the mechanism of surtseyan volcanism during eruption the vent of a surtseyan volcano is occupied by a highly mobile slurry of tephra hyaloclastite and water as magma ascends rapidly through the slurry mixing occurs due to velocity shear acceleration of the fluid fluid contacts and mass incorporation consequent expansion of the admixed water causes the jetting and continuous up rush activity that characterizes surtseyan volcanism there is no evidence of the widely accepted fuel coolant interaction mechanism

evidence for the silicate source of relict soils on the edwards plateau central texas relict soils provide insights into quaternary soil formation and erosion on the edwards plateau of central texas and into soil forming processes in karst terranes late quaternary climate driven soil erosion produced a mosaic of thick and thin soils on the edwards plateau landscape thick soils on uplands of the edwards plateau are interpreted to be relicts of a formerly more extensive soil cover that was eroded during the late pleistocene to middle holocene the relict thick soils are silicate rich and most commonly overlie the relatively silicate poor cretaceous edwards limestone which supports the idea that the thick soils did not form from weathering of the underlying limestone other potential sources of silicates for the relict soils include dust alluvial sediments and the del rio clay a stratigraphically higher but locally eroded clay rich unit here we investigate the geographic distribution texture clay sized mineralogy rare earth element geochemistry and neodymium isotope composition of the relict soils we have found that the relict thick soils are deeply weathered soils that occur dominantly over the edwards limestone and have a high clay content and a neodymium isotope composition that is similar to that of the del rio clay thus we propose that in situ weathering of the del rio clay along with partial weathering of the upper portion of the underlying edwards limestone produced thick chert and clay rich soils over resistant limestone in areas like the edwards plateau where pure limestones are interbedded with clay rich strata the overlying clay rich strata must be considered as a possible silicate source to soils on pure limestone bedrock

effect of regional topography and hydrology on the lacustrine isotopic record of miocene paleoclimate in the rocky mountains drummond c n wilkinson b h lohmann k c and smith g r 1993 effect of regional topography and hydrology on the lacustrine isotopic record of miocene paleoclimate in the rocky mountains palaeogeogr palaeoclimatol palaeoecol 101 67 79 oxygen isotopic compositions of upper miocene 9 2 m y lacustrine limestone from northwestern wyoming range from 21 5 to 35 2 0 pdb and are the lightest yet reported for a non marine carbonate sequence these values require that lake water was greatly depleted in 180 relative to modern meteoric precipitation and indicate that most inflow was sourced as meltwater from glaciers in the adjacent gros ventre range assessment of climatic factors influencing the isotopic composition of global meteoric water indicates either that nearly all of miocene precipitation in the southern rocky mountains was derived from large lake systems in the snake river plain and northern great basin to the west or that gros ventre catchment elevations were up to 2300 m higher than at present because erosion rates in modern alpine regions suggest that subaerial denudation could only account for up to 1200 m of post miocene elevation reduction any additional lowering must reflect the influence of post laramide epeirogeny during basin and range extensional tectonism lacustrine isotopic data therefore provide boundary conditions on the timing and magnitude of changes in late cenozoic paleoclimate topography hydrology and tectonism in the western wyoming portion of the rocky mountains

characterisation and modelling of conduit restricted karst aquifers example of the auja spring jordan valley summary the conduit system of mature karstified carbonate aquifers is typically characterised by a high hydraulic conductivity and does not impose a major flow constriction on catchment discharge as a result discharge at karst springs is usually flashy and displays pronounced peaks following recharge events in contrast some karst springs reported in literature display a discharge maximum attributed to reaching the finite discharge capacity of the conduit system flow threshold this phenomenon also often leads to a non standard recession behaviour a so called convex recession i e an increase in the recession coefficient during flow recession which in turn might be used as an indicator for conduit restricted aquifers the main objective of the study is the characterisation and modelling of those hydrogeologically challenging aquifers the applied approach consists of a combination of hydrometric monitoring a spring hydrograph recession and event analysis as well as the setup and calibration of a non linear reservoir model it is demonstrated for the auja spring the largest freshwater spring in the lower jordan valley the semi arid environment with its short but intensive precipitation events and an extended dry season leads to sharp input signals and undisturbed recession periods the spring displays complex recession behaviour exhibiting exponential coefficient and linear coefficient recession periods numerous different recession coefficients were observed 0 2 to 0 8 d 1 presumably main conduit system 0 004 d 1 fractured matrix 0 0009 d 1 plateau caused by flow threshold being exceeded plus many intermediate values the reasons for this observed behaviour are the outflow threshold at 0 47 m 3 s 1 and a variable conduit matrix cross flow in the aquifer despite system complexity and hence the necessity of incorporating features such as a flow threshold conduit matrix cross flow and a spatially variable soil epikarst field capacity the developed reservoir model is regarded as relatively simplistic as a number of required parameters were calculated from the hydrogeological analysis of the system it requires only six calibration parameters and performs well for the highly variable flow conditions observed calculated groundwater recharge in this semi arid environment displays high interannual variability for example during the 45 year simulation period only five wet winter seasons account for 33 of the total cumulative groundwater recharge

mechanisms of hydrovolcanic pyroclast formation grain size scanning electron microscopy and experimental studies pyroclasts produced by explosive magma water interactions are of various sizes and shapes data from analysis of over 200 samples of hydrovolcanic ash are interpreted by comparison with experimentally produced ash grain size and scanning electron microscopy sem reveal information on the formation of hydrovolcanic pyroclasts strombolian explosions result from limited water interaction with magma and the pyroclasts produced are dominantly centimeter sized with increasing water interaction hydrovolcanism increases in explosivity to surtseyan and vulcanian activity these eruptions produce millimeter to micron sized pyroclasts the abundance of fine ash 63 m diameter increases from 5 to over 30 percent as water interaction reaches an explosive maximum this maximum occurs with interactions of virtually equal volumes of melt and water five dominant pyroclast shape types determined by sem result from hydrovolcanic fragmentation 1 blocky and equant 2 vesicular and irregular with smooth surfaces 3 moss like and convoluted 4 spherical or drop like and 5 plate like types 1 and 2 dominate pyroclasts greater than 100 m in diameter types 3 and 4 are typical of fine ash type 5 pyroclasts characterize ash less than 100 m in diameter resulting from hydrovolcanic fragmentation after strong vesiculation fragmentation mechanisms observed in experimental melt water interactions result from vapor film generation expansion and collapse fragments of congealed melt are products of several alternative mechanisms including stress wave cavitation detonation waves and fluid instability mixing all result in rapid heat transfer these mechanisms can explain the five observed pyroclast shapes stress wave fracturing cavitation of the melt results from high pressure and temperature gradients at the melt water interface simultaneous brittle fracture and quenching produces type 1 pyroclasts type 2 develops smooth fused surfaces due to turbulent mixing with water after fracture and before quenching fluid instabilities promote turbulent mixing of melt and water and produce fine ash this kind of fragmentation occurs during high energy explosions the increased melt surface area due to fine fragmentation promotes high efficiency heat exchange between the melt and water shapes of resulting pyroclasts are determined by maximum surface area type 3 and surface tension effects type 4 type 5 pyroclasts result from nearly simultaneous vesicle burst and melt water fragmentation

nearshore carbonate deposits in lake tanganyika an exceptionally wide variety of carbonate fades dominated by high magnesian calcite occurs along the littoral and shallow sublittoral zones 50 m of lake tanganyika in central africa these facies include exposed and submerged calcite cemented ridges of nearshore terrigenous sand ooid sand shoals and lithified oolite ridges chara meadows of bioturbated calcareous silts gastropod shell blankets and related coquinas and extensive thrombolitic microbial reefs though texturally and compositionally similar to many modern and ancient shallow water marine facies these deposits record carbonate deposition and cementation in a large tropical deep water lake of tectonic origin lithofacies along lake tanganyika represent the broadest spectrum of carbonate deposits yet reported from any modern lake and serve as important analogues for lacustrine carbonate sequences in the stratigraphic record

folding with thermal mechanical feedback discussion abstract a recent paper in this journal by bruce hobbs klaus regenauer lieb and alison ord hobbs b regenauer lieb k ord a 2008 folding with thermal mechanical feedback journal of structural geology 30 1572 1592 presents an alternative theory to the traditional biot ramberg theory for folding of viscous rocks that involves non equilibrium thermodynamics and thermal mechanical feedback the authors convey a strong message throughout their paper that the folds produced by this theoretical and numerical modelling are geologically realistic and provide a better explanation for many natural folds than the traditional theory they promise the same approach for boudinage and present this folding paper as part of a unified framework for rock deformation processes readers of the journal of structural geology might be led to conclude that this paper provides a good alternative model for folding of rocks our discussion will disagree on four counts

numerical simulations of parasitic folding in multilayers we use the finite element method to simulate slow viscous newtonian flow in two dimensions without gravity and to model asymmetric sand z shaped and symmetric m shaped parasitic folds during multilayer folding during multilayer folding the matrix between stiffer layers shows a deformation close to pure shear in the hinge area and a combination of pure and simple shear in the limb areas thinner layers placed between thicker layers develop symmetric parasitic folds in the hinge and eventually asymmetric parasitic folds in the limbs of the larger fold our results verify numerically the theory that asymmetric parasitic folds develop from symmetric buckle folds that are sheared by the hingeward relative displacement of the thick layers in the limbs of the first order fold to develop asymmetric shapes the amplitudes of the parasitic folds must exceed a critical value before the first order fold begins to amplify otherwise the parasitic folds are unfolded during flattening that takes place in the limb area between the thick layers more than five thin layers are necessary to generate distinct asymmetric parasitic folds for the applied model setting more layers generate higher amplification rates in the thin layers and hence higher amplitudes 2006 elsevier ltd all rights reserved

