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1.
The isotopic composition of calcite from travertine deposits of the Tokhana-Verkhnii hot spring in the Elbrus area shows broad variations in δ13C and δ18O (from +3.8 to +16.3‰ and from +24.6 to +28.1‰, respectively). The δ13C and δ18O values increase toward the sole of the travertine dome. The isotopically heaviest carbonates (δ13C of up to +16.3‰) were found near the bottom of the dome and composed ancient travertine, which are now not washed by mineral water. The scatter of the δ13C values of the fresh sample is slightly narrower: from +3.8 to +10‰. Calculations indicate that all carbonates of the Tokhana dome were not in equilibrium with spontaneous carbon dioxide released by the spring (\(\delta ^{13} C_{CO_2 } \) = ?8‰). To explain the generation of isotopically heavy travertine, a physicochemical model was developed for precipitation of Ca carbonates during the gradual degassing of the mineral water. The character of variations in the calculated δ13C values (from +5.5 to +13‰) is in good agreement with the tendency in the variations of the δ13C in the carbonate samples. The calculated and measured pH values are also consistent. Our results demonstrate that the isotopic composition of large travertine masses can be heterogeneous, and this should be taken into account during paleoclimatic and paleohydrogeological reconstruction.  相似文献   

2.
Several geothermal fields are located in a NE-SW trend along a structural lineament around the Sivas basin; one of those is the Ortaköy travertines situated 83?km south-west of Sivas. There are eight fissure-ridge-type travertine localities in the area, although eroded-sheet-type travertines constitute many of the travertines of the region. By evaluating the rocks of the Late Miocene-Early Pliocene K?z?l?rmak Formation, it was determined that fissure axes developed within fissure-ridge-type travertines, and that the structural elements obtained from satellite images together with the fissures that form the fissure-ridge-type travertines are shear and tension fissures, and the NE-SW-oriented opening of the fissures, were a result of NW-SE-directed compression, which was also responsible for the formation of the Sivas Backthrust. Ground-penetrating radar studies have shown that the thickness of fissure fills within the fissure-ridge-type travertines of the Ortaköy geothermal field increase with depth, and that the hydrothermal fluids which brought about the formation of the travertines moved surfaceward via fissure systems. The results of U/Th radiometric dating indicate that the youngest travertine in the region is 17,761 (?268/+269) years old and the oldest 128,286 (?3537/+3662) years old. Using the widths of banded travertines within the fissure-ridge-type travertines as well as these age results, the opening rate of the Sivas Basin was determined to be .06 (?.01/+.05) mm/year.  相似文献   

3.
Formation of travertines from continental waters requires very special conditions. Their porous, cellular and concretionary appearance is often due to calcite incrustations on plants. Therefore the high porosity beside a very low concentration of detrital silicates must be related to a high rate of calcite accumulation (0.1 to 1 mm/year). A high rate of sedimentation from high Ca-concentrations (>0.01%) does not occur in normal continental waters equilibrated with the atmospheric carbon dioxide.Formation of travertines is probably not an indicator of special climatic conditions as often assumed but is related to a special chemical composition of fresh waters. Creeks with continuous travertine deposition, investigated by us, contain about 200 ppm Ca. This is more than ten times the normal concentration of average continental waters. Bicarbonate concentration in these waters is five times that of equilibrium with atmospheric carbondioxide. Many of the productive waters are characterized by high sulfate concentrations and Sr/Ca-ratios (1000 Sr/Ca ranges from 9 to 22; seawater: 20).Except one from the Schwäbische Alb 15 samples (Leine-valley, Teutoburger Wald, Thüringen) are high in sulfate and Sr/Ca-ratio to be accumulated in waters with remarkable concentrations in the respective elements. The Sr/Ca-ratios cannot be explained from dissolved limestones underlying the exposed areas. The assumption of dissolution of gypsum beds very well explains our observations and data. From the S32/S34 ratio an origin from Zechstein (Upper Permian), Muschelkalk (Middle Triassic) or Keuper (Upper Triassic) deposits respectively can be assumed. Like other freshwater limestones the travertines under investigation differ from marine carbonates by their light carbon (mean C13 –8,1) from decomposed organic matter and their light oxygen (mean O18 –6,7) from exchange with freshwaters. The discrimination freshwater- and marine limestones in oxygen isotopes is only valid for those of low age (Upper Mesozoic to Recent).Hence the special conditions of travertine formation are related to bicarbonate spring waters which have circulated on faults where they could dissolve gypsum (and/or calcite) from subsurface beds.Additional examples of travertine deposits from Czechoslovakia (Zyka, 1958), Lüneburger Heide (NW Germany), Italy (Tivoli near Rom) and Jugoslavia can be explained as formations of either sulfate-bicarbonate or of bicarbonate waters.

