Asymmetrical ripples have a steep slope on the downstream side, and a gentle slope on the upstream side. Because of this unique geometry, asymmetrical ripples in the rock record may be used to determine ancient current directions or paleocurrent directions. In waves or oscillating water , symmetrical ripples are produced. These ripples are produced by the interaction of waves and currents in the ridge and runnel system at the beach. Interference ripples in Paleozoic rocks in the Appalachian Valley and Ridge Province of northwestern Georgia Mudcracks are a polygonal pattern of cracks produced on the surface of mud as it dries.
Sole marks are bedding plane structures preserved on the bottom surfaces of beds.
They generally result from the filling in of impressions made into the surface of soft mud by the scouring action of the current, or by the impacts of objects carried by the current. If sand is deposited later over the mud, filling in these structures, they will be preserved in relief on the bottom of the sandstone bed. They are commonly preserved on the lower surfaces of sandstone beds as thin ridges. Tool marks are generally aligned parallel to the direction of current movement. They are commonly preserved as bulbous or mammilary natural casts on the bottoms of sandstone beds.