composite tuff ring cone complexes in jeju island korea possible consequences of substrate collapse and vent migration hydromagmatic volcanoes tuff rings and tuff cones in jeju island korea are divided into holocene volcanoes that were constructed upon rigid plateau forming lavas and early to middle pleistocene volcanoes that underlie the lavas and were constructed upon fragile unconsolidated sediments the older volcanoes are distinguished from the holocene volcanoes in that the former have irregular morphologies the irregular morphologies resulted from superposition or juxtaposition of multiple rim deposits of partial tuff rings and or tuff cones that have contrasting lithofacies characteristics bed attitudes and paleoflow directions the rim deposits are bounded by laterally persistent truncation surfaces which suggest large scale collapse of the substrate together with the overlying tephra piles and or erosion during a break in eruptive activity collapse was probably caused by the instability of the friable sedimentary substrate removal of lateral support because of downward quarrying of volcanic conduits and liquefaction of the water saturated substrate by volcanic seismicity the path of magma supply was diverted in some cases after collapse giving rise to migration of the active vent in other cases the eruption style changed abruptly from cone forming fallout dominated to ring forming surge dominated eruptions after collapse the resultant volcanic edifices thus consist of multiple rim beds of partial tuff rings and or tuff cones commonly with non circular morphologies substrate collapse and lateral vent migration as observed in jeju island appears to be an important phenomenon in hydromagmatic volcanoes because they are commonly constructed upon unstable sedimentary substrates substrate collapse and vent migration needs to be taken into account as an important control on volcano morphology and structures and as a means of lateral enlargement of terrestrial submarine or extraterrestrial volcanoes

el nino southern oscillation pliocene climate and equifinality it has been suggested that during the pliocene ca 5 1 8ma an el nino state existed as a permanent rather than an intermittent feature that is the tropical pacific ocean was characterized by a much weaker east west gradient than today one line of inquiry used to investigate this idea relates modern el nino teleconnections to pliocene proxy data by comparing regional differences in precipitation and surface temperature with climate patterns associated with present day el nino events assuming that agreement between pliocene data and observations of modern el nino events supports this interpretation here we examine this assumption by comparing outputs from a suite of mid pliocene climate simulations carried out with the uk met office climate model regional patterns of climate change associated with changes in model boundary conditions are compared with observed el nino southern oscillation teleconnection patterns our results indicate that many of the proposed permanent el nino surface temperature and precipitation patterns are observable in mid pliocene climate simulations even when they display variability in tropical pacific sea surface temperatures ssts or when forced with a modern east west sst gradient our experiments highlight the possibility that the same outcome may be achieved through different initial conditions equifinality an important consideration for reconstructed patterns of regional mid pliocene climate

the cenozoic climatic and topographic evolution of the western north american cordillera herein we present oxygen isotope records from cretaceous to recent terrestrial sediments in the western north american cordillera the purpose of this analysis is to use oxygen isotope records to understand the coupled surface elevation and climate histories of this region through the cenozoic to do this we constructed 18o maps of surface waters for time intervals that trace the development of topography of western north america these maps are based on 4861 oxygen isotope analyses from both published 4478 and new 383 data we determined the 18o values of surface waters using paleotemperatures derived previously from floral assemblages and the appropriate isotope fractionation factors these data suggest that in the late cretaceous to early eocene the sevier hinterland formed a plateau of unknown height around 50 ma a topographic wave developed in british columbia and eastern washington that swept southward reaching northeastern nevada at 40 to 38 ma and southern nevada 23 ma this southward encroachment of an eocene plateau sweep caused reorganization of drainage patterns such that the intraforeland basins of wyoming and utah drainages extended deep within the sevier hinterland as the wave swept southward the landscape within the sevier hinterland developed into a rugged and high mountain range with the hypsometric mean elevation of 4 km and relief of 1 5 km this eocene highland was bordered on the west by a high sierra nevada ramp and on the east by the intraforeland basins that captured water draining these growing highlands the spatial and temporal evolution of this highland correlates with the timing of volcanism and extension these observations support tectonic models that call for north to south removal of the farallon slab or piecemeal removal of mantle lithosphere the isotopic data show that prior to growth of this highland the north american monsoon nam penetrated much farther north in the paleocene eocene than today the combined effects of global cooling increasing latitudinal temperature gradients and the generation of the orographic barrier created by the growing north to south highland produced a southward migration of the nam front by the oligocene the hydrologic regime that we observe today was in place it has been modified since then as a result of basin and range extension and collapse of the highlands in the mid miocene this collapse allowed the nam to penetrate farther north into the great basin of nevada and utah

exchange of water between conduits and matrix in the floridan aquifer flow through carbonate aquifers may be dominated by conduits where they are present by intergranular or fracture porosity where conduits are missing or may occur in conduits and matrix porosity where both are well developed in the latter case the exchange of water between conduits and matrix could have important implications for water management and hydrodynamic modeling an extensive conduit system has been mapped by dye trace studies and cave diving exploration at the santa fe sinkrrise system located in largely unaltered rocks of the floridan aquifer of north central florida in this area the santa fe river flows underground at the river sink and returns to the surface 5 km to the south at a first magnitude spring called the river rise limited data show that discharge is greater by 27 96 at the river rise than at the sink and that the downstream increase in discharge is inversely related to discharge of the river natural so 2y 4 concentrations indicate that 25 of the water discharging from the rise originates from the sink during low flow conversely so 2y and other solute concentrations indicate that most of the water discharging from the rise originates from 4 the sink during floods ar 40 decrease in na q and cl y concentrations over a 5 1r2 month period at a down gradient water supply well may reflect flow of dilute flood water from the conduits into and through the matrix at rates estimated to be between 9 and 65 mrday calcium concentrations remain constant through time at the well although flood waters have 90 lower ca 2q concentrations than ground water perhaps reflecting dissolution of the matrix rocks this apparent exchange of water between matrix and conduits is important for regional ground water quality and dissolution reactions q 2001 published by elsevier science b v

fish fossils as paleo indicators of ichthyofauna composition and climatic change in lake malawi africa abstract numerous biological and chemical paleorecords have been used to infer paleoclimate lake level fluctuation and faunal composition from the drill cores obtained from lake malawi africa however fish fossils have never been used to examine changes in african great lake vertebrate aquatic communities nor as indicators of changing paleolimnological conditions here we present results of analyses of a lake malawi core dating back 144 ka that describe and quantify the composition and abundance of fish fossils and report on stable carbon isotopic data 13c from fish scale bone and tooth fossils we compared the fossil 13c values to 13c values from extant fish communities to determine whether carbon isotope ratios can be used as indicators of inshore versus offshore pelagic fish assemblages fossil buccal teeth pharyngeal teeth and mills vertebra and scales from the fish families cichlidae and cyprinidae occur in variable abundance throughout the core carbon isotopic ratios from numerous fish fossils throughout the core range between 7 2 and 27 5 similar to those found in contemporary lake malawi benthic and pelagic fish faunas these results are the first paleo record of fish fossils from a lake malawi sediment core and the first reported 13c values from lake malawi fish fossils this approach provides a new methodology and framework for interpreting pelagic versus inshore fish faunas lake level fluctuations and the evolution of the lake malawi fish assemblages

contrasting types of surtseyan tuff cones on marion and prince edward islands southwest indian ocean ten surtseyan tuff cones on marion island 46 54 s 37 46 e and seven on prince edward island 46 38 s 37 57 e were erupted on shallow submerged coastal plains related to normal faulting they range from pleistocene to holocene in age and exhibit a variable degree of erosion by the sea fundamental differences irrespective of age exist between two types type i cones have diameters of 1 1 5 km rim heights of about 200 m and steep 27 outer slopes deposits are plastered against nearby cliffs beds are thin including layers of accretionary lapilli and less than 10 lithic clasts numerous bomb sags soft sediment deformation structures and gravity slides occur on one of these cones mudflows formed small tunnels which resemble lava tubes associated with channels sometimes having oversteepened walls these cones reflect comparatively low energy conditions and probably resulted from extremely wet surges interspersed with mudflows and ballistic falls type ii cones have smaller diameters 0 5 km but widespread fallout surge aprons rim heights are about 100 m and average slope angles are 18 bedding is massive with variable lapilli matrix ratio and more than 10 lithic clasts without bomb sags these cones formed under drier perhaps hotter and more violently explosive conditions than type i though not as energetic as the phreatomagmatic eruptions of terrestrial tuff rings the two types of surtseyan eruptions are explained by invoking not only different water magma ratios in the conduit but also different mechanisms of water magma interaction the slurry model of kokelaar is favoured for type i and a fuel coolant model for type ii the decisive factor is considered to be rate of effusion with rim closure and exclusion of sea water playing a secondary role

