GENERAL CENOZOIC EVOLUTION OF THE MALDIVES CARBONATE SYSTEM (EQUATORIAL INDIAN-OCEAN), 1992, Aubert O, Droxler Aw,

Analyses and interpretation of an industrial multi-channel seismic grid, a 2.3 km-deep industrial well (NMA-1) and two ODP (Sites 715 and 716), have generated new insights into the evolution of the Maldives carbonate system, Equatorial Indian Ocean. The present physiography of the Maldives Archipelago, a double chain of atolls delineating an internal basin, corresponds only to the latest phase of a long and dynamic evolution, far more complex than the simple vertical build-up of reef caps on top of thermally subsiding volcanic edifices. Through the Cenozoic evolution of the Maldives carbonate system, distinct phases of vertical growth (aggradation), exposure, regional or local drowning, and recovery of the shallow banks by lateral growth (progradation) have been recognized. The volcanic basement underlying the Maldives Archipelago is interpreted to be part of a volcanic ridge generated by the northern drift of the Indian plate on top of the hotspot of the island of Reunion. The volcanic basement recovered at well NMA-1 and ODP Site 715 has been radiometrically dated as 57.2 1.8 Ma (late Paleocene) by 40Ar-39Ar. Seismic and magnetic data indicate that this volcanic basement has been affected by a series of NNE-SSW trending subvertical faults, possibly associated with an early Eocene strike-slip motion along an old transform zone. The structural topography of the volcanic basement apprears to have dictated the initial geometry of the Eocene and early Oligocene Maldives carbonate system. Biostratigraphic analyses of samples, recovered by drilling in Site 715 and exploration well NMA-1, show that the Maldives shallow carbonate system was initiated during the early Eocene on top of what were originally subaerial volcanic edifices. The Eocene shallow carbonate sequence, directly overlying the volcanic basement at NMA-1, is dolomitized and remains neritic in nature, suggesting low subsidence rates until the early Oligocene. During this first phase of the Maldives carbonate system evolution, shallow carbonate facies aggraded on top of basement highs and thick deep-water periplatform sediments were deposited in some central seaways, precursors of the current wider internal basins. In the middle Oligocene, a plate reorganization of the equatorial Indian Ocean resulted in the segmentation of the hotspot trace and the spreading of the Maldives away from the transform zone. This plate reorganization resulted in increasing subsidence rates at NMA-1, interpreted to be associated with thermal cooling of the volcanic basement underlying the Maldives carbonate system. This middle Oligocene event also coincides with a regional irregular topographic surface, considered to represent a karst surface produced by a major low-stand. Deep-water carbonate facies, as seen in cuttings from NMA-1, overlie the shallow-water facies beneath the karst surface which can, therefore, be interpreted as a drowning unconformity. In the late Oligocene, following this regional deepening event, one single central basin developed, wider than its Eocene counterparts, and the current intraplatform basin was established. Since the early to middle Miocene, the shallow carbonate facies underwent a stage of local recovery by progradation of neritic environments towards the central basin. The simultaneous onset in the early middle Miocene of the monsoonal wind regime may explain the development of bidirectional slope progradations in the Maldives. During the late Miocene and the early Pliocene, several carbonate banks were locally drowned, whereas others (i.e. Male atoll) display well-developed lateral growth through margin progradations during the same interval. Differential carbonate productivity among the atolls could explain these diverse bank responses. High-frequency glacialeustatic sea-level fluctuations in the late Pliocene and Pleistocene resulted in periodic intervals of bank exposure and flooding, and developed the present-day physiography of atolls, with numerous faros along their rims and within their lagoons

Ring of cenotes (sinkholes), Northwest Yucatan, Mexico; its hydrogeologic characteristics and possible association with the Chicxulub impact crater, 1995, Perry Eugene, Marin Luis E. , Mcclain Jana, Velazquez Guadalupe,

