THE ROLE OF VENDOTHENIAN ALGAE IN THE FORMATION OF THE PETROLEUM GENERATION POTENTIAL OF THE EDIACARAN KALUS BEDS OF THE VOLYN-PODILLIA PLATE

Abstract

The Ediacaran strata of the southwestern slope of the East European Platform dip monoclinally to the southwest in the direction of the Teisseire-Tornquist Zone. These sediments are distributed within the platform from the Black Sea to the Lublin-Podlasie Basin, and their thickness reaches more than 600 m. The Ediacaran sequence is characterized by the presence of organic-rich beds, which have a global distribution and are petroleum source rocks for a number of fields in the world. In Ukraine, in particular, within the Volyn-Podillia Plate, black shale strata are represented by Kalus Beds whose thickness exceeds 90 meters. They locally reach the surface near the Ukrainian Shield and dip in the southwest direction reaching depths of over 4000 m. The rocks are represented by thin-bedded dark gray to black mudstones, enriched with organic matter. Mudstones and clay siltstones are made up of mainly of hydromica and a small amount of kaolinite and montmorillonite with admixture of quartz, feldspar and glauconite. The organic matter of the rocks of the Kalus Beds is mainly represented by fragments of Vendotenides algae and their structureless detritus. Geochemical investigations of these rocks were carried out to establish their petroleum generation potential. The studies covered rocks from both outcrops and deep wells. The total organic carbon content in the rocks of the Kalus Beds ranges from 0.15 to 0.89%, often exceeding 0.5%, which allows us to consider them as the potential petroleum source rocks. Studies of the thermal maturity of rocks have shown that in the territory adjacent to the Ukrainian Shield they are immature. In most of the studied territory, as the depth of the rock increases, they successively enter the oil and gas generation zones. In the part of the Volyn- Podillia Plate adjacent to the Teisseire-Tornquist Zone the rocks are overmature.