Abstract: Structural Development and Petroleum Potential of the Dagestan Foreland Thrust Belt, Terek-Caspian Basin, Russia

Konstantin Sobornov

The Dagestan foreland thrust belt represents a transition zone between the Terek-Caspian basin and Caucasus. Boreholes and seismic data obtained during the last decade in the course of petroleum exploration reveal considerable differences between the surface and subsurface structures of the area. The new data suggest that the allochthonous assemblage of the belt is formed mainly by stacked north-verging thrust sheets made up mostly of Mesozoic carbonates and sandstones bounded at the top and bottom by conjugate detachment surfaces. The thrust sheets are interpreted to be inserted into the clastic section of the Terek-Caspian foredeep along the base of Oligocene-early Miocene mudstones. The interpreted geometry of the thrust-belt front implies a shortening of about 20-50 km.

The blind subsurface thrusts have been active since late Miocene until Holocene. The interpreted structural relationships between Mesozoic-Cenozoic stratigraphic units imply that principal thrusts were formed due to reactivation and inversion of low-angle normal faults, which were active in the Jurassic-early Miocene. Mechanical weakness and low density of the overpressured Oligocene-lower Miocene Maykop Formation aided subsurface thrusting.

The new interpretation of the regional structure offers a petroleum exploration play consisting of structural traps within the buried antiformal stacks. Oil and gas bearing Upper Cretaceous and Upper Jurassic carbonate rocks involved in thrust sheets are considered primary prospecting targets.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994