A 180-km-diameter semicircular band of abundant karst sinkholes (Ring of Cenotes) in Northwest Yucatan, Mexico, coincides approximately with a concentric ring of the buried Chicxulub structure, a circular feature manifested in Cretaceous and older rocks, that has been identified as the product of the impact of a bolide. The ring, expressed in Tertiary rocks, marks a zone of high permeability as shown by (1) the sinkholes themselves, (2) breaks in the coastal dune system and high density of springs where the ring intersects the coast, and (3) water-level transects characterized by a decline in water level toward the ring. Any direct relation that exists between the Ring of Cenotes and the Chicxulub structure bears on regional hydrogeology. If the layer or zone responsible for the ring is deeply buried, it may act as a barrier to the movement of ground water across the main flow direction. Shallower zones of horizontal permeability could result in less complete diversion of ground water. Through its influence on Yucatan aquifer characteristics, the ring may provide a link between modern environmental problems and astrogeology. Possible origins for the Ring of Cenotes are (1) faulting, perhaps reactivated by post-Eocene-mid-Miocene basin loading, (2) permeability in a buried reef complex developed in the shallow Paleocene sea around the crater rim, or (3) breccia collapse occasioned by consolidation or by solution of evaporite components. If the ring developed on ancient faults, it may outline hydrothermal systems and mineral deposits produced during Paleocene cooling of the Chicxulub melt sheet

Genesis of the Neogene interstratal karst-type Pöhrenk fluorite?barite (± lead) deposit (Kırşehir, Central Anatolia, Turkey), 2006, Genç, Yurdal

The Pöhrenk fluorite?barite (± lead) deposit is located 200 km east of Ankara, Central Anatolia, Turkey. The ores are hosted by sedimentary rocks of the east?west trending Tertiary Çiçekdağı foreland basin. The Çiçekdağı Basin is bounded by Paleozoic metamorphic rocks of the Kırşehir Massif in the south, and Upper Cretaceous ophiolites and Paleocene granitoids in the north. The basin contains mainly Eocene and Upper Miocene?Pliocene sediments. The Eocene sediments consist of conglomerate, sandstone, marl and carbonate. These are covered unconformably by red conglomerate, mudstone, sandstone, siltstone and claystone of Late Miocene?Pliocene age. Mineralization occurs both in Eocene (Lutetian) limestones and Neogene detrital rocks. The distribution of ores is controlled by the unconformity surface between limestones and detrital rocks. The main ore types are replacements, open-space fillings, breccias and veins. The Pöhrenk deposit was emplaced epigenetically after the host rocks and shares some characteristics with the paleokarst- and Mississippi-Valley-type deposits. Fluid inclusion and stable isotope data indicate that ore fluids for the mineralization were mildly hot (58 to 154 °C), highly saline (14 to 21 wt.% NaCl equivalent) formation waters and ore deposition occurred in a paleokarst environment. The driving force for fluid migration was both topographic gradients created by uplift and tectonic squeezing of basin sediments. The Paleocene granitoids in the north are considered as the potentially main source of F, Ba and Pb for the Pöhrenk deposit. Release of these elements from granitoids can be tied to erosion and leaching.

Les Microcodium : un traceur naturel des écoulements karstiques dans les craies champenoises à proximité des formations paléocènes (Marne, France)., 2007, Lejeune O. , Devos A. , Fronteau G. , Roche D. , Lefevre A. , Sosson C.

The microcodium: A natural tracer of karstic flowpaths in the Champagne chalk close to the Paleocene formations (Marne, France) - Our study group GEGENA was asked to study the karstic flowpaths witin the Champagne chalk. This work was done within a research program (AQUAL) investigating the agricultural pollutions within the Vesle basin. The absence of good conditions to conduct classical dye tracing experiments led us to search for a natural tracer to prove that karstic circulations do exist. A stratigraphic study permitted to isolate a microcodium fossil, present in the upper parts of the Campagnian chalks, which could be a natural tracer for the chalk karst area around the Montagne de Reims. This tracer is locally associated with archeological elements which permit to state that the flow is karstic. The Trépail spring was used as a test site for the validation of the method. The sediments collected in the spring as well as in other springs nearby do indeed contain many microcodium remains.

Successive Paleocene and Eocene infillings of polyphase paleokarsts within the Cretaceous limestones of the Emporda thrust sheets (Catalan Pyrenees, Spain) : relationships between tectonics and karsti, 2007, Peybernes Bernard, Fondecavewallez Marie Jose, Combes Pierre Jean, Seranne Michel,

