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

climatic implications of the quaternary fluvial tufa record in the ne iberian peninsula over the last 500 ka the drainage area of the iberian ranges ne spain houses one of the most extensive quaternary fluvial tufaceous records in europe in this study tufa deposits in the anamaza mesa piedra and ebron river valleys were mapped stratigraphically described and chronologically referenced from u th disequilibrium series amino acid racemization and radiocarbon methods tufa deposits accumulated in cascades barrage cascades and related damming areas developed in stepped fluvial systems the maximum frequency of tufa deposition was identified at 120 ka marine oxygen isotope stage mis 5e 102 ka mis 5c 85 ka mis 5a and 7 ka mis 1 probably under warmer and wetter conditions than today additional phases of tufa deposition appear at 353 ka end of mis 11 258 180 ka mis 7 and 171 154 ka mis 6 although most tufa deposition episodes are clearly correlated with interstadial periods the occurrence of tufa deposits during the penultimate glaciation mis 6 is remarkable indicating that the onset of this stage was climatically favourable in the iberian peninsula biostatic conditions and the dynamics of karstic systems regulating tufa deposition seem to be sensitive to the precipitation regime controlled by shifts in the position of north atlantic atmospheric belts and summer insolation regulated by orbital forcing

trapping and binding a review of the factors controlling the development of fossil agglutinated microbialites and their distribution in space and time trapping and binding of allochthonous grains by benthic microbial communities has been considered a fundamental process of microbialite accretion since its discovery in popular shallow marine modern examples bahamas and shark bay however agglutinated textures are rare in fossil microbialites and thus the role of trapping and binding has been debated in the last four decades recently renewed attention on this subject has produced new findings of fossil agglutinated microbialites those mainly formed by trapping and binding and analogous to modern examples but they are still few and geologically recent mainly post paleozoic when compared to the 3 5 gyr long record of microbialites in order to better understand this discrepancy between modern and fossil examples an extensive literature review is presented here providing the first thorough database of agglutinated microbialites which shows that all of them are formed in shallow marine environments and most under tidal influence in addition a lower cretaceous example is described including very diverse microbialites each of them formed in a particular paleoenvironment some of these microbialites developed in grainy settings but only those formed in marginal marine tide influenced environments accreted mainly by trapping and binding the surrounding grains being analogous of modern agglutinated microbialites and matching the environmental pattern observed in the literature database the combination of the literature review with the case study allows to discuss the factors that control and enhance trapping and binding a occurrence of grains in the microbialite environment b frequent currents that mobilize the grains and supply them onto the microbialite surface c high concentration and diversity of electrolytes in the water to increase the adhesiveness of the extracellular polymeric substances eps of the microbialite surface and d a caco3 saturation state not high enough to promote early and strong carbonate precipitation within eps which would eventually decrease its availability to adhere grains therefore this review shows that the keys to solve the trapping and binding debate may be environmental because the conjuction of these hydrodynamic and hydrochemical parameters is preferentially achieved in shallow marine settings and especially in those influenced by tides at least since mesozoic times this explains the limited environmental and stratigraphic distribution of microbialites mainly formed by trapping and binding and opens new ways to look geologically and microbiologically at this process so often cited and yet so rare

an investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the united states in the 0 5 4 hz band summary studies of teleseismic p and s wave amplitudes and spectra in the 0 5 4 hz band show large variations in the attenuative properties of the upper mantle under the united states the data indicate that attenuation is greatest under the south western united states including but not confined to the basin and range province the lowest attenuation prevails under the north central shield regions the north eastern part of the country consisting of new england and possibly including a larger area along the eastern seaboard is characterized by moderate attenuation in the mantle the level of the high frequency energy in short period seismic waves and the differences between q values derived from short and long period data indicate that q is frequency dependent the form of frequency dependence of t compatible with the data in the 0 5 4 hz range does not allow a rapid decrease of t with increasing frequency rather it supports a gradual decrease covering the broader 0 1 4 hz range the curves of t versus frequency for shield to shield and mixed shield to western united states type paths are parallel with an average difference of 0 2 s in t in the short period band but may diverge towards the long period band for both curves t p is below 1 s for shield to shield paths t p must be below 0 5 s at 1 hz

