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Concept
Chevron (land form)
Summary
A chevron is a wedge-shaped sediment deposit observed on coastlines and continental interiors around the world. The term chevron was originally used independently by Maxwell and Haynes and Hearty and others for large, V-shaped, sub-linear to parabolic landforms in southwestern Egypt and on islands in the eastern, windward Bahamas.
The Egyptian “chevrons” are active, wind-generated dunes, but the “chevrons” in the Bahamas are inactive and have been variously interpreted. The most common interpretation of large, chevron-shaped bed forms is that they are a form of parabolic dune, and that most examples are generated by wind action.
Many chevrons can be found in Australia, but others are concentrated around the coastlines of the world. For instance there are chevrons in Hither Hills State Park on Long Island and in Madagascar (such as the Fenambosy Chevron), as well as in interior sites of the United States such as the Palouse region of eastern Washington State, the Great Sand Dunes National Park and Preserve, and White Sands National Park.
According to Hansen et al. 2015, powerful storms and changes in sea level rise can explain chevrons. An example of the formation of chevrons can be seen in the Bahamas, where the lightly indurated ooid sand ridges appear to have been created by the impact of strong waves over a long period of time. Subsequently, the internal structure of the chevrons showed that they were "rapidly emplaced by water rather than wind". The notion that chevrons are caused by powerful storm surges rather than wind can also be attributed to tsunami deposits, with examples of complex chevron formations being found several kilometres inland, at high elevations and on shorelines without beaches. The Holocene Impact Research Group hypothesizes that the formations could be caused by tsunamis from meteorite impacts or submarine slides which lift sediment up and carry it hundreds of miles until depositing it on coastlines. Part of the evidence they cite for this hypothesis is that the sediments contain tiny marine fossils; however, such fossils can be moved by the wind, just like sand.
Official source
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