (southern French Alps) to test the reliability of denudation rates derived from <span class="inline-formula"><sup>10</sup>Be</span> analyses of fine sands. The Var basin has a short transfer zone and highly variable morphology, climate, and geology, and we test the impact of these parameters on the observed <span class="inline-formula"><sup>10</sup>Be</span> concentrations. Both analyzed size fractions returned similar <span class="inline-formula"><sup>10</sup>Be</span> concentrations in downstream locations, notably at the Var's
outlet, where concentrations ranged from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">4.02</mn><mo>±</mo><mn mathvariant="normal">0.78</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mn mathvariant="normal">4</mn></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="91pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="aebcf34e8c69a9594bf1900d9f6c1bce"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-7-1059-2019-ie00001.svg" width="91pt" height="15pt" src="esurf-7-1059-2019-ie00001.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">4.40</mn><mo>±</mo><mn mathvariant="normal">0.64</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mn mathvariant="normal">4</mn></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="91pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b28fe01a0209b602a275e5d0e96f5c22"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-7-1059-2019-ie00002.svg" width="91pt" height="15pt" src="esurf-7-1059-2019-ie00002.png"/></svg:svg></span></span> atoms g<span class="inline-formula"><sup>−1</sup></span> of quartz. By comparing expected and observed <span class="inline-formula"><sup>10</sup>Be</span> concentrations at three major river junctions, we interpret that sediment mixing is efficient throughout the Var basin. We resampled four key locations 1 year later, and despite variable climatic parameters during that period, interannual <span class="inline-formula"><sup>10</sup>Be</span> concentrations were in agreement within uncertainties, except for one upper subbasin. The <span class="inline-formula"><sup>10</sup>Be</span>-derived denudation rates of Var subbasins range from <span class="inline-formula">0.10±0.01</span> to <span class="inline-formula">0.57±0.09</span> mm yr<span class="inline-formula"><sup>−1</sup></span>, and spatial variations are primarily controlled by the average subbasin slope. The integrated denudation rate of the entire Var basin is <span class="inline-formula">0.24±0.04</span> mm yr<span class="inline-formula"><sup>−1</sup></span>, in agreement with other methods. Our results demonstrate that fine-grained sediments (50–250 <span class="inline-formula">µ</span>m) may return accurate denudation rates and are thus potentially suitable targets for future <span class="inline-formula"><sup>10</sup>Be</span> applications, such as studies of paleo-denudation rates using offshore sediments.</p> |
| first_indexed | 2024-12-10T18:34:48Z |
| format | Article |
| id | doaj.art-a59ccf7ce52242f08c52efc20b54b32d |
| institution | Directory Open Access Journal |
| issn | 2196-6311 2196-632X |
| language | English |
| last_indexed | 2024-12-10T18:34:48Z |
| publishDate | 2019-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Earth Surface Dynamics |
| spelling | doaj.art-a59ccf7ce52242f08c52efc20b54b32d2022-12-22T01:37:51ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2019-12-0171059107410.5194/esurf-7-1059-2019Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French AlpsA. Mariotti0P.-H. Blard1J. Charreau2C. Petit3S. Molliex4S. Molliex5the ASTER Team6the ASTER Team7Centre de Recherches Pétrographiques et Géochimiques (CRPG), CNRS, Université de Lorraine, UMR 7358, 54500 Vandoeuvre-lès-Nancy, FranceCentre de Recherches Pétrographiques et Géochimiques (CRPG), CNRS, Université de Lorraine, UMR 7358, 54500 Vandoeuvre-lès-Nancy, FranceCentre de Recherches Pétrographiques et Géochimiques (CRPG), CNRS, Université de Lorraine, UMR 7358, 54500 Vandoeuvre-lès-Nancy, FranceGéoazur, Université de Nice, 06905 Sophia Antipolis, FranceCentre de Recherches Pétrographiques et Géochimiques (CRPG), CNRS, Université de Lorraine, UMR 7358, 54500 Vandoeuvre-lès-Nancy, FranceLaboratoire Géosciences Océan, Institut Universitaire Européen de la Mer, 29280 Plouzané, FranceAix-Marseille Université, CNRS, IRD, INRA, Coll France, UM 34 CEREGE, Technopôle de l'Environnement Arbois-Méditerranée, BP80, 13545 Aix-en-Provence, FranceA full list of authors and their affiliations appears at the end of the paper.