determination of skin and aquifer parameters for a slug test with wellbore skin effect slug test is considered to reflect the hydraulic parameters in the vicinity of the test well the aquifer parameters are usually identified by fitting an appropriate mathematical solution or graphical type curves with slug test data in this paper we developed an approach by combining moench a f hsieh p a 1985 analysis of slug test data in a well with finite thickness skin in memoirs of the 17th international congress on the hydrogeology of rocks of low permeability u s a members of the international association of hydrologists tucson az vol 17 pp 17 29 and simulated annealing sa approach to estimate five parameters i e three skin parameters and two aquifer parameters the three skin parameters are hydraulic conductivity specific storage and thickness of the wellbore skin zone while the two aquifer parameters are hydraulic conductivity and specific storage of the formation zone it is worthy to note although the thickness of the wellbore skin zone is usually taken as an input data for the data analyzed software it is actually an unknown parameter that cannot be measured directly this paper proposes a methodology for estimating the thickness of the wellbore skin zone with other hydraulic parameters at the same time eight sets of well water level wwl data of aquifers with both positive and negative skins are generated by moench and hsieh moench and hsieh 1985 and four sets of standard normally distributed noise are then added to each set of wwl data the results indicate that the negative skin cases generally give a better estimated result than that of the positive skin cases sensitivity analysis is also employed to demonstrate the physical behavior when slug test was performed under positive skin effect for the case of an aquifer with a positive skin the use of a longer series of wwl data for analysis is strongly recommended for better estimation of aquifer hydraulic conductivity analyzing the wwl data of the test and observation wells simultaneously could significantly improve the estimations on specific storages impetuously presuming an arbitrary value for the thickness of the wellbore skin zone may lead to poor estimation for the other four parameters

temporal and environmental significance of microbial lamination insights from recent fluvial stromatolites in the river piedra spain despite extensive research the environmental and temporal significance of microbial lamination is still ambiguous because of the complexity of the parameters that control its development a 13 year monitored record of modern fast accreting calcite stromatolites mean 14 mm year 1 from artificial substrates installed in rapid flow in the river piedra north east spain allows comparison of the sedimentological attributes of successive six month depositional packages with the known climatic hydrophysical and hydrochemical parameters of the depositional system the stromatolites are formed of dense porous and macrocrystalline composite laminae the dense and porous composite laminae which are composed of two to eight laminae consisting largely of calcified cyanobacteria are characterized by i dense composite laminae up to 15 mm thick mostly with successive dense laminae and minor alternating dense and porous laminae and ii porous composite laminae up to 12 mm thick consisting mainly of porous laminae alternating with thinner dense laminae most of the dense composite laminae formed during the warm periods april to september whereas most of the porous composite laminae developed in the cool periods october to march each dense and porous composite lamina represents up to or slightly longer than six months the alternation of these two types of composite laminae parallels seasonal changes in temperature the dense and porous laminae result from shorter for example intraseasonal variations in temperature insolation and hydrological conditions the macrocrystalline laminae with crystals 100 m long occur isolated and grouped into composite laminae up to 1 7 mm thick their occurrence suggests the absence or poor development of microbial mats over periods of weeks to several months thus stromatolite lamination can record different order periodic and non periodic changes in the magnitude of environmental parameters over a single year these results hold important implications for the temporal and environmental interpretation of lamination in microbial structures

analysis of well residual drawdown after a constant head test summary a recovery test measures the residual drawdown after an aquifer pumping test has ended and analyzes the recovery data to determine hydrogeological parameters such as transmissivity and storage coefficient to our knowledge the solution for the distribution of residual drawdown following a constanthead test has never been presented in this paper we first develop a mathematical model that describes the residual drawdown taking into consideration the wellbore storage effect and the drawdown distribution occurring at the end of a previous constant head test then the laplace domain solution of the model is developed using the laplace transforms and its time domain solution is obtained using the stehfest algorithm numerical results show that the distribution of residual drawdown depends on the boundary condition related to the well drawdown and the initial condition related to the aquifer drawdown the well residual drawdown i e the residual drawdown at wellbore during the early recovery period will be over estimated by the approximate residual drawdown solution based on the theis type solution and superposition principle due to the neglect of wellbore storage for a large recovery time the effect of wellbore storage is negligible and the approximate residual drawdown solution is therefore applicable

