Upper Pleistocene parabolic ridges (i.e. "chevrons") from the Bahamas: Storm‐wave sediments or aeolian deposits? A quantitative approach

Article Article scientifique Article Upper Pleistocene parabolic ridges (i.e. "chevrons") from the Bahamas: Storm‐wave sediments or aeolian deposits? A quantitative approach eng 2020 author Vimpere Lucas 0000-0001-9315-1243 717196 author Del Piero Nicolo 820972 author Shawwa Nabil 817471 author Beguelin Karim 721759 author Kindler Pascal 28210 author Castelltort Sébastien 0000-0002-6405-4038 761351 10.1111/sed.12828 0037-0746 https://onlinelibrary.wiley.com/doi/10.1111/sed.12828 The Upper Pleistocene (Marine Isotope Stage 5e; ∼120 ka) stratigraphic record from the Bahamas comprises large, km-long parabolic ridges of oolitic composition, that point landward, and have been up to now called “chevrons”. A debate about their genesis has led previous researchers to consider two processes of deposition: 1) a catastrophic event involving giant storm-generated waves produced by specific climatic conditions at the end of MIS 5e; 2) a more uniformitarian process which characterises “chevrons” as aeolian parabolic dunes because of their similar morphology. Since there are few unequivocal sedimentological criteria to discriminate aeolian from water-deposited sediments, only a quantitative, multi-method approach could provide enough arguments to produce a viable diagnosis on the genetic processes involved. Following this reasoning, the quantification of the morphological parameters of “chevrons”, a precise study of their sedimentary structures on previously and newly discovered sections, and several statistical grain-size analyses, all advocate for an aeolian origin. Moreover, when the aforementioned characteristics of “chevrons” are compared with those of storm deposits (e.g. washovers) and parabolic dunes occuring elsewhere on Earth, the dissemblance with the former and the resemblance with the latter is evident. Amino-acid racemization (AAR) dating, together with stratigraphic and petrographic investigations, constrain the “chevrons” age to the late part of MIS 5e. Their occurrence during this specific time interval can be explained by both strengthened easterly winds and drier climatic conditions associated with a changing vegetation cover. Fixation of the arms by a sparse vegetation, coupled with the loose “chevron” nose sediment migrating farther inland, form the peculiar U-shaped morphology of these ridges. Chevron Climate change Storm Parabolic dune Aeolianite Dewey 550 42 Département des sciences de la Terre 154 false 672 Earth Surface Dynamics Sedimentology c54f8b5c-de6b-4412-9158-35474c31b331 Article (Accepted version) Public ChevronsBahamaspreprint.pdf 2620731 application/pdf Restricted 2021-11-11 d50f57e5-9b5b-4270-bf74-4bc9b023ae9b Supplemental data Restricted sed12828-sup-0001-datas1.pdf 593977 application/pdf 5d285336deb0966aba13b927140b165ecf7f162694a24ff731fd3c3bf57199fd openAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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Upper Pleistocene parabolic ridges (i.e. "chevrons") from the Bahamas: Storm‐wave sediments or aeolian deposits? A quantitative approach	Sedimentology			2020	525	244

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Shawwa, Nabil