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MORARIU, DORU CATALIN, Prospectiuni S.A., Bucharest, Romania, and CORNELIU DINU and LIVIU MATENCO, University of Bucharest, Faculty of Geology, Bucharest, Romania

ABSTRACT: Structural Style Analysis as a Hydrocarbon Exploration Basis for the Carpathian Thrust Belt of Romania

As a result of a Cretaceous-Tertiary sedimentary wedge movement over a basal detachment surface, the present structure of the Carpathian Thrust Belt was successively completed by the Miocene compressional stages of the Alpine Orogenesis.

The major basal detachment overpassed on a long-distance the platform, being stopped at different stratigraphic levels as a "blind" thrust. The inner thrust sheets were formed by a fault bend folding mechanism, while the outer sheets by a mainly propagation fold one.

The vertical play of the platform blocks, creating a complex ramp geometry, represented the control key for the deep structural style. The platform thresholds retained the displacement of the thrust sheets, generating duplex systems.

In order to illustrate the main structural features, several regional cross sections have been analyzed and balanced. Selected examples point out how the depositional and structural history of parts of the Thrust Belt and their associated hydrocarbon accumulations can be interpreted and evaluated to reduce the exploration risk.

Considering the mature exploration stage for shallow and medium depth of the Carpathian Thrust Belt petroliferous basins, the difficulties in indentifying new targets consist in the correct understanding of the original distribution of the source and reservoir rocks, as well as of the tectonic mechanism which transported them in an allochthonous position over the platform. Therefore, some restored sections have been used to map the initial location of the hydrocarbon prospective facies. Local structural styles of deep levels have been examined too, in an attempt to find new duplex systems.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.