depositional processes of the suwolbong tuff ring cheju island korea the suwolbong pyroclastic sequence in the western part of cheju island korea comprises partly preserved rim beds of a quaternary basaltic tuff ring whose vent lies about 1 km seaward of the present shoreline the sequence consists of breccia lapillistone lapilli tuff and tuff eighteen sedimentary facies are established and organized into six lateral facies sequences lfs and seven vertical facies sequences vfs the lfs 1 4 and 5 begin with massive lapilli tuff which transforms downcurrent into either planar bedded lfs 1 undulatory bedded lfs 4 or climbing dune bedded lfs 5 lapilli tuff units they are representative of relatively dry base surge whose particle concentration decreases downcurrent with a progressive increase in both tractional processes and sorting the lfs 2 begins with disorganized and massive lapilli tuff and transforms into crudely stratified units downcurrent it results from relatively wet base surge in which sorting is poor due to the cohesion of damp ash the lfs 3 comprises well sorted lapilli tuff and stratified tuff further downcurrent suggestive of deposition from combined fall and surge of relatively dry hydroclastic eruption all seven vertical facies sequences generally comprise two facies units of coarse grained fines depleted lapilli tuff and an overlying fine grained tuff these sequences are suggestive of deposition from base surge that consists of a turbulent head and a low concentration tail depositional processes in the suwolbong tuff ring were dominated by a relatively dry base surge the base surge comprises turbulent and high concentration suspension near the vent whose deposits are generally unstratified due to the lack of tractional transport as the base surge becomes diluted downcurrent through fallout of clasts and mixing of ambient air it develops large scale turbulent eddies and is segregated into coarse grained bedload and overlying fine grained suspension forming thinly stratified units further downcurrent the base surge may be either cooled and deflated or pushed up into the air depending on its temperature the suwolbong tuff ring comprises an overall wet to dry cycle with several dry to wet cycles in it suggestive of overall decrease in abundance of external water and fluctuation in the rate of magma rise

vertical and lateral distribution of lacustrine carbonate lithofacies at the parasequence scale in the miocene hot spring limestone idaho an analog addressing reservoir presence and quality lacustrine carbonate lithofacies in the hot spring limestone vary systematically at meter to decameter scales and record paleobathymetry limnologic conditions and paleogeographic influences this unit accumulated during the late miocene in a lake system in an extensional basin complex closely associated with lava flows and volcaniclastics sedimentology and sequence stratigraphy enable understanding and prediction of the occurrence distribution and character of lacustrine carbonates occurrence of lacustrine carbonates is a function of lake basin type in this case a volcanically mediated balanced filled lake basin that contains various lithofacies microbialite grainstone packstone wackestone and carbonate mudstone distribution of lithofacies is strongly controlled by depositional subenvironment and gradient through water depth bottom energy circulation and accommodation internal character of microbialites i e type size porosity vertical and horizontal permeability associated lithotypes diagenesis is influenced by stratal position at the parasequence scale and location along the depositional profile depositional reservoir quality characteristics such as microbialite porosity and thickness grainstone size and sorting and overall carbonate continuity and connectivity peak in the medial sublittoral zone conversely secondary diagenetic effects such as dissolution carbonate and quartz cement and possible authigenic clays are highest in the updip lake plain littoral zones and are less common lakeward thus the medial sublittoral zone has the optimum potential where primary depositional characteristics are best developed and negative secondary diagenetic effects are minimal these strata share many attributes with the cretaceous presalt systems of the south atlantic and can provide insights about controls on potential reservoir character distribution and connectivity for exploration and development

seasonal dripwater mg ca and sr ca variations driven by cave ventilation implications for and modeling of speleothem paleoclimate records a 4 year study in a central texas cave quantifies multiple mechanisms that control dripwater composition and how these mechanisms vary at different drip sites we monitored cave air compositions in situ calcite growth dripwater composition and drip rate every 4 6 weeks three groups of drip sites are delineated groups 1 3 based on geochemical variations in dripwater composition quantitative modeling of mineral solution reactions within the host carbonate rock and cave environments is used to identify mechanisms that can account for variations in dripwater compositions the covariation of mg ca and sr ca and sr isotopes is key in delineating whether mg ca and sr ca variations are dictated by water rock interaction i e calcite or dolomite recrystallization or prior calcite precipitation pcp group 1 dripwater compositions reflects a narrow range of the extent of water rock interaction followed by varying amounts of prior calcite precipitation pcp group 2 dripwater compositions are controlled by varying amounts of water rock interaction with little to no pcp influence group 3 dripwater compositions are dictated by variable extents of both water rock interaction and pcp group 1 drip sites show seasonal variations in dripwater mg ca and sr ca whereas the other drip sites do not in contrast to the findings of most previous dripwater mg ca sr ca studies these seasonal variations at group 1 drip sites are independent of changes in water flux i e rainfall and or drip rate and instead significantly correlate with changes in cave air co2 concentrations these results are consistent with lower cave air co2 related to cool season ventilation of the cave atmosphere enhancing calcite precipitation and leading to dripwater geochemical evolution via pcp group 1 dripwater mg ca and sr ca seasonality and evidence for pcp as a mechanism that can account for that seasonality have two implications for many other regions where seasonal ventilation of caves is likely 1 speleothem trace element records may provide seasonal signals and 2 such records may be biased toward recording climate conditions during the season when calcite is depositing additionally we use our results to construct a forward model that illustrates the types of speleothem mg ca and sr ca variations that would result from varying controls on dripwater compositions the model provides a basis for interpreting paleodripwater controls from high frequency mg ca and sr ca variations for speleothems from caves at which long term monitoring studies are not feasible 2011 elsevier ltd all rights reserved

dissolved oxygen fluctuations in karst spring flow and implications for endemic species barton springs edwards aquifer texas usa summary karst aquifers and springs provide the dissolved oxygen critical for survival of endemic stygophiles worldwide but little is known about fluctuations of dissolved oxygen concentrations do and factors that control those concentrations we investigated temporal variation in do at barton springs austin texas usa during 2006 2012 do fluctuated by as much as a factor of 2 and at some periods decreased to concentrations that adversely affect the barton springs salamander eurycea sorosum 4 4 mg l a federally listed endangered species endemic to barton springs do was lowest 4 4 mg l when discharge was low 1 m 3 s and spring water temperature was 21 c although not at a maximum the minimum do recorded was 4 0 mg l relatively low do 3 s and maximum t 22 2 c a four segment linear regression model with daily data for discharge and spring water temperature as explanatory variables provided an excellent fit for mean daily do nash sutcliffe coefficient for the validation period of 0 90 do also fluctuated at short term timescales in response to storms and do measured at 15 min intervals could be simulated with a combination of discharge spring temperature and specific conductance as explanatory variables on the basis of the daily data regression model we hypothesize that more frequent low do corresponding to salamander mortality could result from i lower discharge from barton springs resulting from increased groundwater withdrawals or decreased recharge as a result of climate change and or ii higher groundwater temperature as a result of climate change

hydrogeochemical and climatic interpretations of isotopic signals from precipitation to drip waters in liangfeng cave guizhou province china oxygen isotope is a commonly used proxy for paleoclimatic studies on stalagmites in order to understand the transmission of isotopic signals from precipitation to stalagmites meteorological indexes of exterior and interior cave and hydrogeochemical proxies of drip waters in liangfeng cave have been monitored from april 2011 to april 2013 samples of rain and drip waters from three drip sites designated as 1 5 and 6 are collected for hydrogen and oxygen isotopes testing results show that the amount weighted mean 18o value of rain in the first year may 9 2011 to may 1 2012 is lighter than that in the second may 30 2012 to may 2 2013 this may result from different proportions of the pacific indian ocean source moistures the arithmetic mean 18o values of 1 5 and 6 are similar to the multi year amount weighted mean 18o value of precipitation hydrogeochemical analyses of drip waters reveal that the discharge rates increase in the order of 6 1 5 and that water rock reaction fresh old water mixing and co2 degassing exert dominant controls on seepage waters in aquifers hard infiltration of rain during dry season with heavier 18o value due to its small amount may cause lower mean drip water 18o values e g 1 evaporation during the dripping and exuding processes in dry season may result in heavier mean drip water 18o values e g 6 considering calcite depositing mostly during dry season we compare the mean 18o values of drip waters during dry season between the first and second years differences exist and share the same trend with rain the results indicate that drip waters can inherit oxygen isotopic signals of rain but it is critical to have a replication test on 18o records of stalagmites from the same cave for paleoclimatic studies what s more 18o values in stalagmites feeding by drip waters that have no little annual 18o variations may be useful to paleotemperature reconstructions

