Cross-bedding

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.
Cross-bedding in a sandstone dome in the Canyons of the Escalante.
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 here
Formation of cross-stratification
Schematic of eolian cross-bedding
Close up of cross-bedding and scour, Logan Formation, Ohio
Tabular cross-bedding in the Navajo Sandstone in Zion National Park
Tabular cross-bedding in the South Bar Formation in Nova Scotia
Trough cross-bedding in the Lower Cove Formation in Nova Scotia
Trough cross-bedding in the Waddens Cove Formation in Nova Scotia
Animation 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]

  1. ^ Collinson, J.D., Thompson, D.B., 1989, Sedimentary Structures (2nd ed): Academic Division of Unwin Hyman Ltd, Winchester, MA, XXX p.
  2. ^ 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.

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