Formation (geology)

Article

July 5, 2022

Formation - the basic formal lithostratigraphic unit distinguished solely on the basis of lithological features. A formation is a basal lithostratigraphic separation, which means that all other units (e.g., link, group) can only be distinguished on the condition that a formation is first established and must be related to it. The formation includes a group of rocks with a similar lithology and without major incompatibilities. The minimum formation thickness is not specified, but the formation must have a thickness that allows it to be mapped on a map on a scale of 1: 50,000. To formally separate a formation, it is necessary to provide its stratotype and hypostratotypes, define the lower and upper boundaries, and publish it in the scientific press. The name of a formation must contain two parts: the word "formation" and a geographic part, usually associated with the location of the stratotype or reference area. The name may also contain a member that describes the dominant lithological type of the rock. Examples of formation names: Sandstone Formation from Wiśniówka, Górażdże Formation. In the older geological literature, the term formation is also used in the sense of an informal lithostratigraphic unit, to describe various rock packages, sometimes the separation of such formations was made on the basis of, for example, fossils.

Bibliography

G. Racki & M. Narkiewicz (eds.): Polish principles of stratigraphy, Wyd. PGI, Warsaw 2006