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

changing amounts and sources of moisture in the u s southwest since the last glacial maximum in response to global climate change abstract the u s southwest has a limited water supply and is predicted to become drier in the 21st century an improved understanding of factors controlling moisture sources and availability is aided by reconstruction of past responses to global climate change new stable isotope and growth rate records for a central texas speleothem indicate a strong influence of gulf of mexico gom moisture and increased precipitation from 15 5 to 13 5 ka which includes the majority of the bolling allerod warming ba 14 7 12 9 ka coeval speleothem records from 900 and 1200 km to the west allow reconstruction of regional moisture sources and atmospheric circulation the combined isotope and growth rate time series indicates 1 increased gom moisture input during the majority of the ba producing greater precipitation in texas and new mexico and 2 a retreat of gom moisture during younger dryas cooling 12 9 11 5 ka reducing precipitation these results portray how late pleistocene atmospheric circulation and moisture distribution in this region responded to global changes providing information to improve models of future climate

new insights into nitrate dynamics in a karst groundwater system gained from in situ high frequency optical sensor measurements abstract understanding nitrate dynamics in groundwater systems as a function of climatic conditions especially during contrasting patterns of drought and wet cycles is limited by a lack of temporal and spatial data nitrate sensors have the capability for making accurate high frequency measurements of nitrate in situ but have not yet been evaluated for long term use in groundwater wells we measured in situ nitrate continuously in two groundwater monitoring wells one rural and one urban located in the recharge zone of a productive karst aquifer in central texas in order to resolve changes that occur over both short term hourly to daily and long term monthly to yearly periods nitrate concentrations measured as nitrate nitrogen in milligrams per liter mg l during drought conditions showed little or no temporal change as groundwater levels declined during aquifer recharge extremely rapid changes in concentration occurred at both wells as documented by hourly data at both sites nitrate concentrations were affected by recharging surface water as evidenced by nitrate concentrations in groundwater recharge 0 8 1 3 mg l that were similar to previously reported values for regional recharging streams groundwater nitrate concentrations responded differently at urban and rural sites during groundwater recharge concentrations at the rural well approximately 1 0 mg l increased as a result of higher nitrate concentrations in groundwater recharge relative to ambient nitrate concentrations in groundwater whereas concentrations at the urban well approximately 2 7 mg l decreased as a result of the dilution of higher ambient nitrate concentrations relative to those in groundwater recharge notably nitrate concentrations decreased to as low as 0 8 mg l at the urban site during recharge but postrecharge concentrations exceeded 3 0 mg l a return to higher nitrate concentrations postrecharge indicates mobilization of a localized source of elevated nitrate within the urbanized area of the aquifer changes in specific conductance were observed at both sites during groundwater recharge and a significant correlation between specific conductance and nitrate correlation coefficient r 0 455 was evident at the urban site where large 3 fold changes in nitrate occurred nitrate concentrations and specific conductance measured during a depth profile indicated that the water column was generally homogeneous as expected for this karst environment but changes were observed in the most productive zone of the aquifer that might indicate some heterogeneity within the complex network of flow paths resolving the timing and magnitude of changes and characterizing fine scale vertical differences would not be possible using conventional sampling techniques the patterns observed in situ provided new insight into the dynamic nature of nitrate in a karst groundwater system

folding with thermal mechanical feedback folding of viscous layered rocks is traditionally viewed as an instability arising from viscosity differences between layers this approach derives from biot and for purely viscous materials predicts the growth of single wavelength systems the dominant wavelength is sensitive to layer thickness the viscosity ratio between the layers the amount of shortening and the boundary conditions this paper presents one alternative theory of folding to that of biot and addresses the deformation of elastic viscous materials where the viscosity ratio between layers is small and biot theory predicts folds will not form such ratios are consistent with situations in the mid to lower crust as indicated by experimental data folding results from the coupling between temperature dependent viscosity and heat generated by deformation the result is weakening in the hinges of embryonic folds and subsequent buckling this process is distinct from the biot buckling process the structures that develop resemble natural structures in that folds develop at a range of length scales hinges undergo strong thickening and axial plane crenulations form this approach is grounded in non equilibrium thermodynamics the coupling of deformation to fluid flow and chemical reactions is explored as part of a unified framework for rock deformation processes

water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams summary karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes matrix and fractures for more than a century various approaches have used flood recession curves which integrate all hydrodynamic processes in a karst aquifer to infer physical properties of the movement and storage of groundwater these investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves we present analyses of simultaneous discharge and water level time series of two distinctly different karst systems one with low porosity and permeability matrix rocks in southern france and one with high porosity and permeability matrix rocks in north central florida usa we apply simple mathematical models of flood recession using time series representations of recharge storage and discharge processes in the karst aquifer we show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer conduit and matrix porosity which induce two distinct responses at the spring water exchange between conduits and matrix porosity successively control the flow regime at the spring this exchange is governed by hydraulic head differences between conduits and matrix head gradients within conduits and the contrast of permeability between conduits and matrix these observations have consequences for physical interpretations of recession curves and modeling of karst spring flows particularly for the relative magnitudes of base flow and quick flow from karst springs finally these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data but information must be known about the hydrodynamics and physical properties of the aquifer before the results can be correctly interpreted

el nino s tropical climate and teleconnections as a blueprint for pre ice age climates 1 at 2 7 million years ago the warm equable climates of early and middle pliocene time used here to mean from 5 to 2 7 ma were replaced by recurring ice ages most attempts to explain the change appeal either to changes in co2 in the atmosphere or reduced heat transport by the atlantic ocean the sources of the strongest teleconnections in the current climate however lie in the tropics and such connections occur by transport of heat and moisture by the atmosphere the most prominent of these teleconnections link aberrations in sea surface temperatures in the equatorial pacific el nino southern oscillation enso variations with warm and dry or cool and wet anomalies in extratropical climates we show that in most cases early and middle pliocene climate both in equatorial regions and in the extratropics differ from present day climates with the same spatial pattern as that associated with enso for instance not only was canada warmer during early pliocene time than at present as it is during el nino but the region surrounding the gulf of mexico appears to have been cooler and a bit wetter as it commonly is during el nino a virtually permanent el nino like state appears to have characterized pre ice age climates suggesting that transport of heat by the atmosphere was the principal mechanism that maintained extratropical warmth accordingly cooling and the growth of recurring ice sheets in the northern hemisphere resulted from the development of a strong walker circulation and a weakening of the hadley circulation

bank storage in karst aquifers the impact of temporary intrusion of river water on carbonate dissolution and trace metal mobility abstract storms can trigger changes in river stage that alter the hydraulic gradients between rivers and adjacent aquifers in eogenetic carbonate karst aquifer systems storms enable river water to intrude 1 km into the adjacent aquifer systems for days to weeks this process is similar to bank storage of streams in siliciclastic sediments but can have longer temporal and larger spatial scales river intrusion triggers changes in mineral saturation states and redox conditions in the aquifer due to the input of low ph low specific conductivity spc and high dissolved organic carbon doc flood water to assess the effects of river intrusion into karst aquifers we measured spc temperature ph redox state and concentrations of dissolved major and trace elements through an intrusion event at madison blue spring in northern florida usa river water displaced groundwater in the conduit at least 1 km into the aquifer and flowed into the pores of the unconfined aquifer matrix distinct cl concentrations between river water and groundwater provide estimates for mixing fractions the location and magnitude of oxidation of organic matter in the subsurface controlled trace metal concentration redox state and saturation state of the water with respect to calcite sical organic matter oxidation in the phreatic conduits was limited by the terminal electron acceptors teas present in the conduit water calcite dissolution and trace metal sorption were limited by the lower surface area to porosity ratios in the conduits than the matrix organic matter oxidation was enhanced in the matrix by mixing with matrix waters with available do and no3 resulting in greater co2 production and calcite dissolution than in the conduit after the intruded river water discharged conditions remained more reducing in the aquifer than baseflow conditions due to the reduction of do and no3 in the matrix water the organic matter transported into the aquifer during river intrusion drives carbonate dissolution alters redox state and impacts trace metal mobility impacting groundwater and surface water quality

a parsimonious model for simulating flow in a karst aquifer abstract this paper describes the hydrologic system associated with the barton springs portion of the edwards aquifer and presents a lumped parameter model capable of reproducing general historical trends for measured water levels and spring discharge recharge to the aquifer was calculated based on flow loss studies of the creeks crossing the recharge zone and on estimates of the rate of diffuse infiltration of rainfall flow measurements on each creek above and below the recharge zone were used to develop a relationship between flow above the recharge zone and the rate of recharge the five cell groundwater model each cell corresponding to one of the watersheds of the five main creeks crossing the recharge zone was developed to support the management objectives of the city of austin the model differs from previous models in that the aquifer properties within cells are allowed to vary vertically each cell was treated as a tank with an apparent area and the water level of a single well in each cell was used to characterize the conditions in that cell the simple representation of the hydrologic system produced results comparable to traditional groundwater models with fewer data requirements and calibration parameters 1997 elsevier science b v

oligo miocene lacustrine microbial and metazoan buildups from the limagne basin french massif central the limagne basin french massif central is an extensive continental lacustrine system accommodating microbial and metazoan buildups from chattian to aquitanian age a description of these buildups and their associated biotic components in grand gandaillat and crechy quarries provides insights into their spatio temporal distribution patterns flats cauliflowers domes cones and coalescent columnar morphologies have been identified with a main laminated mesofabric and laminated columnar filamentous and caddisfly coated microfabrics two low gradient margin models emerged based on the changes in the distribution morphology and size of the microbial and metazoan rich deposits through time the first model applies to the chattian deposits in the grand gandaillat quarry and the second to the aquitanian deposits in the crechy quarry this study emphasizes the heterogeneity of marginal lacustrine carbonate siliciclastic cycles the lacustrine palustrine cycles of the limagne basin record i lacustrine deposits composed of microbial and metazoan buildups and organic matter rich marls indicating periods of high accommodation and ii palustrine deposits composed of mudstone and clayey paleosoils indicative of periods of low accommodation the cycles differ with thin and symmetrical deposits that dominate the chattian cycles whereas thicker and asymmetrical deposits mark the aquitanian cycles in addition the chattian buildups are exclusively microbial and only a few centimeters thick whereas the aquitanian ones are multiple meters in height and are composed of both microbes and metazoans climatic tectonism volcanic and local parameters are involved in the deposition of buildups and their organization in each different cycle climate may control the long term arid humid sedimentary succession tectonic may explain the difference in the deposit thickness between two cycles of different ages and localizations as well as the specific distribution of the buildups throughout the basin volcanism may control the chemical lacustrine conditions and local physiography may impact the soil removal ability of the lake margin

