Stable Isotope Fractionation

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km 2 , are up to 1 km 3 in volume. Today, spring waters in this area have temperatures of 19 to 57 °C, are of the Ca-Mg-HCO 3 -SO 4 type in the Pamukkale, Kelkaya and Pınarbaşı areas and the Ca-Mg-SO 4 -HCO 3 type at Çukurbağ. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The δ 18 O and δD values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The δ 13 C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (-4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher δ 18 O values (-15.2 to -7.8‰ VPDB) than those of the northern areas (-16.6 to -4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km 2 , are up to 1 km 3 in volume. Today, spring waters in this area have temperatures of 19 to 57 °C, are of the Ca-Mg-HCO 3 -SO 4 type in the Pamukkale, Kelkaya and Pınarbaşı areas and the Ca-Mg-SO 4 -HCO 3 type at Çukurbağ. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The δ 18 O and δD values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The δ 13 C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (-4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher δ 18 O values (-15.2 to -7.8‰ VPDB) than those of the northern areas (-16.6 to -4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

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In the Kavakköy region located at Southwest of Konya (central Turkey), four Quaternary travertine mounds and two recent travertine deposition sites are roughly aligned along the Seydişehir Fault Zone. Water temperature of recent travertine sites is about 39 and 19 °C. Six different facies were determined from the Kavakköy Travertine: crystalline crust travertine, paper-thin raft travertine, coated bubble travertine, pisoid, lithoclast travertine and shrub travertine facies. Sedimentological, morphologic and geochemical characteristics of these facies point toward depositions in slope and depressional depositional systems. Rare element content and isotopic values of different facies are distributed on diagrams as two separate clusters. After comparing with two recent travertines, it is hypothesized that they are most probably related to the temperatures of travertine formation water. High δ 13 C contents and calculated δ 13 C values, using Panichi and Tongiorgi's (in: Proceedings of the 2nd UN symposium on the development and use of geothermal resources, San Francisco, CA, 20-29 May 1975, pp. 815-825, 1976) equation, imply that parent water was charged with CO 2 from a deep origin. Significant differences in the δ 13 C and δ 18 O isotopic values of recent travertines at two different sites have been interpreted as being related to water circulation path and source of CO 2. The travertine precipitated by water with a temperature of 19 °C has comparatively short and shallow fluid flow paths and low (normal) heat flow and has CO 2 isotopic signatures, indicating a comparatively large quantity of CO 2 contribution from decarbonation of limestone. In contrast, the travertine formed by relatively hot water (39 °C) had been conductively heated during percolating through thick Paleozoic-Cenozoic sequence and has incorporated a comparatively large quantity of CO 2 derived from mantle sources.

Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional fluctuations of geothermal fluids flowing (or flowed) from deep reservoirs up to the surface, within fault zones. In this view, these veins represent key tools for decoding those factors that influenced the geochemical variations. We have analyzed veins developed in fractures channeling geothermal fluids forming travertine deposits. The studied veins cut a fossil travertine fissure ridge, near the Larderello geothermal area (Iano area, southern Tuscany) where geothermal fluid circulation is favored by NE-trending strike-to-oblique-slip faults and their intersections with NW-trending normal ones. U-Th dating indicates that fluid circulation occurred from (at least) 172 ka to 21 ka. In this time span, the geothermal fluid changed in composition, and the banded Ca-carbonate veins recorded these variations in terms of mineralogical and stable isotope composition and temperature ( T ) of deposit...

In this study, we aimed to indicate that hydrogeochemical characteristics of the mineralized spring waters of the Garab travertine zone, in the northeast of Iran, are changed in accordance of regional climatic impacts. Some 18 hydrogeological and 8 meteorological variables from docu

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, an Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport.

In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO3. Initially a milky fluid comprising micro-spherules of amorphous CaCO3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-between different species of dissolved inorganic carbon and various CaCO3 polymorphs, this is the first documented evidence for C isotope fractionation between ACC and the calcite it recrystallizes to. This phenomenon may prove important for the interpretation of CaCO3based C isotope environmental proxies.

The formation of crystalline rare earth element (REE) (e.g. La, Ce, Pr, Nd) carbonates from aqueous solutions was examined at ambient temperature using UV-Vis spectrophotometry, combined with X-ray diffraction, high-resolution microscopy and infrared spectroscopy. In all experiments REE-lanthanites (REE2(CO3)3·8H2O) formed via a highly hydrated, nanoparticulate and poorly-ordered REE-carbonate precursor. The lifetime of this precursor as well as the kinetics of crystallization of the various REE-lanthanites were dependent on the specific REE3+ ion involved in the reaction. The induction time and the time needed to fully form the crystalline REE-lanthanite end products increase linearly with the ionic potential. The authors show here that the differences in ion size and ionic potential as well as differences in dehydration energy of the REE3+ ions control the lifetime of the poorly ordered precursor and thus also the crystallization kinetics of the REE-lanthanites; furthermore, they ...

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, an Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport.

Banded Ca-carbonate veins in travertine deposits are efficient recorders of the compositional fluctuations of geothermal fluids flowing (or flowed) from deep reservoirs up to the surface, within fault zones. In this view, these veins represent key tools for decoding those factors that influenced the geochemical variations. We have analyzed veins developed in fractures channeling geothermal fluids forming travertine deposits. The studied veins cut a fossil travertine fissure ridge, near the Larderello geothermal area (Iano area, southern Tuscany) where geothermal fluid circulation is favored by NE-trending strike-to-oblique-slip faults and their intersections with NW-trending normal ones. U-Th dating indicates that fluid circulation occurred from (at least) 172 ka to 21 ka. In this time span, the geothermal fluid changed in composition, and the banded Ca-carbonate veins recorded these variations in terms of mineralogical and stable isotope composition and temperature ( T ) of deposit...

