dolomites and dolomites in mesozoic platform carbonates of the southern apennines geometric distribution petrography and geochemistry abstract a multidisciplinary study of the dolomitized bodies present among the late triassic to late cretaceous carbonate deposits of the monti lattari belt southern apennines of italy compares the different dolomitization styles present within this succession of these mesozoic platform carbonates and furnishes an overview of their formative genetic models the revealing traces of the diverse modes of diagenesis in this region include both surface and subsurface mechanisms utilizing a geometric reconstruction of the dolomitized bodies an integrated facies and petrographic analysis of the components and a geochemical characterization of the sediments including detailed mineralogy and associated stable isotope values the data presented demonstrate that some intervals are characterized by surface related dolomitization processes middle late triassic and cretaceous while others latest triassic to lower middle jurassic and are mainly dominated by later large scale subsurface dolomitization processes all of the middle late triassic norian successions are pervasively dolomitized exhibit fabric preserving textures and have a distinctly heavy stable isotope signature their origin has been related to diagenesis due to particular climatic and palaeoceanographic conditions leading to the formation of extended blankets of shallow warm saline seawater this setting was terminated by climatic and palaeoceanographic changes during the latest triassic which dramatically reduced the significance of surface related dolomitization on a regional scale the overlying latest triassic rhaetian outcrops consist of a widespread coarse fabric destructive massive dolomite with a lighter isotopic signature these dolomites seem genetically related to the ones of the lower middle jurassic which share the same geometrical petrographic and geochemical characteristics caused by large scale fluid circulation this diagenetic pattern apparently started in the early jurassic during burial driven by thermal convection due to the different temperatures between the oceanic waters and the warmer carbonate platform the middle upper jurassic units feature local episodes of early dolomitization that partially replaced the muddy carbonate facies due to tidal pumping and reflux mechanisms dolomitization is not a pervasive feature during this phase of deposition in the cretaceous portion of the succession dolomites have a totally different and distinct character and are generally related to bedding and show variability in textures and mg ca ratios local association with evaporites geometry of dolomitized bodies and stable isotope geochemistry suggest processes comprising evaporative pumping and reflux all related to the surface environment this evidence points to a renewal of a climatic context more favorable for early dolomitization thus this study permits recognition of the presence of three quite different dolomitization styles within the carbonate platform succession of the southern apennines fold thrust belt one ascribed to the norian one to the rhaetian lower jurassic and one to the cretaceous

modeling flow in phreatic and epiphreatic karst conduits in the holloch cave muotatal switzerland the holloch cave is a site where the hydrodynamic behavior of a karst conduit network can be observed with a high degree of precision observed heads discharge rates conduit sizes and conduit lengths have been compiled into a simple hydrodynamic model in order to check their consistency it was possible to calibrate and satisfactorily fit the observed data model results show the following 1 flow models which are able to simulate turbulent flow in variably saturated conduit networks can adequately model conduit flow dominated karst systems 2 karst systems may be strongly nonlinear especially because of the presence of epiphreatic conduits 3 under certain circumstances storage in the epiphreatic conduits and in the fissured limestone matrix can be neglected 4 the typical effective hydraulic conductivity of karst conduits ranges between 1 and 10 m s 1 and the louis formula is adequate to calculate head losses in those conduits 5 indirect measurements of flow velocity using scallop size indicate values of 30 40 of the maximal annual discharge and velocity derived from pebble size indicates values of 150 of the maximal annual discharge

water and air dynamics within a deep vadose zone of a karst massif observations from the lukina jama trojama cave system 1 431 m in dinaric karst croatia extreme heterogeneity of karst systems makes them very challenging to study variousprocesses within the system affect its global response usually measured at karstsprings research conducted in caves provides a unique opportunity for in situ analysisof separate processes in karst underground the aim of the present study was toresearch the water and air dynamics within a deep karst system air and water basicphysical parameters across the lukina jama trojama cave system 1 431 m werecontinuously monitored during a 1 year period recorded hydrograph of the siphonlake at the bottom of the cave was used to interpret the characteristics of an unex plored phreatic epiphreatic conduit network water origin in the siphon was deter mined based on temperature and electrical conductivity air temperature andhumidity monitoring revealed a strong inflow of air of sub zero temperature into theupper portion of the cave during winter cave passage morphology was interpretedas the main determinant of air dynamics which caused ice to accumulate extensivelyin the upper portions of the cave and caused the temperature on the top of thehomothermic zone to be significantly below the mean outside temperature air dynam ics also lowered the temperature of water flowing through the cave vadose zone andfeeding the phreatic zone of the massif the pronounced temperature differencebetween the phreatic zone and the top of the homothermic zone probably contributedto the thermal gradient observed in the cave which is steeper than in ice free caves inthe area our results enabled the development of a conceptual model that describescoupling between air and water dynamics in the cave system and its surroundings

