Travertine Formation Research Articles

Travertine and calcareous tufa occurrences as an indicator of the ongoing tectonic activity of the Central Slovak Fault System inferred from airborne laser scanning data, geomorphometric, and structural analysis (Northern Slovakia)

The travertine formation process, active over the Quaternary, has enabled the origin of one of the largest travertine accumulations in the Western Carpathians. Travertines and calcareous tufas are associated with the tectonic activity of the Central Slovak Fault System, a 45 km wide and 140 km long N-S oriented fault zone. As the geological mapping, structural analysis, geomorphometric and isobase surface analysis revealed, the development of faults was polyphase and the travertine/tufa precipitation was not a continuous process. In addition, numerous travertine/tufa morphofacial varieties have been recognized within the study area, such as travertine/tufa terraces and tufa cascades, hillslope paludal tufa crust, phytoherm framework tufa barrages, lacustrine microdetrital tufas, bryophyte-dominated self-built channel, and fluvial tufa crust, reflecting its local geomorphology and precipitation factors. In the Revúcka dolina Valley, the travertine/tufa geobodies thus represent a reliable indicator of the tectonic activity over the Neogene up to Quaternary. The structural data provided relevant evidence confirming the character of orogen-parallel extension for the current tectonic/neotectonic regime in the Inner Western Carpathians. High-resolution topography derived from airborne laser scanning and the subsequent application of various geomorphometry techniques allowed quick identification of the edges of the terrace cascade systems and morpholineaments. Based on our observations, in this zone, the significant vertical movements of normal faults took place with a maximum estimated offset of 800–1000 m. The achieved results also support the use of the presented multifaceted methodology to understand the interplay between geomorphogenesis, hydrology, and tectonics.

Tectonic and climate changes influences on distribution and morphology of Quaternary travertine, Kurkur oasis, Egypt

The present study aims to investigate the relationship between tectonic activity, climate changes and Quaternary travertine deposition around Kurkur Oasis in the southern Western Desert of Egypt. Our findings, based on field observations and structural investigations, revealed that extensional tectonics played a significant role in the formation and the distribution of travertine deposits in the study area. Three main travertine morphotypes are documented: fissure ridge, spring mound, and terrace mound along with four lithotypes: crystalline crust, fine-grained lithoclast, paper-thin raft, and reed. The spatial distribution of these travertine occurrences indicates that travertines located closest to the springs exhibit crystalline crust and paper-thin raft lithotypes. While, the reed and the fine-grained lithoclastic types are situated farther from the water sources. Terraces mounds are related to pluvial episodes, which led to travertine deposition in the suitable tectonically created depressions. A two-stage hypothesis for travertine deposition are proposed herein, involving tectonic fissuring and the circulation of carbonated water. These results may enhance our understanding of travertine formation and have broader implications for geological research in similar tectonic environments.

Microbial Ecology of an Arctic Travertine Geothermal Spring: Implications for Biosignature Preservation and Astrobiology.

Jotun springs in Svalbard, Norway, is a rare warm environment in the Arctic that actively forms travertine. In this study, we assessed the microbial ecology of Jotun's active (aquatic) spring and dry spring transects. We evaluated the microbial preservation potential and mode, as well as the astrobiological relevance of the travertines to marginal carbonates mapped at Jezero Crater on Mars (the Mars 2020 landing site). Our results revealed that microbial communities exhibited spatial dynamics controlled by temperature, fluid availability, and geochemistry. Amorphous carbonates and silica precipitated within biofilm and on the surface of filamentous microorganisms. The water discharged at the source is warm, with near neutral pH, and undersaturated in silica. Hence, silicification possibly occurred through cooling, dehydration, and partially by a microbial presence or activities that promote silica precipitation. CO2 degassing and possible microbial contributions induced calcite precipitation and travertine formation. Jotun revealed that warm systems that are not very productive in carbonate formation may still produce significant carbonate buildups and provide settings favorable for fossilization through silicification and calcification. Our findings suggest that the potential for amorphous silica precipitation may be essential for Jezero Crater's marginal carbonates because it significantly increases the preservation potential of putative martian organisms.

