Orogen-Parallel Strike-Slip Faulting in Frontal Dinarides and Western Carpathians, and Its Impact on the Hydrocarbon Potential of These Regions

Picha, Frank J., International Petroleum Consultant, Walnut Creek, CA

The frontal zone of Dinarides and its foreland is characterized by the presence of major late orogenic NW-SE faults trending parallel to and locally dissecting the leading edge of the thin-skinned thrust belt. Depending on the distribution of compressional and extensional stresses the motion along these dextral faults created en echelon anticlinal structures, e.g., in the central Adriatic region, or lead to the opening of the pull-apart Albanian foredeep in the southern Adriatic. The strike-slip faulting represents the last stage of the mountain build­ing process. It provides means of tectonic transport from the collision zone of Adria with Northern Europe toward the subduction zone of the Hellenic trench.

In the Western Carpathians the SW-NE trending orogen-parallel strike-slip faulting, occurring mainly within the suture of the Pieniny Klippen belt, facilitated the NW directed migration (escape) of material from the Eastern Alps toward the Carpathian realm. The transtensional stresses associated with this motion also led to the opening of the pull-apart depocenters within the Vienna basin.

The late orogenic strike-slip faulting may create large antiformal structures or deep depocenters and facilitate migration of hydrocarbons from deep source rocks into younger reservoirs. On the negative side, the deeply rooted strike-slip faults may breach the seals and restrict the lateral migration toward the foreland. In that respect, the distribution of com­pressional and extensional stresses and the timing of the late orogenic strike-slip faulting may both positively and negatively affect the hydrocarbon potential of various sectors of the orogenic belts and their forelands.