parameterization of stream channel geometry in the distributed modeling of catchment dynamics a simple and efficient procedure for incorporating the effects of stream channel geometry in the distributed modeling of catchment dynamics is developed at a station and downstream fluvial relationships are combined and the obtained laws of variability in space and time for water surface width and wetted perimeter are incorporated into a diffusion wave routing model based on the muskingum cunge method with variable parameters the parameterization obtained is applied to the approximately 840 km 2 sieve catchment central italian apennines to test the possibility of estimating channel geometry parameters from cross section surveys and to assess the impact of dynamic variations in the channel geometry on catchment dynamics the use of the estimated channel geometry in surface runoff routing produces a significant improvement in the flood hydrograph description at the catchment outlet with respect to less detailed network parameterizations in addition the results obtained from a downstream analysis of the velocity field indicate that the stream characteristics related to the locally varying cross section shape may have a strong control on flow velocities and thus they should be monitored and synthesized for a comprehensive description of the distributed catchment dynamics

new distribution coefficient for the incorporation of strontium into dolomite and its implications for the formation of ancient dolomites late tertiary dolomites form the bahamas exhibit a strong inverse correlation between sr and mol mgco sub 3 it is proposed that this relation is a result of a distribution coefficient dependent on the concentration of ca in dolomite because these dolomites precipitated from water with a sr sup 2 ca sup 2 ratio similar to that of seawater a distribution coefficient d sub sr sup dolomite of 0 0118 is calculated for sr in stoichiometric dolomite this coefficient increases by about 0 0039 for every additional mol caco sub 3 in nonstoichiometric dolomite these data have three important implication first the new d sub sr sup dolomite is substantially lower than previously suggested second a relation has been established among the sr sup 2 ca sup 2 ratio of dolomite forming waters the major element composition of dolomites and the sr content of dolomites allowing the determination of the sr sup 2 ca sup 2 ratio of fluids involved in the formation of ancient dolomites third some published data sets on dolomites show a similar relation between sr content and major element composition suggesting that these dolomites may also have formed from seawater other data sets deviate from the correlation defined by little bahama bank dolomites indicating either dolomitization in fluids other than seawater or changes ofmore the sr sup 2 ca sup 2 ratio of seawater through time less

on the formation of collapse dolines a modelling perspective abstract collapse dolines are among the most striking surface features in karst areas although they can be the result of different formation mechanisms evidence suggests that large collapse dolines form due to chemical and mechanical removal of material at and below the level of groundwater we have applied a genetic model of a two dimensional fracture network to calculate the rate of dissolutional bedrock removal in the heavily fractured crushed zone intersecting a karst conduit in the phreatic zone to account for infilling and breakdown processes in the crushed zone two simple rules were added to the basic model 1 continuous infilling of dissolutionally created voids prevents fractures from growing beyond some limited aperture although the dissolution proceeds 2 discontinuous collapsing causes sudden closure of a fracture once some critical aperture has been reached both rules limit the transmissivity of the network and the related flow rates therefore the constant head difference between the input and the output points is sustained and the flow remains distributed over the entire crushed zone provided that restrictions posed by the two rules permit turbulent flow dissolution rates also remain high in the entire region high surface area of water rock contact and high dissolution rates result in high overall removal rates of rock from the crushed zone one of the necessary conditions for the formation of large closed depressions despite the fact that the model neglects some processes and dynamics that would increase the removal rate the results suggest that large closed depressions could form in the order of 1 million years

