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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 stress, neutral is fluid pressure exerted equally in all directions at a point in a saturated deposit by the head of water. neutral pressure is transmitted to the base of the deposit through the pore water, and does not have a measurable influence on the void ratio or on any other mechanical property of the deposits [21].?

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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 atlantic (Keyword) returned 59 results for the whole karstbase:
Showing 16 to 30 of 59
Vein and Karst Barite Deposits in the Western Jebilet of Morocco: Fluid Inclusion and Isotope (S, O, Sr) Evidence for Regional Fluid Mixing Related to Central Atlantic Rifting, 2000, Valenza Katia, Moritz Robert, Mouttaqi Abdellah, Fontignie Denis, Sharp Zachary,
Numerous vein and karst barite deposits are hosted by Hercynian basement and Triassic rocks of the western Jebilet in Morocco. Sulfur, oxygen, and strontium isotope analyses of barite, combined with fluid inclusion microthermometry on barite, quartz, and calcite were used to reveal the nature and source of the ore-forming fluids and constrain the age of mineralization. The{delta} 34S values of barite between 8.9 and 14.7 per mil are intermediate between the sulfur isotope signatures of Triassic evaporites and Triassic-Jurassic seawater and lighter [IMG]f1.gif' BORDER='0'>, probably derived from the oxidation of dissolved H2S and leaching of sulfides in the Hercynian basement. The 87Sr/86Sr ratios of barite between 0.7093 and 0.7130 range between the radiogenic strontium isotope compositions of micaceous shale and sandstone and the nonradiogenic isotopic signature of Triassic to Jurassic seawater and Cambrian limestone. The{delta} 18O values of barite between 11 and 15 per mil (SMOW) support mixing between two or more fluids, including Late Triassic to Jurassic seawater or a water dissolving Triassic evaporites along its flow path, hot basinal, or metamorphic fluids with{delta} 18O values higher than 0 per mil and/or meteoric fluids with{delta} 18O values lower than 0 per mil. The general trend of decreasing homogenization temperatures and initial ice melting temperatures with increasing salinities of H2O-NaCl {} CaCl2 fluid inclusions trapped in barite, quartz, and calcite indicates that a deep and hot basinal fluid with salinities lower than 6 wt percent NaCl equiv might have mixed with a cooler surficial solution with a mean salinity of 20 wt percent NaCl equiv. Calcium was leached from the Cambrian limestone and the clastic and mafic volcanic rocks of the Hercynian basement. Alkali feldspars and micas contained in the Cambrain sandstones provided most of the Ba to the hydrothermal system. Vein and karst deposits are modeled as a two-component mixing process in which the temperature and the S and Sr isotope composition of the end members changed during the 220 to 155 Ma interval. The hot basinal fluid remained volumetrically dominant during the entire mineralization process. Differences in mean S, O, and Sr isotope compositions among the barite families are interpreted as reflecting differences in mineralization age. Most barite deposits formed before the Kimmeridgian, except for north-south-oriented vein barite, karst barite, and barite cement in the conglomeratic Upper Jurassic, which were deposited later, possibly around 155 Ma. Similar genetic processes have been described for late Paleozoic to Mesozoic F-Ba vein deposits in western Europe. The vein and karst barite in the western Jebilet of Morocco reveals a wide-scale regional mineralization event related to Central Atlantic rifting

Last interglacial reef growth beneath Belize barrier and isolated platform reefs, 2000, Gischler Eberhard, Lomando Anthony J. , Hudson J. Harold, Holmes Charles W. ,
We report the first radiometric dates (thermal-ionization mass spectrometry) from late Pleistocene reef deposits from offshore Belize, the location of the largest modern reef complex in the Atlantic Ocean. The results presented here can be used to explain significant differences in bathymetry, sedimentary facies, and reef development of this major reef area, and the results are significant because they contribute to the knowledge of the regional geology of the eastern Yucatan. The previously held concept of a neotectonically stable eastern Yucatan is challenged. The dates indicate that Pleistocene reefs and shallow-water limestones, which form the basement of modern reefs in the area, accumulated ca. 125-130 ka. Significant differences in elevation of the samples relative to present sea level (>10 m) have several possible causes. Differential subsidence along a series of continental margin fault blocks in combination with variation in karstification are probably the prime causes. Differential subsidence is presumably related to initial extension and later left-lateral movements along the adjacent active boundary between the North American and Caribbean plates. Increasing dissolution toward the south during Pleistocene sea-level lowstands is probably a consequence of higher precipitation rates in mountainous southern Belize

