ABSTRACT: This paper summarizes the development and application of a local (Primorsk) correlation scheme that provides a chronostratigraphic framework for Mississippianâ€“Lower Pennsylvanian beds within the Kashagan oil field/carbonate buildup in western Kazakhstan. Results are based on amulti-well core study of calcareous foraminifers, algae, and incertae sedis. The scheme incorporates regional Russian substage nomenclature, modified to reflect differences in the Kashagan biota and sampling limitations of the core-drilling program. Modifications include the consolidation of some substages within the Tournaisian and Bashkirian into undifferentiated intervals and replacement of most upper Viseanâ€“lower Serpukhovian substageswith five biozones, named after the successive local appearances of the foraminifer Endothyranopsis crassa and the algae Fascifolium pantherinum, Asteroaoujgalia gibshmanae, Calcifolium okense, and Frustulata asiatica. The scheme is suitable for use in the cyclical, grain-supported, shallow-water platform-top beds that form the interior of the Kashagan buildup and may also have application to other open-marine, shallow-water limestones in the Pre-Caspian Basin. Microbialite facies at Kashagan occur along the buildup margin and dominate the upper slope,where they form massive boundstones in the upper Visean and Serpukhovian. They contain an encrusting microbiota that is mostly absent in coeval interior platform-top beds.
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