modeling spatially and temporally varied hydraulic behavior of a folded karst system with dominant conduit drainage at catchment scale hochifen gottesacker alps summary karst aquifers are important for freshwater supply but difficult to manage due to highly variable water levels and spring discharge rates conduits are crucial for groundwater flow in karst aquifers but their location is often unknown thus limiting the applicability and validity of numerical models we have applied a conduit model swmm to simulate highly variable flow in a folded alpine karst aquifer system where the underground drainage pattern is comparatively well known from previous tracer studies the conduit model was coupled with a reservoir model representing recharge storage and transfer of water in the epikarst and unsaturated zone the global optimization approach ga was applied to achieve an efficient model calibration it was possible to simultaneously simulate the highly variable discharge characteristics of an estavelle and overflow spring and a permanent spring draining the conduit system the model allowed for the collection of spatially differentiated information on recharge rapid flow and slow flow in four individual sub catchments the formation of backwater upgradient from conduit restrictions turned out to be a key process in activating overflow springs the proposed modeling approach appears to be transferrable to other karst systems with predominant conduit drainage but requires previous knowledge of the configuration of the conduit system

identifying the characteristics of groundwater flow in the classical karst area slovenia italy by means of tracer tests tracer tests are a widely used research method in karst hydrology in the classical karst area on the border between slovenia and italy they have a long history and for the most part they have been used to research the underground flow in the main karst conduits between the ponors and the springs the results of the tracer test from 2013 presented in the article revealed new knowledge about the central part of the aquifer less well researched to date where the density of caves and the level of karstification are lower two tracers uranine and amidorhodamine g were used at two injection points a research borehole in the central part of the aquifer and the karst surface at a distance of 2 5 km from a drinking water pumping station and six springs a pumping station three boreholes and four karst caves were observed for tracer breakthrough for a full year after injection the results were compared with findings from three other selected older tracer tests in which uranine was likewise used as a tracer but where hydrological conditions varied very low low and medium water levels as did the methods of injecting tracer in a sinking stream in a fracture on the karst surface the comparison showed how different modes of aquifer recharge and the heterogeneity of aquifer structure affect the characteristics of water flow and solute transport in complex karst aquifers

looping caves versus water table caves the role of base level changes and recharge variations in cave development abstract the vertical organisation of karst conduit networks has been the focus of speleogenetic studies for more than a century the four state model of ford and ewers 1978 which still is considered as the most general relates the geometry of caves to the frequency of permeable fissures the model suggests that the water table caves are common in areas with high fissure frequency which is often the case in natural settings however in alpine karst systems water table caves are more the exception than the rule alpine speleogenesis is influenced by high uplift valley incision rates and irregular recharge to study the potential role of these processes for speleogenesis in the dimensions of length and depth we apply a simple mathematical model based on coupling of flow dissolution and transport we assume a master conduit draining the water to the spring at a base level incision of the valley triggers evolution of deeper flow pathways which are initially in a proto conduit state the master conduit evolves into a canyon following the valley incision while the deep pathways evolve towards maturity and tend to capture the water from the master conduits two outcomes are possible a deep pathways evolve fast enough to capture all the recharge leaving the master conduit dry or b the canyon reaches the level of deep pathways before these evolve to maturity we introduce the loop to canyon ratio lcr which predicts which of the two outcomes is more likely to occur in certain settings our model is extended to account for transient flow conditions in the case of an undulating master conduit floodwater is stored in troughs after the flood retreat this water seeps through sub vertical fractures soutirages connecting the master conduit with the deep pathways therefore the loops evolve also during the dry season and the lcr is considerably increased although the model is based on several approximations it leads to some important conclusions for vertical organisation of karst conduit networks and stresses the importance of base level changes and transient recharge conditions it therefore gives an explanation of speleogenesis that relies much more on the dynamic nature of water flow than on the static fracture density