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

body wave amplitude patterns and upper mantle attenuation variations across north america summary a broad band amplitude study of p and sh waves from deep south american events recorded at wwssn stations in the united states provides constraints on upper mantle variations in attenuation the events were selected to minimize contamination due to source complexity radiation pattern and source structure the prevalent feature in the short and longperiod bands is that the sh amplitudes show the same regional variations as the p amplitudes with the regional variations of short periods being similar but enhanced relative to the variations at long periods the amplitudes show some systematic regional difference between the east coast and rocky mountain provinces and both short and long periods are enhanced at the gulf coast and midwestern stations probably due to thick sedimentary bed receiver structure since detailed receiver structures for individual stations are poorly known we used the working hypothesis that the regional amplitude patterns are caused by lateral variations in upper mantle attenuation both a constant q and a frequency dependent attenuation operator were considered with the relative amplitudes and waveforms in short and long period bands used to estimate the acceptable range of at in the constant q model or the acceptable range of the parameter r which describes the high frequency roll off of the absorption band in the frequency dependent model time domain modelling indicates that the short period p and sh amplitudes and waveforms in the 1 10s period range do not unambiguously demand frequency dependent attenuation allowing for the uncertainty in source frequency content and long period absorption band amplitude the short period p amplitudes can be fit with a range in at 0 5 s or a range in r from 0 001 to 0 25s with either single parameter variation consistent with the general short period sh amplitude behaviour a technique for determining the absolute value of t and possible r values appropriate for the 5 20s band was applied to selected data a value of t 0 8 s and small 7 were found for travel paths from the deep events to north america and lower t or large r values were found for paths to southern african stations longperiod amplitude variations cannot be explained by frequency dependent

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

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

high resolution records of rainfall events from clay bands in tufa individual rainfall events are recorded as thin clay bands in annually laminated freshwater carbonate tufa runoff from rainfall events entrains clay that then adheres to the tufa surface a specimen collected from southwest japan exhibits 100 clay bands formed during a 15 yr period from 1988 to 2002 the chronology of the clay bands was determined by using the temperature dependent cycle of oxygen isotope ratios in the carbonate and the clay content was quantified by electron probe microanalysis si x ray strength the obtained si x ray strength curve and actual rainfall record follow a nearly identical pattern the clay content of each band correlates with rainfall amount rainfall of 50 mm week produced sufficient amounts of suspended cave clay to produce clay bands in the tufa because the clay bands survive postdepositional alteration this new method can be applied to ancient tufa deposits and has great potential as a high resolution rainfall record for use in climate studies

relative importance of the saturated and the unsaturated zones in the hydrogeological functioning of karst aquifers the case of alta cadena southern spain summary from analysis of the hydrodynamic and hydrochemical responses of karst springs it is possible to know the behaviour of the aquifers they drain this manuscript aims to contribute to the characterization of infiltration process and to determine the relative importance of the saturated zone and of the unsaturated zone in the hydrogeological functioning of carbonate aquifers using natural hydrochemical tracers thus chemical components together with temperature and electrical conductivity both punctual and continuous records have been monitored in three springs which drain alta cadena carbonate aquifer southern spain an evaluation of the percentage of the electrical conductivity frequency peaks determined for each of the three springs is linked to the chemical parameters that comprise the conductivity signal one of these springs responds rapidly to precipitation conduit flow system due to the existence of a high degree of karstification in the unsaturated zone and in the saturated zone both of which play a similar role in the functioning of the spring another spring responds to precipitation with small increases in water flow somewhat lagged because the aquifer has a low degree of karstification even in the unsaturated zone which seems to influence its functioning more strongly than does the saturated zone the third spring drains a sector of the aquifer with a moderately developed degree of karstification one that is intermediate between the other two in which both the unsaturated zone and the saturated zone participate in the functioning of the spring but with the latter zone having a stronger influence these three springs show different hydrogeological functioning although they are in similar geological and climatic contexts which show the heterogeneity of karst media and the importance of an adequate investigation for groundwater management and protection in karst areas