Evolution of river network at the 'Cevennes-Grands Causses' transition: Consequences for the evaluation of uplift, 2001, Camus H,
The Mediterranean catchment of the Cevennes (S. France) presents deep incision of the river network (fig. 1 and 2). Combined geomorphology and analyses of the residual sedimentary formations allows to reconstruct a complex history of river network evolution, including capture of tributaries of the Herault River (fig. 1, 2 and 3). The history of uplift of the upstream drainage area could be estimated from the provenance studies of the fluvial and karstic deposits, however river incision is also controlled sea-level changes and differential erosion, which makes reconstruction more complex. Allochthonous clasts types Analyses of allochtonous deposits on the Grands Causses surface reveals different origin for sediments from the hill top and the Airoles valley (fig. 4b), which was previously unrecognised. Facies 1 is found on the highest points of the Grands Causses surface (well sorted rounded quartz pebbles in red shale matrix) it corresponds to a weathered residual sediments (dismantling of an ancient cover). Facies 2 is found on the slope of the Airoles Valley (fig. 7). It consists of alluvial crystalline poorly sorted clasts with outsized clasts (up to 50cm) of quartz-vein, schists in a matrix of shales and sand (weathered granite). Between the hill tops and the Airoles Valley, karstic network presents a sediment fill with clasts reworked from facies I and facies 2 (fig. 6). Airoles valley model : an example of diachronic formation of drainage network The Airoles dry valley stretches on the Grands Causses from the north (700 m) to the south into the present thalweg line of the Vis canyon (500 m) (fig. 1b & 3). Crystalline deposits witness an ancient catchment in the Cevennes. Presently, the catchment in the crystalline basement is disconnected and captured by the Arre River flowing eastwards (fig. 3 & 4a). The profile of the Airoles abandoned valley connects with the present Vis Canyon, therefore, at the time of capture, incision of the Vis canyon had reached its present altitude (fig. 4a). The geomorphologic evolution of this area took place in three stages (fig. 8). 1) The Grands Causses acted as piedmont for the crystalline highlands of the Massif Central (fig. 8A). A latter karstic evolution (tropical climate) allowed the weathered residual sediments (facies 1) (fig. 8A). 2) Incision of the Vis karstic canyon implies that the Herault incision and terraces (facies 2) (fig, 8B) of the Airoles valley occurred during this stage. 3) The Arre valley head propagates westward by regressive erosion and finaly captured the Airoles river crystalline catchment (fig. 8C). Consequence for the Cevennes uplift and hydrographic network development Although the values of present vertical incision in the Vis canyon and in the Arre valley are similar, but they achieved at different time. In addition, the narrow and deep canyon of the Vis is due to vertical incision from the karstic surface of the Grands Causses, whereas the Arre wide valley results from (a younger) lateral slops retreat from a low Herault base-level. The Vis karstic canyon developed in a similar way to the major karstic canyons of both Mediterranean and Atlantic catchment (i.e. Tarn). This rules out a Messinian Mediterranean desiccation as incision driving mechanism and suggests tectonic uplift of the Cevennes and surrounding areas. The Tam being already incised by 13 My [Ambert, 1990], it implies a Miocene age for the incision. Conclusion The amplitude of the vertical incision cannot therefore be used in a simple way to interpret the uplift history of the basement. Consequently, geomorphologic analysis appears to be a prerequisite to distinguish the part played by each factor, and to select the site of uplift measurement