The aim of this study is to investigate the relationship between the earthquakes and radon concentrations in thermal waters along faults in the Denizli Basin, an area in Turkey known for its high seismic activity and thermal waters. This area was chosen because it exhibits active crustal movements combined with seismicity and there are numerous outflow thermal waters and gas outputs. In addition, this region has the type of tectonic activity where graben groups and faults take place. Measurements of radon levels and of some chemical and physical characteristics of thermal waters were made at seven sampling stations in the region. Radon concentrations were measured by a ZnS(Ag) scintillation counter in a collector chamber. The activity levels varied between 0.67 and 25.90 kBq m −3 during the period of May-December 2000. In the evaluation of the results, the seismic data reported by Bogaziçi University Kandilli Observatory and Earthquake Research Institute, Seismological Laboratory were used. The increases observed in radon concentration at two stations were probably related to the earthquakes that took place in the region during the study period.

Travertine spring mounds are common in Slovakia; however, their age and depositional temperature are still poorly known. Our study is the first multimethodological investigation involving stable carbon, oxygen, and clumped isotope (Δ47) analyses and U-Th age determination of travertine mounds from different locations in Slovakia (Santovka, Dudince, Čerin, Bešeňová, Liptovský Ján, Liptovské Sliače, Vyšné Ružbachy, Gánovce, and Sivá Brada) to provide information about their age, origin, precipitation conditions, and temperature. The positive δ13C values imply that the parent water was charged with heavy CO2 of deep origin. The δ18O values of spring waters range between −11.4‰ and −8.9‰, whereas the δ2H values vary from −80.5‰ to −58.3, indicating a meteoric origin for spring waters. Clumped isotope compositions (Δ47) correspond to a deposition temperature between 4 °C and 32 °C. The U-Th age data of the studied travertines vary from 1.2 (Liptovské Sliače) to 301 ka (Dudince). Our resu...

The tufa term is described as secondary calcium carbonate deposits which are deposited by biologic and/ or physicochemical processes under cool water conditions and contain macro and micro scales plant, animal remains and bacteria (especially cyanobacteria). Tufas have especially deposited at Quaternary and recent time. The study area, located in Antalya city borders, constituted by primary three main terraces, Döşemealtı Plateau (Upper Terraces), Düden Plateau (Lower Terraces) and the third terraces under the sea level. These terraces contain nine second and the third order small terraces which determined by using GIS. As a result of this study, ten lithofacies which have deposited in fluvial, paludal, lacustrine and cascade-barrage environments are described. These are; 1. phytoherm framestone facies, 2. phytoherm boundstone fades, 3. micritic tufa fades, 4. phytoclastic tufa facies, 5. oncoidal tufa facies, 6. intraclastic tufa facies, 7. microdetrital tufa facies, 8. palaeosols, 9. pisolitic tufa facies (channel and pool types) and 10. intraformational tufa facies. These different types have formed in low regime surface flows/ streams, marshes, lake-pool and cascade-barrage environments that developed from springs and have different hydrologic conditions.

Multiple abiotic and biotic factors combine in nature to influence the formation of calcium carbonate limestone deposits. Systems Geobiology studies of how microorganisms respond to, or sometimes even control, the coupled effects of environmental change and mineralization will permit more accurate interpretation of the fossil record of ancient microbial life. Mammoth Hot Springs in Yellowstone National Park, USA, serves as a natural laboratory for tracking how the dynamic interplay of physical, chemical and biological factors come together to form hot-spring limestone (called 'travertine'). Systematic downstream correlations occur at Mammoth Hot Springs between travertine deposition (geomorphology, crystalline structure and geochemistry), microbial communities (mat morphology, pigmentation, and phylogenetic and metabolic diversity) and spring-water conditions (temperature, pH, geochemistry and flow). Field-based microscale and mesoscale experimentation indicates that microbes directly influence travertine growth rate and crystalline structure. At the macroscale, time-lapse field photography and numerical modelling suggest that travertine terrace geomorphology is influenced strongly by hydrology, heat dispersion and geochemistry. These results from Mammoth Hot Springs allow establishment of a conceptual framework across broad spatial and temporal scales in which to track how multiple geological and biological factors combine to control CaCO 3 crystal precipitation and the resulting formation of travertine deposits.

The aim of this study is to investigate the relationship between the earthquakes and radon concentrations in thermal waters along faults in the Denizli Basin, an area in Turkey known for its high seismic activity and thermal waters. This area was chosen because it exhibits active crustal movements combined with seismicity and there are numerous outflow thermal waters and gas outputs. In addition, this region has the type of tectonic activity where graben groups and faults take place. Measurements of radon levels and of some chemical and physical characteristics of thermal waters were made at seven sampling stations in the region. Radon concentrations were measured by a ZnS(Ag) scintillation counter in a collector chamber. The activity levels varied between 0.67 and 25.90 kBq m −3 during the period of May-December 2000. In the evaluation of the results, the seismic data reported by Bogaziçi University Kandilli Observatory and Earthquake Research Institute, Seismological Laboratory were used. The increases observed in radon concentration at two stations were probably related to the earthquakes that took place in the region during the study period.