Hyperspectral identification of travertine state in Huanglong by the PSO-BPNN method

The Huanglong Scenic and Historic Interest Area in China, a UNESCO World Heritage Site, is famous for its large-scale, diverse, intricately structured, and brightly colored surface travertine landscapes. However, severe degradation of the Huanglong travertine formations, such as blackening and algae erosion, has occurred in recent years, necessitating monitoring and identification. We collected hyperspectral reflectance data of the travertine formations in different states and bare ground using a ground-based hyperspectral radiometer (PSR-2500) from ASD company. After conducting a correlation analysis between the hyperspectral reflectance data and the travertine formations, we identified healthy travertine formations, blackened travertine formations, travertine formations affected by algae erosion, and bare ground. The Siamese network method was employed to generate data labels, and the spectral features of the travertine formations were extracted by combining the sensitive bands with pre-processed and reduced data. The PSO-BPNN classifier was developed by optimizing the back propagation neural network (BPNN) using the particle swarm optimization algorithm (PSO). To verify the effectiveness of PSO-BPNN in accurately distinguishing different states of travertine formations, we compared its performance with that of BPNN using three performance indices. Finally, the proposed method was applied to the real-world hyperspectral image data collected by the Micro-Hyperspectral imaging instrument to classify the travertine formations in different states and bare ground. The test set demonstrated good overall performance, with an average overall accuracy (OA) of 0.93, F1-score of 0.92, and Kappa coefficient of 0.97.

The chemical state of the watershed in Ras Elma region (South of Taza, Morocco) one of the parameters responsible for the decline in the formation of the current travertine formations.

The Ras Elma region, situated to the south of the city of Taza in northern Morocco, boasts abundant travertine formations that continue to develop, albeit selectively in specific sheltered sites. This development is influenced by various parameters, including the role of water chemistry. This article presents a spatio-temporal analysis of various hydrochemical parameters, including conductivity, pH, temperature, magnesium, calcium, and others. It's worth noting that the water from the Ras Elma Vauclusian spring, a key driver of travertinization in the region, is sourced from water infiltrating through faults and flowing into Lake Tompraire, known as Dayat Chikker near the Bab Boudir area. The findings suggest that the water in Ras Elma has turned aggressive, as revealed by the examination of the calcaro-carbonic equilibrium. CaCO3 precipitation occurs predominantly in the summer, significantly impacting the formation of travertines, particularly those of the spring and dam types. However, valley-type travertines exhibit more extensive development compared to the other two types.

Trace elements (REE + Y) reveal marine, subaerial, and hydrothermal controls on an early Archean habitat for life: The 3.48 Ga volcanic-caldera system of the dresser formation, Pilbara Craton

Host to some of Earth's earliest evidence of life, the fossiliferous lowermost chert-barite sequence (DFc1) in the ∼3.5 Ga Dresser Formation of the Pilbara Craton, Western Australia is interpreted to have deposited within a dynamic volcanic-hydrothermal caldera. To date, three end-member fluid compositions (marine, hydrothermal, and subaerial) have been identified using trace and rare earth elements. However, this data has been limited to a few, single rock units, providing only snapshots at various depositional time intervals, and does not represent a synthesis of habitat evolution over time. Here, we present a systematic trace and rare earth element study of 31 whole-rock samples from 10 lithofacies across the entire stratigraphic sequence. Samples include bedded cherts (silicified chemical and clastic sedimentary rocks), hot spring geyserite and sinter terracettes, jaspilitic chert, and silicified volcaniclastic siltstone. Four lithostratrigraphically-defined assemblages (A1-A4) in DFc1 illustrate a transition from marine (underlying pillowed North Star Basalts, deep marine cherts) to shallow water and subaerial conditions (evaporitic carbonate-chert couplets, hot spring geyserite and sinter terracettes, channelized conglomerates and basaltic-evolved volcaniclastics)(A1-A2), followed by a return to deep marine conditions (jaspilitic chert, volcaniclastic siltstone and sandstone)(A3-A4). Our trace and rare earth element data enhance the four-stage model (reflecting, A1-A4 respectively) as follows: stages 1–2, crustal inflation generated the emplacement of a deep-rooted magmatic chamber, leading to surface uplift and a transition from deep water to hydrothermally-influenced semi-restricted lakes, stromatolites, and subaerial hot springs. Trace and rare earth element patterns of A2 geyserite indicate the circulation of low-temperature near-surface, non-marine geothermal fluids through basaltic to more evolved volcaniclastic rocks. REE + Y patterns of sinter terracettes may indicate the formation of hot spring travertine in DFc1; stages 3–4, hydrothermally-influenced jaspilites and volcaniclastic sediments deposited in marine basins driven by caldera collapse. This stifled stromatolite growth and represents the end of subaerial exposure. This work contributes to ongoing efforts to reconstruct Earth's early life habitats, which inform the search for life on Mars and origin of life studies.