<p>Marine sedimentary archives are well dated and often span several glacial cycles; cosmogenic <span class="inline-formula"><sup>10</sup>Be</span> concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past denudation rates. However, these archives often comprise sediments much finer (<span class="inline-formula"><250</span> <span class="inline-formula">µ</span>m) than typically analyzed in <span class="inline-formula"><sup>10</sup>Be</span> studies, and few studies have measured <span class="inline-formula"><sup>10</sup>Be</span> concentrations in quartz grains smaller than 100 <span class="inline-formula">µ</span>m or assessed the impacts of mixing, grain size, and interannual variability on the <span class="inline-formula"><sup>10</sup>Be</span> concentrations of such fine-grained sediments. Here, we analyzed the in situ cosmogenic <span class="inline-formula"><sup>10</sup>Be</span> concentrations of quartz grains in the 50–100 and 100–250 <span class="inline-formula">µ</span>m size fractions of sediments from the Var basin (southern French Alps) to test the reliability of denudation rates derived from <span class="inline-formula"><sup>10</sup>Be</span> analyses of fine sands. The Var basin has a short transfer zone and highly variable morphology, climate, and geology, and we test the impact of these parameters on the observed <span class="inline-formula"><sup>10</sup>Be</span> concentrations. Both analyzed size fractions returned similar <span class="inline-formula"><sup>10</sup>Be</span> concentrations in downstream locations, notably at the Var's outlet, where concentrations ranged from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">4.02</mn><mo>±</mo><mn mathvariant="normal">0.78</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mn mathvariant="normal">4</mn></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="91pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="aebcf34e8c69a9594bf1900d9f6c1bce"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-7-1059-2019-ie00001.svg" width="91pt" height="15pt" src="esurf-7-1059-2019-ie00001.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">4.40</mn><mo>±</mo><mn mathvariant="normal">0.64</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mn mathvariant="normal">4</mn></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="91pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b28fe01a0209b602a275e5d0e96f5c22"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-7-1059-2019-ie00002.svg" width="91pt" height="15pt" src="esurf-7-1059-2019-ie00002.png"/></svg:svg></span></span> atoms g<span class="inline-formula"><sup>−1</sup></span> of quartz. By comparing expected and observed <span class="inline-formula"><sup>10</sup>Be</span> concentrations at three major river junctions, we interpret that sediment mixing is efficient throughout the Var basin. We resampled four key locations 1 year later, and despite variable climatic parameters during that period, interannual <span class="inline-formula"><sup>10</sup>Be</span> concentrations were in agreement within uncertainties, except for one upper subbasin. The <span class="inline-formula"><sup>10</sup>Be</span>-derived denudation rates of Var subbasins range from <span class="inline-formula">0.10±0.01</span> to <span class="inline-formula">0.57±0.09</span> mm yr<span class="inline-formula"><sup>−1</sup></span>, and spatial variations are primarily controlled by the average subbasin slope. The integrated denudation rate of the entire Var basin is <span class="inline-formula">0.24±0.04</span> mm yr<span class="inline-formula"><sup>−1</sup></span>, in agreement with other methods. Our results demonstrate that fine-grained sediments (50–250 <span class="inline-formula">µ</span>m) may return accurate denudation rates and are thus potentially suitable targets for future <span class="inline-formula"><sup>10</sup>Be</span> applications, such as studies of paleo-denudation rates using offshore sediments.</p>https://www.earth-surf-dynam.net/7/1059/2019/esurf-7-1059-2019.pdf |
| spellingShingle | A. Mariotti P.-H. Blard J. Charreau C. Petit S. Molliex S. Molliex the ASTER Team the ASTER Team Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps Earth Surface Dynamics |
| title | Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps |
| title_full | Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps |
| title_fullStr | Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps |
| title_full_unstemmed | Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps |
| title_short | Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps |
| title_sort | denudation systematics inferred from in situ cosmogenic sup 10 sup be concentrations in fine 50 100 thinsp µm and medium 100 250 thinsp µm sediments of the var river basin southern french alps |
| url | https://www.earth-surf-dynam.net/7/1059/2019/esurf-7-1059-2019.pdf |
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