The Mesozoic series of the southern units of the Pyrenean Emporda thrust sheets (Montgri and Figueres nappes, Catalonia, Spain) were finally emplaced over the autochthonous basement and its Cenozoic cover during Eocene times. However, they have originally been folded by the 'Laramian' compressional event (Late Cretaceous/Early Paleocene), while they were still in their root zone more than 50 km to the N-NE. Postdating the Santonian, the emersion of the Cretaceous tectorogen induced karst formation at the expense of Berriasian to Santonian limestone sequences. Karst cavities of this paleokarst 1 (lapiaz and canyons) were subsequently coated with a fine, red or black, Microcodium-bearing, continental silt, and infilled with marine chaotic breccias. Following a new episode of emersion then erosion, the original paleokarst 1 was cross-cut by newly formed cavities of the paleokarst 2, filled with Lutetian-Bartonian marine breccias. Both types of marine breccias (Paleocene then Eocene in age) are now relatively well dated by means of planktonic foraminifera (Globigerinacea) occurring within the argillaceous-sandy matrix, and for the older ones, within the argillaceous-sandy or carbonate, finely laminated, interbedded hemipelagites, that mark the top of marine sequences tens of centimetres thick. The relationships of the 'Laramian' and 'Pyrenean' compressional tectonic events, occurring from latest Cretaceous to Bartonian, with the development of paleokarsts 1 and 2 are analysed in the perspective of the progressive southwards emplacement of the Montgri thrust sheet, during Eocene time

Variation in rates of Karst processes, 2007, Palmer, A. N. ,

The development of karst is not a linear process but instead takes place at irregular rates that typically include episodes of stagnation and even retrograde processes in which the evolution toward maturity is reversed. The magnitude and nature of these irregularities differs with the length of time considered. Contemporary measurements in caves show fluctuations in dissolution rate with changes in season, discharge, and soil conditions. Dissolution is sometimes interrupted by intervals of mineral deposition. Observed dissolution rates can be extrapolated to obtain estimates of long-term growth of a solution feature. But this approach is flawed, because as the time scale increases, the rates are disrupted by climate changes, and by variations that are inherent within the evolutionary history of the karst feature (e.g., increased CO2 loss from caves as entrances develop). At time scales of 105-106 years, karst evolution can be interrupted or accelerated by widespread fluctuations in base level and surface river patterns. An example is the relation between karst and the development of the Ohio River valley in east-central U.S.A. At a scale of 106-108 years, tectonic and stratigraphic events cause long-term changes in the mechanism and style of karst development. For example, much of the karst in the Rocky Mountains of North America has experienced two phases of pre-burial Carboniferous karst, mineral accretion during deep burial from Permian to Cretaceous, extensive cave development during Paleocene-Eocene uplift, and stagnation and partial mineral deposition caused by late Tertiary aggradation. At such large time scales, it is difficult to determine rates of karst development precisely, if at all. Instead it is appropriate to divide the evolutionary history into discrete episodes that correlate with regional tectonic and stratigraphic events.

Palaeohydrogeological control of palaeokarst macro-porosity genesis during a major sea-level lowstand: Danian of the Urbasa–Andia plateau, Navarra, North Spain, 2007, Baceta Juan Ignacio, Wright V. Paul, Beavingtonpenney Simon J. , Pujalte Victoriano

An extensive palaeokarst porosity system, developed during a pronounced mid-Paleocene third-order lowstand of sea level, is hosted in Danian limestones of the Urbasa–Andia plateau in north Spain. These limestones were deposited on a 40–50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse-grained bioclastic accumulations. The sea-level fall that caused karstification was of approximately 80–90 m magnitude and 2.5 Ma in duration. During the exposure, a 450 m wide belt of sub-vertical margin-parallel fractures developed a few hundred metres inboard of the shelf edge. Most fractures are 90–100 m deep, average 1 m in width, and are associated with large erosional features created by collapse of the reefal margin. Inland from the fracture belt, three superimposed laterally extensive cave systems were formed over a distance of 3.5 km perpendicular to shelf edge, at depths ranging from 8–31 m below the exposure surface. The palaeocaves range from 0.3 to 2 m in height, average 1.5 m high. They show no evidence of meteoric processes and are filled with Thanetian grainstones rich in reworked Microcodium, a lithology that also occurs infilling the fractures. The caves are interpreted as due to active corrosion at the saline water–fresh-water mixing zone. Caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing-zone cave development beyond the fracture zone. Towards the platform interior, each cave system passes into a prominent horizon, averaging 1 m in thickness, of spongy porosity with crystal silt infills and red Fe-oxide coatings. The spongy horizons can be traced for 5.5 km inboard from the cave zone and occur at 10.5 m, 25 m and 32 m below the exposure surface. In the inland zone, two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m. All are analogous to Swiss-cheese mixing-zone corrosion in modern carbonate aquifers and probably owe their origins to microbiallymediated dissolution effects associated with a zone of reduced circulation in marine phreatic water. In the most landward sections a number of collapse breccia zones are identified, but their origin is unclear. The palaeokarst system as a whole formed during the pulsed rise that followed the initial sea-level drop, with the three main cave-spongy zones representing three successive sea-level stillstands, recorded by stacked parasequences infilling large erosional scallops along the shelf margin. The geometry of the palaeo-mixing zones indicates a low discharge system, and together with the lack of meteoric karstic features favours a semi-arid to arid climatic regime, which is further supported by extensive calcrete-bearing palaeosols occurring in coeval continental deposits.

