cave pearls the integrated product of abiogenic and biogenic processes abstract cave pearls up to 8 cm long collected from dried out rimstone pools in old man village cave on grand cayman british west indies have nuclei e g bone that are encased by laminated cortices these laminae are composed of trigonal prismatic calcite crystals calcite crystal bushes or particulate calcite that is formed of filamentous microbes four morphotypes spores seven morphotypes extracellular polymers eps disorganized and organized calcite fiber crystals and detrital calcite grains syntaxial overgrowths modified many of the fiber crystals and the trigonal calcite crystals thin laterally discontinuous growth lines are formed of micrite that may have been precipitated in a microbial mat growth of the cave pearls involved abiogenic and biogenic processes the trigonal calcite crystals and crystal bushes probably formed abiogenically whereas the particulate calcite laminae appear to have formed as microbes trapped and bound detrital grains to the surfaces of the cave pearls and indirectly mediated precipitation of the fiber crystals water flow into the rimstone pools which was linked to local rainfall controlled the influx of detrital grains water chemistry and microbe growth into the pools and hence the growth of the cave pearls periods of low water influx led to stagnation of pool waters that seemed to trigger periods of rapid abiogenic calcite precipitation and curtail microbial colonization high flow rates slowed abiogenic calcite precipitation promoted microbe growth and fed detrital materials into the pools despite the lightless environment of the cave the evidence clearly shows that the microbes and their associated eps played a critical role in the growth and development of the cave pearls

seasonal water use patterns of juniperus ashei on the edwards plateau texas based on stable isotopes in water summary naturally occurring stable isotopes of oxygen and hydrogen were used to determine the seasonal water sources of juniperus ashei and its relationship with soil water content on the edwards plateau of central texas honey creek state natural area the patchy nature of juniper stands rooting in the thin soils over karstified carbonate bedrock imparts large spatial heterogeneity in soil water content and isotopic composition largely by differential shading but also by canopy interception there is a seasonal decrease in the oxygen isotope composition of juniper xylem water by 2 during the transition from hot dry summer conditions to the cool moist winter prior to this shift the xylem water isotope composition is similar to local springs presumed to represent local groundwater after this shift the xylem water composition is similar to soil water below 10 cm these results suggest a change in juniper water use from a dominantly deep water source during the summer to a dominantly soil source during the winter over the study period but the timing of this transition will likely vary from year to year

microbial dolomite in fresh water carbonate deposits this article reports evidence for biologically mediated precipitation of dolomite in a fresh water spring in the south east of spain build ups in the spring consisted of calcite minor dolomite barite and gypsum crystals formed by the mineralisation of microbial biofilms and bryophytes a detailed microscopic study coupled with geochemical analysis of the dolomite precipitating biofilms showed that dolomite crystals occurred in association with living coccoid micro organisms providing strong evidence that micro organisms play a fundamental role in the precipitation of this mineral many of the calcite crystals observed were associated with extracellular polymeric substances moreover microbial involvement in the precipitation of calcite was further supported by the presence of living cyanobacteria within the calcite crystals two different types of build up were found in the spring soft spongy moss tufa and laminated crusts two types of crusts were identified as follows simple pink crusts and laminated crusts the latter forming in both sub aquatic and sub aerial environments sub aquatic accumulation of simple detached pink crust fragments occurred sporadically both tufa and the carbonate crusts hosted cyanobacterial dominated biofilms with different bacteria and diatoms and their extracellular polymeric substances the 13c values of calcite showed some biogenic involvement in the origin of this mineral the 18o values were similar in the tufa and carbonate crusts and corresponded to current climatological characteristics the occurrence of different groups of minerals carbonates and sulphates in close spatial association with micro organisms suggests the presence of different macro environmental and micro environmental conditions that facilitate mineral precipitation within biofilms these findings extend the known range of aerobic microbial dolomites to include springs and show that the precipitation of both dolomite and calcite carbonates occurs while organisms are alive

speleothems in a wave cut notch cayman brac british west indies the integrated product of subaerial precipitation dissolution and microbes abstract a wave cut notch that is deeply incised into the vertical cliff faces of cayman brac is adorned with stalactites stalagmites and columns the prefix notch is applied to each type of speleothem in order to distinguish them from cave speleothems these speleothemic deposits must have formed since the highstand 125 000 years ago which was responsible for the development of the notch the laminated notch speleothems are formed largely of aragonite small and large crystals and calcite columnar fiber and grain coating mats along with minor amounts of dolomite a mg si precipitate kerolite gypsum and halite laminae typically the notch speleothems are the integrated product of precipitation and dissolution that was in some places microbially mediated interpretations based on their mineralogy and internal structures indicate that the composition of the formative waters must have temporally fluctuated with periods of precipitation being interrupted by periods of dissolution the microbes that formed the subaerial biofilms may have influenced some of these processes the aragonite calcite and kerolite probably formed as evaporation and loss of ca through precipitation progressively increased the mg ca and the si ca mg ratios the dolomite gypsum and halite probably formed during early diagenesis during the evaporation of seawater that percolated into the interiors of the notch speleothems

trace element distribution in annual stalagmite laminae mapped by micrometer resolution x ray fluorescence implications for incorporation of environmentally significant species abstract stalagmite er78 from grotta di ernesto cave in ne italy displays clear annual lamination consistent with its shallow depth below a forest ecosystem subject to autumnal peaking of water infiltration synchrotron radiation scanning micro x ray fluorescence analyses of heavy elements at european synchrotron radiation facility beamline id22 and light elements at id21 with 1 3 m resolution has been combined with data from ion microprobe analyses to reveal chemical variability across the visible layers of these annual laminae a series of elements display a symmetrical peak centered around the thin dark layer at the top of each lamina the peak concentration is ordered y zn cu and pb p and br this hierarchy is thought to reflect the selectivity of transport of these elements possibly by organic colloids flushed from the soil zone during autumn infiltration ion microprobe analysis indicates na and f also increase as does h the latter reflecting increased microporosity sr displays a trough around the dark and thin autumn layer implying that its incorporation may be limited by competition with other elements mg and s show a different pattern of annual variation and fe displays none the trace metals br and y display peak abundance in the early 20th century which appears to reflect a period of tree felling rather than a climatic anomaly the results demonstrate the power of the high spatial resolution and low detection limits of the synchrotron technique and its ability to produce quantitative maps that allow distinction of layered structure from that of isolated particles or irregular inhomogeneities

