Chevrons: origin and relevance for the reconstruction of past wind regimes

Abstract

Since its first use in the late 80’s, the term chevron has been employed in numerous studies to describe large U- and V-shaped ridges found in or near shorelines worldwide. Most studies have so far focused on Bahamian chevrons that are exclusively of Late Pleistocene age, and on the supposed Holocene chevrons found in S-Madagascar and Australia. In the Bahamas, these deposits have been interpreted as the product of extreme storms at the end of the last interglacial (LIG) warm period. In contrast, the extensive chevrons complex exposed in S-Madagascar and on the western coast of Australia have been associated with a tsunami induced by a meteorite impact. Finally, several authors have also proposed a non-catastrophic (i.e. eolian) origin based on the recognized importance of wind-related processes in these coastal areas, and term such deposits parabolic dunes. In this paper, we collect and synthesize existing data on the morphology, sedimentology and age of these chevrons, and review the different interpretations proposed in the literature with the aim to lay out a consistent database to assist further investigations on these important coastal morphologies. In addition, we generated a synthesis of wind data at the three study areas, which highlights the relationship between present wind regimes and chevrons morphologies. The ubiquity of chevrons (likely actually parabolic dunes) in coastal areas around the globe and their relationship with coastal processes makes them crucial archives for reconstructing past wind regimes.

Modeled storm surge changes in a warmer world: the Last Interglacial

“…These are large boulders and storm ridges whose size and position suggest that they were deposited by storms of higher intensity than recorded in human history. However, there are still debates around the origin of these proxies (Vimpere et al, 2019;Mylroie, 2008Mylroie, , 2018 and the type of storm that created them (Rovere et al, 2017(Rovere et al, , 2018Scheffers and Kelletat, 2020;Hearty and Tormey, 2018). Models of the LIG suggest a strengthening of the winter mid-latitude storm tracks, along with their northward shift and extension to the east (Kaspar et al, 2007) and, more recently, that the LIG might have seen higher-than-today sea surface temperatures and more frequent and stronger tropical cyclones over the western North Atlantic (Yan et al, 2021).…”

A Westward Shift in Tropical Cyclone Potential Intensity and Genesis Regions in the North Atlantic During the Last Interglacial

“…For example, megaboulders are argued to be residual karst towers (Mylroie, 2008, 2018) or transported by waves generated by storms of historical magnitude (Rovere et al., 2017) or a tsunami (Scheffer and Kelletat, 2020). Chevron ridges are suggested to be eolian deposits (Mylroie, 2018; Vimpere et al., 2019), and fenestrae in runup deposits are rainfall slurries (Bain and Kindler, 1994; Mylroie, 2018). Thus, from a perspective of geological evidence, it remains elusive whether the North Atlantic experienced stronger storms during the LIG relative to present‐day.…”