What is "cross-bedding"

In geology, the sedimentary structures known as cross-bedding are the (near-) horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, and the inclined layers are known as cross strata.

Cross bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes, and indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, anti-dunes, sand waves, hummocks, bars, and delta slopes. Cross-bedding is widespread in many environments. Environments in which water movement is fast enough and deep enough to develop large-scale bed forms fall into three natural groupings: rivers, tide-dominated coastal and marine settings.