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

spatial interaction between collapsed pipes and landslides in hilly regions with loess derived soils while most studies focus on the effect of soil pipes on hillslope stability this present study investigates the impact of landsliding on pipe development it is hypothesized that poorly drained active and dormant landslides change the hillslope hydrology through i surface flow obstruction by changing topography as well as ii subsurface flow obstruction by tilting less permeable clay rich substrates hence new preferential flow paths are created at reverse slopes within the landslide zone and at the boundary of the landslide enhancing pipe formation this study aims at a better understanding of the interaction between collapsed pipe cp occurrence and landslide ls occurrence in the flemish ardennes belgium by comparing their respective spatial patterns at least 24 5 of the 139 sites with cp were related to the occurrence of an observed ls poorly drained ls may create favourable conditions for pipe development outside ls natural and anthropogenic e g broken field drains road drainage causes may result in concentrated subsurface flow resulting in pipe development no evidence was found that pipe development enhanced ls probably because the subsurface drainage discharge generated upslope of the ls is too low even when pipes become blocked it is more likely that new pipes develop and new collapses occur than they trigger or reactivate ls a conceptual model is presented summarizing all elements that influence piping erosion in the flemish ardennes including the role of ls copyright 2012 john wiley sons ltd

annual trace element variations in a holocene speleothem high resolution secondary ionization mass spectrometry sims analysis along the growth axis of a holocene speleothem from northern scotland reveals high frequency oscillations and longer term trends in mg ca sr ca and ba ca at the scale of the high frequency oscillations mg ca and sr ca display a well defined anticorrelation while sr ca and ba ca are positively correlated imaging of elemental ratios in two dimensions reveals that the high frequency signal is well preserved and laterally continuous across the sample tims 230th ages and annual ultraviolet luminescence banding provide chronological control and demonstrate that the high frequency cyclicity is annual trace element variations in speleothem calcite are a reflection of hydrochemical processes in the unsaturated zone overlying the cave supply effects and partitioning at the water calcite interface mg partitioning between water and calcite is temperature dependent calculations suggest that the annual mg ca oscillations may be caused by seasonal temperature changes however the longer timescale variations in mg ca are too great to be explained by this mechanism seasonal variations in water residence time in the unsaturated zone which reflect effective precipitation provide a more probable explanation for the observed annual oscillations and also explain the inverse relationship between mg ca and sr ca this record suggests that trace elements in speleothems have the potential to provide the high resolution insights into interannual palaeoclimatic variability required for assessment of general circulation models

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid

instrumented failure of hillslope models with soil pipes abstract soil pipes porous pipes inside a hillslope are often detected in collapsed slopes indicating their influence on slope failure processes only limited studies can be found regarding the impacts of soil pipes on landslide mechanisms hillslope models prepared in a flume are experimented with different soil pipe configurations a no pipe b closed pipe and c open pipe pore water pressures were measured at six different locations along a slope discharges at the outlet of soil pipe and groundwater seepage were also recorded for the above mentioned pipe configurations two types of experiments were conducted a rainfall induced failure and b seepage induced failure experimental results show that a closed pipe accumulates water around its lower end and continuously increases pore water pressure till a failure an open pipe works as a means of hillslope drainage and reduces the pore water pressure of an entire slope however if open pipe is blocked pore water pressure close to its lower end rises rapidly leading to immediate soil mass movement for both seepage and rainfall induced failure experiments the maximum pressure before the failure was larger at a slope with an open pipe once it is closed than a slope with a pipe closed from the beginning or that without a soil pipe this indicates that the blockage of soil pipes makes a slope more susceptible to failure displacement vectors show that soil movement velocity close to the surface was highest at slopes with open pipes after closure and lowest at slopes without pipes because of a higher degree of saturation and pore water pressure at the time of failure of the former before a large failure small fluctuations in pore water pressure were also observed which can be an indicator of impending failure

the preferential association of dolomite with microbes in stalactites from cayman brac british west indies abstract nani cave located in dolostones of the cayman formation miocene on cayman brac contains numerous stalactites that are formed largely of aragonite and calcite along with lesser amounts of calcium rich dolomite gypsum and minor amounts of mg si needles morphologically the dolomite is divided into blocky filamentous mat crust and beehive types whereas the gypsum is divided into the tabular and sheet types a diverse array of filamentous microbes and spores probably actinomycetids and their associated exopolysaccharides eps are unevenly distributed throughout the stalactites although microbes are commonly present on the surfaces of the calcite and aragonite crystals none were found inside these crystals similarly no microbes were found with the gypsum the common association of the dolomite and the mg si needles with the microbes and their eps suggests that the microbes played a formative role in the precipitation of the dolomite and mg si needles the intimate association of microbes and dolomite in these stalactites has significant implications for the origin of dolomite under low temperature and low pressure conditions

growth and development of notch speleothems from cayman brac british west indies response to variable climatic conditions over the last 125 000 years abstract the spectacular wave cut notch on cayman brac which is 6 m above sea level formed during marine isotope stage 5e highstand 128 000 to 116 000 years ago on cayman brac the notch is commonly decorated with speleothems mostly stalactites that are formed of calcite aragonite and micrite these notch speleothems are characterized by numerous growth zones that are delimited by minor and major hiatal surfaces u th dating indicates that the major growth phases which took place 73 000 to 59 000 years ago 46 000 to 49 000 years ago and 4000 to 1000 years ago were separated by periods when erosion and minimal precipitation were the norm the 18ovpdb values range from 6 5 to 0 3 with a mode between 2 and 4 and an average of 3 1 whereas the 13cvpdb values range from 10 5 to 1 9 with one mode between 2 0 and 3 0 a second mode between 7 0 and 8 0 and an overall average of 6 1 the 18o and 13c values co vary the 18ovpdb and 13cvpdb values are similar to those from the young 125 000 years cave speleothems today with the little evidence of active speleothem growth in the notch or caves cayman brac is characterized by dry sub tropical forest and shrubland with xeric components on the elevated eastern end of the island available data indicate that most of the speleothem growth took place during the transitions from marine isotope stage mis 5a to 4 and mis2 to 1 these transitional periods which define the onset and termination of glaciation in the northern latitudes were probably characterized by higher rainfall and development of tropical rainforests it is evident that notch speleothems like those from cayman brac are valuable archives of the paleoclimate conditions that have existed since the highstand associated with mis5e