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

geochemical and statistical evidence of deep carbonate groundwater within overlying volcanic rock aquifers aquitards of southern nevada usa abstract samples collected from springs and wells in southern nevada were analyzed for major solutes and trace elements as part of a larger study to characterize the geochemical signatures of these groundwaters in this study principal component analysis pca was used to reduce the large data sets including the four major cations ca mg na k and 27 trace elements analyzed in these groundwater samples principal components analysis of the major cation data indicates that groundwaters from cenozoic felsic volcanic rock aquifers aquitards of southern nevada exhibit strong chemical associations to each other but weak relationships to groundwaters from the regional carbonate aquifer which were instead chemically similar to each other however pca of the trace element data demonstrates that some groundwaters from the volcanic aquifers aquitards are chemically similar to those of the underlying regional carbonate aquifer the pca also reveals that these groundwaters from the volcanic aquifers aquitards have significantly different trace element compositions than perched groundwaters contained within similar felsic volcanic rocks moreover rare earth element ree data from groundwaters collected from wells finished in the volcanic aquifers aquitards of southern nevada have similar concentrations and similar shale normalized patterns to the carbonate aquifer groundwaters as well as local carbonate rocks these same southern nevada well waters do not exhibit ree concentrations or shale normalized signatures that resemble the perched volcanic groundwaters or the tuffs of southern nevada the ree data and trace element pca along with previous carbon isotope analyses water temperature data hydraulic head relations and results of a recent pump test of a well near yucca mountain suggest close contact of the regional carbonate groundwaters and groundwaters from the overlying volcanic rocks of southern nevada and possible upwelling of the carbonate groundwaters into the overlying volcanic rock units in the vicinity of yucca mountain

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

seasonal pattern in the high elevation fluvial travertine from the jiuzhaigou national nature reserve sichuan southwestern china abstract the jiuzhaigou national nature reserve on the tibetan plateau sichuan southwestern china is characterized by the deposition of fluvial travertine in a spectacular array of shoals waterfalls pool dams and multicolored lakes this is possibly the highest vegetated travertine setting of the world from 2200 to 2900 m above sea level an environment sensitive to minimal changes in temperature and precipitation regime the evolution of the system is driven by two seasonal monsoon climate patterns with a wet spring summer travertine deposition and then a dry fall winter characterized by no precipitation or erosion spring and phreatic vadose deposits transition from laminated columnar calcite to clotted micrite encrustation possibly correlated with a mid holocene peak in precipitation and high lake levels in the northeastern tibetan area connected to glacial advance the most peculiar features are the fluvial shoals a rather uncommon travertine surface consisting of two main superimposed facies of alternating weak and strong turbulence water flow the low turbulence facies consists of clotted micrite encrustation of mosses and cyanobacteria filaments and platy calcite crystals covering algal filaments the high water turbulence facies show seasonal alternation of diatom rich bundles of phormidium sp late spring with algal oocardium stratum levels summer fall upslope and downslope of the shoals the precipitation of calcium carbonate results in the formation of prograding waterfalls and dam pool systems that encrust macrophytes with microspar and clotted micrite encrusted chironomids larvae tubes are present in the waterfall walls up to an elevation of 2860 m possibly the highest ever recorded early diagenetic processes such as dissolution of diatom frustules take place over the span of several years a slower phenomenon compared to other travertine occurrences in this high elevation extreme setting travertine sand and gravel bar deposits are produced by the exposure to severe weathering of a section of the valley that is bypassed through an underground karst system during the winter dry season high elevation travertine probably has a low preservation potential but it appears to be more sensitive to climate changes than other depositional settings especially in the himalayan tibetan area where the extent of the quaternary glacial advances and retreats is still a matter of debate

continuous 60 year stable isotopic and earth alkali element records in a modern laminated tufa jaruga river krka croatia implications for climate reconstruction abstract a continuous 60 year record 1938 1998 of stable isotope compositions of carbon and oxygen as well as trace metal mg sr ba concentrations in a laminated calcite crust precipitated in a short artificial tunnel on a non equilibrium groundwater fed karstic river is presented chemical and isotopic records have been compared to hydrometeorological data available for the last 48 years an attempt is made to relate isotopic and geochemical variations in the crust to environmental parameters such as temperature precipitation and changes in vegetation cover as well as to postdepositional recrystallisation of the older crust material isotopic composition of the crust is largely influenced by non equilibrium precipitation which favours the incorporation of isotopically depleted c and o into the carbonate furthermore because of the complicated hydrological situation there is no observable correlation between the stable oxygen isotope composition of water and temperature the result is that the 18 o isotopic thermometers overestimate the measured precipitation temperatures temperatures calculated from mg ca ratios of water and the carbonate match the 18 o palaeotemperatures within 2 4 c in the older part of the crust precipitated before the onset of industrial pollution of the river it was demonstrated that the application of mg palaeothermometry in natural systems where the mg ca ratio of water is influenced not only by temperature but also by other environmental parameters such as precipitation surface runoff groundwater retention time and anthropogenic influences is subject to a large uncertainty up to 10 c