Petrifying Springs of Lviv Roztocze and adjacent territories: the Retrospective and Modern Condition

Eighty-four hard-water petrifying springs of Lviv Roztocze and adjacent territories, which are forming 18 streams, were examined and their current state was assessed. The geographical position, geomorphological features, conditions of water sources and spring beds, character of tufa-forming processes, shapes of tufa formations and vegetation composition were described for each location. It was established, that travertine springs on the studied territory are related to the sources of small rivers associated with water-erosive landscape complexes. The high mineralization of groundwater, the specific structure of the river-erosion network, the location in a moisture warm climate zone, the development of colonies of calciphilic organisms (cyanobacteria, algae, bryophytes) at the watercourses led to the formation of a large travertine deposits here in the past. At the present time, the complex of natural factors is often accompanied by anthropogenic influence due to a long period of modification of the water resources of The Roztocze region. Now most of the petrifying springs are transformed by human activity, which significantly affects the intensity of tufa-forming processes. It was established, that a high level of anthropopression led to the transformation of most tufagenic watercourses and a decrease in the intensity of their activity: complete (when the processes of tufa genesis are stopped) or partial (when the processes slow downed or returned to the initial stage). Our survey of 84 sources showed that the majority of them are markedly anthropized (63.1%), about a quarter (23.8%) are lightly modified and are semi-natural in origin, and only a small part of them have a natural character now (13.1%). Among the four travertine formations known from the end of the 19th century, only two have survived (Chepin streams, Hamulets streams), while two more have been completely destroyed (Berekavitsa streams, the springhead of the Kabanivka river). It should be noted, that the active zone of tufa accumulation has noticeably decreased on 5 streams with natural or semi-natural sources (cascade on Hamulets stream, cascade on Hrybovytskyi stream, the left tributary of Chyshkivskyi stream, cascade on Chepin stream, a travertine body at the site of the bath container in Lysynytskyi stream). Tufa accumulation processes at 21 sources (25.0%) were artificially returned to the initial stage of formation due to the destruction of previously generated deposits there. Natural travertine formations of the region mainly have the form of cascades, rarely - waterfalls or crests and anthropogenic ones are mostly covered by concrete trunk. Regardless of their artificial origin, anthropogenic wells can be valuable habitats for the habitats of calciphilic bryophytes in urbanized areas. Natural and semi-natural travertine springs with saved biodiversity are can be potential objects of the Emerald network of the Roztocze region.

Magnesium isotope fractionation during natural travertine deposition from Baishuitai, SW China

Travertine samples deposited in Earth's surface environments can be used as an effective archive for paleo-climatic reconstruction. As a common element in carbonates, magnesium (Mg) and its isotopic composition in travertine could provide useful information for evaluating paleo-environment changes. In this study, we investigate the Mg isotope systematics in both endogenic travertines (mainly calcite) and spring/stream waters at Baishuitai, Yunnan, SW China. Our results show a systematic increase in δ26Mg value from −1.37 to −1.26‰ for water samples downstream, but varied δ26Mg values between −4.12 and −3.95‰ (average −4.02‰) for solid carbonates, thus a corresponding fractionation Δ26Mgcalcite-water between −2.76 to −2.59‰ (mean value of −2.69‰). Therefore, the solid carbonates preferentially incorporate light Mg isotopes during travertine formation. More interestingly, the Mg distribution coefficient (KMg/Ca) between travertine and water exhibits two variation trends with the calcite deposition rate (Rp) along the canal, which can be explained by the change of calcite formation mechanism from direct nucleation to precipitation via amorphous calcium carbonate (ACC) intermediate. In the upper-stream, the direct nucleation of calcite results in the rapid incorporation of Mg ions into crystal lattice, while a relatively slow precipitation of calcite downstream would incorporate Mg via ACC formation pathway in a quasi-equilibrium pattern. This is consistent with the grain size distribution and crystal morphology observed under SEM. Our results show the important control of water Mg/Ca ratios on the calcite precipitation during travertine formation, and imply the potential and complexity of using Mg isotopes of travertine deposits to reconstruct paleo-environments.