halogens cl br and i geochemistry in middle triassic carbonates implications for salinity and diagenetic alteration of i ca mg ratios abstract as an important family of elements halogens cl br and i have been widely used to study geological processes particularly in high temperature environments showing great prospects either in fundamental or in applied studies however little work has been conducted for sedimentary and low temperature diagenetic environments re construction although these elements have the potential in theory here we perform a pilot study on this issue using a case study of middle triassic marine dolomitization in south china our results show that the average cl concentrations in limestone dolomitic limestone calcitic dolomite and dolomite are 88 3 ppm 114 7 ppm 121 3 ppm and 142 9 ppm respectively and the corresponding br concentrations are 1 15 ppm 1 42 ppm 1 59 ppm and 2 13 ppm respectively both the concentrations of cl and br increased with the increasing dolomitization degree the increasing tendency of cl and br is similar to the seawater evaporation trajectory before halite precipitation indicating that dolomitization occurs in fluids with elevated salinity meanwhile the difference of cl br ratios between our carbonate samples and seawater may be ascribed to the input of terrestrial water which has variable cl br ratios as for the concentration of i the mean values sharply decreased from 0 36 ppm in limestone to 0 13 ppm in dolomitic limestone samples and it further lowered to 0 09 ppm and 0 08 ppm in calcitic dolomite and dolomite samples respectively the calculated i ca mg ratios in limestones vary between 0 05 and 0 58 mol mol with an average value of 0 29 mol mol indicating that limestone formed in open ocean oxygen minimum zone omzs or anoxic basin environment the average i ca mg ratio decreases from 0 29 mol mol in limestone to 0 06 mol mol in dolomite serving as an important case that dolomitization decreases i ca mg ratios of carbonates rocks halogens in carbonates therefore have promising potential for investigating the sedimentary and diagenetic environments of carbonate rocks

brine rock interaction in the athabasca basement mcarthur river u deposit canada consequences for fluid chemistry and uranium uptake terra nova 22 303 308 2010 abstract the nature of uranium source rocks transport conditions and deposition processes are still highly controversial for world class unconformity related u deposits this article presents the first detailed chemistry of brines associated with the giant mcarthur river u deposit canada la icp ms analysis of individual fluid inclusions suggests mixing between a na ca mg k sr ba brine and a ca mg na k sr ba brine the brines share a common origin evaporated seawater and show evidence for contrasting interaction with basement rocks the na rich brine lost mg and k in alteration haloes around u ores while the ca rich brine results from na ca exchange and sr ba gain u concentrations 0 3 530 g g 1 are anomalously high compared with usual basinal fluids this indicating that u uptake occurred within basement rocks the two brine end members have mixed within the main u deposit area which could be one of the major driving forces for u deposition

cl br ratios and stable chlorine isotope analysis of magmatic hydrothermal fluid inclusions from butte montana and bingham canyon utah a bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry cu deposits in butte montana usa and bingham canyon utah usa the leachates mostly represent low salinity magmatic hydrothermal fluid inclusions their halogen ratios br cl of fluid inclusion leachates were determined by ion chromatography and 37cl values of the leachates were measured by continuous flow isotope ratio mass spectrometry br cl ratios from early pre main stage and later main stage veins at butte range from 0 60 to 1 88 10 3 m ratios are similar in pre main stage veins with sericite bearing selvages and main stage samples ranging from 0 81 to 1 08 10 3 and from 0 92 to 1 88 10 3 m respectively clustering below seawater 1 54 10 3 m and overlapping mantle values 1 2 10 3 m two samples associated with early pre main stage potassic alteration yield distinctly lower br cl ratios of 0 60 and 0 64 10 3 m butte 37cl values range from 0 8 to 2 3 with no significant difference between pre main stage and main stage samples br cl ratios for quartz veins from bingham canyon range from 0 18 to 3 68 10 3 m br cl ratios from bingham range above and below previously reported for porphyry copper deposits in contrast to butte 37cl values for bingham are lower ranging from 0 9 to 4 1 in the absence of any processes which can significantly fractionate chlorine isotopes at high temperatures we suggest that the porphyry system at bingham and to a lesser extent at butte have inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures

a triassic homoclinal ramp from the western tethyan realm western balkanides bulgaria integrated insight with special emphasis on the anisian outer to inner ramp facies transition abstract the triassic carbonate succession exposed in the western balkanides is analyzed in terms of depositional evolution sequence stratigraphy sedimentation rate environmental constraints and biota distribution deposition took place on a storm dominated ramp which existed at the nw end of the tethys ocean from late olenekian to early carnian time subtidal intertidal and supratidal sediments were accumulated in three zones of the ramp profile inner ramp mid ramp and outer ramp the calculated average sedimentation rate is typical for other ancient marine shallow water carbonates including those deposited on ramps newly accomplished sedimentological study on part of the anisian interval reveals a homoclinal ramp model with episodic initial distal steepening two main phases of the ramp evolution are distinguished on the basis of changing relative paleobathymetry transgressive e g retrogradational depositional trend and regressive e g progradational depositional trend the maximum flooding zone is marked by the terebratula beds having late pelsonian age the inferred environmental constraints of the ramp system comprise normal marine to hypersalinity warm well illuminated water aerobic and rarely dysaerobic bottom conditions dominantly soft lime mud substrate intensive storm activity temporal seismic influence presumably related to early triassic rifting the vertical distribution of marine fauna indicates shifting from germanic peri tethyan affinity to alpine tethyan affinity in anisian time the sedimentation was not characterized by formation of large buildups because of the paucity or lack of metazoan and other reef builders the studied rocks are well correlated with the triassic ramp succession outcropping in the tizsa meagunit of southern hungary similarities to the german polish and spanish muschelkalk are also clearly outlined and some parallel can be drawn with other platform carbonates from the nw tethys shelf area and peri tethys basins

hydraulics of epiphreatic flow of a karst aquifer abstract the nature of epiphreatic flow remains an important research challenge in karst hydrology this study focuses on the flood propagation along the epiphreatic system of reka timavo system kras carso plateau slovenia italy it is based on long term monitoring of basic physical parameters pressure level temperature specific electric conductivity of ground water in six active caves belonging to the flow system the system vigorously responds to flood events with stage rising 100 m in some of the caves besides presenting the response of the system to flood events of different scales the work focuses on the interpretation of recorded hydrographs in view of the known distribution and size of conduits and basic hydraulic relations furthermore the hydrographs were used to infer the unknown geometry between the observation points this way the main flow restrictors overflow passages and large epiphreatic storages were identified the assumptions were tested with a hydraulic model where the inversion procedure was used for an additional parameter optimisation time series of temperature and specific electric conductivity were used to assess the apparent velocities of flow between consecutive points

modelling spring discharge and solute transport in conduits by coupling cfpv2 to an epikarst reservoir for a karst aquifer abstract karst aquifers differ from unconsolidated granular aquifers with respect to their groundwater flow behavior because of the dual permeability characteristics discrete conduit network coupled to a fissured matrix the duality of recharge point vs diffuse recharge as well as the duality of flow laminar vs turbulent state in many karst aquifers the epikarst frequently plays an important role in redistributing precipitation as diffuse recharge into the fissured matrix and as point recharge into the conduit network as well as for the temporal distribution of recharge input in this paper a coupled groundwater model ce cfpv2 erch is developed consisting of a combination of a simple reservoir model generating the recharge source function assuming the concept of an epikarst horizon erch with cfpv2 a discrete conduit continuum groundwater flow model of the phreatic karst aquifer the ce model is applied to simulate spring discharge and a tracer breakthrough in a karst aquifer near guilin city in southwest china in order to examine the effect of an added epikarst reservoir model simulations are carried out with cfpv2 but without including erch simulation results of both spring hydrograph and tracer breakthrough indicate that cfpv2 with erch performs much better a sensitivity analysis of the ce reveals the relative importance of parameters characterizing the epikarst reservoir point recharge is a main factor determining the large variation in spring discharge and its proportion to total recharge can reach 58 these simulation results highlight the importance of the temporal and spatial distribution of recharge to karst spring discharge response the coupled model provides an effective approach to include the effect of an epikarst zone in cfpv2 and it can easily be applied for the simulation of karst aquifers with similar characteristics as the study site