Since the beginning of the 1990’s, the travertines at
Pamukkale, south-west Turkey, have faced a serious environmental
pollution problem. The travertines were originally
snow-white in colour, but this colour has been turning
into pale grey. In addition to other features, the snowwhite
colour and the huge mass of rocks on the edge of
Pamukkale plateau make the travertines unique and attractive
to visitors.
Living bacteria exist 1-2 mm beneath the surface of
the travertines in both terrace and water channel types.
The thickness of the bacterial lamina is 1-2 mm in the
water channel type, whilst it is approximately 1 cm for
other types. Absorbance Spectral (AS) data shows that the
living bacteria are cyanobacteria, which are responsible
for the green colour in certain areas of the travertines.
Our investigations show that the major force responsible
for the change of colour in the area is the increasing
level of excess organic matter, which also causes a
shift in the metal content of the travertines. While the
greyish polluted samples have 584 ppm of Total Organic
Carbon (TOC), the unpolluted snow-white samples have
only 177 ppm of TOC. On the other hand, the Al, Fe and
Mn contents of the polluted samples are respectively 144,
62, 6 ppm higher than the unpolluted samples.
As the TOC is the main cause of the pollution, decreasing
the organic matter in the pools would be the first
step to protecting the area. This requires limiting, or even
banning, people who enter the pools for swimming.
Sources of Al, Fe, Mn and other hazardous metals should
be reduced in the region.

KEYWORDS:
Pollution, travertine, Pamukkale, Turkey.

Tufa samples from 16 consecutive barrages along a 13 km section of a groundwater-fed Krka River (Slovenia) were analysed for their petrographical, mineralogical, elemental and stable carbon (δ 13 C) and oxygen (δ 18 O) isotope composition, to establish their relation to current climatic and hydrological conditions. Waters constantly oversaturated with calcite and the steep morphology of the Krka riverbed stimulate rapid CO 2 degassing and subsequent tufa precipitation. The carbon isotope fractionation ( 13 C) between DIC and tufa in the Krka River evolves toward isotopic equilibrium being controlled by continuous CO 2 degassing and tufa precipitation rate downstream. The  13 C increased from 1.9 to 2.5‰ (Vienna PeeDee Belemnite); however, since tufa precipitation rates remain similar downstream, the major controlling factor of carbon isotope exchange is most probably related to the continuous 12 CO 2 degassing downstream leaving the carbon pool enriched in 13 C. In the case of oxygen, the isotope fractionation was found to be from 1.0 to 2.3‰ smaller than reported in the literature. The observed discrepancies are due to different precipitation rates of calcite This article is protected by copyright. All rights reserved. deposits as Krka tufas on cascades grow relatively faster compared to slowly precipitated calcite deposits in cave or stream pools. Due to non-equilibrium oxygen isotope exchange between Krka tufa and water, the  18 O proxy showed from 1.2 to 8.2C higher calculated water temperatures compared to measured water temperatures, demonstrating that  18 O proxy-based temperature equations are not reliable for water temperature calculations of fast growing tufa on cascades. Because Mg is bound to the terrigenous dolomite fraction in the Krka tufa samples, the Mg/Ca was also found to be an unreliable temperature proxy yielding over up to 20C higher calculated water temperatures.

Elemental data from travertines are a treasure of depositional and diagenetic information. However, correct interpretation requires proper data acquisition and treatment. This study shows how results from elemental analyses complement sedimentological and other geochemical, i.e. isotopic, data and thereby contribute to our understanding of fossil travertines. Multivariate statistical element analyses, after multiple travertine digestion methods, demonstrate the link between elements, their mineralogical phases, and ultimately their origin. This study reveals that carbonate-phase related elements in travertines (Sr, S, Ba, Mg and Na) originate dominantly from the fluid source rocks. In combination with the δ 18 O and δ 13 C signatures, they are thus key geochemical variables for comparison of different travertine geobodies. Geochemical data analysis (elemental concentrations and isotope signatures), as illustrated here for the Turkish Ballık travertines, supports interpretation with regard to fluid source rock, distance from the vent and relative intensity of processes like evaporation and degassing. For fossil travertines, geochemical data can thus provide crucial insights for understanding the hydrologic system. In particular when information is restricted to borehole data, like in subsurface reservoirs, their application could be decisive.

Recent fluvial tufa carbonates were investigated from the Szalajka Valley (Bükk Mts., Hungary) and Malom Valley (Balaton Uplands, Hungary) to (1) study the suitability of the published oxygen isotope-based palaeothermometers for tufa deposits, (2) find the most appropriate (closest to equilibrium) places downstream for temperature calculation. A good correlation was observed between 1000lnα and the temperature of the water from which the tufa precipitated close to the spring orifice in the Szalajka and Malom Valleys. Large differences between calculated and measured temperature values were seen in areas where the seasonal water temperature increased and decreased by several degrees during our studied period. The stable isotope composition of the measured Hungarian tufas represents intermediate values between the western and eastern parts of Europe, reflecting increasing continentality in climate from west to east.

