International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

HYDROCARBONS MIGRATION IN TECTONIC ZONES OF THE WESTERN TATRA MOUNTAINS CRYSTALLINE BASEMENT (CENTRAL WESTERN CARPATHIANS)

Pages: 3 - 14

Authors: LESZEK MARYNOWSKI, ALEKSANDRA GAWEDA, STEFAN CEBULAK, MARIUSZ JEDRYSEK

Abstract: In the Western Tatra Mountains crystalline basement a bituminous matter was found in tectonic zones (faults, shatter zones). The tectonic zones run NE-SW cutting both the Variscan crystalline basement and its sedimentary Mesozoic cover. Oxyreactive Thermal Analyses of whole rock samples and Gas Chromatography–Mass Spectroscopy analyses of extractable organic matter revealed that the bitumens in question are heavy fractions of crude oils. The source rocks of the bitumens were marine shales and lacustrine sediments, relatively poor in organic material, accumulated in suboxic shelf conditions. The thermal maturity of the bitumens was determined as the oil-window stage (Rcs = 0.74–0.82 %). The terrestrial organic matter admixture was negligibly small, so we can suggest the age of the source material may be older than Tertiary (by comparison with the other Carpathian oils). The comparison with the Outer Carpathian crude oils showed that the Western Tatra bitumens resemble Jurassic oils more than Paleogene ones. Jurassic and Upper Triassic carbonates and black shales from the overthrust Tatricum sequences seem to be a more plausible source rocks for the investigated bitumens. The tectonic zones, rejuvenated after or during Miocene uplift of the Tatra Block served as the paths for bitumens migration.

Keywords: Tatra Mountains, crystalline basement, hydrocarbons, migration, source rocks, biomarkers, maturity

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