Palaeohydrogeological control of palaeokarst macro-porosity genesis during a major sea-level lowstand: Danian of the Urbasa–Andia plateau, Navarra, North Spain, 2007, Baceta J. I. , Wright V. P. , Beavingtonpenney S. J. , Pujalte V.

An extensive palaeokarst porosity system, developed during a pronounced mid-Paleocene third-order lowstand of sea level, is hosted in Danian limestones of the Urbasa–Andia plateau in north Spain. These limestones were deposited on a 40–50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse-grained bioclastic accumulations. The sea-level fall that caused karstification was of approximately 80–90 m magnitude and 2.5 Ma in duration. During the exposure, a 450 m wide belt of sub-vertical margin-parallel fractures developed a few hundred metres inboard of the shelf edge. Most fractures are 90–100 m deep, average 1 m in width, and are associated with large erosional features created by collapse of the reefal margin. Inland from the fracture belt, three superimposed laterally extensive cave systems were formed over a distance of 3.5 km perpendicular to shelf edge, at depths ranging from 8–31 m below the exposure surface. The palaeocaves range from 0.3 to 2 m in height, average 1.5 m high. They show no evidence of meteoric processes and are filled with Thanetian grainstones rich in reworked Microcodium, a lithology that also occurs infilling the fractures. The caves are interpreted as due to active corrosion at the saline water–fresh-water mixing zone. Caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing-zone cave development beyond the fracture zone. Towards the platform interior, each cave system passes into a prominent horizon, averaging 1 m in thickness, of spongy porosity with crystal silt infills and red Fe-oxide coatings. The spongy horizons can be traced for 5.5 km inboard from the cave zone and occur at 10.5 m, 25 m and 32 m below the exposure surface. In the inland zone, two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m. All are analogous to Swiss-cheese mixing-zone corrosion in modern carbonate aquifers and probably owe their origins to microbially mediated dissolution effects associated with a zone of reduced circulation in marine phreatic water. In the most landward sections a number of collapse breccia zones are identified, but their origin is unclear. The palaeokarst system as a whole formed during the pulsed rise that followed the initial sea-level drop, with the three main cave-spongy zones representing three successive sea-level stillstands, recorded by stacked parasequences infilling large erosional scallops along the shelf margin. The geometry of the palaeo mixing zones indicates a low discharge system, and together with the lack of meteoric karstic features favours a semi-arid to arid climatic regime, which is further supported by extensive calcrete-bearing palaeosols occurring in coeval continental deposits.

STRUCTURAL GEOLOGY OF THE ŠKOCJAN CAVES (slovenija), 2009, Šebela Stanka

The Škocjan Caves are developed inside 300 m thick column of Cretaceous and Paleocene limestones. Most of the underground Reka River flows within the 130 m thick Lipica Formation(K2 4-5). Data from field structural geological mapping (1:500) performed in 1991-1992 (Hankejev Kanal) and in 1997- 2007 (Tiha and ©umeèa Jama) are analysed and presented on a new structural geological map. The Reka River follows bedding-plane strike and dip direction in ©umeèa Jama and Hankejev Kanal. From the western part of Hankejev Kanal to the ponor in Martelova Dvorana the Reka River flows perpendicular to strike direction of bedding-planes with dip direction of the bedding contrary to river flow. Bedding-planes with interbedded slips were especially favourable for the development of initial passages. The bend of the Reka River in Hankejev Kanal is developed at the intersection of multiple fault zones. Cross-Dinaric oriented faults in Podorna Dvorana and at northern edge of Martelova Dvorana can potentially be neotectonically active.

SEISMIC-SAG STRUCTURAL SYSTEMS IN TERTIARY CARBONATE ROCKS BENEATH SOUTHEASTERN FLORIDA, USA: EVIDENCE FOR HYPOGENIC SPELEOGENESIS?, 2009, Cunningham K. , Walker C.

