In geology and related fields, a stratum (plural: "strata") is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural forces. They may extend over hundreds of thousands of square kilometers of the Earth's surface. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs, road cuts, quarries, and river banks. Individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a specific mode of deposition -- river silt, beach sand, coal swamp, sand dune, lava bed, etc.

Geologists study rock strata and categorize them by the material in the beds. Each distinct layer is usually assigned to a "formation" name usually based on a town, river, mountain, or region where the formation is exposed and available for study. For example, the Burgess Shale is a thick exposure of dark, occasionally fossiliferous, shale exposed high in the Canadian Rockies near Burgess Pass. Slight distinctions in material in a formation may be described as "members" or sometimes "beds." Formations are collected into "groups." Groups may be collected into "supergroups."

The stratum is the fundamental unit in a stratigraphic column and forms the basis of the study of stratigraphy.

limestone and shale strata in East Tennessee
Depot Beach, New South Wales
Barstow, California. Folded strata.
Outcrop_of_Upper_Ordovician_limestone_and_minor_shale,_central_Tennessee;_College of Wooster students.
Chennai, India).

ee also

*Polystrate fossil
*Important publications in stratigraphy
*Geologic map
*Geologic unit
*Geologic formation
*Archaeological horizon

External links

* [ GeoWhen Database]

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  • stratum — [ stratɔm ] n. m. • XVIIIe chim.; mot lat. ♦ Histol. Couche. ● stratum nom masculin (latin stratum, couche) Stratum granulosum et stratum lucidum, couches de cellules de l épiderme, entre le réseau muqueux de Malpighi et la couche cornée de l… …   Encyclopédie Universelle

  • Stratum — (n., Pl. Strata, eingedeutscht auch Straten, lat. „Schicht“, „Decke“) bedeutet: in der Archäologie eine bestimmte Schicht der Ausgrabung, siehe Stratum (Archäologie) in der Geologie die kleinste Gesteinseinheit, die sich von anderen Einheiten… …   Deutsch Wikipedia

  • stratum — (n.) horizontal layer, 1590s, from Mod.L. stratum, special use of L. stratum thing spread out, coverlet, pavement, from neuter pp. of sternere to spread out, lay down, stretch out, from PIE *stre to to stretch, extend, from root *stere to spread …   Etymology dictionary

  • stratum — stratum; sub·stratum; su·per·stratum; …   English syllables

  • Stratum — Stra tum, n.; pl. E. {Stratums}, L. {Strata}. The latter is more common. [L., from sternere, stratum, to spread; akin to Gr. ? to spread, strew. See {Strew}, and cf. {Consternation}, {Estrade}, {Prostrate}, {Stratus}, {Street}.] 1. (Geol.) A bed… …   The Collaborative International Dictionary of English

  • stratum — strȃtum m DEFINICIJA 1. anat. sloj stanica ili tkiva na različitim anatomskim lokalizacijama 2. geol. arheol. u geologiji i arheologiji, sloj, naslaga ETIMOLOGIJA lat. stratum: pokrivač …   Hrvatski jezični portal

  • stratum — ► NOUN (pl. strata) 1) a layer or a series of layers of rock. 2) a thin layer within any structure. 3) a level or class of society. DERIVATIVES stratal adjective. USAGE It is incorrect to use strata …   English terms dictionary

  • stratum — [strāt′əm, strat′əm] n. pl. strata [strātə, strat′ə] or stratums [ModL < L, a covering, blanket < stratus, pp. of sternere, to spread, stretch out, cover: for IE base see STREW] 1. a horizontal layer or section of material, esp. any of… …   English World dictionary

  • Stratum — (lat.), 1) überhaupt Schicht; 2) bes. Häute, od. hautartige Gebilde, welche schichtenweise übereinander liegen, s. Strata. Daher S. cellulōsum, eine außen auf der Rinde liegende, bei starker Entwickelung den Kork bildende Lage von Zellengewebe; S …   Pierer's Universal-Lexikon

  • Stratum — (lat.), Schicht; s. Strata …   Meyers Großes Konversations-Lexikon

  • Stratum — Stratum, Mehrzahl strata. lat., Schichte, Lager; stratificiren, schichten; Stratification, die Schichtung der Gebirgsarten …   Herders Conversations-Lexikon

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