Correlation of the eastern segment of Tethyan Upper Jyrassic reef barrier and adjacent facies (Carpathian-Crimean-Caucasian area)
Authors: Zhabina Natalia 
Published: July 2024

The spread of the Oxfordian-Valanginian facial belts of the carbonate shelf is traced on the territory of the eastern segment of Tethyan Upper Jurassic reef barrier by the results of own research and analysis of the published data. It is based on the scheme of distribution of the standard facial belts (D. Wilson, 1980). Complex correlation of the reefogenic and related deposits is done on the basis of comparison of the litofacial and micropaleontological composition. Standard biozonal scheme by Tintinnida and correlative associations of the Foraminifera are used. Most complete reefogenic deposits are presented in the West Ukrainian (Stryi Jurassic deep), where reefal, reef-front and back-reef facies are distributed. They are overlap by the deposits of the open shelf. This carbonate complex is significantly eroded to the East and represented only by Oxfordian back-reef facies on the Kovel ledge and by biohermic belt in the Belarus Brest cavity. In the Pieniny Klippen Belt in the Ukrainian Carpathians, the fragments of the Oxfordian-Valanginian pelagic facies of carbonate shelf are distributed. In the deep basement of the Ukrainian Transcarpathians, the Upper Tithonian, Berriassian and Valanginian deposits of open shelf are presented. To the West, the similar Oxfordian-Valanginian facies of the carbonate shelf are spread out on the adjacent territory of Poland, but they are mostly eroded. Reef belt is represented only by Oxfordian bioherms on the Polish Lowland. Oxfordian and Kimmeridgian back-reef facies and Tithonian-Berriassian deposits are more widespread. Reef-front facies are represented only by the Oxfordian. These deposits are overlaped by the Berriassian–Valanginian open shelf sedimens. In the Polish Carpathian Pieniny Klippen Belt and Tatra Mts, the fragments of the Oxfordian–Valanginian pelagic deposits of carbonate shelf are presented. In the Flysch Carpathians, Tithonian-Berriassian reefal limestone and Oxfordian and Tithonian reef-front facies also are presented. Upper Jurassic reefogenic belt spread on the south-east in Predobrogian deep, where it is very eroded and overlaped by Lower Cretaceous rocks. Reefal facies is represented only by Middle Oxfordian – Lower Kimmeridgian biohermes. Back-reef facies of the Middle Oxfordian – Lower Kimmeridgian and Upper Tithonian – Lower Berriassian are present. Kimmeridgian and Tithonian lagoone-evaporite facies are the most spread. Reef-front facies are represented by the Oxfordian – Lower Kimmeridgian and Upper Tithonian. In the Crimean Orogen, Upper Jurassic reef barrier is represented by destroyed and insufficiently studied sections, because of that the complete regularity of facial directions is not found. Oxfordian – Lower Kimmeridgian and Upper Tithonian – Lower Berriassian reefal facies, as well as Lower Oxfordian, Upper Kimmeridgian – Lower Berriassian facies are presented. In Greater Caucasus, the Upper Jurassic – Lower Cretaceous carbonate complex is completed with the Oxfordian and Tithonian reefal facies and Oxfordian-Tithonian back-reef facies and evaporates, as well as by the Oxfordian-Valanginian pelagic deposits. These sections are fragmental, and the complete regularity of facial directions is not found. So, the eastern segment of Tethyan Upper Jurassic reefogenic complex is spread trough the regions of Carpathian Foredeep, Predobrogean deep, orogens of Carpathians, Crimea and Greater Caucasus. In the orogene structures, this complex is presented fragmentarily, and in the Polish Lowland and Predobrugean deep, it is very eroded. In the Stryi Jurassic deep, the complete complex of reef barrier is presented, and regularity of facial directions are determined. All specified facial belts in these regions are characterized by the similar lithologic composition, as well as by the same associations of Foraminifera and Tintinnida. This made it possible to implement the stratigraphic correlation of the lithofacies formations of the carbonate complex.