Abstract: First Elements of Modelling the Subsidence Evolution in the Peri-Caspian Basin

Marie-Francoise Brunet, Yuri A. Volozh, Alain Mauffret, Leopold L. Lobkovsky, Ulziihishig Purev, Jean-Paul Cadet

The Peri-Caspian basin is one of the most subsiding sedimentary basins, with a deposition o maybe more than 20 kilometers of sediments. The causes of this subsidence are not yet well recognized and several alternate models of the Peri-Caspian basin origin and evolution exist. The main mechanisms are: intracontinental rifting phases of Lower-Paleozoic, Devonian or even Permian age the formation of a residual peri-oceanic basin at Lower-Paleozoic or Devonian; a basalt-eclogite type phase transformation in the lower crust.

Seismostratigraphic analysis of numerous data obtained by drilling and seismic investigations allow to make up a well grounded chronostratigraphic scheme of the Peri-Caspian depression sedimentary cover and to reconstruct sedimentation environment of particular seismo-complexes. It shows that none of the models suggested above can account simply for the obtained reconstruction of thickness and facies distribution of Riphean-Paleozoic sediments.

The main task of the present project in collaboration, in the framework of the International Peri-Tethys Programme, is to create a more adequate model of the Peri-Caspian basin evolution making use of recent data as well as a reinterpretation of already existing schemes.

At first, simple models using several phases of crustal thinning and density modification arc tested to compute the tectonic subsidence through time. The subsidence and paleowater depths in the basin's center are inferred from these models, progressively improved, and compared to the observations and possible hypotheses (paleozoic levels in the basin's center have never been reached by wells).

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France