Weichselian palaeoclimate and palaeoenvironment in Europe: background for palaeogroundwater formation, 2001, Vaikmae R. , Edmunds W. M. , Manzano M. ,
A review is given of palaeoclimatic and palaeoenvironmental evidence across Europe for the Weichselian period relevant to interpreting the emplacement and circulation of groundwaters. In addition, this provides the background against which the evidence of past climates and environments contained in groundwaters in coastal areas of Europe, from the Baltic to the Atlantic Ocean may be compared. For much of the Weichselian, although significantly colder than at present, conditions were favourable for the recharge of groundwater, as shown, for example, by periods of speleothem growth. During the last glacial maximum (LGM) recharge is likely to have ceased over much of permafrost-covered Europe, although shallow groundwater recharge from meltwater (generated by the geothermal gradients) could have taken place beneath the ice where pressure relief through tunnel valleys may have occurred. Modern recharge could have started as early as 13 14C ka BP, but probably interrupted by the Younger Dryas between 11 and 10 14C ka BP. In the Baltic areas, ice-dammed lakes inhibited the start of the modern hydrogeological regimes until c. 10.3 14C ka BP. Tundra conditions prevailed over most of ice-free southern Europe at the time of the LGM. At this time the area south of the Portuguese-Spanish border retained a generally warm and relatively humid climate due to the maintenance of warmer sea-surface temperatures derived from Atlantic Ocean circulation. For most of coastal Europe, however, the most significant impact on groundwater circulation is likely to have been the lowering of sea levels that drained large areas of the shelf, such as the North Sea and the English Channel, and also had a significant impact on the Atlantic coast of the Iberian Peninsula where the maximum lowering of up to 130 m would have been experienced. This, together with the general changes in climate, would also have reorganized the atmospheric chemistry over sites in Europe that is likely to be recorded in the groundwater's chemical and isotopic signatures

Origin of atoll lagoons, 2001, Purdy Edward G. , Winterer Edward L. ,
A database of 301 atolls from the Pacific, Indian, and Atlantic Oceans has been analyzed with respect to factors governing maximum atoll lagoon depth. Statistically significant correlations between maximum atoll lagoon depth and both atoll area and present-day rainfall are viewed as the combined effect of paleorainfall precipitation and catchment area in contributing to overall atoll morphology. This interpretation is supported by the gross saucer-shaped morphology of several of the Lau group of the Fiji Islands, and the subsurface Cretaceous Golden Lane atoll of Mexico, where evidence of reef rim construction is lacking but evidence for significant solution relief is compelling. The contribution of reefs to atoll rim construction appears to be limited generally to [~]10 m, leaving more than 20 m of relief to be explained at most atolls. At a number of these, the last interglacial highstand surface is [~]15-20 m beneath Holocene rim sediments. Subsidence rates of even 5 cm/ k.y. do not suffice to explain the subsea depth of this unconformity, suggesting the dominating influence of solution on relief expression. Calculations of solution rates relative to the residence time of sea level below given depths during the past 700 k.y. suggest that the observed atoll relief is in part inherited from more than one Pleistocene, or perhaps earlier, glacial stage. Whatever the precise time of origin, the data available strongly suggest that atoll morphology is solution determined rather than growth predicated

Karst geoindicators of environmental change: The case of Lithuania, 2002, Taminskas J. , Marcinkevicius V. ,
Karst is the result of an epigenetic geomorphologic process that may involve rapid changes to landscapes and their physical properties, with the newly formed relief complicating regional economic development and the protection of nature. The intensity of the karst process is closely linked with the circulation of surface and groundwater, so that the parameters characterising water circulation and chemical denudation can serve as indicators of the intensity of karstification. In this article, we describe the North Lithuanian karst region, and evaluate the influence of climate and hydrological conditions on karstification. Upper Devonian gypsum and dolomites occur beneath the Quaternary sediments here. Sinkholes frequently appear where the latter are particularly thin and underlain by gypsum, suggesting that karstification is intensifying. This is perhaps related to climate change expressed by an increase in mean annual temperature and runoff, especially during warm winters. To identify the main determinants of the karst processes, monitoring was carried out between 1994 and 1999, and data on river runoff and water chemistry from 1962 to 1999 were examined. From 1978 to 1999, the mean chemical denudation rate in the active gypsum karst zone was 30% higher than from 1962 to 1977, a change mirrored by the increased total volume of new sinkholes that appeared in the 1980s and 1990s. We have calculated the rate of chemical denudation and sink-hole formation in the last four decades and discuss karst activitiy as a geoindicator of environmental change

Key Largo Limestone revisited: Pleistocene shelf-edge facies, Florida Keys, USA, 2002, 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

