stable oxygen and carbon isotopes in late glacial holocene freshwater carbonates from belarus and their palaeoclimatic implications abstract four sets of 18 o and 13 c curves were derived from late glacial to mid holocene spring and lacustrine carbonates from belarus stratigraphic division was carried out by palynological studies and 14 c dating it was revealed that variations of isotopic compositions and the dynamics of terrestrial vegetation were affected to some extent by common climatic forcing birch expanded during relatively warm and or arid phases higher 18 o and or 13 c fir spread during relatively cold and or humid phases lower 18 o and or 13 c and grasses were abundant during relatively cold lower 18 o or arid phases higher 13 c a comparison of four pairs of 18 o and 13 c curves allowed the recognition of several palaeoclimatic events at a regional scale two main cold events interrupted by a warmer interval occurred in the younger dryas a short term episode of active permafrost decay at the end of the younger dryas and in the very beginning of the preboreal caused an abrupt rise of lake levels followed by their rapid fall a shift toward a lower precipitation evaporation balance and lower lake levels took place roughly in the middle of the boreal a trend of decreasing temperatures throughout most of the boreal culminated in a short lived very cold phase at 8100 14 c year bp or 9050 cal 14 c year bp according to the proposed age model in the atlantic 1 warmer phases were coincident with the phases of the lower precipitation evaporation balance an episode of significant short term warming occurred in the last third of the atlantic 1 correlation of the 18 o curve derived from authigenic calcites precipitated between the beginning of the preboreal 2 and the end of atlantic 1 in the ptich river valley with that from the gisp2 greenland ice core allowed good matching of the trends and spikes i e of the air temperature changes under assumption that the ages of the ptich pollen based time model are 600 1000 years too old

environmental factors controlling the δ13c and δ18o variations of recent fluvial tufas a 12 year record from the monasterio de piedra natural park ne iberian peninsula abstract a 12 year study 2000 2012 of the stable isotopes of recent fluvial tufas has been performed in the monasterio de piedra natural park river piedra ne iberian peninsula an area of mediterranean climate with intense tufa deposition since the pleistocene the biannual monitoring of the tufa calcite 13c and 18o signatures and of the water 18o value has demonstrated a clear seasonal pattern for the tufa calcite oxygen isotope composition with less negative values for cool periods which is consistent with regional temperature oscillations the tufa calcite 13c values only occasionally exhibit a pattern which is inconclusive and opposite to the 18o clear pattern the water 18o signature has a distinct seasonal pattern also opposite to the tufa calcite 18o clear pattern the temperature calculations from the tufa calcite 18o values and average water 18o values agree with the seasonal pattern of measured water temperatures with a mean difference of 2 3 c between the calculated and measured temperatures the anomalous values recorded for both the water and the tufa calcite oxygen isotope composition during a two year period are characterized by smoothing of the seasonal variations of the tufa calcite and by reversal of the water pattern there is also an increase in the differences between the measured and estimated temperatures the detected anomaly is roughly synchronous with a change in the isotopic signature of the regional precipitation 18o values this contribution demonstrates that tufas in this depositional and climatic context are good indicators of seasonal temperature oscillations and that tufas can also record other interannual environmental changes such as variations in the isotopic composition of precipitation these results can be extrapolated to ancient tufa systems developed in similar contexts which would expand the potential of tufas as high resolution records of paleoenvironmental conditions

a phase resolving cross shore sediment transport model for beach profile evolution abstract a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the mean undertow and the intra wave sediment concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone even for eroding beaches suggesting that other contributions should not be neglected the present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded

stable isotope geochemical study of pamukkale travertines new evidences of low temperature non equilibrium calcite water fractionation abstract in this paper we present the first detailed geochemical study of the world famous actively forming pamukkale and karahayit travertines denizli basin sw turkey and associated thermal waters sampling was performed along downstream sections through different depositional environments vent artificial channel and lake terrace pools and cascades of proximal slope marshy environment of distal slope 13 c travertine values show significant increase from 6 1 to 11 7 pdb with increasing distance from the spring orifice whereas the 18 o travertine values show only slight increase downstream from 10 7 to 9 1 pdb mainly the co 2 outgassing caused the positive downstream shift 6 in the 13 c travertine values the high 13 c values of pamukkale travertines located closest to the spring orifice not affected by secondary processes suggest the contribution of co 2 liberated by thermometamorphic decarbonation besides magmatic sources based on the gradual downstream increase of the concentration of the conservative na k cl evaporation was estimated to be 2 5 which coincides with the moderate effect of evaporation on the water isotope composition stable isotopic compositions of the pamukkale thermal water springs show of meteoric origin and indicate a local meteoric water line of denizli basin to be between the global meteoric water line craig 1961 and western anatolian meteoric water line imsek 2003 detailed evaluation of several major and trace element contents measured in the water and in the precipitated travertine along the pamukkale mm section revealed which elements are precipitated in the carbonate or concentrated in the detrital minerals former studies on the hungarian egerszalok travertine kele et al 2008a b 2009 had shown that the isotopic equilibrium is rarely maintained under natural conditions during calcite precipitation in the temperature range between 41 and 67 c in this paper besides the detailed geochemical analyses along downstream sections we present new evidences of non equilibrium calcite water fractionation in lower temperature range 13 3 to 51 3 c our measurements and calculations on natural hot water travertine precipitations at pamukkale and egerszalok revealed that the 18 o travertine is equal with the 18 o hco3 at the orifice of the thermal springs which means that practically there is no oxygen isotope fractionation between these two phases high rate of co 2 degassing with rapid precipitation of carbonate could be responsible for this as it was theoretically supposed by o neil et al 1969 thus for the determination of the deposition temperature of a fossil travertine deposit we propose to use the water bicarbonate oxygen isotope equilibrium fractionation instead of the water travertine fractionation which can result 8 9 c difference in the calculated values our study is the first detailed empirical proof of o neil s hypothesis on a natural carbonate depositing system the presented observations can be used to identify more precisely the deposition temperature of fossil travertines during paleoclimate studies

