Erathem


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erathem

[′er·ə‚them]
(geology)
A chronostratigraphic unit, below eonothem and above system, composed of rocks formed during an era of geologic time.

Erathem

 

(geology), a subdivision of the general stratigraphic scale, subordinate to the eonothem and itself subdivided into stratigraphic systems. In the Russian geological literature, the erathem was usually called group. In 1966, the American geologist H. Hedberg suggested the term “erathem,” which was adopted in the USSR in 1976. The time interval during which an erathem forms corresponds to an era. (See alsoSTRATIGRAPHY.)

References in periodicals archive ?
Erathem Era System period Formation Stage age Subsegment Cenozoic Neogene Guantao Ng Paleogene Dongying Ed Shahejie Es Es1 Es2 Es2s Es2x Es3 Es3s Es3m Es3x Es4 Es4cs Es4cx Es4x Kongdian Ek Erathem Era Lithologic characteristic Reservoir-cap nature Cenozoic Thin sand-shale interbedded Reservoir Primarily composed of thick Reservoir sandstone with a pure mudstone top of approximately 50 m Oil shale Regional caprock Grey mudstone Primarily composed of thick Reservoir sandstone Mudstone deposits Partial caprock Mudstone deposits in southern work area with thick bodies and a small range Oil shale Regional caprock Cream mudstone and oil shale Thin sand-shale interbedded Reservoir
a distinction between a hierarchy of material chronostratigraphic units (rock-time) and abstract geochronologic units (Earth time) units was required, and a dual nomenclatural system was codified...." Hence, we can refer to the Maastrichtian Stage of the Cretaceous System of the Mesozoic Erathem in a chronostratigraphic sense or to the Maastrichtian Age of the Cretaceous Period of the Mesozoic Era in a geochronologic sense; similarly, chronostratigraphic units can be subdivided into lower, middle and upper subunits; geochronologic units can be subdivided into early, mid and late subunits.
DRAFFENS SPEAKEASY COCKTAIL BAR, COUTTIE'S WYND ALONG a cobbled wynd (alley) filled with bins, an unmarked fire door leads to this prohibition erathemed speakeasy, which occupies one of Dundee's now defunct department stores.