seasonal water use strategy of cyclobalanopsis glauca in a karst area of southern china subtropical evergreen and deciduous broadleaved mixed forests occur on shallow soils or even barren areas with carbonate bedrock in karst areas of southern china the nature of seasonal water sources is poorly understood in the complex environment of these deeply rooted forests these forests grow well despite frequent seasonal droughts and limited water availability the authors hypothesized that trees here mainly adsorb water from deep root systems that also recharge the surface soil at least during the dry season to test this hypothesis seasonal isotopic hydrogen and oxygen compositions 18o and d of surface different subsurface well and xylem water available to cyclobalanopsis glauca were compared in a subtropical mixed forest near guilin guangxi china levels of 18o and d in soil water decreased with depth in the 0 30 cm soil horizon and increased below 30 cm depth in march july and october however in january the soil water 18o and d values decreased generally with soil depth deep root systems of trees were suspected to redistribute groundwater to shallow surface soils providing the main stable water source for adult c glauca during the growing season march october however isosource outputs indicated that c glauca extracts water mainly from shallow soil throughout the sampling year in the cold and dry season january winter rains recharging soil water may provide most of the water available for transpiration the two tier water structure in this karst environment connected by deep roots appears to help form a closed water circulation of groundwater soil plant atmosphere

processes associated with microbial biofilms in the twilight zone of caves examples from the cayman islands abstract the twilight zone of a cave an environment transitional between the well illuminated environment outside the cave and the dark environment of the cave interior is one of the most unusual microenvironments of the karst terrain walls in the twilight zone of caves on grand cayman and cayman brac are coated with a biofilm that incorporates a diverse assemblage of epilithic microbes and copious mucus most microbes are different from those found elsewhere in the karst terrains of the cayman islands probably because they have adapted to life in the poorly illuminated twilight zone none of the microbes employ an endolithic life mode and less than 10 of them show evidence of calcification the biofilm does however provide a medium in which a broad spectrum of destructive and constructive processes operate etching the dominant destructive process produces residual dolomite residual calcite blocky calcite and spiky calcite constructive processes include precipitation of calcite dolomite gypsum halite and sylvite although filamentous microbes are common examples of detrital grains trapped and bound to the substrate are rare destructive processes are more common than constructive ones

field hydrological monitoring of a sloping shallow pyroclastic deposit many mountainous areas in campania southern italy are characterized by steep slopes covered by unsaturated volcanic deposits shallow landslides are frequently triggered by intense and persistent

geomicrobiology of carbonate silicate microbialites from hawaiian basaltic sea caves abstract modern microbial mats and microbialites are described from basaltic sea caves on the island of kauai hi the mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock scanning sem and transmission electron microscopy tem showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers energy dispersive x ray analysis revealed that copious amounts of extracellular polymeric substances eps are rich in mg si o and ca likely concentrated from solution petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations consisting mainly of alternating calcium carbonate calcite and aragonite and magnesium rich silicate kerolite thin coatings rich in magnesite hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin within the mats minerals tend to form and concentrate within or around dense matrices of eps microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies in addition copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth this combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves as well as the stromatolitic textures of the microbialites

dolomite in caves recent dolomite formation in oxic non sulfate environments castanar cave spain abstract dolomite is a common mineral in the rock record but rare in recent superficial environments where it does occur it is related to anoxic sulfate rich environments and microbial activity the occurrence of some dolomite deposits in caves however indicates that dolomite formation is also possible in oxic non sulfate settings dolomite is forming at 17 c and in oxic vadose conditions on the host rocks and aragonite speleothems of the castanar cave caceres spain it appears as spheroids and dumbbells 50 300 m in diameter that internally consist of micron sized rhombic to rounded crystals initially this dolomite is ca rich non stoichiometric and poorly ordered mg rich solutions allow the precipitation of metastable mg rich carbonates such as huntite this soon transforms into this ca rich dolomite which later ages to form a more stoichiometric dolomite these dolomites show similarities to those grown under anoxic sulfate rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the dolomite problem including their initial formation and later recrystallization processes

the influence of sponge borings on aragonite to calcite inversion in late pleistocene strombus gigas from grand cayman british west indies abstract large robust strombus gigas lived in a variety of habitats in the ironshore lagoon that existed on grand cayman during the late sangamon highstand approximately 125 000 years ago some well preserved shells are still entirely aragonitic whereas others have been transformed completely to calcite permeability of the host rock and sponge boring intensity were the most important controls on the extent of aragonite to calcite inversion sponge borings played a critical role in the inversion process because they provided conduits through which the reactive diagenetic fluids could penetrate the dense gastropod skeleton each boring acted as a nucleus from which inversion fronts could spread into the shell as a result the radial fabric of the neomorphic calcite crystals around th sponge borings contrasts sharply with the mosaic of equant calcite that formed in areas devoid of sponge borings it seems that bioerosion is at least on a local scale as important as other factors in controlling the meteoric alteration of carbonate sediment the 18o values of neomorphic calcite 7 1 to 4 9 approximately 3 more depleted in 18o than the original aragonite confirm the role of meteoric water in the aragonite to calcite transformation 13c values of the diagenetic calcite 0 2 to 4 5 are similar to those in the original aragonite suggesting that the former was inherited from the latter

hydraulic properties of karst fractures filled with soils and regolith materials implication for their ecohydrological functions abstract in regions with shallow soils underlain by fractured bedrock hydrological processes of substrate are no longer only limited to soil layers however ecohydrological functions of bedrock fractures especially those filled with different soil and regolith materials have not been fully understood in this study we aimed to evaluate water transport and supplying capacities of the filled fractures through investigating hydraulic properties and explore their dominant influencing factors three typical fractures a vertical one filled with fine textured soil vsf a vertical one filled with soil and regolith materials vsrf and a non vertical one filled with coarse textured soil nsf were selected from a large newly excavated trench on a karst hillslope of southwest china stratified samples of fracture fillings were collected to measure saturated hydraulic conductivity k s water retention curves and basic physicochemical properties additionally twenty soil profiles in different topographic locations in the same study area were also analyzed in order to support the results derived from the filled fractures all fractures exhibited extremely high k s 87 149 mm h 1 in surface soil 0 10 cm which allowed rapid infiltration of rainwater into subsurface subsurface water transport was smooth when underlying fracture fillings were loamy with relatively high k s about 10 mm h 1 like in nsf but was blocked when they were clayey with low k s 1 like in vsf and vsrf all fracture fillings had abilities to hold water and available water was the most in nsf which provided an extra water source for plant growth in shallow soil regions the ecohydrological functions of the filled fractures often depend on the properties and layering of fracture fillings which was supported by those obtained from the twenty soil profiles these results are helpful for better understanding of the ecohydrological processes and functions of fractures filled with different materials in karst regions