Wir danken der Deutschen Forschungsgemeinschaft für Beihilfen zu dieser Arbeit.  相似文献   

4.
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 (δ18O, δD, and δ13C), 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.  相似文献   

5.
Travertine is present at 20% of the ca 60 hot springs that discharge on Loburu delta plain on the western margin of saline, alkaline Lake Bogoria in the Kenya Rift. Much of the travertine, which forms mounds, low terraces and pool‐rim dams, is sub‐fossil (relict) and undergoing erosion, but calcite‐encrusted artefacts show that carbonate is actively precipitating at several springs. Most of the springs discharge alkaline (pH: 8·3 to 8·9), Na‐HCO3 waters containing little Ca (<2 mg l?1) at temperatures of 94 to 97·5°C. These travertines are unusual because most probably precipitated at temperatures of >80°C. The travertines are composed mainly of dendritic and platy calcite, with minor Mg‐silicates, aragonite, fluorite and opaline silica. Calcite precipitation is attributed mainly to rapid CO2 degassing, which led to high‐disequilibrium crystal morphologies. Stratigraphic evidence shows that the travertine formed during several stages separated by intervals of non‐deposition. Radiometric ages imply that the main phase of travertine formation occurred during the late Pleistocene (ca 32 to 35 ka). Periods of precipitation were influenced strongly by fluctuations in lake level, mostly under climate control, and by related changes in the depth of boiling. During relatively arid phases, meteoric recharge of ground water declines, the lake is low and becomes hypersaline, and the reduced hydrostatic pressure lowers the level of boiling in the plumbing system of the hot springs. Any carbonate precipitation then occurs below the land surface. During humid phases, the dilute meteoric recharge increases, enhancing geothermal circulation, but the rising lake waters, which become relatively dilute, flood most spring vents. Much of the aqueous Ca2+ then precipitates as lacustrine stromatolites on shallow firm substrates, including submerged older travertines. Optimal conditions for subaerial travertine precipitation at Loburu occur when the lake is at intermediate levels, and may be favoured during transitions from humid to drier conditions.  相似文献   

6.
《Geodinamica Acta》2013,26(2):95-105
Abstract

The neotectonic characteristics of the travertines that outcrop near Cambazli Village to the west of the Gediz Graben in the Western Anatolia and the age determination of the travertine were carried out using the 230Th/234,238U disequilibrium method. The Cambazli fissure ridge travertines represent the travertine depositions that develop at a transfer zone. The extent of these travertines is at NW-SE and NE-SW orientations and the ridge crest-trend of these travertines range between approximately 55° and 82° and they are located at an intersecting position. The evaluation of the fissure ridge travertine directions indicated that the compression stress that was responsible for the deposition of the Cambazli travertine was determined to be in the N-S orientation and the extensional stress was determined to be in the E-W orientation. The orientation of the dominant extension in Western Anatolia during the neotectonic period was N-S and this orientation is not in accordance with the directions of stress for the travertines. This situation indicates that the travertines were deposited along a transfer zone in N10W orientation between two normal faults. The travertines were determined to be active since the Upper Pleistocene as indicated by the age determination conducted using the 230Th/234,238U disequilibrium method. The dilation rate of the travertines during dilation and the post-dilation period and the average dilation rate of the Cambazli travertines to the north of the Gediz Graben were calculated as 0.01–0.02 mm yr?1 during deposition and as 0.05 mm yr?1 during the post-dilation period. These dilation rates indicate lower tectonic activity along the northern ridge of the Gediz Graben than along the southern ridge.

