Speleothem oxygen isotopes and growth rates are valuable proxies for reconstructing climate history. There is debate, however, about the conditions that allow speleothems to grow in oxygen isotope equilibrium, and about the correct equilibrium fractionation factors. We report results from a series of carbonate growth experiments in karst-analogue conditions in the laboratory. The setup closely mimics natural processes (e.g. precipitation driven by CO2-degassing, low ionic strength solution, thin solution film) but with a tight control on growth conditions (temperature, pCO2, drip rate, calcite saturation index and the composition of the initial solution). Calcite is dissolved in water in a 20,000 ppmV pCO2 environment. This solution is dripped onto glass plates (coated with seed-carbonate) in a lower pCO2 environment (and rapid depletion of the dissolved inorganic carbon reservoir (rapid DIC-depletion). The impact of evaporation can be large so caves with high relative humidity are also preferable for palaeoclimate reconstruction. Even allowing for the maximum offsets that may have been induced by evaporation and rapid DIC-depletion, d18O measured in some of our experiments remain higher than those predicted by Kim and O’Neil (1997). Our new results are well explained by equilibrium at a significantly higher acalcite–water, with a kinetic-isotope effect that favours 16O incorporation as growth rate increases. This scenario agrees with recent studies by Coplen (2007) and Dietzel et al. (2009). Overall, our results suggest that three separate processes cause d18O to deviate from true isotope equilibrium in the cave environment. Two of these drive d18O to higher values (evaporation and rapid DIC-depletion) while one drives d18O to lower values (preferential incorporation of 16O in the solid carbonate at faster growth rates). While evaporation and DIC-depletion can be avoided in some settings, the third may be inescapable in the cave environment and means that any temperature to d18O relationship is an approximation. The controlled conditions of the present experiments also display limitations in the use of the Hendy test to identifying equilibrium growth.

Lechuguilla Cave in Carlsbad Caverns National Park, Guadalupe Mountains, New Mexico, has a 2010 surveyed length of 130 km. It is a hypogene cave, formed by uprising H₂S-bearing fluids which oxidize to form sulfuric acid when they reach oxygen-bearing meteoric water. The cave is formed in the Permian Capitan Reef Complex. Argon-argon dating suggests that the cave is on the order of 5 million years old. Lechuguilla Cave exhibits dramatic mineralization, particularly gypsum chandeliers, native sulfur, and many massive calcite speleothems. Of particular interest is the microbiology of the cave where microbes, present and past, formed without surface interactions.

Speleothems, mainly stalagmites, are yielding continuous, high-resolution records of past climate. Because calcite in these speleothems can be dated with exceptional accuracy, these records are matching and in some cases exceeding records from lakes, trees, glaciers, and oceans in their importance, and are providing remarkable detail about regional and global climate change history. Multiple records are offered and discussed in this article and show the significance of caves to the field of paleoclimatology.

Central Asia is currently a semiarid-arid region, dominated by the Westerlies. It is important to understand mechanisms of climate and precipitation changes here, as water availability in the region is crucial today and in the future. High-resolution, absolutely-dated oxygen isotope (d18O) records of stalagmites from Kesang Cave characterize a dynamic precipitation history over most of the past 500,000 years. This record demonstrates, for the first time, that climate change in the region exhibits a processional rhythm with abrupt inceptions of low d18O speleothem growth at times of high Northern Hemisphere summer insolation followed by gradual d18O increases that track decreases of insolation. These observations and interpretations contrast with the interpretation of nearby, but higher elevation ice core records. The absolutely-dated cave d18O shifts can be used to correlate the regional climate variability by providing chronological marks. Combined with other paleoclimate records, the Kesang observations suggest that possible incursions of Asian summer monsoon rainfall or related moisture into the Kesang site and/or adjacent areas during the high insolation times may play an important role in changing orbital-scale hydrology of the region. based on our record, arid climate will prevail in this region for the next several millennia, providing that anthropogenic effects do not supersede natural processes.

The petrographic, isotopic and chemical changes occurring around 8.2 ka in two stalagmites, one from the Père Noël cave (Han-sur-lesse, Belgium) and one from the Hotton cave (nearby Marche-en-Famenne, Belgium) are presented. The Père Noël stalagmite presents a particularly dense grey compact calcite around 8.2 ka, while the Hotton stalagmite presents a deposition hiatus of ca 1100 years.
Besides the macroscopic aspect of the stalagmites, changes in their isotopic (δ18O and δ13Ñ) composition and in their chemical (Sr/Ca, Mg/Ca) composition are observed. Regarding the early start and the duration of the climate deterioration, it is impossible to link the onset of the observed wet phase in the studied speleothems as directly related to the so-called 8.2 ka event. The question arises if the climate deterioration around 8.2 ka observed in both stalagmites is one among other deteriorations occurring during the early Holocene.

