"(1) Flute casts are more common in poorly graded or nongraded turbidity current deposits, and groove casts are more common in graded deposits. (2) Flute casts indicate the direction of an earlier stage of turbidity flow than that indicated by groove casts. (3) Multiple sets of groove casts on the undersurface of a sandstone are more common than multiple sets of flute casts. Flute casts and groove casts are different in origin. Flutes are subconical depressions produced where the turbulent water of a turbidity current impinges directly on a muddy sea bottom. Grooves are incised on a muddy sea bottom by the debris of a fluidized sediment mass which is believed to assume laminar motion under a turbidity current. Subsequent filling of the flutes and grooves by sand and silt forms flute casts and groove casts."