U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia
The estimation of sediment transfer times remains a challenge to our understanding of sediment budgets and the relationships between erosion and climate. Uranium (U) and thorium (Th) isotope disequilibria offer a means of more robustly constraining sediment transfer times. Here, we present new u...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/6/121/2018/esurf-6-121-2018.pdf |
| _version_ | 1819211081199910912 |
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| author | A. Cogez F. Herman É. Pelt T. Reuschlé G. Morvan C. M. Darvill K. P. Norton M. Christl L. Märki F. Chabaux |
| author_facet | A. Cogez F. Herman É. Pelt T. Reuschlé G. Morvan C. M. Darvill K. P. Norton M. Christl L. Märki F. Chabaux |
| author_sort | A. Cogez |
| collection | DOAJ |
| description | The estimation of sediment transfer times remains a challenge to our
understanding of sediment budgets and the relationships between
erosion and climate. Uranium (U) and thorium (Th) isotope
disequilibria offer a means of more robustly constraining sediment
transfer times. Here, we present new uranium and thorium
disequilibrium data for a series of nested moraines around Lago
Buenos Aires in Argentine Patagonia. The glacial chronology for the
area is constrained using in situ cosmogenic <sup>10</sup>Be analysis
of glacial outwash. Sediment transfer times within the periglacial
domain were estimated by comparing the deposition ages of moraines
to the theoretical age of sediment production, i.e., the comminution
age inferred from U disequilibrium data and recoil loss factor
estimates. Our data show first that the classical comminution age
approach must include weathering processes accounted for by
measuring Th disequilibrium. Second, our combined data suggest that
the pre-deposition history of the moraine sediments is not
negligible, as evidenced by the large disequilibrium of the youngest
moraines despite the equilibrium of the corresponding glacial
flour. Monte Carlo simulations suggest that weathering was more
intense before the deposition of the moraines and that the transfer
time of the fine sediments to the moraines was on the order of
100–200 kyr. Long transfer times could result from a combination of
long sediment residence times in the proglacial lake (recurrence
time of a glacial cycle) and the remobilization of sediments from
moraines deposited during previous glacial cycles. <sup>10</sup>Be
data suggest that some glacial cycles are absent from the preserved
moraine record (seemingly every second cycle), supporting a model of
reworking moraines and/or fluctuations in the extent of glacial
advances. The chronological pattern is consistent with the U–Th
disequilibrium data and the 100–200 kyr transfer time. This long
transfer time raises the question of the proportion of freshly
eroded sediments that escape (or not) the proglacial environments
during glacial periods. |
| first_indexed | 2024-12-23T06:21:24Z |
| format | Article |
| id | doaj.art-8d755d40901947a495f640bd29f8a5eb |
| institution | Directory Open Access Journal |
| issn | 2196-6311 2196-632X |
| language | English |
| last_indexed | 2024-12-23T06:21:24Z |
| publishDate | 2018-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Earth Surface Dynamics |
| spelling | doaj.art-8d755d40901947a495f640bd29f8a5eb2022-12-21T17:57:11ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2018-03-01612114010.5194/esurf-6-121-2018U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, PatagoniaA. Cogez0F. Herman1É. Pelt2T. Reuschlé3G. Morvan4C. M. Darvill5K. P. Norton6M. Christl7L. Märki8F. Chabaux9University of Lausanne, Institut des Dynamiques de la Surface Terrestre, Quartier Unil-Mouline, Bâtiment Geopolis, 1015 Lausanne, SwitzerlandUniversity of Lausanne, Institut des Dynamiques de la Surface Terrestre, Quartier Unil-Mouline, Bâtiment Geopolis, 1015 Lausanne, SwitzerlandUniversity of Strabourg, Laboratoire d'Hydrologie et de Géochimie de Strasbourg, Strasbourg, FranceUniversity of Strabourg, Institut de Physique du Globe de Strasbourg, Strasbourg, FranceUniversity of Strabourg, Laboratoire d'Hydrologie et de Géochimie de Strasbourg, Strasbourg, FranceGeography Program and Natural Resources and Environmental Studies Institute, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, CanadaVictoria Univeristy of Wellington, School of Geography, Environment, and Earth Sciences, Wellington, New ZealandSwiss Federal Institute of Zürich, Ion Beam Physics Laboratory, Zürich, SwitzerlandUniversity of Lausanne, Institut des Dynamiques de la Surface Terrestre, Quartier Unil-Mouline, Bâtiment Geopolis, 1015 Lausanne, SwitzerlandUniversity of Strabourg, Laboratoire d'Hydrologie et de Géochimie de Strasbourg, Strasbourg, FranceThe estimation of sediment transfer times remains a challenge to our understanding of sediment budgets and the relationships between erosion and climate. Uranium (U) and thorium (Th) isotope disequilibria offer a means of more robustly constraining sediment transfer times. Here, we present new uranium and thorium disequilibrium data for a series of nested moraines around Lago Buenos Aires in Argentine Patagonia. The glacial chronology for the area is constrained using in situ cosmogenic <sup>10</sup>Be analysis of glacial outwash. Sediment transfer times within the periglacial domain were estimated by comparing the deposition ages of moraines to the theoretical age of sediment production, i.e., the comminution age inferred from U disequilibrium data and recoil loss factor estimates. Our data show first that the classical comminution age approach must include weathering processes accounted for by measuring Th disequilibrium. Second, our combined data suggest that the pre-deposition history of the moraine sediments is not negligible, as evidenced by the large disequilibrium of the youngest moraines despite the equilibrium of the corresponding glacial flour. Monte Carlo simulations suggest that weathering was more intense before the deposition of the moraines and that the transfer time of the fine sediments to the moraines was on the order of 100–200 kyr. Long transfer times could result from a combination of long sediment residence times in the proglacial lake (recurrence time of a glacial cycle) and the remobilization of sediments from moraines deposited during previous glacial cycles. <sup>10</sup>Be data suggest that some glacial cycles are absent from the preserved moraine record (seemingly every second cycle), supporting a model of reworking moraines and/or fluctuations in the extent of glacial advances. The chronological pattern is consistent with the U–Th disequilibrium data and the 100–200 kyr transfer time. This long transfer time raises the question of the proportion of freshly eroded sediments that escape (or not) the proglacial environments during glacial periods.https://www.earth-surf-dynam.net/6/121/2018/esurf-6-121-2018.pdf |
| spellingShingle | A. Cogez F. Herman É. Pelt T. Reuschlé G. Morvan C. M. Darvill K. P. Norton M. Christl L. Märki F. Chabaux U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia Earth Surface Dynamics |
| title | U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| title_full | U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| title_fullStr | U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| title_full_unstemmed | U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| title_short | U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| title_sort | u th and sup 10 sup be constraints on sediment recycling in proglacial settings lago buenos aires patagonia |
| url | https://www.earth-surf-dynam.net/6/121/2018/esurf-6-121-2018.pdf |
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