structure and water storage capacity of a small karst aquifer based on stream discharge in southwest china summary karst spring stream discharge reflects the global configuration of the aquifer however quantitative description of the aquifer structure such as effective porosity neff and water storage capacity by the discharge analysis is difficult because of the complex conduit fracture system this study attempted to quantify the characteristics of karst aquifer based on discharge recession and time series analysis methods three recession models including modified maillet mangin and boussinesq models were evaluated to choose the most suitable one for analyzing the aquifer structure and auto correlation and cross correlation functions were applied to study the aquifer response in both year and rainfall event time scales the results showed that the modified maillet model was more suitable in the study catchment with mangin model overestimating and boussinesq model underestimating the discharge the neff was 3 73 for the total aquifer and it was 0 07 0 33 and 3 33 for the conduit fracture and matrix respectively based on a case study of a rainfall event with precipitation of 68 mm the water volumes drained by the three media were 25 43 33 40 and 41 17 respectively this indicates that although conduit network is not very developed with lower neff it is still an important water transmissive element draining more than a quarter of water after the rainfall event the memory time of the aquifer was 4 days for the year scale and 8 h for the rainfall event 68 mm scale this demonstrates that the aquifer has a well developed drainage system with a quick response to the rainfall the above results provide further insights for hydrological processes modeling and water resources management for the small catchment in karst regions

field validation of isotopic procedures for determining sources of water used by plants in a semi arid environment abstract methods for using stable isotopes of water 2 h 18 o for determining the sources of water transpired by plants in a semi arid field situation are validated a comparison of the isotopic composition of the soil water in zones of high soil water potential and hence high plant water availability with that in plants shows that the overall approach is subject to a randomly distributed error of 5 in 2 h isotopic composition with no indication of any bias this includes errors involved in the extraction of water from plants and soil in spatial heterogeneity in soil profiles in heterogeneity within plant canopies in the time of travel of water through the plant and in assumptions about fractionation of isotopes during water uptake by plants these errors are generally smaller than natural variations of isotope thus allowing the isotopic method to be used similarly an estimate for the error in 18 o is is 1 a compartmental model was used to quantify errors associated with an inversion model using isotopic data of water coming from two soil layers the error in the estimation of the fraction of water taken from each compartment was 20 for many hydrological purposes this error is acceptable this is the first study estimating the errors associated with the method

unusual secondary ca mg carbonate kerolite deposits in basaltic caves kauai hawaii abstract aragonite calcite monohydrocalcite dolomite magnesite hydromagnesite and talc like kerolite have been identified in speleothems from basaltic caves on the island of kauai hawaii these secondary minerals have crystallized in the presence of freshwater seeping from the basaltic host rock and the mineralization process is ongoing at some locations the deposits are extremely variable in macroscopic character ranging from millimeter thin powdery coatings to hard crusts several centimeters thick many deposits are associated with actively forming microbial mats and stromatolitic structures are common in the thicker deposits formation of the mineral deposits is a result of a combination of direct precipitation from solution by evaporation and co2 degassing alteration of precursor minerals and or microbial processes and physicochemical conditions within the mats these unusual deposits provide important insights into the mineralogy and geochemistry of low temperature alteration and carb

microbial kinetic controls on calcite morphology in supersaturated solutions recognizing microbial imprints in the morphology of calcium carbonate minerals that form in very supersaturated solutions containing a high level of dissolved inorganic carbon dic is challenging to better define criteria for this purpose we have analyzed the influence of sulfate reducing bacterium desulfovibrio desulfuricans strain g20 on the morphology of calcite in such solutions g20 does not induce large shifts of ph or alkalinity under these conditions but its uptake of millimolar sulfate and lactate decreases the number of anhedral crystals and stimulates growth of subhedral spar crystals relative to the abiotic controls in addition organic compounds associated with the basal growth medium purified exopolymeric substances produced by g20 and lypopolysaccharide stimulate the growth of anhedral crystals and crystals with rounded edges at low supersaturation index si of calcite the effect of organic compounds is reduced at higher si where rhombohedral habits dominate our results suggest that the local production and uptake of kinetic inhibitors within microbial biofilms may be an important control on calcite morphology in supersaturated solutions

phosphatic precipitates associated with actinomycetes in speleothems from grand cayman british west indies abstract calcitic speleothems from a cave located on the north central coast of grand cayman commonly include corrosion surfaces that developed when calcite precipitation ceased and corrosion mediated by condensates became the operative process dissolution features associated with these surfaces including etched crystal surfaces microcavities and solution widened boundaries between crystals are commonly occupied by microbes and microbial mats that have been replaced by calcium phosphate and or coated with calcium phosphate no mineralized microbes were found in the calcite crystals that form the speleothems the morphology of the mineralized hyphae eight morphotypes and spores nine morphotypes are indicative of actinomycetes a group of microbes that are ideally adapted to life in oligotrophic cave environs superb preservation of the delicate hyphae aerial hyphae and delicate ornamentation on the hyphae and spores indicate that the microbes underwent rapid mineralized while close to their original life positions although these actinomycetes were extremely susceptible to replacement by calcium phosphate there is no evidence that they directly or indirectly controlled precipitation nevertheless the association between the p rich precipitates and microbes shows that the use of phosphorus as a proxy for seasonal climate changes in paleoclimate analyses must be treated with caution

sediment and particulate carbon removal by pipe erosion increase over time in blanket peatlands as a consequence of land drainage land drainage is common in peatlands artificially drained blanket peat catchments have been shown to have a significantly greater soil pipe density than intact catchments this paper investigates the role of surface land drains in the enhancement of soil piping in blanket peats the density of piping was found to significantly increase in a linear fashion with the age of the drainage thirty five years after drains were cut slopes would be expected to have twice the density of soil piping than would an undrained blanket peat catchment the rate of pipe erosion increases exponentially over time so that particulate carbon loss from subsurface pipes is greatest where drains are oldest

bacterially induced dolomite precipitation in anoxic culture experiments to study the process of microbial mediated dolomite formation growth experiments were carried out with selected bacterial cultures under anoxic environmental conditions simulating those found in lagoa vermelha a hypersaline lagoon in brazil where dolomite precipitation occurs specifically we report the isolation of a particular strain of sulfate reducing bacteria lvform6 from lagoa vermelha sediment which apparently promotes the formation of nonstoichiometric dolomite sulfate reducing bacteria grown in a synthetic liquid medium produced dolomite during 30 days incubation at 30 c the precipitates have morphologies similar to those observed in lagoa vermelha sediment our results demonstrate that sulfate reducing bacteria can influence dolomite precipitation under controlled lowtemperature anoxic conditions and imply that anaerobic microorganisms can play an important role in carbonate sedimentation they may have been particularly significant in earth s earliest history when a more reducing atmosphere existed