Assessing water quality in aquifers has become increasingly important as water demand and pollution concerns rise. In the Yucatan Peninsula, sinkholes, locally known as cenotes, are karst formations that intercept the water table. Cenotes are distributed across the peninsula, but are particularly dense and aligned along a semicircular formation called the Ring of Cenotes. This area exhibits particular hydrogeological properties because it concentrates, channels, and discharges fresh water toward the coasts. In this study, we identify spatial and temporal variations in chemical and physical variables at twenty-two cenotes to identify groups that share similar characteristics. Water samples from each cenotes were taken at three depths (0.5, 5.5, and 10.5 m) and during three seasons (dry, rainy, and cold-fronts season). Field measurements of pH, temperature, electrical conductivity, and dissolved oxygen were taken, and the concentrations of major ions (K+, Na+, Mg2+, Ca2+, HCO{ 3 , SO2{ 4 , Cl2 and NO{ 3 ) were quantified. Identifying regions of the cenotes were done by applying multivariate statistical techniques (PCA, PERMANOVA, CAP). The chemical variables revealed spatial trends among the cenotes. We identified three main regions. Region 1 is associated with sea-water encroachment and high levels of sulfate that travel through preferential groundwater flowpaths from evaporites in the southern Yucatan Peninsula; Region 2 is a recharge zone, and Region 3 is characterized by sea water encroachment and by the high chemical and physical variability associated with groundwater flow from the east.

The middle Miocene Badenian basin of the Carpathian Foredeep is characterized by complex sedimentary and diagenetic carbonate-evaporite transitions. Six locations have been selected to evaluate the controls on the carbonand oxygen isotopic composition of the Badenian gypsum-associated limestones of the Tyras Formation in WestUkraine. At three locations marine limestones overlie the gypsum, at one location (Anadoly) the gypsum-associatedlimestones are polygenic, and at two localities (Pyshchatyntsi and Lozyna) gypsum deposits are lacking. Thestudied limestones have originated as primary, mostly peloidal carbonates as well as secondary carbonates formed by hypogene sulphate calcitisation. They show a wide range of δ13C (from from -0.9‰ to -39.8‰) and δ18O values(from 0.9‰ to -12.2‰). The Badenian limestones formed in marine environments (either as deposits accumulatedat the bottom of the sea or forming the infillings of solution cavities within gypsum) have less negative δ18O values compared to predominantly diagenetic formations. Wide ranges and usually very negative δ13C values andlow δ18O values of those limestones indicate that they suffered important meteoric diagenesis as supported bycommon sparitic fabrics. In addition, a large range of δ13C values even in the group of samples characterized byless-negative δ18O values shows that bacterial sulphate reduction and methane oxidation were active processes inthe pore fluids of the Tyras Formation. Very low carbon isotopic compositions (δ13C values from -22 to -40‰) of some sparitic limestones in the studied sections indicate the occurrence of oxidized methane within the diagenetic environment. Accordingly, the isotopic signatures of the studied limestones are a combination of both primary and secondary processes, the latter having a primordial importance. The common occurrence of similar negative δ13Cand δ18O values in evaporite-related carbonates in other Miocene evaporite basins suggest that extensive dissolution-reprecipitation in diagenetic or vadose-phreatic environments were common in evaporite-related carbonates.

The middle Miocene Badenian basin of the Carpathian Foredeep is characterized by complex sedimentary and diagenetic carbonate-evaporite transitions. Six locations have been selected to evaluate the controls on the carbonand oxygen isotopic composition of the Badenian gypsum-associated limestones of the Tyras Formation in WestUkraine. At three locations marine limestones overlie the gypsum, at one location (Anadoly) the gypsum-associatedlimestones are polygenic, and at two localities (Pyshchatyntsi and Lozyna) gypsum deposits are lacking. Thestudied limestones have originated as primary, mostly peloidal carbonates as well as secondary carbonates formed by hypogene sulphate calcitisation. They show a wide range of δ13C (from from -0.9‰ to -39.8‰) and δ18O values(from 0.9‰ to -12.2‰). The Badenian limestones formed in marine environments (either as deposits accumulatedat the bottom of the sea or forming the infillings of solution cavities within gypsum) have less negative δ18O values compared to predominantly diagenetic formations. Wide ranges and usually very negative δ13C values andlow δ18O values of those limestones indicate that they suffered important meteoric diagenesis as supported bycommon sparitic fabrics. In addition, a large range of δ13C values even in the group of samples characterized byless-negative δ18O values shows that bacterial sulphate reduction and methane oxidation were active processes inthe pore fluids of the Tyras Formation. Very low carbon isotopic compositions (δ13C values from -22 to -40‰) of some sparitic limestones in the studied sections indicate the occurrence of oxidized methane within the diagenetic environment. Accordingly, the isotopic signatures of the studied limestones are a combination of both primary and secondary processes, the latter having a primordial importance. The common occurrence of similar negative δ13Cand δ18O values in 

