Architecture of the lower terraces and evolution of the Dordogne River at Bergerac (south-west France) during the last glacial-interglacial cycle
Autor: | Norbert Mercier, Colette Sirieix, Marine Frouin, Luca Sitzia, Fabien Naessens, Pascal Bertran, Alain Queffelec, Frédéric Prodeo |
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Rok vydání: | 2013 |
Předmět: |
Marine isotope stage
010506 paleontology geography Eemian geography.geographical_feature_category Paleontology 010502 geochemistry & geophysics 01 natural sciences Arts and Humanities (miscellaneous) Terrace (geology) Interglacial Earth and Planetary Sciences (miscellaneous) Overbank Glacial period River regime Geomorphology Geology Holocene 0105 earth and related environmental sciences |
Zdroj: | Journal of Quaternary Science. 28:605-616 |
ISSN: | 0267-8179 |
Popis: | The lower terraces of the Dordogne River at Bergerac (south-west France) were studied in detail using cores, trenches, ground penetrating radar profiles, and 14 C, optically stimulated luminescence and infrared stimulated luminescence dating. This study shows that the lowest terrace (Fx) is made up of two major lithostratigraphic units: (i) dominantly horizontal gravel strata interpreted as compound bar deposits in a braided river, which pre-date 18-17 ka, and (ii) thick lateral accretion gravel units (point bars) formed in an anabranching river during the Late Pleniglacial and Lateglacial. Most of the anabranching channels were abandoned at ca. 11-10 ka following shrinkage of the river bed into a single meandering channel and were partially filled by gyttjas during the Boreal chronozone. Finally, the channels were plugged by overbank fines until about 5 ka. Floods seldom reached the Fx terrace during the late Holocene and accretion became negligible. The main phase of bedrock incision spanned the Holocene, whereas the period of channel adjustment to change in river regime during late Marine Isotope Stage (MIS) 2 only led to a redistribution of the Pleniglacial gravels. The higher terrace (Fw3) formed before the Eemian and was covered by colluvial fans, mainly during MIS 2 and 3. |
Databáze: | OpenAIRE |
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