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Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions

Luca Sitzia; Pascal Bertran; Adriana Sima; Philippe Chery; Alain Queffelec; Denis-Didier Rousseau

Title:
Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions
Author(s):
Sitzia, Luca
Bertran, Pascal
Sima, Adriana
Chery, Philippe
Queffelec, Alain
Rousseau, Denis-Didier
Date:
Type:
Articles
Department(s):
Lamont-Doherty Earth Observatory
Volume:
170
Persistent URL:
Book/Journal Title:
Quaternary Science Reviews
Geographic Area:
France
Abstract:
Dune pattern, grain-size gradients and geochemistry were used to investigate the sources and dynamics of aeolian deposition during the last glacial in southwest France. The coversands form widespread fields of low-amplitude ridges (zibars), whereas Younger Dryas parabolic dunes mainly concentrate in corridors and along rivers. Spatial modelling of grain-size gradients combined with geochemical analysis points to a genetic relationship between coversands and loess, the latter resulting primarily from dust produced by aeolian abrasion of the coversands. The alluvium of the Garonne river provided also significant amounts of dust at a more local scale. The geochemical composition of loess shows much lower scattering than that of coversands, due to stronger homogenisation during transport in the atmosphere. Overall, sandy loess and loess deposits decrease in thickness away from the coversands. Dune orientation and grain-size gradients suggest that the efficient winds blew respectively from the W to the NW during the glacial, and the W-SW during the Younger Dryas. A comparison between the wind directions derived from the proxy data and those provided by palaeoclimatic simulations suggests a change of the main transport season. Ground surface conditions and their evolution throughout the year, i.e. the length of the season with snow and frozen or moist topsoil, and the seasonal distribution of wind speeds able to cause deflation are thought to have been the main factors that controlled the transport season in the study area.
Subject(s):
Geochemistry
Sand dunes
Last Glacial Maximum
Eolian processes
Publisher DOI:
https://doi.org/10.1016/j.quascirev.2017.06.029
Item views
12
Metadata:
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Suggested Citation:
Luca Sitzia, Pascal Bertran, Adriana Sima, Philippe Chery, Alain Queffelec, Denis-Didier Rousseau, , Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions, Columbia University Academic Commons, .

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