Flute casts

Flute casts are a type of trace left on the surfaces of sediments called sole marks. They are formed when water flow containing sand and gravel erode muddy sediments, and the resulting hollows are filled with sediments. Because of this, when the sediment surface is turned upside down, the mound of a fill sediment is parallel to one another, with the angles of the upstream side being steep while those of the downstream side are shallow. These sedimentary structures are used to reconstruct the direction of water flow, called paleocurrents. Other sole marks include trace fossils of productive activities of life forms and load structures of sediments.