Paleogeographc formatıon condıtıons of Eocene deposıts ın the Black sea–Caucasus region

Background. Eocene sediments are considered one of the key oil source strata that shape the hydrocarbon potential of the South Caspian Basin. Geochemical studies on adjacent land have confirmed the universally high generation properties of Eocene sediments. However, within the Caspian Sea, these strata occur at significant depths and have not been penetrated by wells or studied using geochemical methods. Under these conditions, the geochemical parameters of Eocene sediments in the basin can only be estimated by analogy with those in adjacent land areas, based on established and predicted lateral patterns and facies zonation of paleobasins.

Aim. To perform paleogeographic reconstructions of Paleocene-Eocene sedimentary basins in the Caspian–Caucasus region, analyze the sedimentation conditions and formation of the generation properties of Eocene sediments, and predict their geochemical characteristics, including in the South Caspian.

Materials and methods. The study employed data from published and archived large- and small-scale lithological and paleogeographic maps, rock composition and geochemical properties, as well as those on the actual petroleum potential of the Paleogene interval of the section. Regional-level paleogeographic reconstructions were developed based on lithofacies characteristics and rock thickness maps developed by the authors. The resulting paleogeographic models were used to extrapolate the generation properties and predict the geochemical characteristics of Eocene deposits within the Southern Caspian Sea.

Results. The paleogeographic reconstructions allowed us to characterize the main developmental features of Eocene sedimentary basins in the Caspian–Caucasus region and identify major sedimentation facies zones favorable for the formation of oil source strata. Based on a combined analysis of paleogeographic and geochemical data, a forecast of the petroleum source properties of Eocene sediments and the possible range of their geochemical parameters in the Southern Caspian Sea was made.

Conclusion. The conducted study demonstrated that the petroleum source properties of the re- gional Eocene source strata are controlled by its facies features. Carbonate Eocene sediments, formed under favorable reducing conditions in a shallow basin, possess a high generation potential and are a key source of liquid hydrocarbons in the Caspian–Caucasus region. In deep-water basins of the Eocene basin with high sedimentation rates, including the South Caspian Depression, a deterioration in the petroleum source properties of sediments is predicted as a result of dilution of the terrigenous component of marine organic matter. However, even taking into account the deterior- ation of the initial generation potential of rocks within the modern water area compared to areas of adjacent land, there is a high probability of the presence of oil source strata with satisfactory properties in the water area of the South Caspian.

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