High-resolution, multichannel seismic-re?ection data recently acquired mostly in Biscayne Bay, southeastern Florida, exhibit disturbances in parallel seismic re?ections that correspond to the carbonate rocks of the Floridan aquifer system and lower part of the overlying intermediate con?ning unit. These disruptions in seismic re?ections are indicative of structural characteristics in carbonate rocks of Eocene to middle Miocene age that are interpreted to be related to collapsed paleocaves or collapsed paleocave systems, and include (1) fractures; (2) faults; (3) narrow (hundreds-of-m- scale wide) seismic-sag structural systems; and (4) broad (km-scale wide) seismic-sag structural systems. Commonly, the seismic-sag structural systems are multistoried, re?ecting a vertical arrangement of cyclic zones of structural sags that exhibit a progressive evolution from cave formation; cave collapse; suprastratal sag; and in some cases, ?nal in?ll of the upward termination of sag zones. In the study area, these structural systems are buried by upper Miocene-to-Holocene sedimentary rocks and sediments; however, they may manifest as well-documented, hundreds-of-m-scale wide, sinkholes along the submarine surface of the continental margin in the Straits of Florida. The potential link between the seismic sags and submarine sinkholes suggests the sea?oor sinkholes began to form as early as during the Eocene. We will discuss, speleogenic mechanisms dominating the formation of the narrow, seismic-sag structures that include: vadose, water-table, regional mixing zone corrosive, and ?ank-margin processes. Further, three mechanisms are postulated for the speleogenesis of the paleocave systems associated with the broad seismic-sag structural systems: (1) corrosion by an Eocene mixed fresh-saltwater zone associated with a regional groundwater ?ow system beneath the southern part of the paleo-Florida Platform, (2) hypogenic speleogenesis associated with upward groundwater ?ow driven by Kohout convection and dissolution by mixed fresh and saline groundwater, or (3) hypogenic spelogenesis associated with the upward ascension of hydrogen-sul?de-bearing groundwater charged by dissolution and the reduction of calcium sulfates in deeper Eocene or Paleocene rocks. We will contrast and compare our theories on the timing and processes involved in the formation of seismic-sag structural systems with those proposed in the existing literature for the submarine sinkholes on the continental margin in the Straits of Florida, and discuss how the seismic-sag structural systems and submarine sinkholes may be linked. Future marine seismic data acquisition and interpretation is planned to help develop more accurate timing of formation of paleocaves and paleocave systems, their collapse, and structural impact on suprastratal rocks, and more decisive insight into the speleogenic processes that proceed during the evolution of these seismic-sag structural systems within the Florida Platform.

HYPOGENE SPELEOGENESIS IN THE PIEDMONT CRIMEA RANGE, 2009, Klimchouk A. , Tymokhina E. , Amelichev G.

Intense development of the theory and criteria for identification of hypogenic speleogenesis during the past few years has stimulated re-interpretation of karst phenomena in many regions of the world. Recent research strongly suggests that solution features in the Piedmont Range of the Crimean Mountains, previously believed to be the result of hypergene (epigene) karstification, were in fact formed in a hypogenic environment due to ascending transverse flow in a stratified artesian system. Tectonically, the Piedmont Range of Crimea is an edge of the Scythian Plate, uplifted and partially eroded along the regional fault separating the plate from the folded region of the Crimea Mountains. The Cretaceous and Paleogene sequence dips 5 to 20o to north and north-west, where it plunges beneath a Neogene cover. It is exposed within the Piedmont Range as a series of distinct cuestas generally facing south-east. Karst features are represented by 26 caves and abundant, diverse solution forms at the cuesta escarps. Most of the karst develops in two distinct limestone units of Paleocene (Danian) and Eocene (Lutetian) but some are present in the underlying Maastrichtian unit of Cretaceous. There are strong and systematic evidences that the caves have a hypogenic origin and that most of the solution features along the scarps are remnants of morphologies of hypogenically karstified fractures, the walls of which are now exposed due to block-fall retreat of the scarp faces. The features in various beds demonstrate strong lithostratigraphic control in their distribution and are vertically stacked into transverse complexes. Caves are fracture-controlled, linear, or crude maze clusters, demonstrating the complete suite of morphologies indicative of hypogenic origin. Isolated cavities, expressed in the contemporary scarps as grottoes, niches and as zones of spongework porosity, developed where laterally conductive beds of higher initial porosity were crossed by vertical fractures that once conducted rising fluids from an underlying regional flow system. The Piedmont Range of Crimea was a part of the Crimea Plain artesian basin before the Middle Pliocene. Subsequent uplift and initial erosional entrenchment through the Late Pliocene established the pattern of tectonically and geomorphologically guided zones of upward cross-formational discharge and hypogenic speleogenesis. Further valley entrenchment in the region during late Pliocene and early-middle Pleistocene shaped up the modern cuesta relief and drained the Cretaceous- Paleogene sequence. Hypogenically karstified fractures and caves, which are sub-parallel to valleys, provide zones of structural weakness along which blocks fall at the cuesta escarps exposing relict hypogenic morphologies. The Piedmont Crimea Range, with its perfect and extensive exposures of the hypogene karst sequence, provides outstanding opportunities for studying patterns and morphologies of hypogenic speleogenesis, which is important for understanding its hydrogeological functioning and roles in reservoir formation, especially in the adjacent Crimea Plain artesian basin.