© 2011 Lavoisier SAS. All rights reserved  相似文献   

7.
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8.
《Geodinamica Acta》2013,26(3-4):333-342
Travertine deposits reflect some aspects of the regional tectonics because of the close association between travertine deposits and active fractures, that later of which provide conduits along which travertine-depositing waters may rise. Fissure-ridge travertines form above extensional fissures which are located in the hanging walls of normal faults, in step-over zones between fault segments, or in active or recently active) volcanic provinces. Numerous active and inactive fissure-ridge travertines are located in the hanging walls of normal faults in the Denizli Basin. A typical fissure-ridge comprises a central fissure along its long axis and flanking bedded travertines dipping away from the fissure. Central fissures of travertine ridges have been dilating since the initiation of the fissures. Samples from both the margins and centres of banded travertine deposits were dated by Th/U methods in order to determine dilation rates. Individual fissures have been dilating at average rates of between 0.008 and 0.1 mm yr–1 during travertine deposition, and ~ 0.001 and 0.007 mm yr–1 after cessation of travertine deposition. There is a noticable decrease in dilation rate from west to east in the Denizli Basin, and this decrease in dilation rate may be related to decrease in overall extension in southwest Turkey, which decreases eastward.  相似文献   

9.
层状钙华及其地球化学指标的古气候/环境意义   总被引：8，自引：0，他引：8       下载免费PDF全文
层状钙华作为高分辨率古气候环境重建记录已被国内外许多学者所关注.钙华的微层厚度、氧碳同位素组成和微量元素的含量都呈现出随季节变化的周期性特点.钙华年层的形成与方解石沉积速率或者微生物生长活性的季节变化有关;氧同位素组成的变化主要受温度和沉积水体的δ18O控制,但蒸发作用(尤其是在干旱区)也有重要影响;钙华的稳定碳同位素...  相似文献   

10.
Travertine deposits in western Turkey are very well‐exposed in the area of Kocaba?, in the eastern part of the Denizli Basin. The palaeoclimatic significance of these travertines is discussed using U/Th dates, stable isotope data and palynological evidence. The Kocaba? travertine occurrences are characterized by successions of depositional terraces associated with palaeosols and karstic features. The travertines have been classified into eight lithotypes and one erosional horizon, namely: laminated, coated bubble, reed, paper‐thin raft, intraclasts, micritic travertine with gastropods, extra‐formational pebbles and a palaeosol layer. The analysed travertines mostly formed between 181 ka and 80 ka (Middle to Late Pleistocene) during a series of climatic changes including glacial and interglacial intervals; their δ13C and δ18O values indicate that the depositional waters were mainly of basinal thermal origin, occasionally mixed with surficial meteoric water. Palynological results obtained from the palaeosols showed an abundance of non‐arboreal percentage and xerophytic plants (Oleaceae and Quercus evergreen type) indicating that a drought occurred. Marine Isotope Stage 6 is represented by grassland species but Marine Isotope Stage 5 is represented by Pinaceae–Pinus and Abies, Quercus and Oleaceae. Uranium/thorium analyses of the Kocaba? travertines show that deposition began in Marine Isotope Stage 6 (glacial) and continued to Marine Isotope Stage 4 (glacial), but mostly occurred in Marine Isotope Stage 5 (interglacial). The travertine deposition continued to ca 80 ka in the south‐west of the study area, in one particular depression depositional system. Palaeoenvironmental indicators suggest that the travertine depositional evolution was probably controlled by fault‐related movements that influenced groundwater flow. Good correlation of the stable isotope values and dates of deposition of the travertines and palynological data of palaeosols in the Kocaba? travertines serve as a starting point for further palaeoclimate studies in south‐west Turkey. Additionally, the study can be compared with other regional palaeoclimate archives.  相似文献   