hydrological and hydrochemical processes observed during a large scale infiltration experiment at the super sauze mudslide france rainfall is one of the major triggering factors of landslides and its pattern controls their temporal behaviour characterization of the groundwater processes and possible preferential infiltration of rainfall is necessary challenging and very relevant for landslide hazard analysis the objective of this paper is to identify the groundwater dynamics matrix flow and preferential flow within highly heterogeneous and fissured reworked black marl material using a large scale infiltration test the artificial rainfall experiment over a 100 m2 infiltration plot monitored with several hydrological hydrochemical and geophysical equipments was carried out on the super sauze mudslide south french alps high resolution groundwater and water quality measurements were collected artificial rainfall was applied over a period of 14 days conservative tracers br and cl were used successively during the infiltration period the mean rainfall intensity was 8 5 mm h 1 with a mean tracer concentration of 100 mg l 1 the hydrodynamic and hydrochemical responses of the tracing experiments allowed us to get a new insight into 1 the horizontal and vertical variability of the rain infiltration in unstable black marl hillslopes 2 the effect of shallow fissuration on the groundwater recharge 3 the role of piston flow on the rate of water level changes and the increase of pore water pressures and 4 the effect of material heterogeneity in the development of preferential water flows and local perched water tables copyright 2011 john wiley sons ltd

sediment detachment and transport processes associated with internal erosion of soil pipes subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping the development of perched water tables in duplex soils fosters lateral flow that can result in seepage at the surface of hillslopes and or formation of soil pipes by internal erosion of lateral preferential flow paths continued internal erosion of soil pipes can lead to gullies dam and levee failures however the processes involved in particle and aggregate detachment from soil pipe walls and transport processes within soil pipes have not been well studied or documented this paper reviews the limited research on sediment detachment and transport in macropores and soil pipes and applies the knowledge learned from the much more extensive studies conducted on streams and industrial pipes to hydrogeologic conditions of soil pipes knowledge gaps are identified and recommendations are made for future research on sediment detachment and transport in soil pipes

origin of island dolostones a case study from the cayman formation miocene cayman brac british west indies abstract cayman brac the easternmost of the cayman islands is 19 km long 1 5 to 3 km wide and rises 40 m above sea level at its eastern end geographically isolated by the deep oceanic waters of the caribbean sea this island with its thick succession of pervasively dolomitized tertiary rocks is a natural laboratory for assessing the origin of island dolostones dolostones in the miocene cayman formation 100 m thick with most crystals 55 mol caco3 geochemically they are characterised by 13c values of 1 6 to 3 5 18o values of 2 3 4 0 80 279 ppm sr 52 340 ppm fe and 9 82 ppm mn the inverse correlation between 18o and mol caco3 and positive correlation between sr and mol caco3 largely reflect kinetic effects on oxygen isotope fractionation and the sr partition behaviour between dolomite and water dolomite stoichiometry indicates formation from waters with a high mg ca ratio and 18o values corrected for biases associated with dolomite stoichiometry and phosphoric acid fractionation indicate formation from normal seawater like fluids under near surface conditions the 87sr 86sr ratios point to two phases of dolomitization phase i in the late miocene 6 8 ma caused partial dolomitization of the basal part of the cayman formation phase ii during the pliocene to early pleistocene 1 5 ma completed dolomitization of the cayman formation both phases of dolomitization were mediated by similar fluids although available information suggests that dolomitization was probably linked to sea level fluctuations the timing of dolomitization relative to the transgressive regressive cycle remains open to debate

microbial nucleation of calcium carbonate in the precambrian microbial sulfate reduction is thought to stimulate carbonate precipitation in modern stromatolites yet whether this metabolism was important in shaping precambrian stromatolites is unknown here we use geochemical modeling to suggest that the influence of sulfate reduction on the saturation index of calcite si is negligible when seawater is in equilibrium with high pco 2 as is thought for the precambrian our laboratory experiments with heterotrophic bacteria in a medium mimicking precambrian seawater chemistry show that even if sulfate reduction does not significantly change the si the presence of bacteria stimulates calcite precipitation over sterile controls by effectively increasing the si over a ph range from 7 3 to 7 8 under our experimental conditions dead cells stimulate in situ carbonate precipitation equally if not more than active sulfate reducing bacteria heterogeneous nucleation of calcite by microbial cell material appears to be the driving mechanism that explains this phenomenon

role of sulfide oxidation in dolomitization sediment and pore water geochemistry of a modern hypersaline lagoon system dolomite precipitation has been reported in sediments of marginal marine hypersaline lagoons near rio de janeiro brazil and has been related to microbial sulfate reduction our field study of pore water and sediment geochemistry in two lagoons reveals only modest degrees of so4 reduction and even h2s oxidation significant differences in dolomite contents salinity and carbon sulfur cycling occur in the two lagoons pore waters from the most dolomite rich sediments exhibit significantly elevated so4 cl ratios relative to seawater moreover the o isotope composition of so4 in all lagoonal waters has evolved significantly from seawater values this suggests active sulfur recycling via h2s oxidation which provides acid that decreases pore water saturation state for high mg calcite and aragonite thermodynamically favoring the precipitation of dolomite the open hydrogeochemical nature of these lagoons maintains so4 concentrations below gypsum saturation allowing dolomite to form from fluids with normal marine mg ca

comparison of high resolution sub annual records of trace elements in a modern 1911 1992 speleothem with instrumental climate data from southwest australia high spatial resolution measurements of mg p u sr ba and na using 193 nm excimer laser ablation inductively coupled plasma mass spectrometry has revealed clearly resolvable annual cycles in a modern speleothem from southwestern australia the age of this stalagmite is established by the dates of emplacement and removal of the boardwalk where it grew 1911 1992 this chronological constraint allows for the first confident comparison between the instrumental climate record and speleothem trace element content eleven laser ablation transects across a 0 5 mm wide section of the speleothem growth axis were measured cycles that could be matched between adjacent transects were stacked into a master record to minimise variability between tracks and permit greater confidence in comparing the trace elements to the instrumental climate record p and u positively and mg inversely mimic the sudden 20 decrease in annual rainfall experienced by this region since 1965 we argue that p from seasonal vegetation decay is transported to the speleothem before it is mineralised in the soil owing to the low p retention capacity of southwest australian soils both vegetation activity and the transport of vegetation derived hpo42 are sensitive to rainfall groundwater p concentration may also influence the transport of u through the strong affinity between phosphate and uranyl ions mg appears to be sensitive to groundwater residence time as this affects drip water mg ca composition by preferential loss of ca during drier episodes when calcite precipitates before reaching the stalagmite the effects of groundwater residence time may also be important for sr on inter annual scales however the behaviour of sr on the annual cycle is opposite to mg but compatible with ba and na which are shown to depend on speleothem growth rate