Using stable isotope analysis (delta D-delta O-18) to characterise the regional hydrology of the Sierra de Gador, south east Spain, 2002, Vandenschrick G. , Van Wesemael B. , Frot E. , Pulidobosch A. , Molina L. , Stievenard M. , Souchez R. ,
Water stress is rapidly increasing in many Mediterranean coastal zones mainly due to expansion in agriculture and tourism. In this paper, we focus on the Sierra de Gador-Campo de Dalias aquifer system (southeastern Spain) in order to assess the capability of water stable isotope analysis (deltaD-delta(18)O) to refine the understanding on recharge of this karstic aquifer system. Different types of surface and groundwater were sampled along an altitudinal gradient from the recharge zone in the mountains to the coastal plain. Surface water is restricted to local runoff, collected in closed reservoirs. Runoff amounts, collected in three of these reservoirs were monitored together with the precipitation in their catchments. Meteorological maps were used to detect the origin of the precipitation generating the majority of the runoff. The results were compared to literature data on local and regional precipitation. The use of oxygen and hydrogen isotopic composition has proved to be a useful tool to explain the origin of groundwater in a Mediterranean karstic system. Such studies are, however, not numerous and are often limited to local scale recharge for fast-reacting systems. This paper focuses on the delta(18)O-deltaD relationships of local precipitation to explain the isotopic variability of a large karstic aquifer system. The isotopic compositions of groundwater sampled along an altitudinal gradient from the recharge zone to the coastal plain are well displayed, in a deltaD-delta(18)O diagram, on a mixing line connecting a pole of Mediterranean waters to a pole of Atlantic waters. The Atlantic signature predominates in the shallow groundwater of natural springs, reflecting the rainfall which produced the local runoff sampled. The Mediterranean signature is mainly restricted to deep groundwater from boreholes in the coastal plain. The existence of a degree of spatial separation of groundwater types demonstrates that groundwater flow in a complex karstic system is not always continuous. The Mediterranean signature of deep groundwater could be due to past extreme rainfall events during which connectivity between recharge and reservoir exists, while at the same time the Atlantic signature of recent winter rains dominates in shallow groundwater. The assumption that an equilibrium in isotopic composition is established within a continuous aquifer and that therefore a slope lower than 8 in a deltaD-delta(18)O diagram indicates evaporation is not necessarily valid.

Les travertins de Saint-Antonin : squence gobotanique et climato-anthropique holocne (Bouches-du-Rhne, France), 2003, Guendon Jeanlouis, Ali Adam A. , Roiron Paul, Terral Jeanfrdric, Danna Andr, Diazdelolmo Fernando, Baenaescudero Rafael
Travertine deposit of St-Antonin (Bouches-du-Rhne, France): lithostratigraphy, palaeobotany and Holocene palaeoenvironments - Travertines are carbonate deposits formed generally during temperate climatic periods. The travertine of Saint-Antonin was formed during the Holocene in accordance with this model. They usually present a succession of travertinous units and detrital sedimentary levels containing, respectively, leaf impressions and charcoal; snail shells and archaeological material have also been preserved, essentially in detritial levels. Two kinds of plant remains (leaf imprints and charred wood) have been sampled and analysed, allowing the reconstruction of vegetation dynamics based on a well-defined sedimentary sequence. Our results were compared with those of previous malacalogical, archaeological studies and climatic changes. The Preboreal and Boreal sequence, characterised by travertine unites with detritial deposits, is dominated by a riverside vegetation (Populus alba, Salix sp., Phragmites communis) associated with some pubescent oak growing in the plateau. After this first period, detritial levels and hygrophilous species decrease. Correlatively travertinous facies and leaf impressions of mesophilous forest species increase (Quercus pubescent, Acer monspessulanum). They suggest the existence of homeostatic conditions, such as regular river flow, dense vegetation and few disturbances during deposition. The Middle Atlantic period shows optimal travertinisation and maintenance of forest environment. But this period is characterised by the beginning of the Quercus pubescens regression and the dominance of Acer monspessulanum. From the Atlantic to the first part of Subboreal, important detrital sedimentary levels disturb the deposition of carbonate. They contain reworked archaeological material dating to the Neolithic. Vegetation seems to have been profoundly affected by intensive human exploitation. This process has broken up the forested area into different plant communities and favoured the dominance of heliophilous and thermophilous species (Pinus halepensis, Rubus ulmifolius and Juniperus sp.).

