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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

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That parent material is material from which soil or sediment was formed [16].?

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Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
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Your search for sea-level fall (Keyword) returned 12 results for the whole karstbase:
Miocene sea-level falls related to the geologic history of Midway Atoll, 1987, Lincoln J. M. , Schlanger Seymour O. ,

The influence of climatic change on exposure surface development: a case study from the Late Dinantian of England and Wales, 1996, Vanstone Simon,
Exposure surfaces represent an integral part of Asbian-Brigantian cyclothemic platform carbonates in England and Wales. These are characterized by the association of clay palaeosols, calcrete and palaeokarst and in most instances would appear to have been polygenetic. Alternating calcrete-karst stratigraphies associated with individual exposure surfaces indicate that the climate changed from semi-arid to humid to semi-arid conditions during each sea-level fall/rise cycle. Lowstand intervals were humid and resulted in karstification of the cyclothem-top sediments and the formation of a mineral soil. In contrast, regressive/transgressive phases were semi-arid and resulted in calcretization of the emergent platform carbonates. The influence that climatic cyclicity had upon exposure surface development was modulated by variations in platform bathymetry, subsidence and spatial climatic variation, and platforms exhibit their own individual record of what was essentially an idealized sequence of events. As with the sea-level oscillations responsible for cyclothemic sedimentation, the climatic cyclicity is thought to be the product of orbital forcing and probably reflects either eccentricity-driven shifts in the locus of monsoonal precipitation, or precession-driven variations in monsoonal intensity. If precessional in origin, exposure surface development represents a single minimum to minimum excursion, some 20 ka in duration, whereas if eccentricity-driven this may have been appreciably longer. Nevertheless, the immature nature of the exposure surfaces suggests that emergence was probably only of the order of a few tens of thousands of years

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

Two Ordovician unconformities in North China: Their origins and relationships to regional carbonate-reservoir characteristics, 1997, Liu B. , Wang Y. H. , Qian X. L. ,
The two unconformities developed on the tops of the Lower Ordovician Liangjiashan Formation (UF1) and the Middle Ordovician Majiagou- or Fengfeng Formation (UF2) are essential boundaries that controlled the formation and distribution of the Lower Paleozoic karst-related reservoirs. UF1 and UF2 have been interpreted as representing short-and long-terms of tectonic uplift, respectively, but new evidence led us to conclude that they were created by different original mechanisms and therefore the related reservoirs should be predicted in different ways. UF1 was commonly interpreted as the result of southern upwarping of the basement, but sequence-stratigraphic analysis supports its origin by eustatic sea-level changes. Spatially, the most favorable regional reservoirs controlled by UF1 should be located in the central area of North China, where the carbonate sediments experienced intensive shallow-subsurface dolomitization with following meteoric water leaching. UF2 was created by tectonic event which resulted in an intra-plate downward flexure and subsequent peripheral bulge. In the depression belt of central North China the younger strata (Fengfeng Fm) were protected, but along the bulge meteoric water eroded them. As a result, the potential regional reservoirs related to UF2 are likely to be distributed along the peripheral-uplift belts, especially around the remnant of the Fengfeng Formation. Based on the analysis of these two unconformities, the Early Paleozoic tectono-sedimentary evolution of North China Plate can be largely divided into four stages: (1) the Cambrian Period, characterized by eustatic sea-level rise and tectonic subsidence; (2) early stage of the Early Ordovician, characterized by eustatic-sea-level fall exceeding tectonic subsidence and development of UF1; (3) from the late stage of the Early Ordovician to the Middle Ordovician, featured by eustatic-sea-level rise and slow tectonic subsidence;(4) from the late stage of the Middle Ordovician to the Early Carboniferous, distinguished by vigorous tectonic uplift and development of UF2

Palaeomagnetic research of cave sediments in SW Slovenia, 1998, Bosá, K Pavel, Pruner Petr, Zupan Hajna Nadja