Karst features of the south-west part of the Piedmont Crimea from the standpoint of the theory of hypogene speleogenesis, 2009, Klimchouk A. B. , Amelichev G. N. , Tymîkhina E. I.

The intense development of the theory and criteria of identification of hypogenic speleogenesis during last few years has stimulated re-interpretation of karst phenomena in many regions of the world. Recent research strongly suggest that solution features in the Piedmont Range of the Crimean Mountains, previously believed as being the result of epigenic karstification, were in fact formed in hypogenic environment due to ascending transverse flow in a stratified artesian system. Tectonically, the Piedmont Range of Crimea is an edge of the Scythian Plate, uplifted and partially eroded along the regional fault separating the plate from the folded region of the Mountain Crimea. The Cretaceous and Paleogene sequence is dipping 5 to 20o to north and north-west, where it plunges beneath the Neogene cover. It is exposed within the Piedmont Range as a series of distinct cuestas generally faced to south-east. Karst features are represented by 26 caves and abundant and diverse solution forms at the cuesta escarps. Most of karst features develop in two distinct limestone units of Paleocene (Danian) and Eocene but some are present in the underlying Maastrichtian unit of Cretaceous. There are strong and systematic evidences that the caves have hypogenic origin and that most of solution features at the escarps are remnants of morphologies of hypogenically karstified fractures, which walls are now exposed due to the block-fall retreat of the escarps. The features in various beds demonstrate strong lithostratigraphic control in their distribution and are vertically stacked into transverse complexes. Caves are fracturecontrolled, linear, or crude maze clusters, demonstrating the complete suit of morphologies indicative of hypogenic origin. Isolated cavities, expressed in the contemporary escarps as grottos and niches, as well as zones of spongework porosity, developed where laterally conductive beds of higher initial porosity were crossed by vertical fractures that once conducted rising fluids from a regional flow system.

The Piedmont Range of Crimea was a part of the Plain Crimea artesian basin during the post-Eocene time till the late Pliocene. Uplift and initial erosional entrenchment in the middle through late Pliocene caused the pattern of tectonically and geomorphologically guided zones of upward cross-formational discharge and hypogenic speleogenesis to establish. Further valley entrenchment in the region during Pleistocene shaped up the modern cuesta-like relief and drained the Cretaceous-Paleogene sequence. Hypogenically karstified fractures and caves, which are sub-parallel to valleys, provide zones of structural weakness along which blocks fall at the cuesta escarps exposing relict hypogenic morphologies.

The Piedmont Crimea Range, with its perfect and extensive exposures of the hypogenically karstified sequence, provides outstanding possibilities for studying patterns and morphologies of hypogenic speleogenesis, which is important for understanding its hydrogeological functioning and roles in the reservoir formation, especially in implication to the adjacent Plain Crimea artesian basin.

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.