Filamentous 'Epsilonproteobacteria' dominate microbial mats from sulfidic cave springs, 2003, Engel As, Lee N, Porter Ml, Stern La, Bennett Pc, Wagner M,
Hydrogen sulfide-rich groundwater discharges from springs into Lower Kane Cave, Wyoming, where microbial mats dominated by filamentous morphotypes are found. The full-cycle rRNA approach, including 16S rRNA gene retrieval and fluorescence in situ hybridization (FISH), was used to identify these filaments. The majority of the obtained 16S rRNA gene clones from the mats were affiliated with the 'Epsilonproteobacteria' and formed two distinct clusters, designated LKC group I and LKC group II, within this class. Group I was closely related to uncultured environmental clones from petroleum-contaminated groundwater, sulfidic springs, and sulfidic caves (97 to 99% sequence similarity), while group II formed a novel clade moderately related to deep-sea hydrothermal vent symbionts (90 to 94% sequence similarity). FISH with newly designed probes for both groups specifically stained filamentous bacteria within the mats. FISH-based quantification of the two filament groups in six different microbial mat samples from Lower Kane Cave showed that LKC group II dominated five of the six mat communities. This study further expands our perceptions of the diversity and geographic distribution of 'Epsilonproteobacteria' in extreme environments and demonstrates their biogeochemical importance in subterranean ecosystems

Carbonate-Hosted Zn-Pb Deposits in Upper Silesia, Poland: Origin and Evolution of Mineralizing Fluids and Constraints on Genetic Models, 2003, 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

Geology and Geochemistry of the Reocin Zinc-Lead Deposit, Basque-Cantabrian Basin, Northern Spain, 2003, Velasco Francisco, Herrero Jose Miguel, Yusta Inaki, Alonso Jose Antonio, Seebold Ignacio, Leach David,
The Reocin Zn-Pb deposit, 30 km southwest of Santander, Spain, occurs within Lower Cretaceous dolomitized Urgonian limestones on the southern flank of the Santillana syncline. The Reocin deposit is one of the largest known strata-bound, carbonate-hosted, zinc-lead deposits in Europe. The total metal endowment of the deposit, including past production and remaining reserves, is 62 Mt of ore grading 8.7 percent Zn and 1.0 percent Pb. The epigenetic mineralization consists of sphalerite and galena, with lesser marcasite and trace pyrite with dolomite as gangue. Microprobe analyses of different generations of dolomite revealed nonstoichiometric compositions with various amounts of iron (up to 14 mol % of FeCO3). Replacement of host dolomite, open-space filling of fractures, and cementation of breccias derived from dissolution collapse are the principal types of ore occurrence. Detailed cross-section mapping indicates a stratigraphic and structural control on the deposit. A stratiform morphology is present in the western part of the orebody (Capa Sur), whereas mineralization in the eastern part is highly discordant but strata bound (Barrendera). Stratigraphic studies demonstrate that synsedimentary tectonic activity, related to the rifting of the North Atlantic (Bay of Biscay), was responsible for variation in sedimentation, presence of unconformities (including paleokarsts), local platform emergence and dolomitization along the N60 fault trend. In the Reocin area, two stages of dolomitization are recognized. The first stage is a pervasive dolomitization of the limestone country rocks that was controlled by faulting and locally affected the upper part of the Aptian and the complete Albian sequence. The second dolomitization event occurred after erosion and was controlled by karstic cavities. This later dolomitization was accompanied by ore deposition and, locally, filling of dolomite sands and clastic sediments in karstic cavities. The circulation of hydrothermal fluids responsible for sulfide deposition and the infilling of karst cavities were broadly contemporaneous, indicating a post-Albian age. Vitrinite reflectance data are consistent with previously measured fluid inclusion temperatures and indicate temperatures of ore deposition that were less than 100{degrees}C. Carbon and oxygen isotopic data from samples of regional limestone, host-rock dolostone and ore-stage dolomite suggest an early hydrothermal alteration of limestone to dolostone. This initial dolomitization was followed by a second period of dolomite formation produced by the mixing of basinal metal-rich fluids with local modified seawater. Both dolomitization events occurred under similar conditions from fluids exhibiting characteristics of basinal brines. The{delta} 34S values of sulfides are between -1.8 and .5 per mil, which is consistent with thermochemical sulfate reduction involving organic matter as the main source of reduced sulfur. Galena lead isotope compositions are among the most radiogenic values reported for Zn-Pb occurrences in Europe, and they are distinct from values reported for galena from other Basque-Cantabrian deposits. This suggests that a significant part of the lead was scavenged from the local underlying Asturian sediments. The stratigraphic and structural setting, timing of epigenetic mineralization, mineralogy, and isotopic geochemistry of sulfide and gangue minerals of the Reocin deposit are consistent with the features of most of Mississippi Valley-type ore deposits