Carbon capture and storage technologies (CCS) represent the most suitable solutions related to the high anthropogenic CO 2 emissions to the atmosphere. As a consequence, monitoring of the possible CO 2 leakages from an artificial deep geological CO 2 storage (DGS) is indispensable to guarantee its safety. Fast surficial travertine precipitation related to these CO 2 leakages can be used as an alert for these escapes. Since few studies exist focusing on the long-term behaviour of an artificial CO 2 DGS, natural CO 2 storage affected by natural or artificial escapes must be studied as natural analogues for predicting the long-term behaviour of an artificial CO 2 storage. In this context, a natural CO 2 reservoir affected by artificial CO 2 escapes has been studied in this work. This study has mainly focused on the current travertines precipitation associated with the upwelling CO 2-rich waters from several hydrogeological wells drilled in the Gañuelas-Mazarrón Tertiary basin (SE Spain), and consists of a comprehensive characterisation of parent-waters and their associated carbonates, including elemental and isotopic geochemistry, mineralogy and petrography. Geochemical characterisation of groundwaters has led to recognise 4 hydrofacies from 3 different aquifers. These groundwaters have very high salinity and electrical conductivity; are slightly acid; present high dissolved inorganic carbon (DIC) and free CO 2 ; are oversaturated in both aragonite and calcite; and dissolve, mobilize and transport low quantities of heavy and/or toxic elements. Isotopic values indicate that: i) the origin of parent-waters is related to rainfalls from clouds originated in the Mediterranean Sea or continental areas; ii) the origin of C is mainly inorganic; and iii) sulphate anions come mainly from the dissolution of the Messinian gypsum from the Tertiary Basin sediments. Current travertines precipitation seems to be controlled by a combination of several factors, such as: i) a fast decrease of the hydrostatic pressure and the pCO 2 , resulting in a rapid degassing process; and ii) microbes and algae activity. This process leads to an increase in pH that favours the carbonates precipitation. Although there are not master physicochemical parameters controlling the precipitation of calcite or aragonite from their respective parent-waters, it is suggested that some parent-waters have the most suitable physicochemical features for the precipitation of one or another polymorph. Finally, the δ 13 C values of DIC and carbonates could be used as good tracers for CO 2 leakages from an artificial CO 2 DGS.

Elemental data from travertines are a treasure of depositional and diagenetic information. However, correct interpretation requires proper data acquisition and treatment. This study shows how results from elemental analyses complement sedimentological and other geochemical, i.e. isotopic, data and thereby contribute to our understanding of fossil travertines. Multivariate statistical element analyses, after multiple travertine digestion methods, demonstrate the link between elements, their mineralogical phases, and ultimately their origin. This study reveals that carbonate-phase related elements in travertines (Sr, S, Ba, Mg and Na) originate dominantly from the fluid source rocks. In combination with the δ 18 O and δ 13 C signatures, they are thus key geochemical variables for comparison of different travertine geobodies. Geochemical data analysis (elemental concentrations and isotope signatures), as illustrated here for the Turkish Ballık travertines, supports interpretation with regard to fluid source rock, distance from the vent and relative intensity of processes like evaporation and degassing. For fossil travertines, geochemical data can thus provide crucial insights for understanding the hydrologic system. In particular when information is restricted to borehole data, like in subsurface reservoirs, their application could be decisive.

Petrographical and petrophysical properties of the Turkish Ballık-Belevi travertine shrubs demonstrate the necessity of reservoir oriented classifications for shrub-related lithotypes and associated pore types. The presented shrub-related lithotype classification incorporates morphology, size and fabric, which are linked to specific pore-types and sizes. The travertines show highly complex pore networks, as observed from Computed Tomography reconstructions, making them of interest for the development and optimization of pore characterization methodologies and techniques, following an upscaling approach. Porosity (3e15%) and permeability (0e505 mD) strongly vary for the Ballık-Belevi travertines. The highest porosities and permeabilities are measured for horizontal samples dominated by slightly dissolution enlarged intershrub and interdigit growth framework porosity, mostly found for dendritic shrubs. The presented shrub and pore-type classification can be applied to shrubs worldwide. Studying outcrop analogues of continental carbonates helps to better understand heterogeneities, lateral variability and properties of Pre-Salt Cretaceous continental carbonate reservoirs, offshore Brazil and Angola.

The Denizli Basin in the West Anatolian Extensional Province in western Turkey is well-known for its numerous travertine occurrences. A combined sedimentological, diagenetical and geochemical This article is protected by copyright. All rights reserved. investigation is executed on the Ece and Faber travertines of the Ballık area, the largest travertine site in the Denizli Basin. The first aim of this study is the reconstruction of a three-dimensional geo-model in combination with a detailed sedimentological description from fabric to lithotype, lithofacies and geobody scale, with a focus on integrating pore-typing. The second aim involves the delineation of the CO 2-origin of ancient travertine precipitating waters. Peloidal, phyto and dendritic lithotypes dominate the studied travertines and honeycomb and bacteriform shapes and encrusted bacterial or fungal filaments related to their fabrics suggest a microbial influence. The environment of travertine precipitation evolved from dominantly sub-aqueous, as represented by the sub-horizontal and biostromal reed travertine facies, to dominantly sub-aerial in a thin water film, resulting in the cascade, waterfall and biohermal reed travertine facies. A general progradation of the travertine mound is indicated by the occurrence of stacked waterfall travertines. This results in sigmoidal clinoforms inside a general mound boundary configuration. Strontium and oxygen-carbon isotope signatures of the travertines point to a mixing mechanism of palaeofluids with deeply originated, heavy carbon CO 2 with lighter carbon CO 2 of shallow origin. These deposits can thus be considered as endogenic travertines. Carbonates of the Lycian Nappes acted as main parent carbon source rocks. The relative contribution of the lighter carbon isotopes is most likely to have originated from organic matter or soil CO 2. This study provides a unique three-dimensional insight in the Ballık travertine architecture that potentially can be used as an analogue for subsurface travertine reservoirs worldwide and illustrates the importance of the combined use of δ 13 C and 87 Sr/ 86 Sr signatures in the delineation of the CO 2-origin of travertine precipitating waters.

