Cross-bedding of sandstone near Mt. Carmel road, Zion Canyon, indicating wind action and sand dune formation had occurred prior to formation of the rock.
Sand dune cross-beds can be large, such as in the Jurassic-age erg deposits of Navajo Sandstone in Canyonlands National Park. Aztec Butte shown hereFormation of cross-stratificationSchematic of eolian cross-beddingClose up of cross-bedding and scour, Logan Formation, OhioTabular cross-bedding in the Navajo Sandstone in Zion National ParkTabular cross-bedding in the South Bar Formation in Nova ScotiaTrough cross-bedding in the Lower Cove Formation in Nova ScotiaTrough cross-bedding in the Waddens Cove Formation in Nova ScotiaAnimation showing deposition and erosion of cross-beds
In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The original depositional layering is tilted, such tilting not being the result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, which are known as cross-strata.
Cross-bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes; it 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.[1] 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.[2]
^Collinson, J.D., Thompson, D.B., 1989, Sedimentary Structures (2nd ed): Academic Division of Unwin Hyman Ltd, Winchester, MA, XXX p.
^Ashley, G. (1990) "Classification of Large-Scale Subaqueous Bedforms: A New Look At An Old Problem." Journal of Sedimentary Petrology. 60.1: 160-172. Print.