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

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

sedimentology and depositional architecture of tufas deposited in stepped fluvial systems of changing slope lessons from the quaternary anamaza valley iberian range spain the pleistocene and holocene tufas of the anamaza valley stepped build ups up to 70 m thick along the valley consist of several depositional stages separated by erosional surfaces eight associations of tufa and related carbonate facies plus minor polygenic detrital facies represent the processes that occurred in different fluvial and related environments the bedrock lithology and structure controlled the location of the knickpoints along the valley and allowed separation of two stepped stretches with distinct conceptual facies models the moderate slope model includes extensive standing water areas dammed by barrage cascades in the lakes bioclastic silts sands and limestones along with phytoclastic and marly at places peaty sediments formed abundant stem phytoherms account for extensive palustrine areas the high slope model consists of smaller dammed areas between close up cascades and barrage cascades which were composed primarily of moss phytoherms and phytoclastic tufas an outstanding feature is the extensive steep reach with phytoclastic and polygenic detrital sediments and stepped cascades consisting of stromatolitic and moss phytoherms there the steep slope limited the preservation of stem phytoherms and favoured erosion the geometry and thickness of the sedimentary fill wedge shaped units composed of cascade and barrage cascade deposits downstream and dammed and gentle sloped channel deposits upstream are therefore different for each model multi storey wedges are a distinctive feature of the high slope model the initial knickpoint geometry and the tufa aggradation progradation ratio on such steep surfaces for example related to changes in discharge controlled the growth style of the cascades or barrage cascades and hence the extent thickness and vertical evolution of the upstream deposits the sedimentological attributes and stable isotope composition of the carbonate facies suggest a higher and more variable precipitation evaporation ratio during the pleistocene than during the holocene consistent with an overall decrease in the river discharge this evolution was coupled with warm conditions which prevailed during the stages of tufa formation these results may help to assess architectural patterns in interpreting other basins and underscore the significance of tufas as records of past hydrology and climate

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

solution for flow rates across the wellbore in a two zone confined aquifer a closed form solution for transient flow rates across the wellbore in a confined aquifer is derived from a two zone radial ground water flow equation subject to the boundary condition of keeping a constant head at the well radius an aquifer may be considered as a two zone system if the formation properties near the wellbore are significantly changed due to the well construction and or well development an efficient numerical approach is used to evaluate this newly derived solution values of the transient flow rate are provided in a tabular form and compared with those obtained by numerical inversion for the laplace domain solution the results show that the two solutions are in good agreement this newly derived solution can be used not only for predicting the transient flow rate across the wellbore but also for identifying the effects of a skin with a finite thickness on the estimation of transient flow rates in a ground water system with two different formation properties

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

climatic change recorded by stable isotopes and trace elements in a british holocene tufa combined stable isotope d18o and d13c and trace element mg sr geochemistry from bulk tufa calcite and ostracod shell calcite from an early holocene british tufa reveal clear records of holocene palaeoclimatic change variation in d18o is caused principally by change in the isotopic composition of holocene rainfall recharge itself caused mainly by change in air temperature the d13c variability through much of the deposit reflects increasing influence of soil zone co2 owing to progressive woodland soil development bulk tufa mg ca and sr ca are controlled by their concentrations in the spring water importantly mg ca ratios are not related to d18o values and thus show no temperature dependence first order sympathetic relationships between d13c values and mg ca and sr ca are controlled by aquifer processes residence times co2 degassing and calcite dissolution reprecipitation and probably record intensity of palaeorainfall recharge effects stable isotope records from ostracod shells show evidence of vital effects relative to bulk tufa data the ostracod isotopic records are markedly spiky because the ostracods record snapshots of relatively short duration years whereas the bulk tufa samples record averages of longer time periods probably decades the d18o record appears to show early holocene warming a thermal maximum at ca 8900 cal yr bp and the global 8200 yr bp cold event combined d13c mg ca and sr ca data suggest that early holocene warming was accompanied by decreasing rainfall intensity the mg ca data suggest that the 8200 yr bp cold event was also dry warmer and wetter conditions were re established after the 8200 yr bp cold event until the top of the preserved tufa sequence at ca 7100 cal yr bp