Three profiles of caves sediments (Divača fossil cave, Divaška Jama and Trhlovca Cave) were studied in the Kras near Divača village. Mineralogical study proved relatively uniform mineral composition of the light fraction indicating the main source from weathered sediments of Eocene flysch. Some minerals are derived from weathering profiles and crusts (e.g. gibbsite). Detailed magnetostratigraphic investigations of three profiles defined normal and reverse polarity magnetozones and shows the correlation between the profiles in the Divaška Jama and Trhlovca Cave. The narrow normal magnetozones probably correlate with the Jaramillo polarity event (0.90 to 0.97 Ma) of the Matuyama epoch. Those data indicate the substantial age of cave in which the last phase of filling started before 0.97 Ma and finished before the Brunhes/Matuyama boundary, i.e. around 0.73 Ma. Magnetostratigraphic data of the Divača profile detected two narrow normal magnetozones in the long reverse polarity zone which probably correlate with Olduvai and Reunion polarity events (about 1.67 to 1.87 Ma) of reverse Matuyama epoch or with some of normal magnetozones (about 3.8 to 5.0 Ma) within reverse Gilbert epoch. Data indicate the possibility that the cave was originated during the Messinian period characteristic by sea-level fall and evolution of deep karst in the Mediterranean Basin.


Genesis of the Dogankuzu and Mortas Bauxite Deposits, Taurides, Turkey: Separation of Al, Fe, and Mn and Implications for Passive Margin Metallogeny, 2002, Ozturk Huseyin, Hein James R. , Hanilci Nurullah,
The Taurides region of Turkey is host to a number of important bauxite, Al-rich laterite, and Mn deposits. The most important bauxite deposits, Do[g]ankuzu and Morta[s], are karst-related, unconformity-type deposits in Upper Cretaceous limestone. The bottom contact of the bauxite ore is undulatory, and bauxite fills depressions and sinkholes in the footwall limestone, whereas its top surface is concordant with the hanging-wall limestone. The thickness of the bauxite varies from 1 to 40 m and consists of bohmite, hematite, pyrite, marcasite, anatase, diaspore, gypsum, kaolinite, and smectite. The strata-bound, sulfide- and sulfate-bearing, low-grade lower part of the bauxite ore bed contains pyrite pseudomorphs after hematite and is deep red in outcrop owing to supergene oxidation. The lower part of the bauxite body contains local intercalations of calcareous conglomerate that formed in fault-controlled depressions and sinkholes. Bauxite ore is overlain by fine-grained Fe sulfide-bearing and calcareous claystone and argillaceous limestone, which are in turn overlain by massive, compact limestone of Santonian age. That 50-m-thick limestone is in turn overlain by well-bedded bioclastic limestone of Campanian or Maastrichtian age, rich with rudist fossils. Fracture fillings in the bauxite orebody are up to 1 m thick and consist of bluish-gray-green pyrite and marcasite (20%) with bohmite, diaspore, and anatase. These sulfide veins crosscut and offset the strata-bound sulfide zones. Sulfur for the sulfides was derived from the bacterial reduction of seawater sulfate, and Fe was derived from alteration of oxides in the bauxite. Iron sulfides do not occur within either the immediately underlying or overlying limestone. The platform limestone and shale that host the bauxite deposits formed at a passive margin of the Tethys Ocean. Extensive vegetation developed on land as the result of a humid climate, thereby creating thick and acidic soils and enhancing the transport of large amounts of organic matter to the ocean. Alteration of the organic matter provided CO2 that contributed to formation of a relatively 12C-rich marine footwall limestone. Relative sea-level fall resulted from strike-slip faulting associated with closure of the ocean and local uplift of the passive margin. That uplift resulted in karstification and bauxite formation in topographic lows, as represented by the Do[g]ankuzu and Morta[s] deposits. During stage 1 of bauxite formation, Al, Fe, Mn, and Ti were mobilized from deeply weathered aluminosilicate parent rock under acidic conditions and accumulated as hydroxides at the limestone surface owing to an increase in pH. During stage 2, Al, Fe, and Ti oxides and clays from the incipient bauxite (bauxitic soil) were transported as detrital phases and accumulated in the fault-controlled depressions and sinkholes. During stage 3, the bauxitic material was concentrated by repeated desilicification, which resulted in the transport of Si and Mn to the ocean through a well-developed karst drainage system. The transported Mn was deposited in offshore muds as Mn carbonates. The sulfides also formed in stage 3 during early diagenesis. Transgression into the foreland basin resulted from shortening of the ocean basin and nappe emplacement during the latest Cretaceous. During that time bioclastic limestone was deposited on the nappe ramp, which overlapped bauxite accumulation

Temporal evolution of tertiary dolostones on Grand Cayman as determined by Sr-87/Sr-86, 2003, Jones B. , Luth R. W. ,
On the Cayman Islands, the Tertiary Bluff Group (Brac Formation, Cayman Formation, Pedro Castle Formation) is onlapped and overlain by the Pleistocene Ironshore Formation. On Grand Cayman, the Brac Formation and Cayman Formation are formed of finely crystalline dolostones; whereas the Pedro Castle Formation is formed of finely crystalline dolostones, dolomitized limestones, and limestones. No dolomite has been found in the Ironshore Formation. Dolostones in the Bluff Group, which retained their original depositional textures and lack evidence of any recrystallization, are formed of small (typically 5-15 mum long) interlocking, euhedral dolomite crystals. Dolomite cement is present in the Brac Formation and Cayman Formation but is very rare in the Pedro Castle Formation. Most of the dolomite crystals are characterized by oscillatory zoning with alternating zones of low-Ca calcian dolomite and high-Ca calcian dolomite. Grand Cayman is ideal for assessing the temporal evolution of Tertiary dolostones because the dolostones are young, have not been recrystallized, and are geographically isolated by the deep oceanic waters around the island. Interpretation of 158 new Sr-87/Sr-86 ratios from the dolostones in the Bluff Group indicate that the succession underwent three time-transgressive phases of dolomitization during the Late Miocene, the Late Pliocene, and Pleistocene. Petrographically similar dolomite was produced during each phase of dolomitization that was mediated by the same type of fluid and the same general conditions. Dolomitization was part of a dynamic cycle of processes that followed major lowstands. Karst development during the lowstands preconditioned the limestones for dolomitization by increasing their porosity and permeability. Thus, vast quantities of the dolomitizing fluids could freely circulate through the strata during the subsequent transgression. Dolomitization ceased once a stable highstand had been attained

Relative Sea-Level Changes Recorded on an Isolated Carbonate Platform: Tithonian to Cenomanian Succession, Southern Croatia, 2006, Husinec Antun, Jelaska Vladimir,
Superb sections of Tithonian to Cenomanian carbonates of the Adriatic (Dinaric) platform are exposed on the islands of southern Croatia. A succession approximately 1,800 m thick consists exclusively of shallow-water marine carbonates (limestone, dolomitized limestone, dolomite, and intraformational breccia), formed in a protected and tectonically stable part of the platform interior. Several phases of exposure and incipient drowning are recorded in the platform interior. Four are crucial for understanding the Late Jurassic to mid-Cretaceous evolution of the wider peri-Adriatic area: (1) latest Jurassic-earliest Cretaceous sea-level fall, (2) Aptian drowning, followed by (3) Late Aptian platform exposure, and (4) Late Albian-Early Cenomanian sea-level fall. Deciphering these complex events from the vertical and lateral facies distribution has led to an evaluation of facies dynamics and construction of a relative sea-level curve for the study area. This curve shows that long-term transgression during the Early Tithonian, Hauterivian, Early Aptian, and Early Albian, resulted in generally thicker beds deposited in subtidal environments of lagoons or shoals. Regression was characterized by shallowing-upward peritidal parasequences, with well-developed tidal-flat laminites commonly capped by emersion breccia and/or residual clay sheets (Early Berriasian, Barremian, Late Aptian, Late Albian). The southern part of the Dinarides was tectonically quiet during the Tithonian through Aptian; sea-level oscillations appear to have been the primary control on facies stacking. Some correlation exists between local sea-level fluctuations and the published global eustasy charts for the Tithonian through Aptian. A significant departure is recognized at the Albian-Cenomanian transition, suggesting that it was influenced by tectonics associated with the disintegration of the Adriatic (Dinaric) platform

Geodynamic evolution of the peri-Mediterranean karst during the Messinian and the Pliocene: evidence from the Ardeche and Rhone Valley systems canyons, Southern France, 2006, Mocochain Ludovic, Clauzon Georges, Bigot Jean Yves, Brunet Philippe,
During the Messinian-Pliocene eustatic cycle, the Mediterranean Sea was characterized by a short lived (5.95-5.32[no-break space]Ma) sea-level fall, which attained - 1500[no-break space]m in some areas. The study of benchmark levels permits the chronology and dynamics of this event to be established. In the Rhone's middle valley, our investigations allow a new interpretation for the genesis of the Ardeche endokarst. A fall in base-level was responsible for both the incision of the so-called Messinian canyons as well as a deep karst development. Karst systems were formed in association with the Messinian canyons of the Ardeche and Rhone Rivers. During the flooding of the Mediterranean Basin (5.32[no-break space]Ma), these karst systems were filled by water and plugged by sedimentary infilling of the rias. This mechanism pushed groundwater backward through the karst system, which in turn formed diagnostic 'chimney-shafts'. These pathways were geometrically connected to the position of the Pliocene benchmark levels. Consequently, the Messinian Salinity Crisis was responsible for two karst responses.The first was concomitant with the crisis itself and corresponds to the formation of a karst system. The second followed the Messinian Salinity Crisis and corresponds to the adaptation of this karst system in Vauclusian karsts by the formation of 'chimney-shafts'

The beginning, development and termination of the Middle Miocene Badenian salinity crisis in Central Paratethys, 2006, Peryt Tadeusz Marek,
Middle Miocene Badenian evaporites of the Carpathian region are underlain and overlain by deep-water deposits, the onset of evaporite deposition was sudden but not synchronous in all facies zones and the deposition of evaporites was controlled by the evolution of Carpathian orogen. In the Carpathian Foredeep (and most probably in other basins) the Badenian evaporites represent the lower part of the NN6 zone. Halite and associated deposits in the central part of the Badenian evaporite basin show the same facies successions and marker beds can be traced across and between individual basins. Characteristic marker beds made it possible to correlate various facies zones of the marginal Ca-sulfate platform. These marker beds seem to reflect events that may be related to sudden and widespread changes in water chemistry, which in turn imply major changes in basin hydrology. The onset of the evaporitic deposition in the Carpathian Foredeep was clearly diachronous and the evaporites deposited in the basin centre preceded the beginning of evaporite sedimentation in the marginal basin, however, depositional history in the marginal basin and the basin centre was the same. A general transgressive sequence of evaporites found in the Carpathian Foredeep resulted from the migration of facies zones induced by the nappe movement.Isotopic studies of Badenian foraminifers occurring below evaporites suggest that the interrupted communication of the Paratethys with the ocean was a consequence of eustatic sea-level fall, possibly related to climatic cooling, and it was coupled with a tectonic closure of connection with the Tethys. Thus both tectonics and eustacy have contributed to the origin of salinity crisis. Sedimentological and geochemical data indicate recycling of evaporites throughout most of the evaporite deposition. The recycling at the end of gypsum deposition in the marginal sulfate platform was accompanied by a change in the hydrology of the Central Paratethys that was tectonically-driven, and possibly related to the block tectonic phase manifested in the marginal part of the Carpathian Foredeep Basin. The change in hydrology implied the dilution of brines by inflowing marine water and this terminated the Middle Miocene Badenian salinity crisis. The onset of the Badenian salinity crisis shows great similarities to the onset of the Messinian salinity crisis and the terminations of both crises were different

Palaeohydrogeological control of palaeokarst macro-porosity genesis during a major sea-level lowstand: Danian of the UrbasaAndia 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 UrbasaAndia 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.


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