intra annual perturbations of stable isotopes in tufas effects of hydrological processes abstract tufas which are freshwater carbonates are potential archives of terrestrial paleoclimate time series of stable isotopic compositions commonly show regular seasonal patterns controlled by temperature dependent processes and some perturbation intrinsic to the locality we examined three tufa depositing sites in southwestern japan with similar temperate climates to understand the origin of local characteristics in the isotopic records seasonal change in the oxygen isotope is principally reflected by temperature dependent fractionation between water and calcite but was perturbed after heavy rainfalls overwhelming the stability of the 18o value of the groundwater at one site isotopic mass balance indicates an undersaturated and relatively small aquifer at this locality water 18o values at the other two sites were stable reflecting a regular seasonal change in the 18o value of tufa perturbation of the 13c values in tufa is largely due to co2 degassing from the stream which significantly increases the 13c values of dissolved inorganic carbon dic at a site with remarkably high pco2 in springwater and a sensitive response of flow rate to rainfall the amount of co2 degassing changed distinctly with flow rate in contrast the other two sites having low pco2 springwater reflect a regular seasonal pattern of 13c in dic and tufa specimens

intrinsic and extrinsic controls of spatial and temporal variations in modern fluvial tufa sedimentation a thirteen year record from a semi arid environment sedimentological and hydrochemical parameters of the river piedra north east spain were monitored every six months from 1999 to 2012 at 24 sites at which tablets were installed all along the river the river water is of hco3 so4 ca type and is notably influenced by inputs from upstream karstic springs tufa deposition was first detected 8 km downstream of these springs and greatly increased from there primarily along the steeper stretch i e within the monasterio de piedra natural park then deposition decreased through the most downstream stretch with smaller ground water inputs the spatial evolution of the tufa thickness with parallel variations of pwp plummer wigley parkhurst rates was thus determined by the river water pco2 which was controlled by ground water inputs and by the river bed slope five fluvial subenvironments and seven sedimentary facies were characterized the water flow conditions are the primary factor responsible for the distinct deposition rates of facies mainly through co2 outgassing stromatolites and moss tufa and alga tufa had the highest rates whereas loose tufa formed in slow flowing water and tufa of spray areas had thinner deposition a six month pattern in the deposition rate was detected through thickness measurements that pattern was parallel to the seasonal pwp rates the increased deposition during warm periods spring and summer mean 5 08 mm compared with cool periods autumn and winter mean 2 77 mm is linked chiefly to temperature which controlled the seasonal changes in the physico chemical and biological processes this finding is supported by a principal components analysis seasonal variations of insolation and day duration also contributed to such a deposition pattern large discharge events which provoked erosion of tufa deposits and dilution of water caused the reversal of the seasonal deposition rate pattern stromatolites are likely to preserve the most complete sedimentary record although tufas are a potentially sensitive record of climate related parameters erosion is an intrinsic process that may overwhelm the effects of such parameters this issue should be considered in palaeoclimatic studies based on the tufa record particularly in semi arid conditions

spatial temporal variations of travertine deposition rates and their controlling factors in huanglong ravine china a world s heritage site abstract huanglong well known for its unique natural travertine landscape was listed by unesco as an entry in the world s nature heritage in 1992 and attracts more than one million of tourists from all over the world each year however the landscape has undergone significant degradation notably serious decay of travertine during the past two decades as the tourist numbers have increased remarkably to understand the variations of travertine deposition rates and their controlling factors especially the impact of tourism activities paired water and modern travertine samples deposited on plexiglass substrates were taken along the huanglong stream at regular intervals from early may to early november in 2010 i e in the wet season the travertine deposition rates have declined significantly compared to those in early 90s in all four subsystems in the huanglong ravine the largest decrease 89 5 occurred at the lowest sampling site the reduction in travertine deposition most likely resulted from the phosphate pollution caused by the tourism activities in spite of an increase in concentrations of ca calcite saturation and water temperature which facilitate calcite precipitation deposition rates decreased because of inhibition by po 4 3 ions seasonally three control patterns of travertine deposition rates were distinguished along the ravine they are control by water temperature control by dilution of rainwater and snow melting water and control by po 4 inhibition of calcite precipitation

travertine formation in plitvice national park yugoslavia chemical versus biological control 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

micro erosion meter measurements of travertine deposition rates a case study from louie creek northwest queensland australia although originally designed to measure surface denudation the micro erosion meter mem can be adapted easily to measure deposition rates of chemical sediments such as travertines and speleothems at louie creek northwest queensland australia travertine deposition rates measured using the mem average 4 15 mm a 1 however this figure masks considerable rate variability both purely hydraulic and hydraulically related variables appear to be the major mechanisms controlling deposition rates the most rapid rates occur within relatively high energy hydraulic regimes impact and flow zones whilst deposition rates in pools separating individual travertine barrages standing water zones are relatively slow dsposition rate variations within spray and impact zones are related directly to discharge the highest rates in flow zones correlate with the incorporation into the travertine of in situ and allochthonous biogenic material such as caddis fly larvae green algal mats and phytoclasts which proliferate or are entrapped easily under such hydraulic conditions considerable spatial variability in deposition rates also prevails the highest rates for a given set of hydraulic conditions occur at two sites the upper everglades and the lower everglades the mem also measures net erosion of travertines at louie creek most of the travertine erosion occurs in the wet season and is confined primarily to standing water zones 1997 john wiley sons ltd

cyanobacterial tufa calcification in two freshwater streams ambient environment chemical thresholds and biological processes abstract calcareous freshwater streams near bad urach southwest germany were studied to determine the environmental limits to cyanobacterial calcification daily variations in temperature ph calcium concentration and alkalinity were measured at seasonal intervals from september 1993 to january 1995 in two small woodland streams with lengths of 1 0 and 1 5 km the principal cause of supersaturation in these fast flowing streams is inorganic carbon dioxide outgassing from resurging groundwater locally enhanced by turbulence at waterfalls and cascades photosynthetic uptake of carbon dioxide and temperature effects are negligible nonetheless organic substrates particularly cyanobacteria dominated microbial mats and biofilm significantly localize precipitation by providing suitable nucleation sites precipitation rates on artificial substrates up to 2 2 mm yr on limestone correlate with high saturation index values copper substrates inhibited microbial colonization and received negligible encrustation tufa formation and external calcium carbonate encrustation of cyanobacteria are conspicuous where the annual wateq4f saturation index exceeds 0 8 and are slightly below 0 7 calcium carbonate impregnation of cyanobacterial sheaths has not been observed we infer that in these fast flowing streams cyanobacteria utilize co2 in photosynthesis whereas elsewhere in sluggish freshwater cyanobacteria utilize hco3 leading to sheath impregnation by calcium carbonate even where saturation index is only 0 2 0 3 thus photosynthetic influence on cyanobacterial calcification appears to be negligible in fast flowing co2 rich streams and cyanobacterial calcification takes the form of external encrustation in slow flowing co2 poor streams and lakes cyanobacteria preferentially utilize bicarbonate and sheath impregnation can result modern tropical marine carbonate shelves have saturation indices commonly in the range 0 62 0 82 and cyanobacterial calcification is negligible extrapolation suggests that cyanobacterial calcification could occur in present day seas if saturation index exceeded 0 8 this level corresponding with heavy calcification in the freshwater streams studied may have been widespread in marine environments in the geological past at times when calcified cyanobacteria and environmentally influenced non skeletal calcium carbonate precipitates were abundant