11.
《Applied Geochemistry》2006,21(5):820-825
An analytical approach, based on the electron paramagnetic resonance (EPR) spectroscopy of Mn(II) in travertines, has been developed in order to obtain relevant information about the local inhomogeneity of calcite and about the thermodynamic conditions which control the formation of travertine deposits. This information is crucial to constrain the precipitation of travertine under different geochemical contexts. An empirical correlation between the spectral features and the zero-field splitting (ZFS) interaction has been established through numerical simulations of EPR spectra. The variability of the investigated parameters and the applicability of the method have been tested on several travertines from Central Italy.  相似文献   

12.
Quaternary travertine capping the metamorphic (cement) zones in Uleimat Quarries, central Jordan, has been precipitated from hyperalkaline paleogroundwaters. Such waters are similar to the cement pore water and to the present day hyperalkaline seepages (pH 12.5) in Maqarin, north Jordan. The isotopic depletions observed in Uleimat travertine, with δ13C values as low as −25.45‰, suggest that they have been precipitated during CO2 uptake by highly alkaline calcium hydroxide waters. The travertine in Uleimat Quarries indicates a long-term analog of carbonation and remobilization of silica in cementitious barriers for radioactive waste repositories. The presence of Cr-rich smectites and relatively high levels of Cr (4.1%), V (657 ppm), Ni (163 ppm), Zn (634 ppm) and U (34 ppm) in the green travertine and the associated opaline silica phases suggests the use of the Uleimat travertines as analogs with the repository disturbed zone. Smectites and silica phases are expected to be a sink for alteration products in the late stage evolution of a high pH plume. Co-precipitation of these elements in mineral phases is of great importance to control the concentration of these elements in groundwater.  相似文献   

13.
A continuous high-resolution (monthly) record of stable isotopes (δ13C and δ18O) in a well-laminated freshwater travertine deposited at Baishuitai, SW China from May 1998 to November 2001 was presented. The travertine exhibits clear annual bands with coupled brown/white color laminations. Throughout field investigation, it was found that the thin (1.5–2.2 mm), brown porous lamina was formed in the monsoonal rainy season from April to September, whereas the thick (5–8 mm), dense white lamina was formed in the dry season from October to March. The comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physicochemical proxies in the travertine record. Sympathetic variations in lamina thickness, δ13C and δ18O along the sampled profile reflect changes in hydrogeochemistry, showing that thin lamina and low δ13C and δ18O values occur in warm and rainy seasons. The decreased amount of calcite precipitation and low δ13C values during the warm and rainy seasons is caused by dilution of overland flow after rainfall. The low δ18O values are believed to be related to the rainfall amount effect in subtropical monsoonal regions. This process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold. Accordingly, distinct minima in lamina thickness, δ13C and δ18O are interpreted to reflect events with above-average rainfall, possibly heavy floods, and vice versa. This study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations.  相似文献   

14.
Secondary carbonate formations, such as travertine and calcareous tufa deposits, are important archives for quaternary continental climate studies and archaeology. The extremely complex growth mechanisms result in some serious problems for precise mass spectrometric uranium-series dating. Often, detrital and organic particles contaminate the carbonate and large pore volumes yield a great potential for open system behavior. We utilized microscopic, mineralogical and geochemical methods prior to sample selection to determine the abundance of primary calcite, i.e. micrite and spar. Furthermore, the state of alteration was characterized by cathodoluminescence and trace-element analysis. We conclude that travertine and calcareous tufa are appropriate for precise U-series age determination if a) micrite and/or spar are the dominant phases; b) cathodoluminescence of both phases is weak or absent; c) Fe and Al levels are low; and d) Sr concentrations are close to the average of the studied site. We mapped and sampled solely areas of major micrite/spar abundance having minor alteration for accurate U-series dating. When this new method was applied, travertines located in eastern Germany (sites Bad Langensalza, Burgtonna and Weimar-Ehringsdorf) gave single 230Th/238U-ages consistent with the lithological growth sequence and greatly improved compared to previously published chronologies. In addition, we determined 230Th/U isochron ages on bulk samples that confirm our single ages. In contrast to primary calcite, pore cements are homogeneously distributed throughout the travertine fabric and reflect early diagenetic processes and/or weathering.  相似文献   