Travertines of the South-Eastern Gorny Altai (Russia): Implications for Paleoseismology and Paleoenvironmental Conditions

The south-eastern Gorny Altai is one of the most hazardous seismogenic area in the north of Central Asia. We present a synthesis of field, 230Th-U geochronological, mineralogical and geochemical data collected on seven Quaternary travertines. All travertines occur within the zones of active faults that border the Chuya and Kurai intermontane basins. Travertine cement mainly comprises calcite (with minor amounts of aragonite), which cements alluvial, alluvial fan, and colluvial deposits. The results of 230Th-U dating suggest that deposition of the travertines was triggered by large paleoearthquakes in the last eight thousand years. Several stages of travertine formation with ages 9–11 ka BP correspond to the known period of strong paleoseismicity in the region (8–16 ka BP). The 123 ka BP travertine resulted from a slip triggered by the Middle Pleistocene deglaciation, while that of 400 ka BP represents seismic motions likely associated with the main Cenozoic orogenic phase. All travertine forming events fall within warm and wet climatic phases (interglacials). Large earthquakes activated faults and caused a rapid rise along them of ambient-temperature bicarbonate groundwater, which was previously sealed in deep-seated Upper Neoproterozoic–Paleozoic limestone-dolostone aquifers. Rapid CO2 degassing of the spring water was the most important control of calcite or aragonite precipitation. Such travertines represent an important tool for paleoseismological research in seismically active regions.

Analysis of a travertine system controlled by the transpressional activity of the Alhama de Murcia fault: The Carraclaca site, eastern Betic Cordillera, Spain

Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing as it emerges at the Earth’s surface, are often associated with major crustal-scale faults. The Carraclaca site, in the Lorca-Totana section of the Alhama de Murcia Fault, Spain, presents a complex geomorphological landscape controlled by active tectonics. The geology here records the interaction between Quaternary alluvial fans, travertines, and a pop-up structure developed in a transpressional section of the fault. The Alhama de Murcia Fault is an 80 km long left-lateral strike-slip fault that is one of the main seismogenic structures in the Iberian Peninsula. In this work, we examined the relation between travertine precipitation in the Carraclaca site and the tectonic activity of this fault zone through morphological and geochemical studies. The δ13C and δ18O isotopic signals indicate that the carbonate deposits are hydrothermal. In addition, the 87Sr/86Sr ratios in the samples suggest subsurface fluid interaction with the Miocene sediments and the Alpujárride basement, located below the alluvial deposits. Tectonic activity in the Alhama de Murcia Fault might generate the opening of deep water circulation in the crust every time a seismic event occurs, giving rise to hydrothermally derived carbonates precipitation. Deep waters rise and reach the surface interacting with meteoric waters, resulting in travertine formation. Therefore, the Carraclaca carbonate deposits study can inform us about the seismogenic cycle of the fault in the Lorca-Totana section.

Large Holocene paleoseismic events and synchronized travertine formation: a case study of the Kurai fault zone (Gorny Altai, Russia)

ABSTRACT The Kurai Fault Zone (KFZ) is one of the most hazardous seismogenic structures in the Gorny Altai (Russia), which bounds the largest Kurai and Chuya intermontane basins from the north. Trenching studies, radiocarbon dating of colluvial wedge deposits, and 230Th-U dating of seismogenic travertine of the Meshtuyaryk field showed that the fault scarp in the northwestern part of the Chuya Depression was formed by earthquakes that occurred ca. 9.5, 7.7, 5.8, and 4.8–3.4 ka BP. The last two palaeoearthquakes are younger than 3.2 ka BP. The parameters of seismogenic ruptures, as well as the distances between coeval seismogenic travertines along the KFZ, yielded estimates of the Mw of the four oldest palaeoearthquakes as 6.8–7.6 and ESI 2007 shaking intensities of VIII–XI. The results of 230Th-U dating suggest that deposition of the Meshtuyaryk travertines was triggered by three strong palaeoearthquakes at ca. 9.5, 7.7, and 4.8–3.4 ka BP, which activated faults and caused a rapid rise along them of ambient-temperature bicarbonate groundwaters previously sealed in deep-seated limestone aquifers.

