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Flute cast: (geology) A raised, oblong, or subconical welt on the bottom surface of a siltstone or sandstone bed formed by the filling of a flute. a Flute casts are irregular ridges that display a marked asymmetry. The asymmetry of these structures allows for determination of paleocurrent direction—flows originate from the direction of the steeper side of the flute. Flute casts typically have a "pointy" end, oriented in the upstream direction, and a more gentle, flared end that merges downstream into the bed surface. Flute casts along the base of a given bed are usually of approximately the same size, but between beds or formations, may vary greatly in size. Byddwn yn ddiolchgar am unrhyw gymorth. Siân