physical mechanisms of river waterfall tufa travertine formation waterfall tufa is widely distributed around the world especially in tropical and subtropical karst areas in these areas river water is generally supersaturated with respect to calcite and the precipitation occurs mainly at waterfall and cascade sites development of waterfall tufa has been described as simply being the result of water turbulence we believe however that three physical effects can lead to tufa deposition at waterfall sites aeration jet flow and low pressure effects the three physical effects are induced by two basic changes in the water an accelerated flow velocity and enlargement of the air water interface area these two changes increase the rate of co2 outgassing and the sic so that a high degree of supersaturation is achieved which then induces calcite precipitation these waterfall effects have been simulated in laboratory and field experiments and each of them can accelerate or trigger calcite precipitation field measurements of river water chemistry also show that tufa deposition occurred only at waterfall sites in these experiments and observations waterfall effects play the most important role in triggering and accelerating co2 outgassing rates field and laboratory observations indicate that plants and evaporation also play important roles in tufa formation growth of algae and mosses on tufa surfaces can provide substrates for calcite nucleation and can trap detrital calcite accelerating tufa deposition however the prerequisite for such deposition at waterfall sites is a high degree of supersaturation in river water which is mainly caused by waterfall effects evaporation can lead to supersaturation in sprays and thin water films at a waterfall site and cause the precipitation of dissolved caco3 but the amount of such deposition is relatively small

geochemical and statistical evidence of recharge mixing and controls on spring discharge in an eogenetic karst aquifer summary information about sources of recharge distributions of flow paths and the extent of water rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge to investigate the relationship between spring characteristics and the complexities of karst aquifers we couple variations in surface and groundwater chemistry to physical conditions including river stage precipitation and evapotranspiration et within a sink rise system through a 6 km portion of the upper floridan aquifer ufa in north central florida principal component analysis pca of time series major element compositions suggests that at least three sources of water affect spring discharge including allogenic recharge into a swallet diffuse recharge through a thin vadose zone and water upwelling from deep within the aquifer the deep water source exerts the strongest influence on water chemistry by providing a majority of na mg2 k cl and so 4 2 to the system anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m year mass balance calculations suggest diffuse recharge and deep water upwelling can provide up to 50 of the spring discharge however their contributions depend on head gradients between the conduit and surrounding aquifer matrix which are influenced by variations in precipitation et and river stage our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer such as water sources and flow paths these results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits

origin of annual laminations in tufa deposits southwest japan abstract laminated tufas and a tufa depositing stream in sw japan shirokawa ehime prefecture were studied monthly over a 3 yr period a series of samples from the tufa clearly reveals the pattern of annual laminations the annual layering pattern was primarily controlled by changes in the rate of calcite precipitation as calculated from water chemistry the concentration of dissolved caco 3 which correlates with the precipitation rate was high in summer autumn and low in winter spring owing to changes in the partial pressure of co 2 in underground air regular seasonal changes in underground pco 2 probably resulted from two temperature dependent processes the diffusion of soil co 2 and the ventilation of underground air these changes in addition to water temperature changes altered the precipitation rate which has a clear seasonal pattern especially in the lower stream the seasonal precipitation rate was high in summer autumn and low in winter spring which is consistent with the seasonal lamination pattern seen in the tufas the textures of collected samples show that the laminations consist of densely calcified summer autumn june october laminae and lightly calcified winter spring november may laminae we infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures this interpretation is supported by the lowered organic inorganic carbon production ratio in summer autumn seasonal variations in cyanobacterial assemblages are present but do not reflect the seasonal lamination pattern because the relevant processes are temperature dependent the seasonal lamination pattern at shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates however a reversed pattern can result from local and climatic circumstances dense laminae were deposited in winter near the source of the spring at shirokawa because calcite precipitation was high owing to low underground pco 2 in winter reversed patterns reported from northwestern europe were probably influenced by seasonal rainfall which is reflected in hydrological conditions

the chemical evolution of a travertine depositing stream geochemical processes and mass transfer reactions this field study focuses on quantitatively defining the chemical changes occurring in falling spring creek a travertine depositing stream located in alleghany county virginia the processes of co sub 2 outgassing and calcite precipitation or dissolution control the chemical evolution of the stream the observed chemical composition of the water was used with the computerized geochemical model wateqf to calculate aqueous speciation saturation indices and co sub 2 partial pressure values mass balance calculations were performed to obtain mass transfers of co sub 2 and calcite reaction times estimated from stream discharge were used with the mass transfer results to calculate rates of co sub 2 outgassing and calcite precipitation between consecutive sampling points the stream which is fed by a carbonate spring is supersaturated with respect to co sub 2 along the entire 5 2 km flow path outgassing of co sub 2 drives the solution to high degrees of supersaturation with respect to calcite metabolic uptake of co sub 2 by photosynthetic plants is insignificant because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic co sub 2 outgassing to occur calcite precipitation is kinetically inhibited until near the crest of amore 20 m vertical waterfall calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of co sub 2 physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1 0 km below the falls net calcite precipitation occurs at all times of the year but is greatest during low flow conditions in the summer and early fall less