Dosimetric and radiocarbon chronology of a pre-Wisconsinan mastodon fossil locality at East Milford, Nova Scotia, Canada, 2003, Godfreysmith D. I. , Grist A. M. , Stea R. R. ,
We report the final results of a multidisciplinary geochronological study of two subfossil mastodon remains and the sediments associated with them. from the East Milford, N.S. mastodon locality discovered in 1991. The mastodons, which were found in a karstic sinkhole system, are the latest and the most complete of several mastodon remains discovered in Nova Scotia, New Brunswick and Maine over the last 170 years. The unconsolidated sediments containing the adult specimen were dated using optical dating (IRSL); the mastodon dental enamel was dated using electron spin resonance (ESR); and bone collagen from both individuals plus associated wood were dated using radiocarbon (C-14) dating. Two samples of sediment adhering to the walls of the karstic cavity at the elevation corresponding to the location of the adult specimen yielded statistically indistinguishable IRSL ages of 127 13 (EMM1) and 143 16 ka (EMM2), with a weighted mean of 133 6 ka. This is consistent with pollen data which indicate an interglacial climate. On the basis of its stratigraphic position with respect to overlying till units, the locality is attributed to oxygen isotope stage 5. Three ESR dates on dental enamel (natural prompt, deproteinated prompt, and deproteinated delayed) yielded statistically indistinguishable ages whose weighted mean is 74.9 5.0 ka. This indicates consignment to the geologic record of the mastodon tooth during terminal oxygen isotope stage 5a, when the climatic cooling leading to the Wisconsinan glacial period had already begun. Fission-track analysis of the enamel and dentine cross sections showed minimal U uptake, resulting in no need for early, linear, or late uptake modelling. The direct ESR age indicates that the specimen either became mired in a cavity that was already at least partly infilled with older, probably waterlogged, sediments, or that the sediment's IRSL signal was not completely erased during deposition. The dosimetric ages are consistent with limiting radiocarbon ages on bone collagen (juvenile > 45,760 years BP; adult greater than or equal to 37,040 1730 BP) and wood (near the adult mastodon > 51,000 BP; organic-rich horizon above the karst surface > 50,000 BP). These results provide the first direct age on a mastodon fossil from Atlantic Canada, and the first numeric estimate to demonstrate that mammoths were present in this region during pre-Wisconsinan times, specifically during late oxygen isotope stage 5a. (C) 2003 Elsevier Science Ltd. All rights reserved

Palaeoenvironments in semi-arid northeastern Brazil inferred from high precision mass spectrometric speleothem and travertine ages and the dynamics of South American rainforests, 2004, Auler A. S. , Wang X. , Edwards R. L. , Cheng H. , Cristalli P. S. , Smart P. L. , Richards D. A.