The Denizli Basin is a fault-bounded Neogene-Quaternary depression located in the Western Anatolian Extensional Province, Western Turkey. The basin is a unique geological site with abundant active and fossil (Quaternary) travertine and tufa deposits. Fluid inclusion microthermometry and isotopic analysis were applied to study the genesis of the Ballık fossil travertine deposits, located in the southeastern part of the basin. Microthermometry on fluid inclusions indicates that the main travertine precipitating and cementing fluids are characterized by low-salinity (<0.7 wt% NaCl equivalent) and variable temperature that cluster at <50°C and ca 100°C. Fluids of meteoric origin have been heated by migration to the deeper subsurface, possibly in a local high geothermal gradient setting. A latter uncommon cementation phase is related to a fluid with a significantly higher salinity (25.5 to 26.0 wt% bulk). The fluid obtained its salinity by interaction with Late Triassic evaporite layers. Sr isotopes indicate that the parent carbonate source rock of the different travertine precipitates is very likely to be the Triassic limestone of the Lycian Nappes. Carbon isotopes suggest that the parent CO 2 gas originated from thermal decarbonation of the Lycian limestones with minor contributions of magmatic degassing and organic soil CO 2. Oxygen isotopes confirm the meteoric origin of the fluids and indicate disequilibrium precipitation because of evaporation and degassing. Results were integrated within the available geological data of the Denizli basin in a generalized travertine precipitation model, which enhanced the understanding of fossil travertine systems. The study highlights the novel application of fluid inclusion research in unravelling the genesis of continental carbonates and provides several recommendations for hydrocarbon exploration in travertine-bearing sedimentary basins. The findings suggest that travertine bodies and their parent carbonate source rocks have the This article is protected by copyright. All rights reserved. potential to constitute interesting subsurface hydrocarbon reservoirs.

The Kucaj-Beljanica massif represents a complex hydrological karst system that possesses enormous potential for further groundwater extraction and regional water supply uses. In this paper, the influencing factors on groundwater quality in this area were discussed using hydrochemical analysis and the factor analysis method with 123 water and 20 rain/snow water samples. Hydrochemical analysis of the cation composition of cold springs, thermal springs/wells and sinkhole waters in the test area indicates that Ca 2+ and Mg 2+ are the dominant cations, representing 73-98% of ion equivalent. The anion composition of water indicates that HCO 3 − is the dominant anion, represented by 73-91% of ion equivalent. Only in the No. 30 thermal spring is characterized by K + + Na + and HCO 3 − + SO 4 2−. The P CO2 of thermal springs/wells, cold springs and sinkhole waters decreases gradually by an average of 10,247, 3444, 319 ppmv (part per million of volume ratio), respectively. The average δ 13 C DIC of thermal springs/wells, cold springs and sinkhole waters is − 6.56‰, − 10.19‰ and − 13.46‰, respectively. Corresponding to δ 13 C DIC , the mole ratios of (Ca 2+ + Mg 2+)/HCO 3 − are 0.48, 0.55 and 0.60, respectively. Factor analysis identifies 3 sources of solutes: (a) precipitation; (b) water-rock interactions; and (c) soil leaching. Ions of Na + , K + , Cl − and SO 4 2− indicate the predominant influence of atmospheric precipitation, but the No. 30 thermal spring sample is probably the result of deep water-rock interaction (volcanic rock) or is influenced by connate water mixed with shallow karst water. The dissolution of carbonate rocks is the primary factor affecting the Ca 2+ , Mg 2+ and HCO 3 − contents of groundwater, and soil leaching is the primary factor controlling the concentration of NO 3 − in water. These results provide a scientific basis for rational exploitation, protection and land use planning in the test area. Keywords Kucaj-Beljanica massif • Karst hydrochemistry • Factor analysis • Ion sources This article is a part of a Topical Collection in Environmental Earth Sciences on Sustainable Management of Karst Natural Resources, guest edited by Drs. Sasa Malinovic and Zoran Stevanovic.

The Denizli Basin in the West Anatolian Extensional Province in western Turkey is well-known for its numerous travertine occurrences. A combined sedimentological, diagenetical and geochemical This article is protected by copyright. All rights reserved. investigation is executed on the Ece and Faber travertines of the Ballık area, the largest travertine site in the Denizli Basin. The first aim of this study is the reconstruction of a three-dimensional geo-model in combination with a detailed sedimentological description from fabric to lithotype, lithofacies and geobody scale, with a focus on integrating pore-typing. The second aim involves the delineation of the CO 2-origin of ancient travertine precipitating waters. Peloidal, phyto and dendritic lithotypes dominate the studied travertines and honeycomb and bacteriform shapes and encrusted bacterial or fungal filaments related to their fabrics suggest a microbial influence. The environment of travertine precipitation evolved from dominantly sub-aqueous, as represented by the sub-horizontal and biostromal reed travertine facies, to dominantly sub-aerial in a thin water film, resulting in the cascade, waterfall and biohermal reed travertine facies. A general progradation of the travertine mound is indicated by the occurrence of stacked waterfall travertines. This results in sigmoidal clinoforms inside a general mound boundary configuration. Strontium and oxygen-carbon isotope signatures of the travertines point to a mixing mechanism of palaeofluids with deeply originated, heavy carbon CO 2 with lighter carbon CO 2 of shallow origin. These deposits can thus be considered as endogenic travertines. Carbonates of the Lycian Nappes acted as main parent carbon source rocks. The relative contribution of the lighter carbon isotopes is most likely to have originated from organic matter or soil CO 2. This study provides a unique three-dimensional insight in the Ballık travertine architecture that potentially can be used as an analogue for subsurface travertine reservoirs worldwide and illustrates the importance of the combined use of δ 13 C and 87 Sr/ 86 Sr signatures in the delineation of the CO 2-origin of travertine precipitating waters.

