Excavations made by the feeding activity of rays (elasmobranchs) are extremely abundant in tidal flats and in estuarine sand bars and channels of the Georgia coast. Rays make excavations by flapping their "wings" in order to erode the substrate hydraulically and thereby obtain benthic organisms for food. Subsequently, the hole is refilled with new sediment. The structure that results from this feeding activity is composed of two parts: a broad, shallow, surface depression that is dish-shaped and a lower, roughly circular hole as much as 30 cm deep. Feeding depressions formed by rays are distinctive sedimentary structures that are easily recognized in cores from Holocene sediments. Recently they have also been found in Pleistocene and Cretaceous outcrops.