Electronic cartographic GIS models of the environmental state of the Dniester canyon

The Dniester Canyon is a deep gorge, 100-120-140 m, between the Podil Upland on the left bank and the Carpathian and Prut-Dniester Uplands on the right bank. The canyon is famous for its classic geological sections of the Silurian and Devonian systems, between which there is a gradual transition. There are only four such incisions in the world: ours, as well as in the Czech Republic, Scotland and the United States. Great geomorphological attractiveness of the canyon: two Upper Pleocene supra-canyon and five Quaternary intra-canyon river terraces; caves, waterfalls, travertine formations, bizarre rocks of physical and chemical weathering. The rocky flora and fauna are protected by natural monuments, reserves, regional landscapes and natural national parks. These objects are listed in the Red and Green Books. Therefore, the Dniester Canyon was chosen as one of the seven wonders of nature. That is why it is necessary to preserve this national heritage for present and future generations. To do this, environmental safety systems are developed by GIS mapping methods. The electronic cartographic material in geoinformation systems are digital or vector maps. The Vector maps are created based on the registration of raster scanned map material or satellite images. Vector layers can be interpolated or created from thematic maps using databases. Most often, measuring operations in GIS packages are implemented in the form of special functions and presented as a separate menu item. Such functions include: measurement (determination) of point coordinates; measurement of distances between two specified coordinates (with or without taking into account the three-dimensional coordinate system); measuring the length of a straight or broken line; measuring the length of the perimeter of the polygon; measuring the area of the landfill; measurement of volumes using the surface and cutting plane. Selection operations help the user to get exactly the information he needs at the moment of working with GIS. The selection of the necessary part of information from one or more cartographic databases is carried out using queries.

Interplay between abiotic and microbial biofilm-mediated processes for travertine formation: Insights from a thermal spring (Piscine Carletti, Viterbo, Italy).

Active hydrothermal travertine systems are ideal environments to investigate how abiotic and biotic processes affect mineralization mechanisms and mineral fabric formation. In this study, a biogeochemical characterization of waters, dissolved gases, and microbial mats was performed together with a mineralogical investigation on travertine encrustations occurring at the outflow channel of a thermal spring. The comprehensive model, compiled by means of TOUGHREACT computational tool from measured parameters, revealed that mineral phases were differently influenced by either abiotic conditions or microbially driven processes. Microbial mats are shaped by light availability and temperature gradient of waters flowing along the channel. Mineralogical features were homogeneous throughout the system, with euhedral calcite crystals, related to inorganic precipitation induced by CO2 degassing, and calcite shrubs associated with organomineralization processes, thus indicating an indirect microbial participation to the mineral deposition (microbially influenced calcite). The microbial activity played a role in driving calcite redissolution processes, resulting in circular pits on calcite crystal surfaces possibly related to the metabolic activity of sulfur-oxidizing bacteria found at a high relative abundance within the biofilm community. Sulfur oxidation might also explain the occurrence of gypsum crystals embedded in microbial mats, since gypsum precipitation could be induced by a local increase in sulfate concentration mediated by S-oxidizing bacteria, regardless of the overall undersaturated environmental conditions. Moreover, the absence of gypsum dissolution suggested the capability of microbial biofilm in modulating the mobility of chemical species by providing a protective envelope on gypsum crystals.