The Denizli Basin is a fault-bounded Neogene-Quaternary depression located in the Western Anatolian Extensional Province, Western Turkey. The basin is a unique geological site with abundant active and fossil (Quaternary) travertine and tufa deposits. Fluid inclusion microthermometry and isotopic analysis were applied to study the genesis of the Ballık fossil travertine deposits, located in the southeastern part of the basin. Microthermometry on fluid inclusions indicates that the main travertine precipitating and cementing fluids are characterized by low-salinity (<0.7 wt% NaCl equivalent) and variable temperature that cluster at <50°C and ca 100°C. Fluids of meteoric origin have been heated by migration to the deeper subsurface, possibly in a local high geothermal gradient setting. A latter uncommon cementation phase is related to a fluid with a significantly higher salinity (25.5 to 26.0 wt% bulk). The fluid obtained its salinity by interaction with Late Triassic evaporite layers. Sr isotopes indicate that the parent carbonate source rock of the different travertine precipitates is very likely to be the Triassic limestone of the Lycian Nappes. Carbon isotopes suggest that the parent CO 2 gas originated from thermal decarbonation of the Lycian limestones with minor contributions of magmatic degassing and organic soil CO 2. Oxygen isotopes confirm the meteoric origin of the fluids and indicate disequilibrium precipitation because of evaporation and degassing. Results were integrated within the available geological data of the Denizli basin in a generalized travertine precipitation model, which enhanced the understanding of fossil travertine systems. The study highlights the novel application of fluid inclusion research in unravelling the genesis of continental carbonates and provides several recommendations for hydrocarbon exploration in travertine-bearing sedimentary basins. The findings suggest that travertine bodies and their parent carbonate source rocks have the This article is protected by copyright. All rights reserved. potential to constitute interesting subsurface hydrocarbon reservoirs.

100 µl H 2 O Resin cleaning 1300 µl 6 M HCl Cleaning & conversion to Clform 600 µl 0.5 M HCl Resin cleaning 300 µl 3 M HCl Resin equilibration Sample in ~500 µl 3 M HCl Sample loading 100 µl 3 M HCl Elute matrix 1500 µl 0.5 M HCl Elute matrix (incl. In, Mo) 500 µl 1 M HCl Elute matrix (incl. Mo) 500 µl 2 M HCl Elute matrix 600 µl 6 M HCl Elute matrix (incl. Ag) 600 µl 0.1 M HBr-0.5 M HNO 3 Elute Zn and In 100 µl 2 M HNO 3 Wash

Introduction Travertine deposits located 24 km northwest of Karakoçan (Elazığ) and 60 km southwest of Mazgirt (Tunceli) (Figures 1a and 1b) are on the Karakoçan Fault Zone (KFZ) and Pamuklu Fault Zone (PFZ) and segments of the faults. The terms 'travertine' and 'carbonate tufa' are often used indiscriminately. 'Travertine' is frequently used to refer to carbonate rocks formed from thermal water deposits on the earth's surface, forming various deposit morphologies such as cascades, apron and channel travertines, fissure ridges, plateaus, and towers (Pedley, 2009; Pedley and Rogerson, 2010; Fouke, 2011). According to Andrews (2006) and Capezzuoli et al. (2014), tufas are terrestrial carbonates that form under surficial open-air conditions in streams, rivers, and lakes. Tufa is a product of physicochemical and microbiological biomediation processes. Because tufas form under exposure to light, they contain microbial (bacterial and cyanobacterial) and sometimes other algal components; many tufas encrust higher plants that live on the margins of streams, waterfalls, and wetlands (Pentecost et al., 1997). Tufa carbonates precipitate at ambient temperature from the calcium-bicarbonate waters derived from the dissolution of carbonate bedrock. Travertines are freshwater carbonates precipitated by organic or inorganic processes from the resources of calcium-and bicarbonaterich underground waters (Guo and Riding, 1998). Rapid travertine precipitation initiates when the CO 2 gas within the outcropping waters is emitted to the atmosphere. These freshwater carbonates have an internal structure that frequently changes laterally and vertically. Many conditions, such as differences in the lateral and vertical facies, the position of the resource, the base topography, fluctuations in the amount of the waters storing travertine, and changes in the flow rate and direction of water, organic activities, and surface waters, are frequently encountered in travertine fields due to seasonal climatic factors and tectonic zones. Topography plays a determinative role in the development of facies and in the storing of travertines. The climatic changes' influence on algal growth and travertine precipitation, besides tectonic settings, may produce a significant effect on depositional geometry of the hydrothermal travertine formation. These conditions

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, an Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport.

The graben faults of Aegean Graben system have produced many destructive earthquakes in historical and instrumental periods and the process is still going on. The surface traces of some of these faults, which have formed surface ruptures, may have been lost over time and/or the Holocene aged sediments have been caped. Therefore, difficulties may be encountered in determining the fault lines. This could be vital for microzoning studies in urban areas. In this study, a geological, morphotectonic and geophysical data ware used to identify a buried faulted line in Karsiyaka District of Denizli province. It cannot be observed because of the young sediments on the surface while it can be traced by morphological characteristics in some locations. The fault line has been identified using by geological data, geophysical (resistivity) tools. The results have been verified by trench studies.

