According to Hansen et al. 2015, powerful storms and changes in sea level rise can explain chevrons , as the study elaborates: The lightly indurated ooid sand ridges are several kilometers long (Bahamas) and appear to have originated from the action of long-period waves from a northeasterly Atlantic source. The chevron ridges contain bands of beach fenestrae, formed by air bubbles trapped in fine ooid sand inundated by water and quickly indurated. The internal sedimentary structures including the beach fenestrae and scour structures (Tormey, 2015) show that the chevrons were rapidly emplaced by water rather than wind (Hearty et al. , 1998). These landforms were deposited near the end of a sea level high stand, when sea level was just beginning to fall, otherwise they would have been reworked subsequently by stable or rising seas. Some chevrons contain multiple smaller ridges “nested” in a seaward direction (Hearty et al., 1998), providing further evidence that sea level was falling fast enough to strand and preserve older chevrons as distinct landforms. Older ridges adjacent to the chevron ridges have wave runup deposits that reach heights nearly 40 m above present sea level, far above the reach of a quiescent 5e sea surface. Such elevated beach fenestrae are considered to result from runup of very large waves (Wanless and Dravis, 1989). These stratigraphically youngest depositson the shore-parallel ridges are 1-5 m thick fenestrae-filled seaward-sloping tabular beds of stage 5e age that mantle older MIS 5e dune deposits (Neumann and Moore, 1975; Chen at al., 1991; Neumann and Hearty, 1996; Tormey, 2015). Runup beds reach more than a kilometer from the present coast, mantling the eastern flanks of stage 5e ridges (Hearty et al., 1998). Bain and Kindler (1994) suggested the fenestrae could be raingenerated, but the fenestrae at high elevations are widespread and exclusive to the late 5e deposits. They are not commonly found in older dune ridges (Hearty et al., 1998). Movement of these sediments, including chevrons, run-up deposits and boulders, required a potent sustained energy source. Anticipating our interpretation in terms of powerful storms driven by an unusually warm tropical ocean and strong zonal temperature gradients in the North Atlantic, we must ask whether there should not be evidence of comparable end-Eemian storms in Bermuda. Indeed, there are seaward sloping planar beds rising to about +20 m along several kilometers of the north coast of Bermuda (Land et al., 1967; Vacher and Rowe, 1997; Hearty et al., 1998).%DIFDELCMD < %DIFDELCMD < %%% In an alternative view, 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.Gusiakov, V. Abbott, D.H., Bryant, E.A., Masse, W.B., and Breger, D., 2010. Mega tsunami of the world oceans: Chevron dune formation, micro-ejecta, and rapid climate change as the evidence of recent oceanic bolide impacts: T. Beer (ed.), Geophysical Hazards, p. 197-227; Springer Publ. 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.   The impact idea is controversial not only because chevrons are similar to wind-blown landforms found far from the ocean, but also because it is unlikely that there have been enough large impacts and landslides to explain the observed chevrons. Moreover, some computer models and sediment-transport analysis do not support this theory. For example, the orientation of chevrons along the southern coast of Madagascar do not line up with what these models of mega-tsunamis have simulated. Additional evidence against the mega-tsunami hypothesis is that the force of the water would not produce such regular bed forms.
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 %DIFDELCMD < %DIFDELCMD < %%% 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.Gusiakov, V. Abbott, D.H., Bryant, E.A., Masse, W.B., and Breger, D., 2010. Mega tsunami of the world oceans: Chevron dune formation, micro-ejecta, and rapid climate change as the evidence of recent oceanic bolide impacts: T. Beer (ed.), Geophysical Hazards, p. 197-227; Springer Publ. 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. As Abbott et al. 2017 describes; "In particular, the Madagascar chevrons contain significant proportions of early Holocene carbonate tests resembling shells of marine foraminifera, including some that are partially dolomitized, and some that are infilled with mud. These observations suggest that marine carbonate tests in the chevrons were eroded from the continental shelf, and not from modern beaches." The impact idea is controversial not only because chevrons are similar to wind-blown landforms found far from the ocean, but also because it is unlikely that there have been enough large impacts and landslides to explain the observed chevrons. Moreover, some computer models and sediment-transport analysis do not support this theory. For example, the orientation of chevrons along the southern coast of Madagascar do not line up with what these models of mega-tsunamis have simulated. Additional evidence against the mega-tsunami hypothesis is that the force of the water would not produce such regular bed forms.
R
, as the study elaborates: The
. An example of the formation of chevrons can be seen in the Bahamas, where the
D
are several kilometers long (Bahamas) and
R
originated from the action of long-period waves from a northeasterly Atlantic source. The chevron ridges contain bands of beach fenestrae, formed by air bubbles trapped in fine ooid sand inundated by water and quickly indurated. The internal sedimentary structures including the beach fenestrae and scour structures (Tormey, 2015) show that the chevrons were
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 "
R
(Hearty et al.
". The notion that chevrons are caused by powerful storm surges rather than wind can also be attributed to tsunami deposits
D
1998). These landforms were deposited near the end of a sea level high stand, when sea level was just beginning to fall, otherwise they would have been reworked subsequently by stable or rising seas. Some chevrons contain multiple smaller ridges “nested” in a seaward direction (Hearty et al., 1998), providing further evidence that sea level was falling fast enough to strand and preserve older chevrons as distinct landforms.
R
Older ridges adjacent to the chevron ridges have wave runup deposits that reach heights nearly 40 m above present sea level, far above the reach of a quiescent 5e sea surface. Such elevated beach fenestrae are considered to result from runup of very large waves (Wanless and Dravis, 1989). These stratigraphically youngest depositson the shore-parallel ridges are 1-5 m thick fenestrae-filled seaward-sloping tabular beds of stage 5e age that mantle older MIS 5e dune deposits (Neumann and Moore, 1975; Chen at al., 1991; Neumann and Hearty, 1996; Tormey, 2015). Runup beds reach more than a kilometer from the present coast, mantling the eastern flanks of stage 5e ridges (Hearty et al., 1998). Bain and Kindler (1994) suggested the fenestrae could be raingenerated, but the fenestrae
with examples of complex chevron formations being found several kilometres inland,
D
are widespread and exclusive to the late 5e deposits. They are not commonly found in older dune ridges (Hearty et al., 1998).
D
Movement of these sediments, including chevrons, run-up deposits and boulders, required a potent sustained energy source. Anticipating our interpretation in terms of powerful storms driven by an unusually warm tropical ocean and strong zonal temperature gradients in the North Atlantic, we must ask whether there should not be evidence of comparable end-Eemian storms in Bermuda. Indeed, there are seaward sloping planar beds rising to about +20 m along several kilometers of the north coast of Bermuda (Land et al., 1967; Vacher and Rowe, 1997; Hearty et al., 1998).
R
In an alternative view, the
and on shorelines without beaches. The
A
As Abbott et al. 2017 describes;
A
"In particular, the Madagascar chevrons contain significant proportions of early Holocene carbonate tests resembling shells of marine foraminifera, including some that are partially dolomitized, and some that are infilled with mud. These observations suggest that marine carbonate tests in the chevrons were eroded from the continental shelf, and not from modern beaches."