Atmospheric precipitation was sampled for isotopic analyses according to GNIP protocol at two stations in Crimea, Ukraine: Simferopol (24 months) and Chatyrdag (15 months). In addition, several karstic springs and one well tapping deep karstic aquifer were sampled. The δD vs. δ18O relationship is only slightly differs from global Meteoric Water Line. Variable degrees of correlation with the air temperature and the precipitation amount suggest that the isotopic composition of precipitation is affected by several processes (e.g., air temperature and supply of moisture from different sources). Interestingly, drastically different makeups of precipitation were observed simultaneously at two stations located only 23 km apart. Waters in seven karstic springs discharging at Dolgorukovsky massif (2), Chatirdag (1), Baidarsky basin (3), and Mangup-kale (1) have isotopic compositions that follow local meteoric water line but are lighter than weighted annual mean values for their respective catchment areas. Isotopic composition of the underground stream in Krasnaya (Red) cave is nearly constant and thus, decoupled from changes in both the isotopic composition of atmospheric precipitation in the recharge area and the flow regime (flood or base flow). This suggests a strong buffering and homogenizing role of the soil cover and the epikarst zone, as well as the predominant role of winter recharge on these karst massifs. Still lighter isotopic composition of deep karstic water tapped by a borehole is tentatively explained by old, pre-Holocene age of this water

Many hypogene caves are formed by sulfuric acid produced by the oxidation of sulfides, particularly hydrogen sulfide. This cave development can take place below, at, or above the water table. Most cave enlargement is subaerial, in water films and droplets that absorb gaseous hydrogen sulfide and oxygen. Sulfuric acid caves have irregular patterns with large variations in cross section and elevation, with relatively few subhorizontal passages formed along the water table. Cave origin is scattered, localized, and sporadic. Sulfuric acid caves provide evidence for regional geomorphic and tectonic history, groundwater flow patterns, and redox geochemistry.

The cave atmosphere is placed in context as a geomorphic agent. The composition of cave air in well-ventilated caves isgoverned by exchange between surface and cave air. In poorly ventilated caves, its composition can be altered by dilution and production, and depletion of its components in the cave. Relative humidity is used to introduce water vapor as a critical component of cave air and its variations that result in evaporation of water and condensation of water vapor. The biogenicand inorganic reactions of oxygen and carbon dioxide control solution of limestone and precipitation of calcite. Condensation corrosion is a visual manifestation of atmospheric processes on bedrock and speleothems. Theories and experiment shave resulted in rates for condensation corrosion, which allow a preliminary assessment of its role as aspeleogenetic agent. The cave air carries particulates of both biogenic and inorganic origin; these can influence geomorphic processes in caves and provide significant paleoenvironmental information so as to past cave and surface events and climates. It is concluded that anthropogenic impacts can alter the atmospheric processes in caves.

Chemically aggressive water is needed in order to promote bedrock dissolution and karstification. Aggressiveness is generated through a number of processes that include acids from the atmosphere and soil zone (epigenic acids) and from deep-seated mechanisms (hypogenic acids). Carbon dioxide and hydrogen sulfide are the main players, although additional acidity may be provided by processes that involve mixing of solutions with different degrees of saturation, temperature effects, and microbiological agents. Rainfall will generally have an acid pH due to natural CO2 and mostly anthropogenic gases such as H2S in the atmosphere. The soil zone will further boost acidity levels due to abundant CO2 production in the root and plant horizons. Although the buffering capacity of the carbonate will cause groundwater to quickly achieve saturation, mixing corrosion effects may rejuvenate aggressiveness in situations where waters of different chemistry are in contact. Bacterially mediated processes will both enhance and mediate processes of acid generation and dissolution. Mixing zones between fresh and salt water and between oxygen-rich groundwater (mostly epigenic) and rising thermal water will be important zones where increased levels of acidity will accelerate cave formation. The degree and effectiveness of aggressiveness will depend on a number of variables, such as the geological setting, solubility of the rock, position of the bedrock, and climate, sometimes operating together at various scales and strengths.