Abstract
In the present paper the effects of rapid, high-amplitude base-level changes during the last glacial-interglacial transition were studied for the Ain River in eastern France. During the Würm glacial maximum (MIS 2) rapid aggradation by deep-water Gilbert-type deltas and shallow-water fan deltas occurred at the margins of a 20 to 50m deep proglacial lake. A temporal high-amplitude lake-level fall of 60m resulted in gravel deposition by forced-regressive deltas, followed by rapid lake-level rise and fine-grained glaciolacustrine deposition. During the final deglaciation, a rapid base-level fall of 40m resulted in a complex fluvial response. Knickpoint formation and headward incision of the highstand deltas and concomitant deposition of gravel sheets by forced-regressive deltas and braided systems occurred in several depocentres on the former glacial lake floor. Preservation of highstand and falling-stage deposits and terrace formation in the incised valley depended on vertical incision and lateral channel migration. Terraces are well developed in the former lake-floor depressions, whereas vertical incision was dominant in the higher lake-floor areas. The Ain terrace staircase was likely formed by autogenic processes during a single allogenic base-level fall. This case study possibly offers an analogue for the preservation of interglacial highstand coastal deltas during sea-level fall at warm-to-cold climate transitions, although the rates of base-level fall are different. © 2013 Collegium Boreas. Published by John Wiley & Sons Ltd.
Original language | English |
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Pages (from-to) | 403-421 |
Journal | Boreas |
Volume | 43 |
DOIs | |
Publication status | Published - 2014 |