The recent discoveries of deeply buried Cretaceous reservoir bodies in the Atlantic Ocean revealed that relationships between the distribution of spring carbonate deposits and faults are poorly understood. The well-exposed Quaternary deposits at Obruktepe (Denizli Basin, Turkey) provide an opportunity to reconstruct the three-dimensional sedimentary architecture of such a system. Integration of sedimentological, lithofacies and geochemical analyses reveals complexity in the lateral relationships between sedimentary environments, faults and geothermal spring carbonates. Five environmental systems are distinguished based on the lithofacies analysis: (i) vent; (ii) smooth slope; (iii) travertine-terrace; (iv) tufa-barrage; and (v) flood systems. Encrusting, baffling and settling sedimentary processes are reflected in data acquired at several scales, from lithofacies observations to the morphology and arrangement of geobodies, together with microfabrics and stable carbon and oxygen isotope data. Mean values of +4.9‰ δ 13 C and-8.74‰ δ 18 O Vienna PeeDee Belemnite reflect geothermal circulation of springwaters. The environmental distribution and lithofacies indicate a This article is protected by copyright. All rights reserved. lateral continuum between travertine and tufa deposits within this hot spring system. This finding supports two depositional models in which water flow variation is the main control on both CaCO 3 precipitation and the resulting formation of travertine and tufa. The proposed models address the factors responsible for the development of these complex mound-shaped carbonate spring deposits, and how they are related to fluid circulation at depth and in association with faults.

Physical activity can influence the development of postural control and balance. Therefore, the aim of study was to use posturography assessment to compare balance control on the Romberg test between athletes in two very different sports, taekwondo and tennis. [Participants and Methods] Twenty-nine young athletes participated in the study, 11 forming the taekwondo group and 18 the tennis group. Posturography was performed using the FreeMed system (Sensor Medica). Between-group differences were evaluated using unpaired Student's t-test. [Results] There was a significance between-group difference in the centre of pressure and the ellipse surface area with no between-group difference in frontal and sagittal plane postural control. [Conclusion] The taekwondo athletes displayed greater stability than tennis athletes, with a smaller ellipse area and a decrease in the amplitude of oscillations of the centre of pressure along the frontal plane, adaptations which likely reflect the demands of the taekwondo. Further studies are needed to support these conclusions.

Laminated travertine forms in and around an active hot spring on the west coast of Tamiahua Lagoon, north of the state of Veracruz, Mexico. Fluid chemistry is characterized by discharging slightly acidic pH hot water and gas at a constant flow rate. Moreover, finely interbedded mineralogical products from discharging waters at 70 °C host scattered hydrocarbons. The mineralogy and geochemistry of the travertine formations were characterized to determine their origin. Rock samples were collected and further studied by transmitted light petrography, X-ray diffraction, and EDS-coupled scanning electron microprobe. Identified mineralogy from outcrop samples includes aragonite, gypsum, anhydrite, and elemental sulfur as essential minerals, with calcite, celestine, barite, jarosite, opal, and fluorite as accessory minerals. Isotopic analyses for C and O were determined in carbonates, S isotope ratios on both elemental sulfur and sulfates, whereas measurements for trace elements and lanthan...

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km 2 , are up to 1 km 3 in volume. Today, spring waters in this area have temperatures of 19 to 57°C, are of the Ca-Mg-HCO 3-SO 4 type in the Pamukkale, Kelkaya and Pınarbaşı areas and the Ca-Mg-SO 4-HCO 3 type at Çukurbağ. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The δ 18 O and δD values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The δ 13 C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (−4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher δ 18 O values (−15.2 to −7.8‰ VPDB) than those of the northern areas (−16.6 to −4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

The study area, located in the eastern part of the continental rift zone of the Büyük Menderes within the Menderes Massif, western Anatolia, is composed of Paleozoic metamorphic rocks, Mesozoic limestones and Eocene via Pliocene to Quaternary sediments. Paleozoic marbles, quartzites and carbonate schists, Mesozoic limestone, Pliocene sediments and Quaternary alluvium and travertine serve as permeable rocks for the geothermal waters. The geothermal waters in Pamukkale and environs with outlet temperatures of about 35 °C and reservoir temperatures up to 250 °C can be considered as Ca-Mg-SO4-HCO3 type waters. The formation of the travertine in Pamukkale is one of the world&#39;s wonders, directly connected with decreasing temperatures and CO2 partial pressures. The formation of travertine deposits depends upon the solubility of CaCO3 controlled principally by CO2 partial pressure, temperature and pH values, in which reaction equilibriums play an important role. Moreover, the travertine...

The tufa term is described as secondary calcium carbonate deposits which are deposited by biologic and/ or physicochemical processes under cool water conditions and contain macro and micro scales plant, animal remains and bacteria ( especially cyanobacteria ). Tufas have especially deposited at Quaternary and recent time. The study area, located in Antalya city borders, constituted by primary three main terraces, Döşemealtı Plateau (Upper Terraces), Düden Plateau (Lower Terraces) and the third terraces under the sea level. These terraces contain nine second and the third order small terraces which determined by using GIS. As a result of this study, ten lithofacies which have deposited in fluvial, paludal, lacustrine and cascade-barrage environments are described. These are; 1. phytoherm framestone facies, 2. phytoherm boundstone fades, 3. micritic tufa fades, 4. phytoclastic tufa facies, 5. oncoidal tufa facies, 6. intraclastic tufa facies, 7. microdetrital tufa facies, 8. palaeosols, 9. pisolitic tufa facies (channel and pool types) and 10. intraformational tufa facies. These different types have formed in low regime surface flows/ streams, marshes, lake-pool and cascade-barrage environments that developed from springs and have different hydrologic conditions.