mechanisms of heat exchange between water and rock in karst conduits 1 previous studies motivated by understanding water quality have explored the mechanisms for heat transport and heat exchange in surface streams in karst aquifers temperature signals play an additional important role since they carry information about internal aquifer structures models for heat transport in karst conduits have previously been developed however these models make different sometimes contradictory assumptions additionally previous models of heat transport in karst conduits have not been validated using field data from conduits with known geometries here we use analytical solutions of heat transfer to examine the relative importance of heat exchange mechanisms and the validity of the assumptions made by previous models the relative importance of convection conduction and radiation is a function of time using a characteristic timescale we show that models neglecting rock conduction produce spurious results in realistic cases in contrast to the behavior of surface streams where conduction is often negligible conduction through the rock surrounding a conduit determines heat flux at timescales of weeks and longer in open channel conduits radiative heat flux can be significant in contrast convective heat exchange through the conduit air is often negligible using the rules derived from our analytical analysis we develop a numerical model for heat transport in a karst conduit our model compares favorably to thermal responses observed in two different karst settings a cave stream fed via autogenic recharge during a snowmelt event and an allogenically recharged cave stream that experiences continuous temperature fluctuations on many timescales

preliminary evidence for fractionation of stable chlorine isotopes in ore forming hydrothermal systems chloride from fluid inclusions in hydrothermal minerals is found to have variable and distinctive delta sup 37 cl values spanning the range 1 1 0 per thousand to 0 8 per thousand in mississippi valley type deposits of tennessee brines of high 0 per thousand and low near 1 per thousand delta sup 37 cl are present high delta sup 37 cl brines may be saline formation waters but low delta sup 37 cl brines remain unexplained in porphyry copper deposits both high delta sup 37 cl 0 8 per thousand 0 3 per thousand and low delta sup 37 cl 1 1 per thousand 0 7 per thousand hypersaline brines of probable magmatic origin occur high salinity magmatic brines with low delta sup 37 cl values contrast isotopically with high delta sup 37 cl less concentrated brines responsible for quartz sericite pyrite assemblages

understanding flooding in poljes a modelling perspective abstract poljes are large flat closed depressions that can be found in most karst areas around the world they are prone to regular flooding which occurs after abundant rainfall or snowmelt events the floods can form several meters deep intermittent lakes that can persist for months human settlements around poljes have been traditionally positioned above the level of the most severe floods however many neighbouring villages expanded during the last decades to areas that might be endangered by large flood events in addition a recent study has shown that several poljes encountered floods of more severe amplitude in mid holocene due to a prevailing humid climate as current knowledge of polje s hydrology appears to be still insufficient further research is needed this work aims to identify the factors controlling polje flooding and evaluates their impact on the flood amplitude and duration to do so a list of parameters potentially controlling flooding is established the relevance of each parameter is tested by using two idealized numerical models the first one considers exclusively the polje from the springs to the ponors whereas the second integrates the aquifer adjacent to the polje outflow side first results show the usefulness of simple numerical models to identify the effect of each parameter on the flood amplitude and duration the findings are combined to simulate a flood of medium intensity and long duration that occurred on a typical polje a comparison of the results with real data demonstrates that the aquifer draining the polje needs to be considered to understand properly the flooding dynamics the approach presented within this work has the potential to be used in other poljes encountering similar hydrological situations but also lays foundation for flooding modelling in other karst areas

modeling of storm responses in conduit flow aquifers with reservoirs abstract in aquifers containing large voids such as karst aquifers with caves or basaltic aquifers with lava tubes hydrographs at wells or springs are used to analyze the structure and response of the hydrogeological system numerical modeling of hydrograph response is commonly based on either inverse techniques or postulated flow geometries however the range of mechanisms for generating hydrograph responses have not been fully investigated physical modeling of these complex non darcian systems permits better understanding of the storm responses that conduit systems may generate using a numerical model of conduit flow systems which incorporates turbulent flow some of the mechanisms that can alter storm pulses were investigated by treating them as combinations of pipes that connect reservoirs the results indicate that the response of a conduit flow aquifer can range from what has been called diffuse or steady to conduit or flashy without employing a diffusive component a full range of behavior can be the result of changes from phreatic to epiphreatic conditions in a conduit changes in conduit geometry or multiple springs draining the same system the results provide a quantitative tool to assess spring and well hydrographs and illustrate mechanisms that can generate observed responses which have previously been qualitatively interpreted