deep source co2 in natural waters and its role in extensive tufa deposition in the huanglong ravines sichuan china abstract the aqueous geochemistry of huanglong ravine sichuan china where tufa is being deposited extensively is discussed using chemical composition data together with the carbon and oxygen stable isotope ratios the water quality of tufa depositing surface streams in this area is basically controlled by the mixing of two source waters fault bounded spring water and snow and or glacier melt water the spring water contains high concentrations of co 2 supplied via faults the resulting high concentration of dissolved co 2 gives rise to much greater dissolution of carbonate rocks than is usual in karst springs and also to the dissolution of silicate rocks upstream spring waters in the ravine are close to equilibrium with respect to calcite concentrations of dissolved inorganic carbon dic and their 13 c values result from the interaction of about 0 02 mol l 1 co 2 aq of 13 c 3 with carbonate rocks of 13 c 3 under closed system conditions about 70 of the co 2 is estimated to be supplied from the upper mantle the data for all the springs fall in the kaolinite stability field in agreement with observed dissolutional aggressiveness towards na and ca feldspar and that the dissolution rates of these minerals are too slow to move the composition of these waters into the feldspar stability field the dic species in the surface streams are in isotopic equilibrium variations in 13 c dic found at different sites are mainly due to differences in the degree of co 2 degassing from the water there is a linear relationship between 18 o values and the altitude at which samples were collected the oxygen isotope composition of surface stream water in this area is controlled by evaporation water chemistry in daytime and nighttime and daily change of ph in the surface water flowing on the tufa deposition indicate that biological activities contribute to the carbonate precipitation although their extent is not great the daily precipitation rate in this area is estimated to be 4300 kg as caco 3 day 1 over a surface area of 0 9 km 2 i e 0 1 cm year 1

wet dry seasonal and spatial variations in the δ13c and δ18o values of the modern endogenic travertine at baishuitai yunnan sw china and their paleoclimatic and paleoenvironmental implications abstract seasonal and spatial variations in the 13 c and 18 o 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 13 c and 18 o values it was found that both 13 c and 18 o 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 18 o values in warm rainy season were mainly related to the higher water temperature and the lower 18 o values of rainwater and the low 13 c values are caused by the dilution effect of overland flow with low 13 c values in the warm rainy season and the reduced co 2 degassing of canal water caused by the dilution effect of the overland flow the linear negative correlation between the travertine 18 o or 13 c values and rainfall amount may be used for paleo rainfall reconstruction if one knows the 18 o or 13 c 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 18 o and 13 c values of the travertine along the canal the former being mainly due to the preferential evaporation of h 2 16 o to the atmosphere and the latter to the preferential release of 12 co 2 to the atmosphere during co 2 degassing however the downstream increase of the travertine 18 o and 13 c values was less intensive in rainy season because of the reduced evaporation and co 2 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

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

periodicity in stromatolitic lamination a potential record of enso nao and sunspot in the miocene lacustrine record of the ebro basin spain abstract the spectral decomposition of time series obtained from ancient rock records can be used to study the similarity between the dynamics of present day and past climate systems a high resolution periodicity analysis of luminance and lamina thickness of lacustrine stromatolites in the ebro basin northeast of iberian peninsula reveals a significant signal of interannual and decadal climatic variability in the miocene this is one out of very few works that presents the use of spectral analysis to estimate the potential of stromatolite lamination as multiple scale recorders of climate parameters the effects of precipitation and evaporation variations on stromatolite lamination have been detected at three orders of cyclicity based on textural and high resolution stable isotope analyses c and o obtained in prior studies these analyses also revealed that the light and dark simple lamina couplets are identified with annual cycles third order isotopic cycles in the present study the spectral analysis results obtained through different paths in five stromatolite specimens reveal significant periods in the power spectrum at around 2 5 3 7 5 7 10 and 22 years these cycles can be correlated with the typical oscillation bands of different climate related agents the 2 5 year period corresponds to the quasi biennial oscillation qbo or to the biennial component of the el nino southern oscillation enso or to the north atlantic oscillation nao the 3 to 5 and 5 to 7 year bands can be linked to enso or nao variability second order isotopic cycles the 8 to 11 year bands fit the 11 year schwabe first order isotopic cycles and 22 to 23 year fit the 22 year hale sunspot cycles thus the stromatolite growth was controlled by enso nao and solar activity cycles the close relationship between these climate related agents makes it difficult to specify the dominant agent controlling the stromatolite growth nevertheless the significant periods obtained from this study within interannual 2 5 3 7 5 7 years decadal 10 22 years and even multidecadal bands 37 42 years support the existence and concurrence of enso and nao precursors during the early and middle miocene

tufa forming biofilms of german karstwater streams microorganisms exopolymers hydrochemistry and calcification to understand mechanisms of tufa biofilm calcification selected karstwater stream stromatolites in germany have been investigated with regard to their hydrochemistry biofilm community exopolymers physicochemical microgradients calcification pattern and lamination in stream waters co2 degassing drives the increase in calcite saturation to maximum values of approximately 10 fold independent from the initial ca2 alkalinity ratio for the cyanobacteria of tufa biofilms a culture independent molecular approach showed that microscopy of resinembedded biofilm thin sections underestimated the actual diversity of cyanobacteria i e the six cyanobacteria morphotypes were opposed to nine different lineages of the 16s rdna phylogeny the same morphotype may even represent two genetically distant cyanobacteria and the closest relatives of tufa biofilm cyanobacteria may be from quite different habitats diatom diversity was even higher in the biofilm at the studied exemplar site than that of the cyanobacteria i e 13 diatom species opposed to 9 cyanobacterial lineages the non phototrophic prokaryotic biofilm community is clearly different from the soil derived community of the stream waters and largely composed of flavobacteria firmicutes proteobacteria and actinobacteria the exopolymeric biofilm matrix can be divided into three structural domains by fluorescence lectin binding analysis seasonal and spatial variability of these structural eps domains is low in the investigated streams as indicated by microsensor data biofilm photosynthesis is the driving mechanism in tufa stromatolite formation however photosynthesis induced biofilm calcification accounts for only 10 20 of the total ca2 loss in the streams and occurs in parallel to inorganic precipitation driven by co2 degassing within the water column and on biofilm free surfaces annual stromatolite laminae reflect seasonal changes in temperature and light supply the stable carbon isotope composition of the laminae is not affected by photosynthesis induced microgradients but from pedley h m rogerson m eds tufas and speleothems unravelling the microbial and physical controls geological society london special publications 336 83 118 doi 10 1144 sp336 6 0305 8719 10 15 00 the geological society of london 2010 mirrors that of the bulk water body only reflecting climate fluctuations tufa stromatolites with their cyanobacterial photosynthesis related calcification fabrics form an analogue to porostromate cyanobacterial stromatolites in fossil settings high in caco3 mineral supersaturation but comparatively low in dissolved inorganic carbon here the sum effect of heterotrophic exopolymerdegradation and secondary ca2 release rather decreases calcite saturation contrary to settings high in dissolved inorganic carbon such as soda lakes geobiological significance of tufa