relationships between colour and diagenesis in the aragonite calcite speleothems in basajaun etxea cave spain abstract basajaun etxea cave north spain contains a wide morphological and colour variety of speleothems most of them are composed of aragonite but calcite speleothems are also found their most common colour is white but there are also pink green and turquoise speleothems in different areas of the cave mg rich dissolution waters from the cave s crystalline dolostone and magnesite host rock favour aragonite precipitation and drive important diagenetic changes in this paper we will discuss how diagenesis modifies speleothem texture mineralogy and geochemistry causing significant changes in the colour we also discuss how speleothems that have undergone diagenesis may also be useful indictors of paleoclimatic conditions our work shows that diagenesis changes the colour of the speleothems because of the mobility of the chromophore elements during this process along with this elemental alteration comes the loss of the primary isotopic signals of speleothems detailed petrological studies of speleothems should precede their analysis for palaeoclimatic reconstruction so that influence of areas affected by diagenesis can be eliminated in addition diagenetic signals also contain valuable information on the changes of the waters within the cave and the overall evolution of speleothems and the cave itself

soil structure and nutrient contents in underground fissures in a rock mantled slope in the karst rocky desertification area near surface karst fissures are filled with soils these soils are often derived from the erosion and transport of surface soil but have different properties than the surface soil in karst rocky desertification regions this study was undertaken to determine the soil structure and nutrient contents in underground fissures with different grades of rocky desertification no potential mild moderate and severe based on field surveys near surface karst fissures were selected in a typical karst plateau area soil particle compositions particularly nutrient characteristics were determined through field sampling and laboratory experiments the results indicated that the higher the rock desertification grade was the higher the soil sand 0 02 2 mm content and the lower the clay 0 002 mm content the soil in both limestone and dolomite fissures was basically neutral to weakly alkaline the surface soil in dolomite fissures presented a higher soil organic matter content than that in limestone fissures but the opposite was true for the subsurface soil from the surface to the lower layer the total nitrogen content generally decreased and the total phosphorus content generally decreased in dolomite fissures but exhibited a more complex pattern in limestone fissures the total phosphorus content of the surface soil was higher than that of the subsurface soil but the total potassium content was lower there was no significant difference among different soil layers near surface fissures are a good place to promote vegetation restoration projects because they provide good soil structure and nutritional conditions for plant growth

water source utilization by woody plants growing on dolomite outcrops and nearby soils during dry seasons in karst region of southwest china summary in the seasonally dry karst region of southwest china woodland vegetation is frequently associated with rocky outcrops we used stable isotope techniques to determine the water sources of two woody plant species the semideciduous tree rademachera sinica and the deciduous shrub alchornea trewioides across three surface types continuous and isolated dolomite outcrops as well as adjacent surfaces with soils main water sources for r sinica growing on the continuous outcrops shifted from deep water sources e g water in the saturated zone on march 23 2009 the late dry season of 2008 2009 to rainwater stored in rock fissures of the unsaturated zone on november 8 2009 the early dry season of 2009 2010 r sinica growing on nearby thin soils exhibited a similar shift of main water sources from deep water sources in the late dry season to shallow soil water 0 30 cm in the early dry season however they extracted deep water sources from the bottom of nearby outcrops rather than from deeper layers below the soil surface main water sources for r sinica growing on the isolated outcrops shifted from previous one to two months ago rainwater in the late dry season to the mixture of recent within the last one month and previous rainwater in the early dry season while using little or no deep water sources in contrast a trewioides growing on these two kinds of outcrops always relied on recent rainwater while those growing on soils always relied on shallow soil water the shift of water sources for tree species especially those growing on continuous rock outcrops and nearby soils may allow them to maintain normal transpiration throughout the year which increases the amount of evapotranspiration in the watershed and further enhances the water storage capacity of the study area

ca carbonates precipitation and limestone genesis the microbiogeologist point of view abstract experiments show that the production of carbonate particles by heterotrophic bacteria follows different ways in heterotrophy the passive carbonatogenesis is generated by modifications of the medium that lead to the accumulation of carbonate and bicarbonate ions and to the precipitation of solid particles it is induced by several metabolic pathways of the nitrogen cycle ammonification of amino acids degradation of urea and uric acid dissimilatory reduction of nitrates and of the sulphur cycle dissimilatory reduction of sulphates the active carbonatogenesis is independent of the mentioned metabolic pathways the carbonate particles are produced by ionic exchanges through the cell membrane following still poorly known mechanisms in autotrophy non methylotrophic methanogenesis and cyanobacterial photosynthesis also may contribute to the precipitation of carbonates autotrophic carbonates as carbonatogenesis is neither restricted to particular taxonomic groups of bacteria nor to specific environments it has been an ubiquitous phenomenon since precambrian times carbonatogenesis is the response of heterotrophic bacterial communities to an enrichment of the milieu in organic matter after a phase of latency there is an exponential increase of bacterial numbers together with the accumulation of metabolic end products these induce a ph increase and an accumulation of carbonate and hydrogenocarbonate ions in the medium this phase ends into a steady state when most part of the initial enrichment is consumed and there is a balance between death and growth in bacterial populations particulate carbonatogenesis occurs during the exponential phase and ends more or less after the beginning of the steady state the active carbonatogenesis seems to start first and to be followed by the passive one which induces the growth of initially produced particles in eutrophic conditions the first solid products are patches that appear on the surface of the bacterial bodies and coalesce until forming a rigid coating and or particles excreted from the cell all these tiny particles assemble into biomineral aggregates which often display precrystalline structures these aggregates grow and form biocrystalline build ups which progressively display more crystalline structures with growth in oligotrophic conditions the primary solid products are rapidly smoothed in the crystalline structure and leave no trace in present aqueous environments apart from deep ocean the potential efficiency of heterotrophic bacterial carbonatogenesis in ca carbonate sedimentation is much higher than autotrophic or abiotic processes it much more likely accounts for extensive apparently abiotic limestone formation than any of the latter as far as biodetrital particles are concerned it may be observed that the shells and tests of organisms are built from the activity of cellular organites which are nowadays considered by a number of biologists as endosymbiotic bacteria thus apart from probably mythical purely evaporitic and autotrophic ones most limestones must be considered as principally of heterotrophic bacterial origin as the carbon of limestones is issued from organic matter bacterial heterotrophic carbonatogenesis appears as a fundamental phenomenon in the relationships between atmosphere and lithosphere during the biogeological evolution of the earth

