There are several common primary sedimentary structures that indicate quite a bit about the environment in which they formed. ripple marks are small waves of sand that form linear patterns perpendicular to the movement or flow of water or wind. they can be asymmetrical in shape, indicating unidirectional flow, or symmetrical (called oscillating), which indicates a “sloshing” back and forth of water. cross-bedding forms as sand particles are continuously moved up and over a sand ripple or dune. this feature indicates the direction of movement of water or wind. this type of structure can only be seen in a cross section of sediment or sedimentary rock. mud cracks indicate that the sediment was alternating between wet and dry. mud cracks are produced by the shrinking of fine sediment as it slowly dries. focus in on the light brown areas in the foreground where the students placed the small, plastic figures. what is the name given to this type of sedimentary structure, and what does it indicate about the environment