factors controlling present day tufa dynamics in the monasterio de piedra natural park iberian range spain depositional environmental settings sedimentation rates and hydrochemistry the tufa record and hydrochemical characteristics of the river piedra in the monasterio de piedra natural park ne spain were studied for 6 years the mean discharge of this river was 1 22 m3 s the water was supersaturated with calcium carbonate the hco3 ca2 and tdic concentrations decreased along the 0 5 km long studied stretch whereas the calcite si showed no systematic downstream or seasonal variation over the same stretch several sedimentary subenvironments exist in which four broad types of tufa facies form 1 dense laminated tufa stromatolites 2 dense to porous massive tufa 3 porous coarsely laminated tufa with bryophytes and algae and 4 dense hard laminated deposits in caves the half yearly period thickness and weight of sediment accumulated on 14 tablets installed in several subenvironments showed that the deposition rate was greater in fast flowing river areas and in stepped waterfalls and lower in slow flowing or standing river areas and in spray and splash areas mechanical co2 outgassing is the main factor controlling calcite precipitation on the river bed and in waterfalls but this process does not explain the seasonal changes in depositional rates the deposition rates showed a half yearly period pattern recorded in all fluvial subenvironments persistent over time 5 26 mm 0 86 g cm2 in warm periods 2 26 mm 0 13 g cm2 in cool periods mass balance calculations showed higher calcite mass values in warm 21 58 mg l than in cool 13 68 mg l periods this biannual variation is mainly attributed to the seasonal differences in temperature that caused changes in inorganic calcite precipitation rate and in biomass and the correlative photosynthetic activity tufa sedimentation was therefore controlled by both physicochemical and biological processes the results of this study may help test depositional rates and their environmental controls and thus assess the climatic and hydrological significance of ancient tufas in semi arid conditions in particular in the quaternary

seasonal variation in water chemistry and depositional processes in a tufa bearing stream in sw japan based on 5 years of monthly observations abstract annually laminated freshwater carbonate tufa is a potential source of high resolution terrestrial paleoclimate data in order to understand the processes and characteristics of climate information recorded in tufa the chemical components of carbonate rich water its flow rate and soil pco2 were recorded monthly during a 5 year period december 1997 to december 2002 at shimokuraida niimi city okayama prefecture sw japan water issues from a limestone cave there flows along a 450 m long stream and deposits tufa that commonly exhibits distinct annual laminations among observed properties the co2 partial pressures in the soil and the spring water show the clearest seasonal patterns which are similarly high in summer autumn and low in winter spring the spring water pco2 partly reflects soil pco2 but is controlled by another temperature dependent process natural ventilation between the subsurface and the atmosphere the concentration of dissolved caco3 does not mirror the seasonal pattern of spring water pco2 but is largely influenced by rainfall dilution the development of annual laminations results from seasonal changes in the depositional rate of caco3 which was faster from summer to autumn and slower from winter to spring this seasonal pattern is initially controlled by relatively regular changes in water temperature and flow rate both of which correlated positively with the calcite precipitation rate high calcite precipitation in summer autumn formed a densely calcified texture whereas a precipitation low rate winter spring formed a porous texture changes in the concentrations of minor dissolved components mg2 na k cl no3 so42 and sio2 exhibited no seasonal pattern because the amplitude of the mg ca change is very high at shimokuraida the mg ca ratio of tufa calcite does not reflect paleotemperatures while mg ca ratio of water does not correspond to rainfall intensity too

oxygen isotope composition of annually banded modern and mid holocene travertine and evidence of paleomonsoon floods grand canyon arizona usa abstract holocene and modern travertine formed in spring fed havasu creek of the grand canyon arizona was studied to determine the factors governing its oxygen isotope composition analysis of substrate grown travertine indicates that calculated calcite formation temperatures compare favorably with measured water temperatures and include silt rich laminae deposited by monsoon driven floods ancient spring pool travertine is dated by u series at 7380 110 yr and consists of 14 travertine silt couplets of probable annual deposition one hundred eighty high resolution 18o analyses of this mid holocene sample average 11 0 pdb the average value for modern travertine is 0 5 lower perhaps because mid holocene temperature was higher or there was proportionally greater summer recharge 18o cyclicity in the mid holocene travertine has average amplitude of 1 9 0 5 pdb slightly less than the inferred modern day annual temperature range of havasu creek the annual temperature range might have been reduced during the 14 yr interval compared to present although other non temperature factors could account for the muted annual variation silt rich laminae within isotopically lower calcite in the modern and mid holocene travertine verifies the seasonal resolution of both samples and suggests that similar temperature precipitation conditions as well as monsoon generated summer floods prevailed in the mid holocene as they do throughout the grand canyon region today

geochemical and hydrological controls on biannual lamination of tufa deposits abstract fluvial tufa deposits in southwest japan commonly develop biannual lamination consisting of dense summer layers and porous winter layers and the clearness of the laminae varies among the sites the laminae have been largely attributed to a seasonally variable inorganic precipitation rate of calcite this rate controlled hypothesis was examined by using quantitative data for calcite packing density cpd and the precipitation rate of calcite pwp rate calculated from water chemistry the results for four tufa depositing sites in sw japan show that a positive correlation between cpd and pwp rate becomes less certain with increasing pwp rate in the temperature realm of sw japan tufas develop regular distinct seasonal change in cpd when deposited in water containing ca values less than 65 mg l which results in a relatively low precipitation rate the cpd of tufa deposits rarely exceeds 65 owing to pore space between fine grained calcite crystals and to porosity derived from decomposed cyanobacteria and other microorganisms by increasing the ca content to more than 65 mg l the cpd often attains an upper limit and becomes insensitive to seasonal changes in the pwp rate therefore seasonal variations in cpd at sites with a higher ca content are unclear as seen in two examples from tropical islands in southern japan and in one locality in a temperate climate the flow rate and microbial density on the tufa surface are subordinate factors with respect to the cpd seasonal changes in these two factors often enhance the porous dense contrast of biannual lamination in sw japan