Orbital-scale hydroclimate variations in the southern Tibetan Plateau over the past 414,000 years

Speleothem oxygen isotope (δ18O) constitutes one of key proxies to reconstruct the Indian and East Asian summer monsoon (ISM and EASM) hydroclimate history on a wide range of timescales. Here, we use three new well-dated speleothem δ18O records from Tianmen cave, in the south-central Tibetan Plateau (TP), together with previous records from the same cave, to reconstruct a composite Tianmen record spanning over the past 414,000 years. The Tianmen δ18O record follows Northern Hemisphere summer insolation (NHSI), broadly coherent with speleothem δ18O records from both ISM and EASM regimes. In comparison with previous model simulations and modern hydroclimate analyses, the Tianmen δ18O was interpreted primarily as a proxy indicating the ISM intensity. The Tianmen δ18O record comprises both high and low NHSI time periods, which reveals an exceptional large amplitude (∼14‰) of δ18O variations at the precession band, possibly resulted from a combination effect of precipitation amount, moisture source, transport pathway, high elevation and rainout. Besides, a broad consistency on orbital-scale variability among Tianmen δ18O, δ13C and trace element records is found, suggesting that the ISM intensity regulates the effective rainfall at the cave site as well. Notably, Tianmen speleothem growth occurred merely during warm-wet interglacial periods, even during low NHSI times near the precession maximum, and in contrast, hiatuses persistently occurred throughout cold-dry glacial periods. This pattern is similar to that found in travertine formations in the region, both suggesting that the interglacial temperature might be a prerequisite for speleothem/travertine formations in the region, while the strong ISM precipitation in turn provides a sufficient condition. Our new Tianmen record, combined with a large set of speleothem records from both Asian Westerlies and Asian monsoon domains, gives further evidence to reinforce a previous hypothesis: a consistent temporal pattern in the δ18O of precipitation on orbital and millennial scales over the vast Asian monsoon and Westerlies regimes. As such, in order to reconcile the precipitation δ18O variations between speleothem and TP ice cores, we argue that the Guliya ice-core chronology may have a basal age of ∼70 ka BP, which is supported by recent dating results from the Guliya ice cap.

Caves in clastic rocks (Muğla, SW Türkiye)

Caves evolution is controlled by lithological properties, discontinuities, water, climate, and physico-mechanical properties of soluble rocks, vegetation and human impact. This study investigates the cave formation in Upper Miocene-Pliocene clastic rock in Menteşe town of Muğla. The lithology, physico-mechanical properties and hydrogeologic factors of host rocks and morphology of the caves in Asar Hill and Damlam stream valley were examined. The caves are 1.47-9.71 m long, 2.24-19.36 m wide and 1.38-27 m high. Four joint sets and bedding planes affect the clastics in the Asar Hill area. Mudstones (low plasticity clay, sandy clay) are in soft-very soft rock, while conglomerate is in moderate-hard rock class. The mudstone removal has started the formation of the caves. The vegetation roots act as groundwater circulation paths in the Damlam stream area. Water has eroded mudstone and muddy matrix of conglomerate following cracks and led to the formation of the caves. Water infiltration may have led to stalactite, flowstone and travertine formation in Damlam stream caves. Possible cave collapse could threaten life and property in the Asar Hill area, and may cause the destruction of internal structures of the caves in the Damlam stream. Thus, precautionary measures such as continuous monitoring and protection must be taken in both cave areas.

Mineralogy, Geochemistry, and Stable Isotopes (C, O, S) of Hot Spring Waters and Associated Travertines near Tamiahua Lagoon, Veracruz, Gulf of Mexico (Mexico)

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 lanthanides were performed on carbonates. A suit of brines and condensates from gas samples was collected for H and O isotopic analyses and concentration determinations of the main ions and major and trace elements. Isotopic values of δ13C and δ18O of aragonite are in the range of +1.75‰ to +2.37‰ and −1.70‰ to −0.78‰, respectively. The δ34S isotopic values of native sulfur and sulfates ranged from −4.0‰ to +1.2‰. The isotopic values of δ2H (−5.50‰) and δ18O (+7.77‰) of hot water samples collected in terraces where aragonite precipitates suggest a mixture between meteoric water and the Gulf of Mexico oil-field related waters. It was concluded that the aragonitic formations near Tamiahua Lagoon are hypogenic and were generated by CO2 and H2S emanations of deep origin and by oxidation-reduction reactions that can be linked to surficial bacterial activity.