Understanding past environmental changes in tropical rainforests is extremely important in order to assess the response of such environments to present and future climatic changes and understand causes and the present patterns of biodiversity.
Earlier hypothesis on the origin of biodiversity have stressed the role of past climatic changes in promoting speciation. According to the “refuge hypothesis” (Haffer, 1982), dry periods could have led to forest fragmentation, isolating more humid forested zones (called refuges) within an environment largely dominated by savannas. The refuge hypothesis does not assign timescales for rainforest fragmentation, although recent studies have suggested that speciation could have occurred over timescales of millions of years (Knapp and Mallet, 2003). Although the focus of heavy criticism (Colinvaux, et a., 2000), the refuge hypothesis has generated a large amount of research. In general, pollen studies (Colinvaux, et a., 1996, Haberle and Maslin, 1999) tend to support a continuous forest cover throughout late Quaternary climatic shifts, although large variations in rainfall have also been demonstrated by other pollen and isotopic studies (van der Hammen and Absy, 1994; Maslin and Burns, 2000).
Amazon and Atlantic rainforests are the two major forested zones in South America. Amazon rainforest, the largest rainforest in the world, comprise a total original area of 4.1 million km2 and is renowned for hosting the large biodiversity in the world (30% of all the world’s known plant and animal species). Atlantic rainforest, also a biodiversity hotspot, occurs along the coast and has been subjected to heavy deforestation since European arrival. Nowadays only c. 7% of its original forested area of 1.3 million km2 remains. These two rainforests are separated by drought-prone semi-arid northeastern (NE) Brazil. Our study does not address the refuge hypothesis directly although it sheds new light on the dynamics of forest expansion in the past as well as indicates alternative ways of promoting speciation. It has long been hypothesized, due to botanical (Mori, 1989; Andrade-Lima, 1982) and faunistic (Costa, 2003) similarities, that the Amazon and Atlantic rainforests were once linked in the past. Although numerous connecting routes have been postulated (Bigarella, et al, 1975; Por, 1992; De Oliveira, et al, 1999), the timing of forest expansion and their possible recurrence have remained elusive.
The study area lies in the driest portion of NE Brazil “dry corridor”, close to the village of Laje dos Negros, northern state of Bahia. Mean annual precipitation is around 480 mm and potential evapotranspiration is in excess of 1,400 mm/year (Fig.1). Present vegetation comprises a low arbustive scrubland known locally as caatinga. The area contains a well-developed underground karst (Auler and Smart, 2003) with abundant secondary calcite precipitates, both underground (speleothems) and on the surface (travertines).

Palaeoclimatic implications of the growth history and stable isotope ([delta]18O and [delta]13C) geochemistry of a Middle to Late Pleistocene stalagmite from central-western Italy, 2004, Drysdale Rn, Zanchetta G, Hellstrom Jc, Fallick Ae, Zhao Jx, Isola I, Bruschi G,
The age structure and stable isotope composition of a stalagmite (CC1) from an upland cave in central-western Italy were studied to investigate regional response to global climatic changes. Four growth phases are constrained by 28 thermal ionization and multi-collector inductively coupled plasma mass spectrometry Th-U ages and reveal intermittent deposition through the period between Marine Isotope Stage (MIS) 11 and 3 (~380 and ~43 kyr). Most of the growth took place between ~380 and ~280 kyr, a period punctuated briefly by a hiatus in deposition through the glacial maximum of MIS 10. Growth was terminated abruptly at 280 kyr just prior to the MIS 8 glacial maximum. With a present-day chamber temperature of 7.5 [deg]C, the timing of hiatuses close to these glacial maxima point to freezing conditions at the time. No deposition was recorded through the entirety of MIS 7 and most of MIS 6, whilst two minor growth phases occurred at ~141-125 and ~43 kyr. Growth at 141 kyr indicates temperatures >0 [deg]C at a time when MIS 6 ice volumes were close to their maximum. High stable carbon isotope ([delta]13C) values (-2.8[per mille sign] to .1[per mille sign]) throughout the stalagmite's growth reflect a persistently low input of biogenic CO2, indicating that the steep, barren and alpine-like recharge area of today has been in existence for at least the last ~380 kyr. During MIS 9, the lowest [delta]13C values occur well after maximum interglacial conditions, suggesting a lag in the development of post-glacial soils in this high-altitude karst. The stable oxygen isotope ([delta]18O) trends match the main structural features of the major climate proxy records (SPECMAP, Vostok and Devils Hole), suggesting that the [delta]18O of CC1 has responded to global-scale climate changes, whilst remarkable similarity exists between CC1 [delta]18O and regional sea-surface temperature reconstructions from North Atlantic core ODP980 and southwest Pacific marine core MD97-2120 through the most detailed part of the CC1 record, MIS 9-8. The results suggest that CC1 and other stalagmites from the cave have the potential to capture a long record of regional temperature trends, particularly in regards to the relative severity of Pleistocene glacial stages

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