single layer folding in simple shear abstract despite the common occurrence of simple shear deformation laboratory and numerical simulations of folding have so far been almost exclusively in pure shear here we present a series of finite element simulations of single layer folding in simple shear up to high shear strains 4 and up to 75 shortening of the folding layer in the simulations we vary the viscosity contrast between layer and its surroundings 25 100 the stress exponent 1 or 3 and the kinematics of deformation pure versus simple shear in simple shear fold trains do not show a clear asymmetry axial planes form perpendicular to the developing fold train and rotate along with the fold train differences in geometries between folds formed in simple and pure shear folds are thus difficult to distinguish visually with simple shear folds slightly more irregular and with more variable axial plane orientation than in pure shear asymmetric refraction of an axial planar cleavage is a clearer indication of folding in simple shear the main effect of an increase in stress exponent is an increase in effective viscosity contrast with only a secondary effect on fold geometry naturally folded aplite dykes in a granodiorite are found in a shear zone in roses ne spain comparison of the folded dykes with our numerical simulations indicates a viscosity contrast of around 25 and a stress exponent of 3 the natural folds confirm that at this moderate viscosity contrast a significant amount of shortening 20 30 is achieved by layer thickening instead of folding

isotopic reconstruction of past continental environments abstract vertebrate fossils and continental sediments provide a rich record of variations in the isotopic composition of surface environments to interpret these records a greater understanding of isotopic sources as well as fractionations associated with animal physiology soil geochemistry and diagenesis has been essential tooth enamel and fish otoliths yield subannual records of surface environments whereas soil minerals may integrate signals over many thousands of years carbon isotope variations in fossil vertebrates and soils record changes in the structure of vegetation and the isotope composition and concentration of atmospheric co2 oxygen isotope variations may be indirectly related to climate through reconstruction of the oxygen isotope composition of meteoric water or directly related to temperature through application of oxygen isotope paleothermometry to soil minerals or otoliths in africa nitrogen isotope variations show promise as a proxy for rainfall abundance though the gen

origin of the joya honda maar san luis potosi mexico abstract joya honda is a quaternary maar of unusual type from the mexican basin and range province its 300 m deep crater is excavated in cretaceous limestones the surrounding tephra deposit which in places is 100 m thick begins with a series of weakly indurated pyroclastic surge and fall layers that we interpret as dry surge deposits these are overlain by the main sequence of strongly indurated massive tuff breccias that we interpret as wet surge deposits joya honda formed subaerially from the interaction of groundwater with rapidly ascending intraplate type basanitic magma carrying peridotitic mantle xenoliths local aquifer characteristics controlled the style of eruption and the nature of the deposits groundwater in the limestone hosted aquifer beneath joya honda was apparently contained within solution enhanced fractures at the onset of the eruption magma began to interact with a moderate amount of groundwater producing the dry surge deposits which are typical of deposits found at many maars and tuff rings as the eruption continued the crater grew and the hydromagmatic blasts fractured the limestones around the explosion foci a marked increase in the water magma ratio of the system followed when a large fracture or a portion of the limestone with enhanced secondary permeability was intersected by the expanding crater subsequent phreatomagmatic explosions occurred in a system with groundwater flow rates several orders of magnitude larger than in the initial dry surge stage at the maar rim these wet eruptions led to the emplacement of massive tuff breccias through a combination of fallout surges and mudflows these steeply dipping tuff breccias are similar to deposits found at many tuff cones juvenile clasts in the near vent deposits show marked upward increases in both hydration palagonitization and vesicularity the increased palagonitization with height in the section appears to be a consequence of the overall increased wetness of the eruption with time correlating with greater carbonate cementation and lithification in the upper part of the deposit the transition toward higher vesicularity is interpreted as evidence of a gradual reduction in the confining pressure for the ascending magma prior to explosive fragmentation perhaps related to unroofing during progressive excavation of the overlying maar crater thus joya honda does not support maar formation models that invoke downward displacement of explosion foci caused by formation of a cone of depression in the aquifer in order to maintain the confining pressure for the hydromagmatic blasts

controls on the spatial and temporal variability of vadose dripwater geochemistry edwards aquifer central texas abstract a 4 yr study of spatial and temporal variability in the geochemistry of vadose groundwaters from caves within the edwards aquifer region of central texas offers new insights into controls on vadose groundwater evolution the relationship between vadose and phreatic groundwaters and the fundamental influence of soil composition on groundwater geochemistry variations in sr isotopes and trace elements mg ca and sr ca ratios of dripwaters and soils from different caves as well as phreatic groundwaters provide the potential to distinguish between local variability and regional processes controlling fluid geochemistry and a framework for understanding the links between climatic and hydrologic processes the sr isotope compositions of vadose cave dripwaters mean 87sr 86sr 0 7087 and phreatic groundwaters mean 87sr 86sr 0 7079 generally fall between values for host carbonates mean 87sr 86sr 0 7076 and exchangeable sr in overlying soils mean 87sr 86sr 0 7088 dripwaters have lower mg ca and sr ca ratios and higher 87sr 86sr values than phreatic groundwaters dripwater 87sr 86sr values also inversely correlate with both mg ca and sr ca ratios mass balance modeling combined with these geochemical relationships suggest that variations in fluid compositions are predominantly controlled by groundwater residence times and water rock interaction with overlying soils and host aquifer carbonate rocks consistent differences in dripwater geochemistry i e 87sr 86sr mg ca and sr ca between individual caves are similar to compositional differences in soils above the caves while these differences appear to exert significant control on local fluid evolution geochemical and isotopic variations suggest that the controlling processes are regionally extensive temporal variations in 87sr 86sr values and mg ca ratios of dripwaters from some sites over the 4 yr interval correspond with changes in both aquifer and climatic parameters these results have important implications for the interpretation of trace element and isotopic variations in speleothems as paleoclimate records as well as the understanding of controls on water chemistry for both present day and ancient carbonate aquifers

types of phreatomagmatic volcanoes in the western snake river plain idaho usa abstract the western snake river plain graben in southwestern idaho includes a large hydrovolcanic field which was produced in late miocene to pleistocene time by the interaction of rising basaltic magmas with the waters and water saturated deposits of an enormous freshwater lake lake idaho the phreatomagmatic volcanoes in this field may be grouped into three types emergent subaqueous and subaerial emergent volcanoes which began erupting under water and built up above the lake level are relatively large and symmetrical are dominated by bedded tuffs and late magmatic deposits and are excellent indicators of water depth at the time of the eruption subaqueous volcanoes which never built up above the lake level are relatively small and asymmetrical are dominated by basal massive deposits and are potentially useful in discriminating between deep and very deep water settings subaerial volcanoes which were formed when magmas intercepted buried aquifers and interacted explosively with water are small tuff rings and maars with variable shapes are composed of subequal although variable proportions of basal massive deposits bedded tuffs and late magmatic deposits and are useful in determining the stratigraphic successions underlying them

oxygen isotope evidence for progressive uplift of the cascade range oregon oxygen isotope compositions of fossil equid teeth in the cascade rainshadow reveal a v5x decrease in mean n 18 o since 27 ma isotopic changes are inconsistent with expected effects from global climate change because a the expected isotopic shift to tooth n 18 o values due to global climate change v1x is much smaller than the observed shift b predicted and observed isotopic trends are opposite for oligocene vs miocene samples and c average compositions and ranges in compositions remained unchanged for samples from before and after major global cooling in the mid miocene accounting for a decrease in relative humidity of at least 15 we infer a topographically driven secular shift in the n 18 o value of rainwater of 6 8x since the late oligocene which is approximately equivalent to the modern day difference in n 18 o values of precipitation and surface waters across the central cascades rise of the central cascades apparently occurred monotonically over the last 27 ma with a hiatus between v15 4 and 7 2 ma possibly related to eruption of the columbia river basalts progressive volcanic accumulation over tens of millions of years best explains the data rather than a short lived uplift event paleoseasonality as inferred from isotope zoning and intertooth variability decreased dramatically from 7 9x at 15 4 7 ma to v3x at 3 ma then increased to 6 8x today the cause of the decrease in seasonality at 3 ma may reflect either brief warming during the mid pliocene within the context of global tectonic reorganization or consumption by equids of water from an isotopically buffered lake idaho 2002 elsevier science b v all rights reserved

comparing species diversity in the modern and fossil record of lakes abstract lake faunal diversity has been the focus of many modern studies however there have been few studies comparing the lacustrine diversity in the modern and fossil record whether or not this comparison is possible is dependent on preservation by comparing the exceptional preservation of the konservat lagerstatten of the eocene green river formation with its various modern analogs in east africa unique factors controlling diversity within a lake system can be determined such factors would include lake surface area lake longevity productivity and lake type in order to effectively compare lake diversity in the modern and fossil record we first estimated the potential preservational bias of the fauna from modern lake tanganyika and determined that at maximum approximately 43 8 of species 59 3 of genera and 65 8 of families would be identifiable with this taphonomic filter in place we compared fish species diversity versus lake area no strong relationship was found faunal species div