15.
Hydrochemical studies of the Plitvice Lakes and their tributaries (Croatia/Yugoslavia) were coupled with micromorphological investigations on carbonate lake sediments and recent travertines. Karst springs discharge water from aquifers in Triassic and Jurassic dolomites and limestones and collect in lakes, which are ponded behind accreting travertine dams. Waters at springs have a high CO2 partial-pressure (greater than 7000 ppm) and are slightly undersaturated with respect to calcite (saturation index less than —0·03). CO2 partial pressure is quickly reduced in swift running streams, leading to very high supersaturation with carbonate minerals (saturation indices between 0·74 and 0·53). Calcite deposition, however, is restricted to the lake bottoms (formation of lake marl) and to the tufa dams. The annual carbonate precipitating capacity of the system based on water balance and downstream loss of dissolved ions is estimated to be on the order of 10 000 t CaCO3 as cascade deposits (tufa dams) or as micrite in lakes behind the travertine dams. The initial stages of travertine formation as a result of morphological, biological, and chemical factors are (i) moss settling on small ridges in the creek courses, (ii) epiphytes (diatoms and cyanobacteria) settling on the moss surface, (iii) micrite particles resuspending from lake bottoms and being trapped on mucous excretions from bacteria and diatoms, and (iv) inorganic calcite precipitating as sparite at nucleation sites provided by these crystal seeds. Geochemical studies of the lake marl and tufa dams show that amino acids are dominated by aspartic acid. Carbohydrates come from structural polysaccharides of diatoms. The sticky excretions, rich in aspartic acid, are necessary for the initiation of calcite precipitation. They may be a response of algal and bacterial metabolism to environmental stress by either nutrient depletion or high calcium concentrations in ambient waters. The formation of tufa and micrite (lake marl) appears to be initiated by localized biological factors and is not governed by mere calcite supersaturation of the water. Oligotrophy may be an essential precondition for the formation of fresh water carbonate deposits.  相似文献   

16.
In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre displacement, located in the eastern margin of the Neogene–Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C) flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene (24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest. Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding a helpful example for studying the relationship between faulting and travertine deposition.  相似文献   

17.
The quaternary travertine deposits of Europe and Asia Minor   总被引：7，自引：0，他引：7  
A summary is provided of the published information relating to all aspects of Quaternary travertine formation in Europe west of the Ural Mountains. The deposits have been divided into two broad groups, the meteogene travertines, which result primarily from the degassing of soil-borne aqueous CO2, and thermogene deposits resulting from the degassing of thermally generated CO2. Meteogene deposits are rare above latitude 58°N, and in regions where the mean annual air temperature is below 5°C. A significant positive correlation exists between mean air temperature and travertine deposit thickness. The combined effects of temperature and rainfall are used to provide a zoned map showing the travertine-forming potential of limestones within the region. Information from 14C dating indicates that deposition reached a maximum in the period 5–10 ka BP) and is currently limited by land and water management practices in the populated areas. Thermogene deposits occur in regions of high CO2 discharge resulting from tectonic activity, such as Italy and Turkey where there is much vulcanism. These travertines are frequently more massive and less readily weathered than meteogene deposits. Fully referenced information is provided for 320 important, mostly well studied sites (227 meteogene, 93 thermogene), of which 156 are currently active.  相似文献   

