This is something completely familiar. With every low tide, the surface of the sand on the beach shows the work of ripples. These figures show the work or mark left by the ripple cross-laminae. Here, it produces a curved lee slope giving the curved cross laminae, as well as the flow and downstream angles so that it appears like a random shape of a "W". It is called a linguoid ripple.
I believe that the things that appear in the following pictures are also the things which ripples are also involved in forming.
This is my entry for the #monomad challenge