introduction aapg hedberg research conference on microbial carbonate reservoir characterization conference summary and selected papers with the recent discovery of hydrocarbons in microbial carbonate reservoir facies along the south atlantic margins industry is keen to further the understanding of the origin and development of nonmarine lacustrine to marine microbial carbonates the nature of the depositional and diagenetic characteristics of microbialite and associated facies and the sedimentary and petrophysical properties of microbial carbonate petroleum reservoirs in this regard the authors of aapg getting started series 19 microbial carbonate reservoirs mancini et al 2010 found that a vast literature on microbes and their functions in geological processes and products ranging from biogeochemistry to geomicrobiology sedimentary petrology and stratigraphy was available however only a small part of this literature deals with microbial carbonates as petroleum reservoirs further these authors reported that sparse available literature exists on microbial carbonate reservoirs formed in lacustrine and continental settings and on carbonate reservoirs of abiotic origin in general to help address these shortcomings an aapg hedberg research conference was proposed to focus on microbial carbonate reservoir characterization with an emphasis on depositional settings of microbial and abiotic carbonate reservoirs especially in lacustrine settings associated with rift basins the proposal was accepted august 21 2010 and the hedberg conference was held in houston texas last june 3 8 2012 with 85 attendees from 10 countries the conference was dedicated to wayne m ahr who passed away in november 2011 he was one of the conference organizers one of the intended field trip leaders and a friend to many at the conference the following overview of microbial carbonates is modified from sections 1 and 2 of aapg getting started series 19 microbial carbonate reservoirs mancini et al 2010 microbes are defined as microorganisms visible only under a microscope some examples are bacteria fungi molds algae and protozoa unlike the older classification of living organisms

peperite a review of magma sediment mingling the study of peperite is important for understanding magma water interaction and explosive hydrovolcanic hazards this paper reviews the processes and products of peperite genesis peperite is common in arc related and other volcano sedimentary sequences where it can be voluminous and dispersed widely from the parent intrusions it also occurs in phreatomagmatic vent filling deposits and along contacts between sediment and intrusions lavas and hot volcaniclastic deposits in many environments peperite can often be described on the basis of juvenile clast morphology as blocky or fluidal but other shapes occur and mixtures of different clast shapes are also found magma is dominantly fragmented by quenching hydromagmatic explosions magma sediment density contrasts and mechanical stress as a consequence of inflation or movement of magma or lava magma fragmentation by fluid fluid shearing and surface tension effects is probably also important in fluidal peperite fluidisation of host sediment hydromagmatic explosions forceful intrusion of magma and sediment liquefaction and shear liquification are probably the most important mechanisms by which juvenile clasts and host sediment are mingled and dispersed factors which could influence fragmentation and mingling processes include magma host sediment and peperite rheologies magma injection velocity volatile content of magma total volumes of magma and sediment involved total volume of pore water heated presence or absence of shock waves confining pressure and the nature of local and regional stress fields sediment rheology may be affected by dewatering compaction cementation vesiculation fracturing fragmentation fluidisation liquefaction shear liquification and melting during magma intrusion and peperite formation the presence of peperite intraclasts within peperite and single juvenile clasts with both sub planar and fluidal margins imply that peperite formation can be a multi stage process that varies both spatially and temporally mingling of juvenile clast populations formed under different thermal and mechanical conditions complicates the interpretation of magma fragmentation and mingling mechanisms

north american continental seasonality during the last millennium high resolution analysis of sagittal otoliths abstract 18 o caco 3 values of late holocene sagittal fish otoliths from lake erie provide a record of seasonal temperature variation for mid western north america freshwater drum aplodinotus grunniens sagittal otoliths obtained from paleo indian middens ranging in age from a d 985 to a d 1530 as well as a recent specimen were sampled at a resolution representing time averaging of as little as 3 5 days to estimate seasonal climatic variation over the last thousand years regional differences in climate as well as asynchronous variation inferred by comparison with historical records of europe greenland and iceland suggest that the climate trends of eastern north america may not always correspond to those of europe or even the north atlantic results suggest that summer temperatures of the laurentian great lakes region at the beginning of the millennium were 2 6 c warmer while winter temperatures may have been nearly 2 c cooler than the 20th century average by the late 1200s summer temperatures decreased to nearly modern values in the 1400s and through the 1500s summer maxima exhibited enhanced intra annual variation as well as temperatures which were as much as 8 c cooler while winter temperatures were 0 4 2 7 c warmer than 20th century values an additional outcome of this research is the estimation of lake water 18 o values for several time periods throughout the holocene mean annual temperatures inferred from 18 o h 2 o values display a decrease from a d 985 through at least a d 1530 concomitant with summer temperature trends the long residence time of these large lakes suggests that secular trends in 18 o values must represent long term variation in climate which can be used in concert with the short term high resolution temperature record for a comprehensive estimation of climatic trends temperature variation and paleohydrology of the great lakes region is discussed in terms of variation in storm tracks and source region with time 18 o values of lake water coupled with paleotemperature data suggest that changing climate is the result of secular variation in the position shape and strength of the circumpolar vortex

middle pliocene vegetation reconstructions paleoclimatic inferences and boundary conditions for climate modeling abstract the general characteristics of global vegetation during the middle pliocene warm period can be reconstructed from fossil pollen and plant megafossil data the largest differences between pliocene vegetation and that of today occurred at high latitudes in both hemispheres where warming was pronounced relative to today in the northern hemisphere coniferous forests lived in the modern tundra and polar desert regions whereas in the southern hemisphere southern beech apparently grew in coastal areas of antarctica pliocene middle latitude vegetation differed less although moister than modern conditions supported forest and woodland growth in some regions now covered by steppe or grassland pliocene tropical vegetation reflects essentially modem conditions in some regions and slightly cooler than or warmer than modern climates in other areas changes in topography induced by tectonics may be responsible for many of the climatic changes since the pliocene in both middle and lower latitudes however the overall latitudinal progression of climatic conditions on land parallels that seen in the reconstruction of middle pliocene sea surface temperatures pliocene paleovegetational data was employed to construct a 2 2 global grid of estimated mid pliocene vegetational cover for use as boundary conditions for numerical general circulation model simulations of middle pliocene climates continental outlines and topography were first modified to represent the pliocene landscape on the 2 2 grid a modern 1 1 vegetation grid was simplified and mapped on this pliocene grid and then modified following general geographic trends evident in the pliocene paleovegetation data set

changes in sources and storage in a karst aquifer during a transition from drought to wet conditions summary understanding the sources and processes that control groundwater compositions and the timing and magnitude of groundwater vulnerability to potential surface water contamination under varying meteorologic conditions is critical to informing groundwater protection policies and practices this is especially true in karst terrains where infiltrating surface water can rapidly affect groundwater quality we analyzed the evolution of groundwater compositions major ions and sr isotopes during the transition from extreme drought to wet conditions and used inverse geochemical modeling phreeqc to constrain controls on groundwater compositions during this evolution spring water and groundwater from two wells dominantly receiving diffuse and conduit flow termed diffuse site and conduit site respectively in the barton springs segment of the edwards aquifer central texas usa and surface water from losing streams that recharge the aquifer were sampled every 3 4 weeks during november 2008 march 2010 during this period water compositions at the spring and conduit sites changed rapidly but there was no change at the diffuse site illustrating the dual nature i e diffuse vs conduit of flow in this karst system geochemical modeling demonstrated that within a month of the onset of wet conditions the majority of spring water and groundwater at the conduit site was composed of surface water providing quantitative information on the timing and magnitude of the vulnerability of groundwater to potential surface water contamination the temporal pattern of increasing spring discharge and changing pattern of covariation between spring discharge and surface water steam recharge indicates that that there were two modes of aquifer response one with a small amount of storage and a second that accommodates more storage

the submarine eruption and erosion of surtla surtsey iceland abstract surtla is the site of a short lived submarine vent which built basaltic elastic deposits almost to sea level in 1963 early in the eruption of surtsey since then wave and current activity have eroded the volcanic pile such that in july 1981 its top was a fairly level plateau 45 m below sea level and its surface comprised a lag deposit of sparse blocks of lava in a bed mainly of glass granules this winnowed layer was underlain by a nonreworked poorly sorted and finer deposit of glassy clasts formed by a combination of disruption by magmatic volatiles steam explosions and quench brecciation during the eruption the explosion violence and associated comminution increased as the pile built up to shallower water depths it is argued that at times of continuous effusion a cupola of steam was situated over the vent as indicated by scoriaceous spatter which shows agglutination and bread crust features that can only have developed in conditions more akin to subaerial than hitherto envisaged in a subaqueous eruption

evaluation of geochemical and hydrogeological processes by geochemical modeling in an area affected by evaporite karstification the ebro valley in the outskirts of zaragoza ne spain is severely affected by evaporite karstification leading to multiple problems related to subsidence and sinkhole formation in this work a combination of inverse mixing mass balance and forward reaction path geochemical calculations is applied for the quantification of the main karstification processes and seasonal variations in this area the obtained results prove the suitability of the applied methodology for the characterization of similar problems in other areas with scarce geological and hydrogeological information the hydrogeology and hydrochemistry of the system can be mainly attributed to the mixing of variable proportions of concentrated groundwater from the evaporitic aquifer and more dilute water from the overlying alluvial aquifer the existence of a good connection between these aquifers is supported by 1 the fast changes in the hydrochemistry of the karst aquifer related to recharge by irrigation and 2 the deduced input of evaporitic groundwater in the alluvial materials the evolution in some parts of the alluvial evaporitic aquifer system is clearly dominated by the seasonal variations in the recharge by dilute irrigation waters up to 95 of water volume in some sinkhole ponds whereas other points seem to be clearly determined by the hydrochemistry of the concentrated evaporitic aquifer groundwater up to 50 of the water volume in some springs the following reactions previous or superimposed to mixing processes explain the observed hydrochemistry in the studied area dissolution of halite naci gypsum caso4 2h 2 o anhydrite caso4 and dolomite camg co3 2 co2 b input and degassing and calcite caco3 dissolution precipitation the modeling results suggest the existence of a large spatial variability in the composition of the evaporitic groundwater mainly caused by large differences in the availability of halite in contact with the groundwater active subsidence associated with halite dissolution is expected to continue in the study area together with the episodic increase of gypsum dissolution associated with the input of dilute irrigation waters c 2015 elsevier b v all rights reserved