microbial fossilization in carbonate sediments a result of the bacterial surface involvement in dolomite precipitation recent dolomitic sediment samples from lagoa vermelha brazil were examined microscopically to study the process of bacterial fossilization in carbonate sediments bacteria like bodies were intimately associated with carbonate mineral surfaces and coatings on the former demonstrate the calcification of single bacterial cells the bacterial fossilization process in lagoa vermelha sediments was simulated in the laboratory by cultivation of mixed and pure cultures of sulphate reducing bacteria which were isolated from the lagoa vermelha sediments these cultures produced carbonate minerals that were studied to provide insight into the initiation of the fossilization process in mixed culture experiments bacterial colonies became calcified whereas in pure culture experiments single bacterial cells were associated with dolomite surfaces dolomite nucleated exclusively in bacterial colonies intimately associated with extracellular organic matter and bacterial cells electrophoretic mobility measurements of the bacterial cells in electrolyte solutions demonstrated the specific adsorption of ca 2 and mg 2 onto the cell surfaces indicating the role of the bacterial surface in carbonate nucleation and bacterial fossilization the affinity of the cells for mg 2 was related to the capability of the strains to mediate dolomite formation combined with sulphate uptake which dissociates the mgso 4 o ion pair and increases the mg 2 availability the concentration of mg 2 ions in the microenvironment around the cells where the conditions are favourable for dolomite precipitation may be the key to overcome the kinetic barrier to dolomite formation these results demonstrate that bacterial fossilization is a consequence of the cell surface involvement in carbonate precipitation implying that fossilized bacterial bodies can be used as a tool to recognize microbially mediated carbonates

microbes in caves agents of calcite corrosion and precipitation abstract diverse biogenic and abiogenic processes produce calcite speleothems from a biogenic perspective cave microbes mediate a wide range of destructive and constructive processes that collectively influence the growth of calcite speleothems and their internal fabrics destructive processes include substrate breakdown by dissolution boring and residue micrite production whereas constructive processes include microbe calcification trapping and binding of detrital particles to substrates and microbial induced calcite precipitation biogenesis can be established from 1 the presence of mineralized microbes 2 fabrics such as stromatolite like structures that can be attributed to microbial activity and or 3 geochemical proxies carbon and oxygen isotopes lipid biomarkers considered indicative of microbe activity such criteria have for example been used to demonstrate microbial involvement in the formation of pool fingers stalactites stalagmites cave pisoliths and moonmilk nevertheless absolute proof of microbial biogenesis in calcitic speleothems is commonly difficult because taphonomic processes and or diagenetic processes commonly mask evidence of microbial activity the assumption that calcitic speleothems are abiogenic which has been tacitly assumed in many studies is dangerous as there is clear evidence that microbes thrive in most caves and can directly and indirectly influence calcite precipitation in many different ways

rainfall induced landslides and debris flows in this preface we introduce the special issue on rainfall induced landslides and debris flows the topic is of high interest for many practical and scientific reasons in fact rainfall is the most relevant factor for the triggering of both shallow and deep seated landslides and rainfall analysis is the most frequently adopted approach for forecasting the occurrence of such phenomena the six papers of the special issue cover most of the key issues relative to rainfall induced landslides starting from the analysis of these contributions we identify and discuss in this paper several main topics that deserve further research in the field of rainfall induced landslide such as the uncertainty of the data the quality of geotechnical analysis the validation of the models and the applicability of results in the framework of natural hazards copyright 2007 john wiley sons ltd

cave fills in miocene pliocene strata on cayman brac british west indies implications for the geological evolution of an isolated oceanic island abstract an 8 m high wall in a quarry on the west end of cayman brac exposes the upper part of the cayman formation miocene the lower part of the overlying pedro castle formation pliocene and the cayman unconformity which is a karstic unconformity that separates these formations the modern day karst surface caps the pedro castle formation this exposure also includes cross sections through two filled caves the lower cave 8 m long up to 2 5 m high and upper cave 23 m long up to 2 m high that are housed in the cayman formation and pedro castle formation respectively the lower cave is filled with caymanite which is formed of laminated varicolored dolomitized mudstones and grainstones that contain scattered marine fossils e g foraminifera red algae this cave connected to the cayman unconformity by a small diameter tunnel evolved as part of the karst system that developed during the messinian lowstand 7 3 5 3 ma the cave was filled and dolomitized prior to deposition of the pedro castle formation the upper cave is filled with a wide spectrum of lithotypes including dolostones calcareous mudstones terra rossa gastropod coquina coated grains and speleothems u th dating indicates that some of the flowstones are 500 000 years old whereas others are only 21 000 years old dolostones and mudstones in the basal part of the upper cave contain marine fossils foraminifera red algae whereas the younger deposits are devoid of such fossils the upper cave and its deposits developed after the sediments of the pedro castle formation had been deposited and lithified development of the cave filling deposits which includes a clear transition from marine to non marine influences was controlled by eustatic sea level changes and or westward tectonic tilting of cayman brac that occurred after the pedro castle formation became exposed probably during the late pliocene

