Dunes. Antidunes. General Information. Planar Bedding. Cross-bedding. Small-ripple Bedding. Megaripple Bedding. Wave-ripple Bedding. Wind-ripple Bedding. Sections normal to flow may be horizontal, defining planar cross lamination (2-D ripples) or may be trough-shaped, defining trough cross lamination (3-D ripples). Note the trough cross-bedding on the cut that is perpendicular to flow (i.e. the v-w cut) This figure shows flow along the bed across a set of sinuous-crested bedforms. Sand-sized grains comprising the planar cross-bedding found in a Late Wisconsinan outwash deposit near Caledon, Ontario, show an obliquely downslope preferred o. Detailed examination of grain fabric makes it possible to distinguish the planar cross-bedding of a micro-deltaic origin from that of other types of bar deposit built either partly or predominantly by lateral accretion.
Formation of Cross Beds When a depositional environment has sand in it and water or air moves the sand grains around, those grains can build up into piles of sediment. This is planar cross-bedding and the surface at the bottom of the cross-beds is flat and close to horizontal because of the absence of scouring in the trough. Field photograph showing tabular planar cross-bedding (above) and recumbend foreset (below) in the sandstones of the Naqus Formation in Gabal Gunna, west central Sinai.