A form of cross-bedding (see cross-stratification) characterized by cross-laminations which have both concave and convex-upwards forms. The cross sets cut across one another with concave and convex-upwards surfaces, and the cross-beds have an external form of convex-upwards hummocks with wavelengths of about 1–5 m. The structure has been recognized only in ancient sediments and is thought to be the product of storm waves. See swaley cross-bedding.