The tufa term is described as secondary calcium carbonate deposits which are deposited by biologic and/ or physicochemical processes under cool water conditions and contain macro and micro scales plant, animal remains and bacteria (especially cyanobacteria). Tufas have especially deposited at Quaternary and recent time. The study area, located in Antalya city borders, constituted by primary three main terraces, Döşemealtı Plateau (Upper Terraces), Düden Plateau (Lower Terraces) and the third terraces under the sea level. These terraces contain nine second and the third order small terraces which determined by using GIS. As a result of this study, ten lithofacies which have deposited in fluvial, paludal, lacustrine and cascade-barrage environments are described. These are; 1. phytoherm framestone facies, 2. phytoherm boundstone fades, 3. micritic tufa fades, 4. phytoclastic tufa facies, 5. oncoidal tufa facies, 6. intraclastic tufa facies, 7. microdetrital tufa facies, 8. palaeosols, 9. pisolitic tufa facies (channel and pool types) and 10. intraformational tufa facies. These different types have formed in low regime surface flows/ streams, marshes, lake-pool and cascade-barrage environments that developed from springs and have different hydrologic conditions.

Scaling by calcium carbonate precipitation is an important challenge during exploitation of geothermal water or geothermal district heating systems. Water decarbonation is a promising solution to mitigate calcium carbonate precipitation and reduce the scaling risks. In the current work, the decarbonation of geothermal water by coupling atmospheric air bubbling with seeding was investigated. For that, several operating conditions were studied and optimized such as air and water flows, hydrodynamics, residence time, and bubbling rate. Synthetic and real solutions were tested. To reveal the efficiency of the proposed process, the addition of chemicals was avoided. Results showed that, using continuously operating reactor and under optimized operating conditions, the decarbonation rate of a calcium carbonate solution tested (4 mmol/L of CaCO 3 , T = 50°C) can exceed 30% without using chemicals. It was also shown that he residence time in the reactor is relatively short (2.5 min) and the protection of the walls from precipitate adherence was guaranteed.

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km 2 , are up to 1 km 3 in volume. Today, spring waters in this area have temperatures of 19 to 57°C, are of the Ca-Mg-HCO 3-SO 4 type in the Pamukkale, Kelkaya and Pınarbaşı areas and the Ca-Mg-SO 4-HCO 3 type at Çukurbağ. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The δ 18 O and δD values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The δ 13 C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (−4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher δ 18 O values (−15.2 to −7.8‰ VPDB) than those of the northern areas (−16.6 to −4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO3. Initially a milky fluid comprising micro-spherules of amorphous CaCO3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-between different species of dissolved inorganic carbon and various CaCO3 polymorphs, this is the first documented evidence for C isotope fractionation between ACC and the calcite it recrystallizes to. This phenomenon may prove important for the interpretation of CaCO3based C isotope environmental proxies.

A multidisciplinary characterization of an active thermal spring in central Italy has been undertaken with the aim of (i) ascertaining whether microbiological activity plays a relevant role in hot-depositing travertines and (ii) establishing an experimental protocol able to identify similar effects in fossil travertines. Water, gas, and travertine samples were investigated by chemical (ICP/MS, SEM/EDS), physical (DTA-DTG), isotopic (d 18 O, dD, and d 13 C), mineralogical (XRPD), and spectroscopic (EPR) techniques. Twenty-four samples (three for each phase) were collected every 5°C temperature drop, along a $100 m long artificial channel near Viterbo (Bullicame 3, Latium, central Italy). A microbiological characterization was carried out in parallel, sampling the channel every 10°C temperature drop. The Bullicame 3 system is revealed to be composed of two markedly different subsystems: a water/gas interface, where a kinetically fast exchange allows equilibrium of components both in water and in gases; a solid/water interface, where travertine precipitation occurs, influenced by microbiological activity. A peculiar lattice shrinking of calcite was identified, as well as an anomalous value of the zero-field splitting parameter from the EPR measurements. The interpretation of these anomalies is confirmed by the identification of calcifying cyanobacteria throughout the channel path. Our results point out that microbiological activity can play a significant role in travertine deposition from hot springs. Furthermore, the proposed approach, representing a tool to identify crystal chemical remnants of past microbiological activity, could be applicable to fossil travertines.

The Bahçecik travertines, located in Gümüşhane (NE-Turkey) have been investigated for the first time using a multidisciplinary approach, which included sedimentological (lithofacies, depositional system), petrographic, radiometric 230 Th dating, geochemical analysis (stable isotopes), palynomorphs and geophysics (GPR). A carbonate build-up, 12 m thick, was formed with some interruptions, through the middle Pleistocene period. For this study, two travertine sections (F and D) were extensively used to figure out palaeoenvironmental and palaeoclimatic proxies. The main precipitation cycles, separated by palaeosol levels, have been described and interpreted from a sedimentological perspective. The carbonate deposits consist of shrubs, crystalline crust, reed, laminated (micritic), pisoids, oncoids, calcite thin rafts and coated gas bubbles, lithoclasts, and palaeosol levels. The sedimentological fieldwork and petrographic analysis show that the Bahçecik travertines formed in depression depositional and slope depositional systems. Moreover, the first 230 Th ages, stable isotopic results and palynofloral data in this study, prove that the Bahçecik travertines might have been affected by climatic and tectonic interruptions. According to dating results, the travertine occurrences began to precipitate during the 353 ka and continued into the 263 ka. Based on the palynological data, an abundance of herbaceous plants species was recorded in the warming period of climate. The thickness ranges from 2 to 12 m of the Bahçecik travertines. This precise thickness and also the presence of two different travertine formations, separated by a palaeosol erosional surface, were recorded by the ground penetrating radar (GPR) geophysical method.