current tufa sedimentation in a changing slope valley the river anamaza iberian range ne spain abstract a three year study of modern carbonate sedimentation was conducted through analysis of sedimentological and hydrochemical parameters measured every six months at 10 sites along a high slope river in northeastern spain river anamaza three stretches of the river were characterised the dominant water inputs from the upstream karstic springs primarily from the jurassic rock aquifer determined the so4 hco3 ca composition of the river water from this area decreasing trends in alkalinity calcium and total dissolved inorganic carbon occurred downstream in both the warm and cool periods as a result of calcite precipitation tufa thickness variations were consistent with such hydrochemical evolution deposition rates increased downstream primarily where the gradient is steeper middle stretch and subsequently decreased at the downstream gently sloped stretch therefore the slope along the river and the distance from the main upstream springs conditioned the spatial distribution of tufa deposits by determining the chemical characteristics of the water the monitored sites represent four primary fluvial subenvironments with distinct sedimentary facies the highest carbonate deposition rates were measured in fast flow conditions stromatolites facies a deposits with calcite coated algae and mosses facies c formed in cascades and small jumps with very fast flowing water exhibited lower deposition rates and typical erosion lower rates corresponded to slow flow conditions in which thin stromatolite crusts and or filamentous and calcareous algae and tufa fragments facies b accumulated in slow flowing water areas near springs upstream stretch calcite was absent linked to the higher pco2 of water microbial films and aquatic flora composed the biofacies facies d in such subenvironment therefore tufa deposition rates in each fluvial subenvironment were controlled by the amount of co2 outgassing linked to local flow conditions the biological substrate type and the chemical attributes of the water along each stretch a six month pattern of deposition rates best marked in the steeper stretch was recorded from thickness measurements spring summer periods 4 30 mm autumn winter periods 1 22 mm parallel variations were recorded using pwp plummer wigley parkhurst and calcite mass balance calculations multivariate statistical analyses hca and pca clearly separated hydrochemical and sedimentological attributes in samples from warm and cool periods exceptions to this pattern were related to changes in the water discharge high discharge events caused the dilution of the chemical composition and erosion of the tufa deposits therefore temperature dependent factors i e physico chemical and biological processes coupled with discharge changes controlled the seasonal variations in deposition rates the stable isotope composition of calcite and river water also reflected the discharge effects however the seasonal variation signature of temperature was preserved in the 18o of sediment

climatic conditions and hydrological change recorded in a high resolution stable isotope profile of a recent laminated tufa on a subtropical island southern japan abstract the stable isotope composition of a tufa collected on subtropical miyako island southern japan records climatic and hydrologic changes over a 15 year period 1989 2003 a total of 450 subsamples taken at increments of 0 2 mm define the high resolution isotopic profile of a 9 cm long sample the oxygen isotope values clearly exhibit cyclical changes that generally correlate with the annual lamination pattern of the tufa the observed stability of water 18o values confirms that the seasonal records of water temperature are reflected in the cyclic change of tufa 18o values the oxygen isotope profile also exhibits a long term decreasing trend that is equivalent to a 2 5 c temperature increase over the 15 year period the range of the long term change in 18o values is at least partly compensated for by a warming trend of 0 95 c seen in metrological data for miyako island however the carbon isotope profile does not vary cyclically and the values are clearly higher than for previously reported tufas from the temperate japanese mainland vegetation on miyako island which is dominated by c4 type sugar cane is largely responsible for the high 13c values of the tufa the high resolution isotopic profile provides data on the annual deposition rate which clearly increased from 1996 to 1998 when the groundwater table was raised by the construction of two underground dams near the tufa locality increased water flow from the spring activated calcite precipitation and increased the depositional rate in the upper part of the core up to 1 cm year this rate is much larger than those recorded for tufas from temperate settings in japan

carbonate deposition in a fluvial tufa system processes and products corvino valley southern italy in a multi scale approach to the study of the organic and mineral components in an active barrage type tufa system of southern italy neo formed deposits in both natural depositional sites and on inorganic substrates placed in the stream for this study were observed and compared through one year of monitoring dams and lobes representing the basic morpho facies of the deposits are composed of two depositional facies vacuolar tufa a mixture of phytoclastic and framestone tufa and stromatolitic tufa phytoherm boundstone tufa three petrographic components comprise both facies micrite and microsparite often forming peloidal to aphanitc laminar and dendrolitic fabrics and sparite which occurs as isolated to coalescent fan shaped crystals forming botryoids or continuous crusts all fabrics occurring in all depositional facies are organized into layers with a more or less well developed cyclicity which has its best expression in stromatolitic lamination the precipitation of all types of calcite with mg 1 0 to 3 2 mole and sr 0 5 to 0 8 mole takes place more or less constantly during all seasons in spite of the low saturation state of the water the saturation index range is 0 75 to 0 89 within the active depositional zone the latter extends for a few hundred microns through the external surface of the deposit the active depositional zone has a particular micro morphology composed of porous micro columns 50 to 150 m in size separated by interstitial channels mineral precipitation occurs upon both external surfaces and within internal cavities of the micro columns while further point sites of precipitation occur suspended within the masses of cyanobacterial tufts sub spherical mineral units nano spheres 10 to 20 nm in diameter are the basic biotic neo precipitate they commonly form by replacing non living degrading organic matter and at point sites along the external surface of living cyanobacterial sheaths nano spheres agglutinate to form first rod shaped aggregates 100 to 200 nm which then evolve into triads of fibres or polyhedral structures successively both triads and polyhedral solids coalesce to form larger calcite crystals mainly tetrahedrons tens of microns in size that represent the fundamental bricks for the construction of the micro columns in the active depositional zone precipitation is attributed to the presence of a widespread biofilm that occurs in the active depositional zone this is composed of a heterogeneous community comprising epilithic and endolithic filamentous cyanobacteria green algae unicellular prokaryotes actinobacteria and fungi with a variable amount of extracellular polymeric substances no precipitation takes place where the biofilm is absent indicating that the biological activities of the biofilm are crucial with its living organisms and non living organic matter basic aggregates of neo precipitates do not form in association with any one particular type of organic matter substrate but appear to be related to the seasonal temperature variation polyhedral micro crystals mainly precipitate in the colder season short triads in the intermediate seasons and long triads in the warmest conditions these three basic crystal aggregates have a petrographic counterpart respectively in the spar microspar and micrite