Pioneer species of Cyanobacteria in hot springs and their role to travertine formation: The case of Aedipsos hot springs, Euboea (Evia), Greece

AbstractCyanobacteria are considered to be among the first microorganisms to settle in hot springs where they form a favourable environment for further biological establishment. Nevertheless, the exact pioneer species and how early they start participating in the biomineralisation processes remain unknown. The aim of the present study was twofold, that is, to identify the pioneer Cyanobacteria in hot springs (i.e. Aedipsos area, Greece) and to record their early biomineralisation processes. The in situ experimental approach included the setup of sterile glass and/or plexiglass slides in several locations to facilitate colonisation by Cyanobacteria, and removal of slides for study after 48–202 h. Synechococcales (37%) and Oscillatoriales (33%) were the dominant orders, followed by Chroococcales (15%) and Spirulinales (11%); whereas Chroococcidiopsidales (4%) was found only in a few sites. The order Nostocales was not observed at the early stages of colonisation although it was present in mature stages. Forty‐three species of Cyanobacteria were identified as pioneer microorganisms, with Spirulina subtilissima being the most frequently found. The most common pioneers were multicellular filamentous Cyanobacteria, that is, organisms with a large surface area able to form significant amounts of extracellular polymeric substances. Among the pioneers, thermophilic species of Cyanobacteria were typical such as Chroococcidiopsis thermalis, Chroococcus thermalis, Leptolyngbya thermalis, S. subtilissima and Symploca thermalis, as well as typical limestone substrate species such as Chroococcus lithophilus and Leptolyngbya laminosa. Temperature seems to affect biodiversity. Also, pioneers were found to contribute to the biomineralisation processes from their first appearance. In the studied samples, three biomineralisation processes were identified, that is, (i) calcification of cyanobacterial sheaths, (ii) trapping of carbonate crystals on a crystal retention lattice formed by extracellular polymeric substances and filaments and (iii) trapping and confinement of carbonate crystals around filamentous Cyanobacteria.

Chemical component depositions in the microbial mats and travertine in the Khoito-Gol thermal spring (Eastern Sayan)

The results of studies of the chemical composition of water, travertine, and microbial mats in the Khoito-Gol mineral spring (Eastern Sayan) are presented. It was shown that the formation of mineral deposits, travertine, and microbial mat is connected with the active functioning of microorganisms and geological and geodynamic conditions. It has been revealed that the diversity of cyanobacterial and sulfur microbial mats increases as the distance from the springs of the thermal water grows. Microbial mats are hardened with carbonates being converted into solid travertine crusts that are built upon the top of older structures to form multi-meter domes. The concentration function of the microbial mats and thermal water showed higher coefficients of accumulation of nickel and beryllium.

The multidisciplinary approaches on facies developments and depositional systems of the Bahçecik travertines, Gümü!hane, NE-Turkey

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 230Th 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 230Th 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.

U-Th ages and facies properties of Edremit travertines and tufas, Van, Eastern Anatolia: implications for the neotectonics of the region

Travertine formation is one of the most important archives of active tectonics in a region and provides information about climate, water temperature and quantity, and biological activity. The Edremit travertines and tufas extend over nearly160 km2 within the boundaries of the Edremit area to the east of Lake Van (eastern Turkey), and yield important evidence towards understanding the neotectonics of the region. The Edremit travertines and tufas were studied throughout their full stratigraphic extent, the factors controlling the formation of these deposits were examined, and the succession was sampled for U/Th analysis. Travertine formation was found to occur from 542–29.7 ka, with two different tufa formation periods: from 29.7–5.8 ka and 5.8–2.08 ka. Pauses in travertine formation (palaeosols) were identified from 510–470 ka, 289–269 ka and 91–34 ka. Our study showed that climate parameters affected the formation of tufa, while the Edremit travertines developed under the control of tectonism. The Van Fault is directly associated with travertine development and its age was identified as 542 ka or older. Since the Gurpιnar Fault, one of the most important faults in the region, is effective in shaping the southern slope of the travertines and limiting the movement of the Van Fault, its age should be younger than 542.4 ka. The Elmalιk Fault played an active role in the formation of the Edremit tufas and is proposed to be 29.7 ka in age, from stratigraphic relationships in the region.