Orogen

(redirected from orogens)
Also found in: Dictionary.

orogen

[′ȯr·ə·jən]
(geology)

Orogen

 

a term introduced in 1921 by the Austrian geologist L. Kober for the second stage of development of geosynclines or tectonically mobile belts of the earth’s crust. This stage is characterized by the predominance of ascending movements and the emergence of mountains. By analogy with the tectonic structure of the Alps, Kober felt that every orogen has a symmetrical structure and is located between rigid masses called kratogens, or cratons, under whose pressure the orogen arises.

Kober divided the orogen into a series of zones. The central part is occupied by rigid granite masses called internides, on both sides of which are the centralides, zones composed of sedimentary and volcanic rocks in the form of enormous overthrust nappes in the direction of the kratogens. The metamorphides, composed of metamorphosed sedimentary rocks and magmatic rocks (ophiolites), adjoin the centralides. The marginal zones of the orogen, called the externides, are composed of flysch.

Kober’s scheme fails to take into account the full diversity of the structure of the mobile belts; the overthrust overlapping of some zones by others, for example, is not obligatory. Moreover, Kober overestimates the role of symmetry in the structure of the orogen. In present-day terminology the term “orogen” is often replaced by such synonyms as “folded mountain structure” or, less precisely, “geosyncline” (in the broad sense of the word) or “geosynclinal system.”

V. E. KHAIN

References in periodicals archive ?
The largest (absolute) values of this gravity gradient correspond with the largest spatial variations of the Moho geometry under orogens attributed to a high correlation of the consolidated crust-stripped gravity disturbances with the Moho geometry (cf.
Mixed provenance includes input from continental block, magmatic arc and recycled orogen environment.
Complications arise by virtue of the overlapping of Variscides arc of BM by the Carpathian arc of Alpine Orogen.
Events shown for the Cordilleran region and the events associated with the Cordilleran orogen in Alberta are based on the southern Alberta-British Columbia transect described in the field guides by Price et al.
The plate tectonic revolution of the 1960's provided the framework for detailed models on the structure of orogens and basins, summarized in a 1995 textbook edited by Busby and Ingersoll.
1999), whereas the two recent orogenies are related to non-collisional or Andean-type orogens (Ramos, 1988).
3a and b) suggest that both sandstones of the Ispikan group and Panjgur Formation have comparable provenance of recycled and mixed terrains, most plausibly the Himalaya-Karakorum- Hindukush orogens and associated magmatic arcsof Kohistan and Chagai-Raskoh and Bela-Muslimbagh-Waziristan ophiolites.
The tectonics of orogens are moderated by climate through erosion.
PROVENANCE OF CENOZOIC UNITS OF THE GUADUAS SYNCLINE: IMPLICATION IN THE TECTONIC EVOLUTION OF THE SOUTH OF MIDDLE MAGDALENA VALLEY AND ADJACENT OROGENS
Venus is selectively targeting concealed parts of Proterozoic orogens where cover is interpreted from geophysics to be relatively thin (