Karst caves in the Odessa region. Dep. Paper No.953 UK95 (Ukraine), 1995, Pronin K. K.

Petroleum geology of the Black Sea, 1996, Robinson A. G. , Rudat J. H. , Banks C. J. , Wiles R. L. F. ,

The Black Sea comprises two extensional basins formed in a back-arc setting above the northward subducting Tethys Ocean, close to the southern margin of Eurasia. The two basins coalesced late in their post-rift phases in the Pliocene, forming the present single depocentre. The Western Black Sea was initiated in the Aptian, when a part of the Moesian Platform (now the Western Pontides of Turkey) began to rift and move away to the south-east. The Eastern Black Sea probably formed by separation of the Mid-Black Sea High from the Shatsky Ridge during the Palaeocene to Eocene. Subsequent to rifting, the basins were the sites of mainly deep water deposition; only during the Late Miocene was there a major sea-level fall, leading to the development of a relatively shallow lake. Most of the margins of the Black Sea have been extensively modified by Late Eocene to recent compression associated with closure of the Tethys Ocean. Gas chromatography--mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the Black Sea can be explained by generation from an oil-prone source rock of most probably Late Eocene age (although a wider age range is possible in the basin centres). Burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post-rift basin. A Palaeozoic source rock may have generated gas condensate in the Gulf of Odessa. In Bulgarian waters, the main plays are associated with the development of an Eocene foreland basin (Kamchia Trough) and in extensional structures related to Western Black Sea rifting. The latter continue into the Romanian shelf where there is also potential in rollover anticlines due to gravity sliding of Neogene sediments. In the Gulf of Odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures. Small gas and oil discoveries around the Sea of Azov point to further potential offshore around the Central Azov High. In offshore Russia and Georgia there are large culminations on the Shatsky Ridge, but these are mainly in deep water and may have poor reservoirs. There are small compressional structures off the northern Turkish coast related to the Pontide deformation; these may include Eocene turbidite reservoirs. The extensional fault blocks of the Andrusov Ridge (Mid-Black Sea High) are seen as having the best potential for large hydrocarbon volumes, but in 2200 m of water

Paleontological expedition to caves of Odessa, 2009, Ridush B. Ò. , Pronin K. K

Speleogenesis in the Pontian limestones of Odessa, 2010, Klimchouk A. B. , Pronin K. K. , Timokhina E. I.

Ancient underground mines in the Pontian (Middle Miocene) limestones in the Odessa area (locally called ‘catacombs’) intercept numerous karst caves and karstified fractures. This paper analyses their conditions of occurrence, structure and morphology, as well as features of cave sediments. It is shown that the origin of these caves fits well to the model of transverse hypogene speleogenesis in stratified artesian structures. Caves were formed by ascending waters under conditions of a leaky confined aquifer system, with increasing leakage during the period of breaching by erosional entrenchment. 

Caves and karstified fractures in the Pontian limestones of Odessa represent an unambiguous model example, the typological standard of hypogenic karstification in stratified platform sequences.  By virtue of some features, the caves of Odessa provide a key for regional interpretation of karst through the huge area of the south Ukraine and Moldova, as well as of the Plain and Piedmont regions of the Crimea Peninsula.

Research and genetic interpretation of caves in the Pontian limestones of Odessa is of great importance for an assessment of hydrogeological and engineering-geological conditions of the area. The scheme of evolution of karst caves developed in article in a regional paleogeographic context provides a new basis for solving of some disputable questions of paleogeography of the region and eliminates some misunderstanding in treatment of the cave palaeontologic sites of Paleocene fauna.

Speleogenetic effects of interaction between deeply derived fracture-conduit and intrastratal matrix flow in hypogene karst settings, 2012, Klimchouk A. B. , Tymokhina E. I. , Amelichev G. N.

In carbonate rocks, especially in those with high primary porosity such as most Cenozoic carbonates, the interaction between deeply derived rising flow through sub-vertical fracture-controlled conduits and intrastratal matrix flow of shallower systems can invoke mixing corrosion and result in prominent speleogenetic effects. This paper outlines a conceptual model of such interaction and provides instructive field examples of relevant morphological effects from two different regions within the Prichernomorsky (north Black Sea) basin, where karst features are developed in lower Pliocene, Eocene and Paleocene limestones. In the Crimean fore-mountain region, extensive steep to vertical limestone scarps formed through recent exposure of hypogenic fracture-controlled conduits provide outstanding possibilities to directly examine details of the original karstic porosity. The morphological effects of the conduit/matrix interaction, documented in both caves and exposed scarps, include lateral widening of sub-vertical conduits within the interaction intervals (formation of lateral notches and niches) and the development of side bedding-parallel conduits, pockets and vuggy-spongework zones. Natural convection circulation, invoked by interaction of the two flow systems, spreads the morphological effects throughout the conduit space above the interaction interval. Where the interaction of the two flow systems is particularly strongly localized, such as along junctions of two vertical fracture sets, the resultant morphological effect can take the form of isolated chambers. The variety of speleogenetic features developed through the conduit/matrix interaction, can be broadly grouped into two categories: 1) variously shaped swells of the major fracture conduit itself (morphological features of its walls – niches and pockets), and 2) features of the vuggy-spongework halo surrounding the conduit. This halo includes clustered and stratiform cavities, spongework zones and lateral side conduits. The speleogenetic features due to conduit/matrix flow interaction, especially the halo forms, often demonstrate distinct asymmetry between opposite walls of the conduits. The prominent phenomenon of the vuggy-spongework halo around fracture-controlled conduits has important hydrogeological implications. A comparison of karst features in different regions and rock formations clearly shows that in spite of some distinctions imposed by local structural, sedimentological and paleo-hydrogeological peculiarities, hypogenic speleoforms in limestones of different age and of different degree of diagenetic maturity demonstrate remarkable similarities.