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

estimating formation properties from early time recovery in wells subject to turbulent head losses abstract a mathematical model is developed to interpret the early time recovering water level following the termination of pumping in wells subject to turbulent head losses the model assumes that turbulent head losses dissipate immediately when pumping ends in wells subject to both borehole storage and turbulent head losses the early time recovery exhibits a slope equal to 1 2 on log log plots of the recovery versus time this half slope response should not be confused with the half slope response associated with a linear flow regime during aquifer tests the presence of a borehole skin due to formation damage or stimulation around the pumped well alters the early time recovery in wells subject to turbulent head losses and gives the appearance of borehole storage where the recovery exhibits a unit slope on log log plots of recovery versus time type curves can be used to estimate the formation storativity from the early time recovery data in wells that are suspected of having formation damage or stimulation the type curves can be used to estimate the effective radius of the pumped well if an estimate of the formation storativity is available from observation wells or other information type curves for a homogeneous and isotropic dual porosity aquifer are developed and applied to estimate formation properties and the effect of formation stimulation from a single well test conducted in the madison limestone near rapid city south dakota

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

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

climatic significance of seasonal trace element and stable isotope variations in a modern freshwater tufa abstract we present a continuous 14 yr long 1985 to 1999 high resolution record of trace element mg sr ba u and stable isotope 13c 18o variations in a modern freshwater tufa from northwestern queensland australia by utilizing the temperature dependence of the 18o signal an accurate chronology was developed for the sampled profile which allowed a comparison of the chemical records with hydrological and meteorological observations as a consequence it was possible to constrain the relevant geochemical processes relating climate variables such as temperature and precipitation to their chemical proxies in the tufa record temperatures calculated from the mg concentrations of the tufa samples provide close approximations of average annual water temperature variations furthermore we demonstrate that temporal changes in mg ca water can be estimated using an empirically derived equation relating mg ca water to the sr ba ratio measured in the tufa samples by means of this relationship it is theoretically possible to determine the mg ca ratio of paleowaters and hence to derive reliable estimates of former water temperatures from the mg concentrations of fossil tufas from the study area sympathetic variations in sr ba and 13c along the sampled profile record changes in water chemistry which are most probably caused by variable amounts of calcite precipitation within the vadose zone of the karst aquifer this process is thought to be markedly subdued whenever the amount of wet season precipitation exceeds a given threshold accordingly distinct minima in sr ba and 13c are interpreted to reflect years with above average rainfall the pronounced seasonal and annual variability of the u concentration along the profile is thought to primarily record changes in the u flux from the soil to the water table we suggest that during intensive rain events u is transported to the phreatic zone by complexing organic colloids giving rise to conspicuous u maxima in the tufa after above average wet seasons this study demonstrates the potential of freshwater tufas to provide valuable information on seasonal temperature and rainfall variations if tufa deposits turn out to be reasonably resistant to secondary processes combined investigation of speleothems and tufas from the same area could become a promising approach in future research while speleothems offer continuous records of long term paleoenvironmental changes tufas could provide high resolution time windows into selected periods of the past

geochemical processes evidence and thermodynamic behavior of dissolved and precipitated carbonate minerals in a modern seawater freshwater mixing zone of a small tropical island abstract the geochemical processes and thermodynamic behavior of dissolved and precipitated carbonate minerals controlling the hydrochemistry of an aquifer in the seawater freshwater mixing zone of a small island are identified field and laboratory analyses geochemical modeling phreeqc and multivariate statistical analysis msa provide a quantitative interpretation for the geochemistry of the carbonate dominated aquifer geochemical analyses and modeling results show that dissolution and re precipitation of caco3 are the prevalent processes governing geochemical reactions in the mixing zone furthermore this was confirmed by coherent statistical output that incorporates principle component analysis pca and k means cluster analysis k ca generally the composition of the lowland sandy soil was rather homogeneous and was primarily composed of quartz aragonite calcite and mg calcite thermodynamic model calculations indicate that the carbonate minerals calcite aragonite and dolomite are supersaturated in the mixing zone nevertheless powder x ray diffraction pxrd and scanning electron microscope sem examination verified the occurrence of low mg calcite lmc and the absence of dolomite attributed to thermodynamic kinetic hindrance cation disorder and the presence of dolomite crystal growth rate inhibitors such as so4 the results suggest that dissolution of aragonite and precipitation of lmc drives the solid phase geochemistry in the small tropical island aquifer