information from folds a review abstract folds are spectacular geological structures that are seen in layered rock on many different scales to mark 30 years of the journal of structural geology we review the information that can be gained from studies of folds in theory experiment and nature we first review theoretical considerations and modeling from classical approaches to current developments the subject is dominated by single layer fold theory with the assumption of perfect layer parallel shortening but we also review multilayer fold theory and modeling and folding of layers that are oblique to principal stresses and strains this work demonstrates that viscosity ratio degree of non linearity of the flow law anisotropy and the thickness and spacing distribution of layers of different competence are all important in determining the nature and strength of the folding instability theory and modeling provide the basis for obtaining rheological information from natural folds through analysis of wavelength thickness ratios of single layer folds and fold shapes they also provide a basis for estimating the bulk strain from folded layers information about folding mechanisms can be obtained by analysis of cleavage and fabric patterns in folded rocks and the history of deformation can be revealed by understanding how asymmetry can develop in folds by how folds develop in shear zones and how folds develop in more complex three dimensional deformations

miocene hydrovolcanism in nw colorado usa fuelled by explosive mixing of basic magma and wet unconsolidated sediment the yampa and elkhead mountains volcanic fields were erupted into sediment filled fault basins during miocene crustal extension in nw colorado post miocene uplift and erosion has exposed alkali basalt lavas pyroclastic deposits volcanic necks and dykes which record hydrovolcanic and strombolian phenomena at different erosion depths the occurrence of these different phenomena was related to the degree of lithification of the rocks through which the magmas rose hydrovolcanic interactions only occurred where rising basaltic magma encountered wet porous non lithified sediments of the 600 m thick miocene brown s park formation the interactions were fuelled by groundwater in these sediments there was probably no standing surface water dykes intruded into the sediments have pillowed sides and local swirled inclusions of sediment that were injected while fluidized in steam from heated pore water volcanic necks in the sediments consist of basaltic tuff sediment blocks and separated grains derived from the sediments lithic blocks mostly derived from a conglomerate forming the local base of the brown s park formation and dykes composed of disaggregated sediment the necks are cut by contemporaneous basalt dykes hydrovolcanic pyroclastic deposits formed tuff cones up to 100 m thick consisting of bedded air fall pyroclastic surge and massive poorly sorted deposits mpsds all these contain sub equal volumes of basaltic tuff and disaggregated sediment grains from the brown s park formation possible explosive and effusive modes of formation for the mpsds are discussed contemporaneous strombolian scoria deposits overlie lithified cretaceous sedimentary rocks or thick basalt lavas volcanic necks intruded into the cretaceous rocks consist of basalt clasts some with spindle shape lithic clasts and megacrysts derived from the magma and are cut by basalt dykes rarely strombolian deposits are interbedded with hydrovolcanic pyroclastic deposits recording changes in eruption behaviour during one eruption the hydrovolcanic eruptions occurred by interaction of magma with groundwater in the brown s park sediments the explosive interactions disaggregated the sediment such direct digestion of sediment by the magma in the vents would probably not have released enough water to maintain a water magma mass ratio sufficient for hydrovolcanic explosions to produce the tuff cones probably additional water perhaps 76 of the total was derived by flow through the permeable sediments especially the basal conglomerate to the formation and into the vents

a 35 myr north american leaf wax compound specific carbon and hydrogen isotope record implications for c4 grasslands and hydrologic cycle dynamics article i nfo hydrology source region and timing of precipitation are important controls on the climate of the great plains of north america and the composition of terrestrial ecosystems moisture delivered to the great plains varies seasonally and predominately derives from the gulf of mexico atlantic ocean with minor contributions from the pacific ocean and arctic region for this work we evaluate long term relationships for the past 35 million years between north american hydrology climate and floral change using isotopic records and average carbon chain lengths of higher plant n alkanes from gulf of mexico sediments dsdp site 94 we find that carbon isotope values 13 c of n alkanes corrected for variations in the 13 c value of atmospheric co2 provide minor evidence for contributions of c4 plants prior to the middle miocene a sharp spike in c4 input is identified during the middle miocene climatic optimum and the influence of c4 plants steadily increased during the late miocene into the pleistocene consistent with other north american records chain length distributions of n alkanes indicative of the composition of higher plant communities remained remarkably constant from 33 to 4 ma however a trend toward longer chain lengths occurred during the past 4 million years concurrent with an increase in 13 c values indicating increased c4 plant influence and potentially aridity the hydrogen isotope values d of n alkanes are relatively invariant between 33 and 9 ma and then become substantially more negative 75 from 9 to 2 ma changes in the plant community and temperature of precipitation can solely account for the observed variations in d from 33 to 5 ma but cannot account for plio pleistocene d variations and imply substantial changes in the source region of precipitation and seasonality of moisture delivery we posit that hydrological changes were linked to tectonic and oceanographic processes including the shoaling and closure of the panamanian seaway amplification of north atlantic deep water production and an associated increase of meridional winds the southerly movement of the intertropical convergence zone near 4 ma allowed for the development of a near modern pressure storm track system driving increased aridity and changes in seasonality within the north american interior

mio pliocene seasonality on the snake river plain comparison of faunal and oxygen isotopic evidence smith g r and patterson w p 1994 mio pliocene seasonality on the snake river plain comparison of faunal and oxygen isotopic evidence palaeogeogr pataeoctimatol palaeoecol 107 291 302 analysis of fish faunas and oxygen isotopic composition of a fish otolith from lacustrine deposits of southwestern idaho provide a means of evaluating regional miocene and pliocene climates a disharmonious assemblage consisting of coldwater salmon and trout and warmwater sunfish and catfish from the chalk hills formation of the snake river plain indicates that the climate of the late miocene was warm and moist with cool summers and mild winters colonization of the lake by deepwater sculpins and whitefish in the pliocene indicates that the climate was moist and equable but with summers cooler than either the miocene or quaternary oxygen isotopic variation among seasonal growth rings in an aragonitic otolith of a pliocene littoral sunfish suggests a seasonal range of temperatures locally more equable than at present extremely depleted values of 6180 in carbonates suggest that the lake was maintained by tributaries from high elevation watersheds with locally low evaporation rather than high precipitation

quantifying the place of karst aquifers in the groundwater to surface water continuum a time series analysis study of storm behavior in pennsylvania water resources summary though karst aquifers have commonly been identified with respect to their behavior as intermediate between ground and surface water their putative location between these end members is generally descriptive rather than quantitative autocorrelation and spectral analysis of data from four karst springs three wells and eight stream gauges in pennsylvania illustrate that specific karst water resources exhibit widely varying inertia with lag times that overlap those of groundwater and surface water when analyzed in the frequency domain the same data reveal distinctive patterns for each type of water resource the four springs display characteristic lag times ranging from 5 to 25 days compared to 1 10 days for streams and 11 46 days for wells physically karst waters may behave as a mix of porous media fracture and open channel flow but in temporal terms the balance of this mix results in a range of system behaviors with characteristic periodicities evident in the karst aquifers in the frequency domain karst aquifers manifested slow flow paths as a gradual fall off at lower frequency and quick flow paths as a flattening at high frequency our comparison of water resources across different time periods revealed that the period considered can have strong effects on results one spring displayed characteristic lag times of 12 and 25 days for two different time spans to directly compare water resources over relatively short time scales precipitation inputs must be similar and data sets must cover the same period otherwise substantial differences in lag times can be due to data collection and input differences rather than system characteristics this limitation is less when the same data are analyzed in the frequency domain

magma water interactions in subaqueous and emergent basaltic in the subaqueous growth and emergence of a basaltic volcano clasts are formed by one or a combination of 1 explosive release of magmatic volatiles 2 explosive expansion and collapse of steam formed at magma water contact surfaces 3 explosive expansion of steam following enclosure of water in magma or entrapment of water close to magma and 4 cooling contraction these processes named respectivelymagmatic explosivity contact surface steam explosivity bulk interaction steam explosivity andcooling contraction granulation can be enhanced by mutual interaction and feedback the first three explosive processes are limited at certain water depths hydrostatic pressures and become increasingly vigorous at shallower levels the depth of onset of magmatic explosivity depends largely on juvenile volatile content it is up to 200 m for tholeiitic magmas and up to 1 km for alkalic magmas at the depth where formation of clastic deposits becomes predominant over effusion of lavas magmatic explosivity is subordinate to steam explosivity as a clast forming process the upward transition to accumulation of dominantly clastic deposits is not simply related to the onset of substantial exsolution of magmatic volatiles and can occur without it contact surface explosivity commonly requires initiation by a vigorous impact between magma and water and although no certain depth limit is known likelihood of such explosivity decreases rapidly with depth clast generation by bulk interaction explosivity appears to be restricted to depths much shallower than that of the critical pressure of water which in sea water is at about 3 km cooling contraction granulation can occur in any depth of water but at shallow levels may be replaced by contact surface explosivity during continuous eruption under water tephra can be ejected and deposited within a cupola of steam such that rapid quenching does not occur emergent volcanoes are characterized by distinctive steam explosive activity that results primarily from a bulk interaction between rapidly ascending magma and a highly mobile slurry of clastic material water and steam the water gets into the vent by flooding across or through the top of the tephra pile and violent explosions cease when this access is sealed the eruptions during emergence of surtsey and capelinhos typify the distinctive explosive activity the style and controls of which are different from those of maar volcanoes

