casts Groove casts are straight parallel ridges that are raised a few millimeters from the bedding surface. These structures were named and defined by Shrock in 1948 because of their long and narrow appearance, and they were formed from the filling in of grooves. Even though they may seem similar to flute casts, they each have many distinguishing characteristics, and the two are generally not found in the same vicinity. Groove casts are closely spaced, but not on top of each other, and exist in pairs, triples, and even larger groups. Groove casts form when high velocity flows (e.g. turbidite) create a pattern on an underlying bed. In 1957, Kuenen published that "groove cast" was a general term encompassing both drag marks and slide marks. A slide mark is a long, relatively wide, but shallow gouge left in a muddy bed caused by sliding of a soft-body object such as a bed of algae or slumping of sediment. Drag marks are narrower and deeper than slide marks, but retain the same length. Drag marks create a groove or striation caused by a physically hard object like a rock or shell. Load casts Load casts are secondary structures that are preserved as bulbous depressions on the base of a bed. They form as dense, overlying sediment (usually sand) settles into less dense, water-saturated sediment (usually mud) below. References Sedimentary structures