Isotopic indications of water-rock interaction in the hypogene Tavrskaya cave, Crimea, Ukraine, 2011, Dublyansky Yuri, Klimchouk Alexander, Timokhina Elisaveta, Spö, Tl Christoph

The Inner Range of the Crimea Mountains has recently been identified as an area of previously unrecognized hypogene speleogenesis (Klimchouk et al. 2009). The entrance of the Tavrskaya cave is located in the middle of the 25 m-high scarp of the cuesta built up of Paleocene limestone. The cave comprises two parallel major passages (ca. 180 m long, up to 7-8 m high and up to 5-6 m wide) connected by a smaller passage. The major passages are slightly inclined toward the north-west following the dip of bedding. The morphology of the cave bears strong indications of dissolution at conditions of ascending flow in a confined aquifer setting.
A massive calcite crust, studied in this paper, was first found in a small cave located ca. 200 m from Tavrskaya cave along the cuesta scarp. According to its position and morphology, the cave corresponds to the rift-like “feeder” zone of Tavrskaya cave. Recently, similar calcite crust was found in Tavrskaya cave, in a rift-like passage of the  near-scarp zone. The crust is built up of a brownish translucent calcite whose columnar crystals (bounded by competitive growth surfaces) are arranged in a characteristic radiating pattern. Calcite contains only all-liquid inclusions indicating deposition at less than ca. 50ºC. It also contains filamentous biological material (possibly fungi or cyanobacteria), which sometimes facilitated entrapment of fluid inclusions. This calcite body is tentatively
interpreted as a paleo-spring deposit (ascending flow). In order to characterize the isotopic properties of this calcite and the bedrock limestone we drilled small-diameter cores through the calcite formation, as well as through the wall of a cavity devoid of calcite. Stable isotope analyses were performed along these cores. To provide a basis for comparison several samples from the same lithostratigraphic units were collected far from the cave. Along a 15 cm-long profile, both oxygen and carbon isotopes of the limestone remain stable at 18O = -4.3 0.2
h and 13C = -1.7 0.3 h (1). Only within the 1.5 cm-thick zone immediately underlying the calcite 18O and 13C values plunge to ca. -8 h and -9 h respectively,. It appears from this data that water rock-interaction associated with the deposition of this calcite produced only a thin alteration halo in the limestone. However, when data from the cave-wall cores are compared with those collected far from the cave, it appears that the “constant” values from cave walls are shifted relative to the presumably unaltered limestone values toward lower values by
ca. 1.5-3.0 h (oxygen) and 3-4 h (carbon). On the 18O-13C cross-plot the data for unaltered limestone, cave wall limestone, alteration halo, and secondary calcite plot along a well-defined line (R2=0.99).
We propose that the Paleocene limestone in the vicinity of the Tavrskaya cave has experienced a two-stage alteration. During the first stage, presumably associated with the process of cave excavation, the bedrock has been altered (18O depleted by 1.5 to 3.0 h and 13C by 3 to 4 %). The thickness of this zone of early alteration is unknown but must be larger than 15 cm (length of our cores). The second stage of alteration was associated with the deposition of calcite; during this stage the isotopic composition was further depleted (by 4-5 h in 18O and 8-10 h in 13C). The extent of alteration was much smaller, though, and restricted to zones where calcite was deposited (ca. 15 mm beneath the calcite).

Hypogene speleogenesis in the Cenozoic carbonates of the Prichernomorsky artesian basin (north Black Sea region), 2011, Klimchouk A. B. , Timokhina E. I. , Amelichev G. N.

This paper demonstrates the dominant hypogenic origin of caves and other karst features in the Prichernomorsky artesian basin, a major hydrogeological structure of the north Black Sea region. The basin occupies the south of the continental part of Ukraine and the north-central plain part of the Crimea Peninsula and is dominated by the Neogene (lower through middle Miocene) and Paleogene (Eocene through Paleocene) carbonate rocks, intercalated with sands, sandstones, clays and marls. The key study areas, in which some limestone members are exposed and partially drained, lie in the opposed sides of the basin: the north Black Sea region in the continental part (caves in Early Pliocene and Miocene limestones) and the Inner Range of the fore-mountain Crimea in the south, where the basin borders with the fold-trust Alpine mountain region (caves in Eocene and Paleocene limestones). The hypogenic origin of caves is strongly suggested by the analysis of cave morphology and occurrence relative to lithostratigraphy and structural features, cave sediments, isotopic and mineralogical data, and paleohydrogeological analysis. Despite of differences in age and diagenetic maturity of the host rocks, the caves demonstrate remarkable common features imposed by their common origin. The hypogenic speleogenetic model well explains observed specific hydrogeological and geochemical features of the regional multi-storey aquifer system in the central confined part of the basin. Hypogene speleogenesis is likely to play a role in the formation of carbonate-hosted reservoirs, as well as in the migration and accumulation of hydrocarbons in the Prichernomorsky basin.