M-F. Brunet¹, A. V. Ersov², Y. A. Volozh³, M. V. Korotaev², M. P. Antipov³, and J-P. Cadet¹

¹CNRS-University P. & M. Curie, Paris, France
²Moscow State University, Moscow, Russia
³Russian Academy of Sciences, Moscow, Russia

ABSTRACT: Subsidence Evolution of Two Superdeep Basins : Precaspian and South Caspian Basins

The Precaspian (PCB) and South Caspian (SCB) basins are two superdeep basins. Their modeling has been undertaken in the frame of the international Peri-Tethys Program. PCB is situated to the north of the Caspian Sea mainly on land, and has been trapped at the border of the East-European Platform with the closure of the Urals ocean during Carboniferous. It is also influenced by the repercussions of Tethys closure during Cenozoic, with the Caucasus compression to the South-West.

PCB contains about 20 km of clastic and carbonates sediments deposited since perhaps as old as the Riphean. It comprises a 4 km salt layer of Kungurian age (lower Permian). Salt movements produce numerous salt structures that prevent a precise analysis of the post salt subsidence.
The basement of the Central Precaspian depression is characterized by a thin crust (around 10 km) where low velocity layer is absent. Its origin is still controversial; it could be either thinned continental or oceanic crust. At the base of the crust, a 8-10 km layer of velocity 8-8.1 km/s is recognized by seismic and gravity observations : anomalously high velocities at the base of the crust are coinciding in place with intense gravitational maximums. Analysis of some peculiarities of the structure, gravitational field and composition of the crust leads to suppose that this layer may be interpreted as eclogite.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado