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Enviroscan Ukrainian Institute of Speleology and Karstology

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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. ...

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. ...

Did you know?

That interstratal karst is karst topography that is covered by and developed beneath prekarst rock or sediment and may or may not be part of the contemporary landscape. it is younger than its cover and is formed by the solution of soluble rock in the subsurface, most commonly beneath relatively insoluble rock such as sandstone or chert. the term refers to areal solution rather than to cave development but is also applicable to rejuvenated mantled karst and rejuvenated buried karst. subsoil karst is transitional to interstratal karst [17]. synonyms: (french.) karst sous-jacent; (german.) unterirdisches karstphanomen; (greek.) kalymenon karst; (italian.) carso coperto; (spanish.) karst interstradal; (turkish.) tabakalar arasi karst. see also buried karst; denuded karst; covered karst.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

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KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
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
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for oxygen-isotope (Keyword) returned 39 results for the whole karstbase:
Showing 1 to 15 of 39
Climatostratigraphic scheme of the Black Sea pleistocene and its correlation with the oxygen-isotope scale and glacial events, 1988,
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Zubakov V. A. ,
New evidence from the Asov Sea-Black Sea region shows that after the Cobb Mountain magnetic event (1.1 myr) there were 8 saline water events, with Mediterranean molluscs penetrating into the Asov Sea (five times farther than the western Manych Strait), and 7 or 10 cold freshwater events. During the freshening phase, the Caspian Sea molluscan fauna penetrated into the Black Sea; each time the Caspian mollusc assemblage was characterized by a new species of Didacna. Thus, some 18-20 bioclimatostratigraphic units can be distinguished in the Asov Sea-Black Sea section for the last 1 myr. Their numerical age is estimated by some dozen thermoluminescence dates and 12 magnetic-polarity datum planes. The Karangatian s. lato corresponds to the interval 300,000-50,000 yr, the Uzunlarian to 580,000-300,000 yr, and the Chaudian to 1,100,000-600,000 yr. The Karangatian and Tyrrhenian marine terraces correspond to marine isotope stages 5 and 7, the Uzunlarian and Milazzian to stages 11-15, and the Chaudian and Sicilian to stages 16-28. The number and ages of glacial-interglacial cycles in continental Europe are identical to the climatic cycles in the Black Sea and Mediterranean

The astronomical theory of climate and the age of the Brunhes-Matuyama magnetic reversal, 1994,
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Bassinot Fc, Labeyrie Ld, Vincent E, Quidelleur X, Shackleton Nj, Lancelot Y,
Below oxygen isotope stage 16, the orbitally derived time-scale developed by Shackleton et al. [1] from ODP site 677 in the equatorial Pacific differs significantly from previous ones [e.g., 2-5], yielding estimated ages for the last Earth magnetic reversals that are 5-7% older than the K/Ar values [6-8] but are in good agreement with recent Ar/Ar dating [9-11]. These results suggest that in the lower Brunhes and upper Matuyama chronozones most deep-sea climatic records retrieved so far apparently missed or misinterpreted several oscillations predicted by the astronomical theory of climate. To test this hypothesis, we studied a high-resolution oxygen isotope record from giant piston core MD900963 (Maldives area, tropical Indian Ocean) in which precession-related oscillations in [delta]18O are particularly well expressed, owing to the superimposition of a local salinity signal on the global ice volume signal [12]. Three additional precession-related cycles are observed in oxygen isotope stages 17 and 18 of core MD900963, compared to the composite curves [4,13], and stage 21 clearly presents three precession oscillations, as predicted by Shackleton et al. [1]. The precession peaks found in the [delta]18O record from core MD900963 are in excellent agreement with climatic oscillations predicted by the astronomical theory of climate. Our [delta]18O record therefore permits the development of an accurate astronomical time-scale. Based on our age model, the Brunhes-Matuyama reversal is dated at 775 10 ka, in good agreement with the age estimate of 780 ka obtained by Shackleton et al. [1] and recent radiochronological Ar/Ar datings on lavas [9-11]. We developed a new low-latitude, Upper Pleistocene [delta]18O reference record by stacking and tuning the [delta]18O records from core MD900963 and site 677 to orbital forcing functions

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Mylroie J. E. , Carew J. L. ,
The exposed carbonates of the Bahamas consist of late Quaternary limestones that were deposited during glacio-eustatic highstands of sea level. Each highstand event produced transgressive-phase, stillstand-phase, and regressive-phase units. Because of slow platform subsidence, Pleistocene carbonates deposited on highstands prior to the last interglacial (oxygen isotope substage 5e, circa 125,000 years ago) are represented solely by eolianites. The Owl's Hole Formation comprises these eolianites, which are generally fossiliferous pelsparites. The deposits of the last interglacial form the Grotto Beach Formation, and contain a complete sequence of subtidal intertidal and eolian carbonates. These deposits are predominantly oolitic. Holocene deposits are represented by the Rice Bay Formation, which consists of intertidal and eolian pelsparites deposited during the transgressive-phase and stillstand-phase of the current sea-level highstand. The three formations are separated from one another by well-developed terra-rossa paleosols or other erosion surfaces that formed predominantly during intervening sea-level lowstands. The karst landforms of San Salvador consist of karren, depressions, caves, and blue holes. Karren are small-scale dissolutional etchings on exposed and soil-covered bedrock that grade downward into the epikarst, the system of tubes and holes that drain the bedrock surface. Depressions are constructional features, such as swales between eolian ridges, but they have been dissolutionally maintained. Pit caves are vertical voids in the vadose zone that link the epikarst to the water table. Flank margin caves are horizontal voids that formed in the distal margin of a past fresh-water lens; whereas banana holes are horizontal voids that developed at the top of a past fresh-water lens, landward of the lens margin. Lake drains are conduits that connect some flooded depressions to the sea. Blue holes are flooded vertical shafts, of polygenetic origin, that may lead into caves systems at depth. The paleokarst of San Salvador is represented by flank margin caves and banana holes formed in a past fresh-water lens elevated by the last interglacial sea-level highstand, and by epikarst buried under paleosols formed during sea-level lowstands. Both carbonate deposition and its subsequent karstification is controlled by glacio-eustatic sea-level position. On San Salvador, the geographic isolation of the island, its small size, and the rapidity of past sea level changes have placed major constraints on the production of the paleokarst

Ancient helictites and the formation of vadose crystal silt in upper Jurassic carbonates (Southern Germany), 1998,
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Reinhold C. ,
Speleothems and vadose crystal silt are effective indications for karstification processes in the fossil record. Upper Jurassic limestones in Southern Germany that have undergone vadose diagenesis contain on crystal margins and tips of coarse bladed calcites numerous fibrous calcite crystals, formed by abnormal growth conditions, and internal sediment within fractures and vugs, Fibrous calcite crystals grew as crusts, in fence and mesh-like arrangements. Fibrous crystals, which have a length:width ratio of greater than 1:10, are made up of stacked subcrystals composed of an alternation of hexagonal prisms and rhombohedra, They exhibit a central to somewhat eccentric capillary. Electron probe microanalysis shows low-Mg calcite mineralogy with negligible amounts of Fe, Mn, and Sr as well as dis seminated clay and metal hydroxide impurities. Stable-isotope data show relatively C-13-enriched and O-18-depleted values (delta(13)C similar to parts per thousand PDB, delta(18)O similar to -6 parts per thousand PDB), suggesting a meteoric environment and CO2 degassing as the main process of formation, Fibrous calcite crystals form from capillary fluids that are highly supersaturated with respect to calcium carbonate, contaminated with alien mineral impurities. The abnormal growth pattern is suggested to be substrate-controlled and attributed to mineral impurities that produce numerous crystallization nuclei. Fibrous calcite crystals are comparable to helictites of the filiform type that are reported only from Quaternary caves. Nevertheless, the diagenetic sequence and oxygen isotope data suggest a Late Cretaceous to early Tertiary age for their formation. The internal sediment consists exclusively of silt-size fragments of fibrous crystals and therefore is comparable to vadose crystal silt. Crystal silt is generated by the erosion of fibrous crystals both by va dose seepage and air currents. This study is the first observation of ancient helictites and related vadose crystal silt, documenting the close relationship between pore ceiling vadose cements and the generation of crystal silt

Speleothem evidence for Holocene fluctuations of the prairie-forest ecotone, north-central USA, 1999,
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Denniston Rf, Gonzalez La, Baker Rg, Asmerom Y, Reagan Mk, Edwards Rl, Alexander Ec,
Carbon and oxygen isotopic trends from seven Midwestern speleothems record significant offsets in the timing of middle-Holocene vegetation change. Interactions of dry Pacific and moist Gulf of Mexico air masses maintained a sharp moisture gradient across Iowa, Minnesota, and Wisconsin such that the arrival of prairie was offset by 2000 years between caves and pollen sites located only 50 km apart. Oxygen isotopes shift concomitantly with carbon in most cases, although these changes are believed to represent increased evaporative enrichment of 18O prior to infiltration during the prairie period

Speleothem evidence from Oman for continental pluvial events during interglacial periods, 2001,
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Burns Sj, Fleitmann D, Matter A, Neff U, Mangini A,
Growth periods and stable isotope analyses of speleothems from Hoti Cave in northern Oman provide a record of continental pluvial periods extending back over the past four of Earth's glacial-interglacial cycles. Rapid speleothem growth occurred during the early to middle Holocene (6-10.5 ka B.P.), 78-82 ka B.P., 120-135 ka B.P., 180-200 ka B.P., and 300-325 ka B.P. The speleothem calcite deposited during each of these episodes is highly depleted in 18O compared to modern speleothems. The {delta}18O values for calcite deposited within pluvial periods generally fall in the range of -4{per thousand} to -8{per thousand} relative to the Vienna Peedee belemnite standard, whereas modern speleothems range from -1{per thousand} to -3{per thousand}. The growth and isotopic records indicate that during peak interglacial periods, the limit of the monsoon rainfall was shifted far north of its present location and each pluvial period was coincident with an interglacial stage of the marine oxygen isotope record. The association of continental pluvial periods with peak interglacial conditions suggests that glacial boundary conditions, and not changes in solar radiation, are the primary control on continental wetness on glacial-interglacial time scales

Thermal ionization mass spectrometry U-series dating of a hominid site near Nanjing, China, 2001,
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Zhao Jian Xin, Hu Kai, Collerson Kenneth D. , Xu Han Kui,
Mass spectrometric U-series dating of speleothems from Tangshan Cave, combined with ecological and paleoclimatic evidence, indicates that Nanjing Man, a typical Homo erectus morphologically correlated with Peking Man at Zhoukoudian, should be at least 580 k.y. old, or more likely lived during the glacial oxygen isotope stage 16 ([~]620 ka). Such an age estimate, which is [~]270 ka older than previous electron spin resonance and alpha-counting U-series dates, has significant implications for the evolution of Asian H. erectus. Dentine and enamel samples from the coexisting fossil layer yield significantly younger apparent ages, that of the enamel sample being only less than one-fourth of the minimum age of Nanjing Man. This suggests that U uptake history is far more complex than existing models can handle. As a result, great care must be taken in the interpretation of electron spin resonance and U-series dates of fossil teeth

Stable isotope stratigraphy of Holocene speleothems: examples from a cave system in Rana, northern Norway, 2001,
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Linge H. , Lauritzen S. E. , Lundberg J. , Berstad I. M. ,
High-precision TIMS U-series dates and continuous stable oxygen and carbon isotope profiles of a 4000 year stalagmite record from Rana, northern Norway, are presented and compared with data from two other speleothems from the same cave. The dating results yield ages from 387534 to 2963 years before AD2000, with 2[sigma] errors from 0.5 to 1%. The overall growth rate is 35 mm/ka, corresponding to a temporal resolution of 29 years/mm. The stalagmite is tested for isotopic equilibrium conditions, where all `Hendy' tests, except one, indicate isotopic equilibrium or quasi equilibrium deposition. Both the stable oxygen and carbon isotope records reveal a strong and abrupt enrichment in the near-top measurements. This corresponds in time to the opening of a second cave entrance in the late 1960s, which caused changes in the cave air circulation. The stable oxygen isotope signal is enriched compared to the modern value over the last 300 years, indicating a negative response to temperature changes. Likewise, the stable carbon isotope record is enriched in this period. However, both of the stable isotope records are shown to be significantly enriched compared to the isotope ranges displayed by other stalagmites in the same cave, and this questions the reliability of the proxy records derived from the presented stalagmite. Still, a general good correspondence of large scale fluctuations is found between the three stable oxygen isotope records from this cave. The stable carbon isotope records show large variations within the cave and are believed to be governed by soil-zone conditions, percolation pathways and possibly driprates

Key Largo Limestone revisited: Pleistocene shelf-edge facies, Florida Keys, USA, 2002,
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Multer H. G. , Gischler E. , Lundberg J. , Simmons K. R. , Shinn E. A. ,
New dates and analysis of 12 deep and 57 shallow cores allow a more detailed interpretation of the Pleistocene shelf edge of the Florida Platform as found in various facies of the Key Largo Limestone beneath the Florida Keys. In this study a three-phase evolution of the Quaternary units (Q1-Q5) of the Key Largo is presented with new subdivision of the Q5. (1) In the first phase, the Q1 and Q2 (perhaps deposited during oxygen-isotope stage 11) deep-water quartz-rich environment evolved into a shallow carbonate phase. (2) Subsequently, a Q3 (presumably corresponding to oxygen-isotope stage 9) flourishing reef and productive high-platform sediment phase developed. (3) Finally, a Q4 and Q5 (corresponding to oxygen-isotope stages 7 and 5) stabilization phase occurred with reefs and leeward productive lagoons, followed by lower sea levels presenting a sequence of younger (isotope substages 5c, 5a) shelf-margin wedges, sediment veneers and outlier reefs. The Key Largo Limestone provides an accessible model of a carbonate shelf edge with fluctuating water depth, bordering a deep seaward basin for a period of at least 300 ka. During this time, at least four onlaps/offlaps, often separated by periods of karst development with associated diagenetic alterations, took place. The story presented by this limestone not only allows a better understanding of the history of south Florida but also aids in the interpretation of similar persistent shelf-edge sites bordering deep basins in other areas

Climatic conditions during marine oxygen isotope stage 6 in the eastern Mediterranean region from the isotopic composition of speleothems of Soreq Cave, Israel, 2002,
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Ayalon A, Barmatthews M, Kaufman A,
At several times during marine oxygen isotope stage 6, the eastern Mediterranean region was influenced by two extreme climatic systems: the large ice sheet over northern Europe and the wet tropics associated with African monsoons. During this interval, two major climatic events occurred in the region; the sapropel S6 layer formed ca. 176 ka in the eastern Mediterranean basin owing to the increase in the African monsoon, and another event, although not large enough to form sapropel, occurred ca. 151 ka. The isotopic composition of Soreq Cave speleothems seems to record these events as very low {delta}18O-{delta}13C values dated as ca. 178 and 152 ka. The very low {delta}18O-{delta}13C values of -6{per thousand} and -11{per thousand} to -12{per thousand}, respectively, are typical of interglacial intervals, but here they were recorded during a glacial interval. Such low peaks indicate that in this part of the eastern Mediterranean region, i.e., Israel, the rainfall amount increased dramatically. Moreover, the isotopic record of the speleothems also shows that during the entire stage 6, although the climate was as cold as much of the last glacial, the conditions were never as dry

Start of the last interglacial period at 135 ka: Evidence from a high Alpine speleothem, 2002,
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Spotl Christoph, Mangini Augusto, Frank Norbert, Eichstadter Rene, Burns Stephen J. ,
A detailed study of growth periods of a flowstone from Spannagel Cave in the Zillertal Alps (Austria) at [~]2500 m above sea level, a site highly sensitive to climate changes, offers unprecedented new insights into Pleistocene climate change in Central Europe. Flowstone sample SPA 52 has a high U content (to 116 ppm); analyses of this sample reveal that episodes of calcite deposition started at 204 {} 3 ka, 135 {} 1.2 ka, and 122 ka, suggesting that at these times, the mean air temperature at this high Alpine site was within 1.5 {degrees}C of the present-day condition. The beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 {} 2.5 ka, as deduced from the absolutely dated oxygen isotope curve in sediments from the Bahamas, as well as with recent coral evidence from Barbados indicating a high sea level already by 135.8 {} 0.8 ka. This set of data supports evidence against Northern Hemisphere forcing of termination II, because the insolation maximum is at 127 ka

Constraints on Black Sea outflow to the Sea of Marmara during the last glacial-interglacial transition, 2002,
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Major Candace, Ryan William, Lericolais Gilles, Hajdas Irka,
New cores from the upper continental slope off Romania in the western Black Sea provide a continuous, high-resolution record of sedimentation rates, clay mineralogy, calcium carbonate content, and stable isotopes of oxygen and carbon over the last 20[punctuation space]000 yr in the western Black Sea. These records all indicate major changes occurring at 15[punctuation space]000, 12[punctuation space]800, 8400, and 7100 yr before present. These results are interpreted to reflect an evolving balance between water supplied by melting glacial ice and other river runoff and water removed by evaporation and outflow. The marked retreat of the Fennoscandian and Alpine ice between 15[punctuation space]000 and 14[punctuation space]000 yr is recorded by an increase in clays indicative of northern provenance in Black Sea sediments. A short return toward glacial values in all the measured series occurs during the Younger Dryas cold period. The timing of the first marine inflow to the Black Sea is dependent on the sill depths of the Bosporus and Dardanelles channels. The depth of the latter is known to be -805 m, which is consistent with first evidence of marine inundation in the Sea of Marmara around 12[punctuation space]000 yr. The bedrock gorge of the Bosporus reaches depths in excess of -100 m (relative to present sea level), though it is now filled with sediments to depths as shallow as -32 m. Two scenarios are developed for the connection of the Black Sea with the Sea of Marmara. One is based on a deep Bosporus sill depth (effectively equivalent to the Dardanelles), and the other is based on a shallow Bosporus sill (less than -35 m). In the deep sill scenario the Black Sea's surface rises in tandem with the Sea of Marmara once the latter connected with the Aegean Sea, and Black Sea outflow remains continuous with inflowing marine water gradually displacing the freshwater in the deep basin. The increase in the [delta]18O of mollusk shells at 12[punctuation space]800 yr and the simultaneous appearance of inorganic calcite with low [delta]18O is compatible with such an early marine water influx causing periodic weak stratification of the water column. In the shallow sill scenario the Black Sea level is decoupled from world sea level and experiences rise and fall depending on the regional water budget until water from the rising Sea of Marmara breaches the shallow sill. In this case the oxygen isotope trend and the inorganic calcite precipitation is caused by increased evaporation in the basin, and the other changes in sediment properties reflect climate-driven river runoff variations within the Black Sea watershed. The presence of saline ponds on the Black Sea shelf circa 9600 yr support such evaporative draw-down, but a sensitive geochemical indicator of marine water, one that is not subject to temperature, salinity, or biological fractionation, is required to resolve whether the sill was deep or shallow

Eustatic sea-level and climate changes over the last 600 ka as derived from mollusc-based ESR-chronostratigraphy and pollen evidence in Northern Eurasia, 2002,
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Molodkov Anatoly N. , Bolikhovskaya Nataliya S. ,
We reconstruct and correlate palaeoclimatic events and deposits from shelf, glacial, periglacial, and extraglacial zones of northern Eurasia over the last 600,000 years. The chronostratigraphical correlation of identified palaeoenvironmental and sea-level events and corresponding horizons is based on electron spin resonance (ESR) analysis of subfossil mollusc skeletal remains from marine, freshwater and Acheulian-bearing cave-site deposits. Over 230 shell samples from more than 40 sites along the continental margin of Eurasian north, in the Black and Caspian sea basins and terrestrial shells from a Lower Palaeolithic cave-site in the Northern Caucasus were dated via ESR to produce a late Quaternary geochronology. The Pleistocene composite section of the loess-palaeosoil formation includes two reference sections--Likhvin and Arapovichi--from the centre of the East-European plain. The palyno-chronostratigraphic record is interpreted as the product of six warm-climate/high sea-level events including the current interglacial, and six glacial events. They are presented either as complete climatic rhythms of glacial and interglacial rank, or by considerable portions of climatic-phytocoenotic phases constituents of the rhythm. The full-interglacial conditions are centred at about 580, 400, 310, 220 and between 145-70 calendar ka. A broad correspondence between long palynological sequence, directly ESR-dated warm-climate-related events and other palaeoenvironmental records described in the literature has been noted for 11 upper oxygen isotope stages (11 to 1). The results obtained in this study exemplify the potential of integrated chrono-climatostratigraphic sequences in linking marine and terrestrial palaeoclimate records that may eventually span the whole Brunhes chron

Carbonate-Hosted Zn-Pb Deposits in Upper Silesia, Poland: Origin and Evolution of Mineralizing Fluids and Constraints on Genetic Models, 2003,
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Heijlen Wouter, Muchez Philippe, Banks David A. , Schneider Jens, Kucha Henryk, Keppens Eddy,
Microthermometric and crush-leach analyses of fluid inclusions in ore and gangue minerals of the Upper Silesian Zn-Pb deposits, Poland, along with first results of Rb-Sr geochronology on sulfides, provide important constraints on the paleohydrogeologic and metallogenetic models for the origin of these ores. The analyzed samples comprise two generations of dolomite, two generations of sphalerite, galena, and late calcite. The two dolomite generations and the late calcite were also analyzed for their oxygen and carbon isotope compositions, allowing a characterization of the mineralizing fluids. The ore-forming fluids represent highly saline (20-23 wt % CaCl2 equiv) Na-Ca-Cl brines, episodically introduced into the Triassic host carbonates. They had an oxygen isotope composition of ~0 per mil V-SMOW. Their Na-Cl-Br content (molar Na/Br and Cl/Br ratios between 99 and 337 and between 248 and 560, respectively) suggests that they originated by evaporation of seawater, which most likely occurred in the Permian-Triassic. The relative concentrations of potassium (molar K/Cl between 0.0147 and 0.0746) and lithium (molar Li/Cl between 0.0004 and 0.0031) further indicate that the fluids significantly interacted with siliciclastic rocks. The ionic and calculated oxygen isotope compositions of the fluids indicate that they were more evolved than present-day brines in the Upper Silesian coal basin, and the present-day brines show more extensive mixing with low-salinity fluids. The first results of direct Rb-Sr dating of ore-stage sulfides yield an isochron model age of 135 {} 4 Ma for the mineralizing event. This is consistent with hydrothermal activity and ore formation in Upper Silesia occurring in response to Early Cretaceous crustal extension preceding the opening of the northern Atlantic Ocean. The data presented support a model in which bittern brines migrated down into the deep subsurface and evolved into mineralizing fluids owing to extensive water-rock interaction. They were episodically expelled along deeply penetrating faults during the Early Cretaceous to form Zn-Pb deposits in the overlying Mesozoic carbonate rocks

Regional Quaternary submarine geomorphology in the Florida Keys, 2003,
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Lidz Barbara H. , Reich Christopher D. , Shinn Eugene A. ,
High-quality seismic reflection profiles fill a major gap in geophysical data along the south Florida shelf, allowing updated interpretations of the history of the Quaternary coral reef system. Incorporation of the new and existing data sets provides the basis for detailed color maps of the Pleistocene surface and thickness of overlying Holocene accretions. The maps cover the Florida Keys to a margin-wide upper-slope terrace (30 to 40 m deep) and extend from The Elbow Reef (north Key Largo) to Rebecca Shoal (Gulf of Mexico). The data indicate that Pleistocene bedrock is several meters deeper to the southwest than to the north east, yet in general, Holocene sediments are [~]3 to 4 m thick shelf-wide. The Pleistocene map demonstrates the significance of a westward-dipping bedrock surface to Holocene flooding history and coral reef evolution. Seismic facies show evidence for two possible Holocene stillstands. Aerial photographs provide information on the seabed surface, much of which is below seismic resolution. The photographs define a prominent, regional nearshore rock ledge that extends [~]2.5 km seaward from the keys' shoreline. They show that bands of rock ridges exist along the outer shelf and on the upper-slope terrace. The photographs also reveal four tracts of outlier reefs on the terrace, one more than had been documented seismically. Seismic and photographic data indicate the tracts are >200 km long, nearly four times longer than previously thought. New interpretations provide insights into a youngest possible terrace age (ca. 175 ka?) and the likelihood that precise ages of oxygen isotope substage 5e ooid tidal-bar and coral reef components may differ. The tidal-bar/reef complex forms the Florida Keys

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