Horizon (geology)
In geology, a horizon refers to either a bedding surface where there is marked change in the lithology within a sequence of sedimentary or volcanic rocks, or a distinctive layer or thin bed with a characteristic lithology or fossil content within a sequence.[1] In the interpretation of seismic reflection data, horizons are the reflectors (or seismic events) picked on individual profiles. These reflectors represent a change in rock properties across a boundary between two layers of rock, particularly seismic velocity and density.[2]
Marker horizon
Marker horizons are stratigraphic units of distinctive lithology (different from the bulk of the sequence) with a wide geographical extent that are used in stratigraphic correlation. Layers of tuff (lithified volcanic ash) are often used for this purpose.
Event horizon
An event horizon is a bed that marks a geological event, such as an earthquake or a meteorite impact. It is the basic unit used in event stratigraphy.[3]
Gorizont
The fundamental unit of Russian stratigraphy, the gorizont, can be anglicized as "horizon". However, this concept is not equivalent to the term used in western geological systems. While the western term "horizon" pertains to a small lithological section within a geological formation, a gorizont is a broad biostratigraphic unit. It may encompass several "svitas" (lithological units equivalent to a formation). Both gorizonts and svitas are also considered chronostratigraphic units (correlated with a distinct time interval), while western geologists have separate chronological and stratigraphic systems.[4]
References
- ^ Rey, J. (2008). "Stratigraphy: Foundations and Perspectives". In Rey J. & Galeotti S. (ed.). Stratigraphy: Terminology and Practice. Editions OPHRYS. p. 10. ISBN 9782710809104. Retrieved 28 January 2013.
- ^ Schlumberger Limited (2013). "horizon". Oilfield Glossary. Retrieved 30 January 2013.
- ^ Grippo, A. (9 May 2011). "Event stratigraphy". Archived from the original on 13 June 2015. Retrieved 28 January 2013.
- ^ Benton, Michael J. (2000). "Conventions in Russian and Mongolian Palaeontological Literature". In Benton, M.J.; Shishkin, M.A.; Unwin, D.M.; Kurochkin, E.N. (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. xvi–xxxviii. ISBN 9780521545822.