ABSTRACT: Seismic Expression of the Pre-Kungurian Carbonate Platform and Domes in the Pricaspian Basin, Kazakhstan

VOTSALEFSKY, EDGAR S., and VIKTOR M. PILIFOSSOV, Institute of Geological Sciences, Kazakh Academy of Sciences, Kazakhstan; and ROBERT RESSETAR* and STEVEN SCHAMEL, University of South Carolina, Columbia, SC

The main oil and gas deposits in the Pricaspian basin, including Karachaganak, Tengiz, and Astrakhan, are within large carbonate structures. The important carbonate deposits of Artinskian-Asselian, Moscovian-Visean, and Famennian-Givetian age are developed principally around the margins of the deep circular basin. Two types of structures are recognized in high-resolution seismic reflection lines: multistoried carbonate platforms having sharply delineated frontal scarps; and interbasin domes.

The interbasin carbonate domes are the more productive and geologically controversial features in the basin. They have elliptical dimensions on the order of several to tens of kilometers and they are commonly multistoried. Two hypotheses have been advanced to explain their origin. The first considers them erosional remnants of a deeply karstified, but originally extensive, carbonate shelf. The second view is that the carbonate domes are wholly constructional atolls and ringing reefs developed on elevated portions of the basin floor. The substrate on which the principal interbasin carbonate domes and small platforms formed was the Astrakhan-Aktyubinsk arch which from Middle Devonian to mid-Permian time separated the Pricaspian depression into two distinct subbasins.

High-resolution seismic reflection lines provide the best clues to the internal structure and origin of the pre-Kungurian (sub-salt) carbonate platforms and domes in the Pricaspian basin.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)