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

Abstract

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 the platform, ending at different stratigraphic levels as a [open quotes]blind[close quotes] thrust. The inner thrust sheets were formed by a fault bend folding mechanism, while the outer sheets were formed, primarily, by a propagation fold. The vertical play of the platform blocks created a complex ramp geometry which represents the main control 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 intense exploration of the shallow and medium depths of the Carpathian Thrust Belt petroliferous basins, indentification of new targets relies upon understanding the original distribution of the source and reservoir rocks and the tectonic transport mechanisms which placed them inmore » 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 also been examined in an attempt to discover new duplex systems.« less