Commune: Cieszyn (pow. cieszyński, woj. śląskie)
Framework element or context represented:
Magmatic rock named teschenites sensu lato forming intrusions in the Silesian unit of the western part Outer Carpathian.
Primary geological/geomorphological interest:
Magmatic, intrusive rocks.
Comparative assessment justification:
The typed site represents the best (well accessible) legally protected outcrop of the teschenites, which are unique igneous intrusions occurred in the oldest sediments of the Outer Carpathians and related to the early phase of development of geosynclinal basin of the northern, peripherial part of the Neotethys ocean.
Protection status and accessibility:
Documentary site (2002), well accessible.
Character of site: Artificial outcrop.
Area: 0.2 ha
Altitude: 290 m a.s.l.
Lithology: other igneous rocks, sandstones, limestones, marls, shales
Discipline: Petrography, Tectonics
Process Age: *all periods
Bedrock Age: Cretaceous, *all periods
Description of primary interest:
Recently exposed and legally protected outcrop of granular, mesocratic teschenitic rock (teschenite sensu stricte ?). Teschenitic rocks (teschenites sensu lato) represent numerous relatively small magmatic intrusions (mainly sills, also dikes with numerous apophyses), which occurrence is restricted to uppermost Jurassic and Cretaceous rocks of Cieszyn Beds (marls, shales, limestones and sandstones) of Cieszyn subunit, Silesian unit of the western, marginal segment of the Outer (Flysch) Carpathians. Their formation is connected with Early Cretaceous volcanism occurring in the Moravia (Czech Rep.). Teschenitic rocks represent silica-undersaturated, mesocratic and melanocratic, locally leucocratic rocks, characterized by distinct structural-textural variability as well as diversity of mineralogical and chemical composition. The most common types distinguished among them are: 1) rocks of coarse-grained texture belonging to essexite or theralite groups and featured by analcite occurrence as the main feldspathoid, represented by teschenites sensu stricte as well as bekinites and lugarites abunding with analcite (which replaces feldspars); 2) diabases of ophitic-granular texture with plagioclase, augite and chlorite aggregates; 3) monchiquites forming usually small intrusive bodies and displaying aphanitic or fine porphyritic texture with titanaugite and lamprobolite, somewhere also olivine and biotite phenocrystals; 4) picrites rich in olivine, containing also titanaugite, lamprobolite and biotite aggregates. Variability of the rocks indicates two- or three-stage differentiation of primary magma and contribution of water originated from host rocks in this process.
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