Some rocks seen in cliffs display chevrons, as pictured here. Unlike this image, the "Vs" point sideways in such rocks.
Rocks that display a chevron or herringbone pattern are a geological feature called chevron (or herringbone) cross bedding. The name comes from their appearance, which resembles a row of chevrons lying on their side. Such layers are usually several inches thick.
Appearance
Chevron cross bedding typically occurs in a layer several inches thick, and it is not uncommon to see several such layers in a cliff face. The bedding looks like a large number of thin, V-shaped structures all stacked together and then laid sideways. The alternate name, "herringbone cross bedding," describes the resemblance to the ribs of a fish skeleton.
Origin
Chevron cross beds occur when sand and similar-sized grains are transported by a medium that alternates between two opposing directions. The direction of transport is the direction of slope on tiny layers of sand that make the V shapes.
Interpretation
Geologists believe chevron cross beds are most commonly deposited in tidal environments. The regular ebb and flow of tides creates the reversal of flow direction needed to deposit this sedimentary structure. Some larger cross bed deposits are deposited by wind, but these are less common.
Tags: cross bedding, Chevron cross, chevron herringbone, cross beds, herringbone cross, herringbone cross bedding, inches thick