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

the effect of vegetation on infiltration in shallow soils underlain by fissured bedrock abstract mean annual infiltration above the high level waste repository proposed to be sited at yucca mountain nevada has a large impact on assessments of repository performance ongoing investigations of infiltration processes have identified the relatively horizontal caprock environment above portions of the repository as a potentially large source of infiltrating waters due to shallow permeable soils above a moderately welded tuff with large soil filled fissures the combination of shallow soils and fissured bedrock allows rapid penetration of wetting pulses to below the rooting zone plant uptake can strongly reduce net infiltration in arid environments with high water storage capacity and despite the low water storage capacity there is a relatively high vegetation density in this environment the apparent discrepancy between high vegetation density and low water storage motivates the study of plant hydrologic interactions in this semiarid environment field observations were coupled with plant and landscape scale models to provide insight into plant hydrologic interactions several lines of evidence including i linear plant growth features observed on aerial photographs ii comparisons of plant cover within the fissured environment and comparable environments lacking fissures and iii direct excavations all suggest that the widely spaced soil filled fissures are conducive to plant growth even when fissures are buried at soil depths exceeding 30 cm results from a mechanistic simulation model for root growth into fissures suggest that the additional sheltered plant available soil water within fissures provides a competitive advantage for plant establishment therefore plants that germinate above a fissure are more likely to survive in turn developing linear features above fissures having established that plants preferentially root within soil filled fissures in the caprock environment a set of simulations were performed to examine the hydrologic consequence of plant roots within fissures at the landscape scale the response to three rainfall amounts was simulated for the largest storm fluxes at the fissure bottom peaked at 1 4 weeks after the storm when plant uptake was not active but were eliminated when fissures had active vegetation when plants were active within a fissure uptake eliminated net infiltration in the fissure regardless of the size of the storm two plant related mechanisms reduced total flux through the plant filled fissures i transpiration during fissure flow and ii wetting pulse retardation due to drier fissures prior to rain the first mechanism appears to be dominant in these simulations results suggest that transpiration may strongly limit net infiltration i e total deep percolation flux escaping the plant root zone significant infiltration can occur however when plants are dormant so that most infiltration would be expected to occur during winter

environmental controls of speleothem mineralogy in a karstic dolomitic terrain soreq cave israel pleistocene speleothems of the soreq cave beth shemesh israel situated within karstic cretaceous dolomitic rocks consist of two major mineralogical types 1 monomineralic low magnesium calcite lmc 0 5 and 7 5 mol mgco 3 straw stalactites stalagmites helictites and pool deposits 2 mineralogically heterogeneous deposits in the form of conical stalactites flowstones and cave corals produced from thin flowing solution films or sprays in which lmc alternates with high magnesium calcite hmc 13 to 33 mol mgco 3 dolomite 33 50 mol mgco 3 and lmc laminations a unique feature of the type 2 is the continuous 0 50 mol range of mgco 3 sem and delta 18 o studies show that all calcites and dolomites grew by direct precipitation from local groundwater solutions lmc formation represents equilibrium precipitation from dripping water solution with mg ca 2 whereas hmc and dolomite precipitation occurred from solution films enriched in mg as the result of prior clos

use of tree rings as indicator for groundwater level drawdown caused by tunnel excavation in zhongliang mountains chongqing southwest china tunnel excavation causes geological hydrological environmental and social changes the effects of groundwater level changes caused by tunnelling on tree growth have been poorly understood dendrochronology was used to evaluate the impact of groundwater level drawdown on tree growth tree cores of masson pines were collected from the areas affected by tunnel construction in the zhongliang mountains of chongqing in south western china to study the effects of tunnel excavation on the growth rate of trees by comparing with tree cores collected from unaffected areas excavation and early operation of the first tunnel in the zhongliang mountains from 1968 to 1984 caused a groundwater table drawdown in both karst aquifer and non karst aquifer the lowered groundwater table significantly reduced the growth rate of pine trees and the low growth rate remained for 15 years the effect was experienced up to at least 1 km from the tunnel axis the decline in tree growth was higher in karst than in non karst areas though the effects on the trees of the karst areas were lagging the high precipitation in 1998 contributed to groundwater recovery after which the tree growth recovered moderately but not to the original level groundwater leakage of the recently excavated tunnels did not affect pine trees heavily probably because the pines had adapted to the new hydrogeological conditions and new strategies in tunnel inflow management were adopted in the recently excavated tunnels the use of tree growth rate as an indicator of groundwater table change in tunnelling areas offers a new option to study environmental impacts and the extent of tunnelling effects

complex speleothem growth processes revealed by trace element mapping and scanning electron microscopy of annual layers closely spaced transects measured by excimer laser ablation inductively coupled plasma mass spectrometry ela icpms at 5 and 32 m spatial resolution are used to generate trace element composition maps ba sr mg u na p and al from mnd s1 a previously studied modern stalagmite from southwest australia treble et al 2003 epsl216 141 rainfall at the site is highly seasonal and trace elements in mnd s1 show strong seasonal variation trace element maps show that ba sr u and na concentrations coherently follow annual growth layers identified from scanning electron microscopy sem images the sem images also reveal that stalagmite growth did not proceed uniformly growth layers vary in thickness and locally pinch out highly preferential crystal growth determined by nucleation sites left by the previous year s growth may be responsible for this uneven growth layering differential crystal growth apparently causes variability of trace element concentrations along each annual layer although additional disequilibrium processes affect mg which is less distinctly banded than ba sr u and na uneven and discontinuous growth layers influence the number of annual cycles their wavelengths and seasonal amplitudes measured in any one transect this has clear implications for studies that use annual trace element cycles as chronological markers growth rate or seasonality proxies

an advanced process based distributed model for the investigation of rainfall induced landslides the effect of process representation and boundary conditions extreme rainfall events are the major driver of shallow landslide occurrences in mountainous and steep terrain regions around the world subsurface hydrology has a dominant role on the initiation of rainfall induced shallow landslides since changes in the soil water content affect significantly the soil shear strength rainfall infiltration produces an increase of soil water potential which is followed by a rapid drop in apparent cohesion especially on steep slopes of shallow soils this loss of shear strength can lead to failure even in unsaturated conditions before positive water pressures are developed we present hydrolisthisis a process based model fully distributed in space with fine time resolution in order to investigate the interactions between surface and subsurface hydrology and shallow landslides initiation fundamental elements of the approach are the dependence of shear strength on the three dimensional 3 d field of soil water potential as well as the temporal evolution of soil water potential during the wetting and drying phases specifically 3 d variably saturated flow conditions including soil hydraulic hysteresis and preferential flow phenomena are simulated for the subsurface flow coupled with a surface runoff routine based on the kinematic wave approximation the geotechnical component of the model is based on a multidimensional limit equilibrium analysis which takes into account the basic principles of unsaturated soil mechanics a series of numerical simulations were carried out with various boundary conditions and using different hydrological and geotechnical components boundary conditions in terms of distributed soil depth were generated using both empirical and process based models the effect of including preferential flow and soil hydraulic hysteresis was tested together with the replacement of the infinite slope assumption with the multidimensional limit equilibrium analysis the results show that boundary conditions play a crucial role in the model performance and that the introduced hydrological preferential flow and soil hydraulic hysteresis and geotechnical components multidimensional limit equilibrium analysis significantly improve predictive capabilities in the presented case study