18.
The Jifei hot spring emerges in the form of a spring group in the Tibet–Yunnan geothermal zone, southwest of Yunnan Province, China. The temperatures of spring waters range from 35 to 81°C and are mainly of HCO3–Na·Ca type. The total discharge of the hot spring is about 10 L/s. The spring is characterized by its huge travertine terrace with an area of about 4,000 m2 and as many as 18 travertine cones of different sizes. The tallest travertine cone is as high as 7.1 m. The travertine formation and evolution can be divided into three periods: travertine terrace deposition period, travertine cone formation period and death period. The hydrochemical characteristics of the Jifei hot spring was analyzed and compared with a local non-travertine hot spring and six other famous travertine springs. The results indicate that the necessary hydrochemical conditions of travertine and travertine cones deposition in the Jifei area are (1) high concentration of HCO3 − and CO2; (2) about 52.9% deep source CO2 with significantly high value; (3) very high milliequivalent percentage of HCO3 − (97.4%) with not very high milliequivalent percentage of Ca2+ (24.4%); and (4) a large saturation index of calcite and aragonite of the hot water.  相似文献   

19.
弄清钙华生物沉积作用有助于更好地理解钙华微岩相结构和地球化学特征的气候环境指示意义。总结和综述了与钙华沉积相关的生物群落、生物成因钙华微岩相结构、钙华生物沉积作用过程及其对钙华地球化学特征影响的研究进展,并展望了未来的研究重点。细菌、藻类和苔藓等广泛参与到钙华沉积中,形成了许多不同类型的孔隙结构、晶体结构和纹层结构。生物沉积过程主要包括:①生物生长扰动水流使得CO2逸出;②代谢作用(如光合作用)过程诱导碳酸钙沉积;③"表面控制"过程影响晶体成核及生长。生物沉积作用驱动了元素的迁移转化,对沉积水体和钙华地球化学特征具有重要影响。钙华在地球生物学研究中具有重要潜力,未来需要加强现代钙华沉积中的物理化学和生物过程相互作用机制及其各自贡献的量化研究,以便准确地解译钙华沉积记录。  相似文献   

20.
Seasonal and spatial variations in the δ13C and δ18O values of the modern endogenic (thermogene) travertine deposited in a calcite-depositing canal at Baishuitai, Yunnan, SW China were examined to understand their potential for paleoclimatic and paleoenvironmental implications. The sampling sites were set in the upstream, middle reach and downstream of the canal, and the modern endogenic travertine samples were collected semimonthly to measure their δ13C and δ18O values. It was found that both δ13C and δ18O values of the endogenic travertine were low in the warm rainy season and high in the cold dry season, and correlated with each other. The low δ18O values in warm rainy season were mainly related to the higher water temperature and the lower δ18O values of rainwater, and the low δ13C values are caused by the dilution effect of overland flow with low δ13C values in the warm rainy season and the reduced CO2-degassing of canal-water caused by the dilution effect of the overland flow. The linear negative correlation between the travertine δ18O (or δ13C) values and rainfall amount may be used for paleo-rainfall reconstruction if one knows the δ18O (or δ13C) values of the fossil endogenic travertine at Baishuitai though the reconstruction was not straightforward. It was also found that there was a progressive downstream increase of the δ18O and δ13C values of the travertine along the canal, the former being mainly due to the preferential evaporation of H216O to the atmosphere and the latter to the preferential release of 12CO2 to the atmosphere during CO2-degassing. However, the downstream increase of the travertine δ18O and δ13C values was less intensive in rainy season because of the reduced evaporation and CO2-degassing during the rainy season. To conclude, the downstream travertine sites could be more favorable for the paleo-rainfall reconstruction while the upstream travertine sites are more favorable for the paleo-temperature reconstruction. So, this study demonstrates that endogenic travertine, like epigenic (meteogene) tufa, could also be a good candidate for high-resolution paleoclimatic and paleoenvironmental reconstruction.  相似文献   

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