three dimensional geological modelling and multivariate statistical analysis of water chemistry data to analyse and visualise aquifer structure and groundwater composition in the wairau plain marlborough district new zealand summary concerns regarding groundwater contamination with nitrate and the long term sustainability of groundwater resources have prompted the development of a multi layered three dimensional 3d geological model to characterise the aquifer geometry of the wairau plain marlborough district new zealand the 3d geological model which consists of eight litho stratigraphic units has been subsequently used to synthesise hydrogeological and hydrogeochemical data for different aquifers in an approach that aims to demonstrate how integration of water chemistry data within the physical framework of a 3d geological model can help to better understand and conceptualise groundwater systems in complex geological settings multivariate statistical techniques e g principal component analysis and hierarchical cluster analysis were applied to groundwater chemistry data to identify hydrochemical facies which are characteristic of distinct evolutionary pathways and a common hydrologic history of groundwaters principal component analysis on hydrochemical data demonstrated that natural water rock interactions redox potential and human agricultural impact are the key controls of groundwater quality in the wairau plain hierarchical cluster analysis revealed distinct hydrochemical water quality groups in the wairau plain groundwater system visualisation of the results of the multivariate statistical analyses and distribution of groundwater nitrate concentrations in the context of aquifer lithology highlighted the link between groundwater chemistry and the lithology of host aquifers the methodology followed in this study can be applied in a variety of hydrogeological settings to synthesise geological hydrogeological and hydrochemical data and present them in a format readily understood by a wide range of stakeholders this enables a more efficient communication of the results of scientific studies to the wider community

calcite precipitation rates in the field measurement and prediction for a travertine depositing stream abstract rates of calcite precipitation from a travertine depositing stream were determined from changes in stream composition between consecutive sampling points and were compared with rates predicted from a laboratory derived rate law plummer et al 1978 the agreement in rates was generally within an order of magnitude and routinely within a factor of 3 least agreement between measured and predicted rates was obtained for sections of flowpath where relatively little change in bulk chemical composition occurred which were the sections with the greatest mass transfer calculation error and for the stream segment including a waterfall which was the section with the greatest error in estimated surface area reaction rate obtained from the mass of calcite precipitated onto seed crystals placed in the stream significantly underestimated the mass transfer rate for the travertine depositing stream of warm river cave and falling spring creek virginia the coupling of equilibrium speciation models with mass balance calculations and simple field measurements allowed successful field based quantification of reaction rates

factors controlling tufa deposition in natural waters at waterfall sites abstract study on calcite precipitation has major implications for both the hydrochemical evolutions of river systems and the global carbon cycle the precipitation of calcite generally requires the water to be 5 10 times supersaturated with respect to calcite which is usually achieved by the removal of co2 formation of waterfall tufa has been often simply described as the result of water turbulence in fast flowing water in this paper the formation mechanisms of waterfall tufa are discussed and a series of laboratory experiments are designed to simulate the hydrological conditions at waterfall sites the influences of the air water interface the water flow velocity and the solid water interface on co2 outgassing and calcite precipitation are compared and evaluated quantitatively the results show that the principal cause of waterfall tufa formation is the enhanced inorganic carbon dioxide outgassing resulted from the sudden hydrological changes occurring at waterfall sites rather than organisms evaporation or the solid water interface the air water interface area and the water flow velocity are greatly increased at waterfall sites as a result of the aeration effect low pressure effect and jet flow effect which greatly accelerate co2 outgassing inorganic co2 outgassing drives the waters to become highly supersaturated with respect to calcite and consequently results in much calcite deposition the solid water interface is less important as the air water interface in affecting calcite precipitation at waterfall sites field measurements showed that conductivity ca2 and hco3 concentrations along tianhe creek and hot creek decrease downstream while ph rises field observations also showed that tufa deposition occurred mainly at waterfall sites

freshwater calcite precipitates from in vitro mesocosm flume experiments a case for biomediation of tufas freshwater carbonates tufas develop today from the arctic to the tropics many being localized about springs and upper water courses some quaternary tufas especially in the mediterranean region extend over tens of square kilometres and exceed 30 m in thickness radiometric dating of holocene deposits shows that many have accumulated at an average rate of 1 mm year 1 however local precipitation may be much faster and some holocene deposits may even have outpaced their tropical marine carbonate counterparts recently the study of active sites has attempted to quantify the precipitation mechanisms which lead to tufa deposition however field observation and sampling procedures suffer from the inherent disadvantages of uncontrolled fluctuations in environmental conditions during the study programme these disadvantages compromise any interpretations particularly where controls on spar versus micrite precipitation are concerned many of these problems have been overcome in the current study by the construction and operation of laboratory mesocosm flumes which simulate the natural conditions e g ph flow rate ambient temperature and daylight in which freshwater carbonate tufa is deposited three mesocosms were supplied with natural river water from tufa precipitating streams and two mesocosms were supplied with uv treated sterile river water from the same source one of the untreated flume mesocosms was linked with a calcium reactor which replaced calcium ions removed during the precipitation process in order to maintain tufa growth over extended experimental runs low magnesium calcite precipitates both rhombic sparite grown from long crystallite dendrites and short crystallite dendrite triad precursors and micrite peloids grown from spherulitic precursors were precipitated in intimate association with biofilm extracellular polymeric substances within the four mesocosms supplied with natural river water virtually no tufa like precipitate was obtained from the flumes supplied with uv treated river water a second extended run flume experiment was also carried out for comparison purposes using a calcium hydroxide solution in deionized water collectively these experiments provide convincing evidence confirming that the presence of a microbial biofilm strongly influences the precipitation of carbonates in riverine freshwater settings in particular experimental results show that micropeloidal micrite and short crystallite calcite dendrites are only produced in the presence of microbial extracellular polymeric substances

current tufa sedimentation in a high discharge river a comparison with other synchronous tufa records in the iberian range spain abstract the results from sedimentological isotopic and hydrochemical analyses of current tufa sedimentation conducted in a high discharge river ebron river northeastern spain 1 49 m 3 s through six month monitoring over 3 5 years are discussed in terms of the factors that control local carbonate deposition through space and time and compared with results from other synchronous tufa records in the same climatic domain the findings allow for discerning the influence of the riverbed slope hydrochemistry discharge and groundwater inputs on tufa attributes and assess the significance of tufa as archives of certain climatic events on a regional scale in the ebron river the dominant upstream karstic springs from a jurassic rock aquifer determined the river s hco 3 ca composition two river stretches were differentiated according to localised increments in both pco 2 resulting from additional groundwater inputs and so 4 content influenced by evaporite bearing units the variations in tufa s thickness through space were strongly controlled by co 2 rich springs and local slope variations the monitored sites represent four primary subenvironments with distinct sedimentary facies whose attributes suggest that 1 the tufa deposition rates in each fluvial subenvironment are mainly controlled by the co 2 outgassing intensity linked to local flow conditions and the biological substrate type and 2 stromatolites represent the thickest and most complete record the six month variations in tufa thickness and calculated calcite mass in the ebron river were controlled by temperature dependent physico chemical and biological parameters coupled with high discharge events that provoked tufa erosion the smaller deposition of the ebron river compared to two other synchronous tufa records in the iberian range is linked to 1 the absence of long areas of increased slope 2 the occurrence of significant co 2 rich groundwater springs in the middle reach and 3 the higher discharge and water depth certain high discharge events were recorded as lower deposition rates concurrent in the three rivers moreover anomalous water temperatures calculated from the calcite 18 o in the three rivers for a coincident time span support a regional anomaly in the precipitation 18 o thus the evolution of the short term tufa deposition rates and calcite 18 o composition through time can detect regional climate and hydrology changes and therefore can be robust criteria for correlation in the geological record

a diatom maximum horizon in upper quaternary deposits diatom maxima have been observed in three sediment cores two from the skagerrak norwegian sea area and one from the fram strait the maxima occur between 11 000 b p and 9 000 b p in the skagerrak norwegian sea and between about 9 000 b p and 4 500 b p in the fram strait it is thus likely that high diatom productivity as reflected by the diatom maximum horizons are time transgressive and follow the movements of the oceanic polar front the occurrence of diatom maximum horizons can therefore be used as a signal indicating the presence of the polar front at the time of deposition in both the skagerrak and norwegian sea cores the maximum consist of two distinct peaks the oldest characterized by cold water species thalassiosira antarctica the youngest characterized by temperate species reflecting the present diatom flora

c and o stable isotope variability in recent freshwater carbonates river krka croatia three types of recent carbonate precipitates from the river krka croatia were analysed 1 bulk tufa from four main cascades in a 34 km long section of the river flow through the krka national park 2 a laminar stromatolite like incrustation formed in the tunnel of a hydroelectric power plant close to the lowest cascade and 3 recent precipitates collected on artificial substrates during winter spring and summer periods stable isotope compositions of carbon d 13 c and oxygen d 18 o in the carbonate and organic carbon d 13 corg were determined and compared with d 18 o of water and d 13 c of dissolved inorganic carbon dic the source of dic which provides c for tufa precipitation was determined from the slope of the line dic dic0 1 vs d 13 c dic dic dic0 sayles curry 1988 the d 13 c value of added dic was 13ae6 corresponding to the dissolution of co2 with d 13 c between 19ae5 and 23ae0 vienna pee dee belemnite vpdb the observed difference between the measured and calculated equilibrium temperature of precipitation of bulk tufa barriers indicates that the higher the water temperature the larger the error in the estimated temperature of precipitation this implies that the climatic signals may be valid only in tufas precipitated at lower and relatively stable temperatures the laminar crust comprising a continuous record of the last 40 years of precipitation shows a consistent trend of increasing d 13 c and decreasing d 18 o the lack of covariation between d 13 c and d 18 o indicates that precipitation of calcite was not kinetically controlled for either of the elements d 13 c and d 18 o of precipitates collected on different artificial substrates show that surface characteristics both of substrates and colonizing biota play an important role in c and o isotope fractionation during carbonate precipitation

contrasts in variations of the carbon and oxygen isotopic composition of travertines formed in pools and a ramp stream at huanglong ravine china implications for paleoclimatic interpretations abstract water samples and modern endogenic thermogene travertine calcite deposited on plexiglass substrates in travertine pools and a ramp stream were collected along the huanglong ravine sichuan sw china at regular 10 day intervals from early may to early november in 2010 including both wet and dry conditions temporal and spatial variations in the 13 c and 18 o values of the modern travertine were examined to understand their potential for paleoclimatic and paleoenvironmental interpretations it was found that 13 c and 18 o of travertine formed in the ramp stream were low in the warm rainy season and high in the cold dry season their positive correlation was mainly due to dilution and rainfall seasonal effects on 13 c and 18 o values respectively i e low 13 c values were caused by dilution by overland flow with depleted 13 c values and reduced co 2 degassing in the warm rainy season while low 18 o values of travertine were because of low 18 o values of water induced by seasonal variation in oxygen isotopic ratios of rainwater meanwhile kinetic effect on oxygen isotopic fractionation during ramp travertine deposition existed and reduced this positive correlation in contrast the 13 c and 18 o values of the pool travertines displayed a converse behavior which was caused mainly by the temperature effect low 18 o values and high 13 c values in the warm rainy season were correlated chiefly with the higher water temperatures therefore the 13 c and 18 o values of the travertine may be used for paleo rainfall or paleotemperature reconstruction respectively this study demonstrates that endogenic travertine like epigenic meteogene tufa may be a suitable candidate for high resolution paleoclimatic and paleoenvironmental reconstructions however since travertines deposited under differing hydrodynamic conditions e g pools with still water contrasted to fast flow streams have different climatic responses it is necessary to check the depositional facies of fossil travertine samples before they can be used for palaeoclimate temperature and or rainfall reconstruction