effects of partial and full pipe flow on hydrochemographs of logsdon river mammoth cave kentucky usa summary logsdon river within kentucky s mammoth cave system drains the 25 km2 cave city groundwater basin temperature specific conductance stage and velocity were measured at the river s downstream end within the cave with 2 min resolution for one year beginning on may 5 1995 new interpretation of these data show relationships to the conduit s geometry and fluid transport behavior the 37 observed storm hydrographs chemographs are classified into two groups open channel flow and pipe flow conduit filled in the 16 pipe flow events logsdon river exceeded the capacity of its conduit raising the water table above the conduit ceiling with some storm water thus temporarily stored within the aquifer adjacent to the conduit pipe flow events were characterized by depression of specific conductance spc before peak discharge a peak in spc at peak discharge and a second depression in spc after peak discharge the first spc minimum represents the maximum concentration of passing storm water and the second is interpreted as the result of recent storm water draining back into the conduit having been temporarily stored in the aquifer adjacent to the conduit mean velocity decreases in the transition from partial to full pipe flow due to increased head loss at full pipe flow compared to nearly full pipe flow each of the open channel flow cases shows a depression in spc either coincident with or after peak discharge while the hydrochemographs of pipe flow are mainly controlled by the aquifer conduit network geometry in open channel cases they are mainly controlled by external recharge conditions including behavior of sinking streams

the genesis and evolution of carbonate minerals in shale oil formations from dongying depression bohai bay basin china abstract shale oil is attracting increasing attention in the petroleum industry as an essential target of unconventional oil and gas exploration recent exploration efforts have indicated that laminar carbonates are closely related to the favorable depositional strata of shale oil this research focused on inter bedded layers of laminar carbonates as well as mudstone and shale in the dongying depression of the bohai bay basin in eastern china and attempted to reveal the genesis and evolution of the carbonates by means of drill core observations thin sections high resolution scanning electron microscopic observations and fluorometric cathodoluminescence and geochemical analyses the results demonstrated that 1 the carbonates could be categorized into two groups crystalline carbonates and micritic carbonates 2 the crystalline carbonates were well crystallized and greenish under fluorescent light and 3 the micritic carbonates were not well crystallized and had biotic textures it was discovered that the crystalline carbonates were mainly developed in the shale layer and were formed from the late filling effects of the diagenetic cracks along the shale fissility planes shale layers with crystalline carbonates are usually favorable for shale oil reserves the micritic carbonates were formed from direct deposition controlled by biological effects in the stratified flows of the seasonal lake basins and are unfavorable for shale oil reserves

the isotopic record of ocean chemistry and diagenesis preserved in non luminescent brachiopods from mississippian carbonate rocks illinois and missouri fossil brachiopod shells are commonly used as a faithful record of the chemical and isotopic composition of the ancient ocean water in which they grew owing to their stable mineralogy and their presence in marine strata throughout phanerozoic time the utility of these fossils for preserving ocean water compositions is evaluated through analyses of multiple specimens that grew in contemporaneous sea water at individual stratigraphic horizons in the mississippian age burlington keokuk formation of mid continent north america significant variations in sr c and o isotopic compositions are observed in contemporaneous non luminescent shells indicating that apparently pristine brachiopod shell material has been altered by post depositional processes of diagenesis the least altered compositions at each horizon are used to estimate secular variations of 87 sr 86 sr in early mississippian ocean water the estimated rates of change of ocean water 87 sr 86 sr are comparable in magnitude to the rapid sr isotopic changes documented for cenozoic ocean water for which high frequency glacial cycles are inferred as a driving mechanism the rigorous assessment of diagenetic effects on the isotopic signatures of marine phases is requisite for the advancement of high resolution reconstructions of paleo ocean chemistry

inferring source waters from measurements of carbonate spring response to storms abstract we infer information about the nature of groundwater flow within a karst aquifer from the physical and chemical response of a spring to storm events the spring discharges from the maynardville limestone in bear creek valley tennessee initially spring discharge peaks approximately 1 2 h from the midpoint of summer storms the initial peak is likely due to surface loading which pressurizes the aquifer and results in water moving out of storage all of the storms monitored exhibited recessions that follow a master recession curve very closely indicating that storm response is fairly consistent and repeatable independent of the time between storms and the configuration of the rain event itself electrical conductivity initially increases for 0 5 2 9 days longer for smaller storms the result of moving older water out of storage this is followed by a 2 1 2 5 day decrease in conductivity resulting from an increasing portion of low conductivity recharge water entering the spring stable carbon isotope data and the calcite saturation index of the spring water also support this conceptual model spring flow is likely controlled by displaced water from the aquifer rather than by direct recharge through the soil zone

miocene lacustrine algal reefs southwestern snake river plain idaho straccia f g wilkinson b h and smith g r 1990 miocene lacustrine algal reefs southwestern snake river plain idaho sediment geol 67 7 23 the hot spring limestone is a shallow water algal carbonate within a late tertiary transgressive lacustrine sequence exposed in the southwestern snake river plain this 5 m thick lensoid sequence crops out over an 80 km 2 area that closely approximates original areal extent of nearshore carbonate accumulation reefal bodies consist of closely packed algal cylinders several decimeters in height each of which includes a dense laminated carbonate wall surrounding porous digitate carbonate that radiates outward and upward from one or more hollow tubes these coalesce upsection into separate vertical columns several meters in diameter moderately well sorted terrigenous and molluscan debris deposited between columns during growth indicates these structures were resistant to wave erosion and therefore were true reefs thick rings of littoral carbonate surrounding the upper walls of each column record the final stages of reef development structural attributes exhibited by these miocene carbonate bodies are also common to a number of tertiary and quaternary algal buildups reported from other lacustrine settings although features within the hot spring limestone are complex in gross morphology and structural detail both columnar reefs and algal cylinders display little variation in size shape or internal structure between areas of varying water depth and wave energy thus reflecting the importance of biological processes as well as physical processes during reef development

karst aquifer characterization using storm event analysis for black dragon springshed beijing china beijing is a megacity suffering from acute water shortage the characterization of karst aquifers in beijing s outlying districts is critical to inform sustainable policies and practices in groundwater development we captured spring hydrogeochemical dynamics during an intense storm event 721 storm by installing a data logger in the weir which presents an opportunity for defining and characterizing the recharging sources of discharge from black dragon bd springshed multivariate techniques including pca 2d hca heat map and piper diagram were used to characterize the waters and investigate their geochemical evolution the results in combination with hydrological evidence suggest bd spring was dominated by interaction with dolomite host limestone rock during dry season whereas it was fed by a second water supply dolomite aquifer during storm events the infiltration coefficients were calculated based on the water balance model and it was found that the 721 storm has resulted in less infiltration due to the high rainfall intensity we presented a novel methodology combining high frequency data sets and routine manual flow measurements with traditional geochemical sampling techniques this methodology appears to be very efficient at characterizing a karst aquifer and seems to be potentially applicable to other karst aquifers

seismic expression and geological significance of a lacustrine delta in neogene deposits of the western snake river plain idaho high resolution seismic reflection profiles and well data from the western snake river plain basin are used to identify a buried lacustrine delta system within neogene idaho group sediments near caldwell idaho the delta system is detected 305 m 1000 ft deep near the center of the basin by progradational clinoform reflections having dips of 2 5 a slope typical of prodelta surfaces of modern lacustrine delta systems the prodelta slope relief corrected for compaction indicates the delta system prograded northwestward into a lake basin 255 m 837 ft deep resistivity logs in the prodelta mud and clay facies are characterized by gradual upward increase in resistivity and grain size over a thickness of about 100 m 300 ft lithology of the prodelta is mostly c lcareous claystone with several layers of fine sand some of which fine upward indicating a density flow mechanism of transport and deposition delta plain and front sediments are mostly very fine grained well sorted sand separated by thin mud layers these sediments produce several to five cycles of horizontal high amplitude reflections with a toplap relationship to prodelta clinoforms the sands have an abrupt lower contact with prodelta muds and have high resistivity on logs in this study permeable lacustrine sands within a predominantly mud and clay section are located by using high resolution seismic reflection data identification of a delta system in the idaho group provides insight into the history of pliocene lake idaho the present depth of the delta prodelta facies contact of 305 m 1000 ft is 445 to 575 m 1460 1900 ft below the lake deposits on the margins estimated subsidence from compaction is 220 m 656 ft and the remaining 225 to 325 m 740 1066 ft is attributed to tectonic downwarping and faulting the original lake area had been reduced to one third of the original 13 000 km2 5000 mi2 by the time the delta front prograded to the caldwell area the original lake area may have been sufficient to evaporate most of the inflow and the lake may have only occasionally spilled into other basins diminished area for evaporation later in the history of the lake combined with reduced evaporation accompanying onset of the ice ages may have caused the lake to rise and overtop a basin sill about 2 ma and subsequently deepen hells canyon

response of cave air co2 and drip water to brush clearing in central texas implications for recharge and soil co2 dynamics 1 brush removal is commonly conducted to increase water availability in arid areas such as central texas where water resources are stressed the effectiveness of brush clearing to enhance recharge however remains uncertain as numerous studies have yielded contradictory results this study assesses the effects of brush clearing on recharge to a cave at natural bridge caverns central texas by evaluating changes in drip rate drip water compositions cave air co2 concentrations and calcite growth in a cave underlying an area cleared of brush drip sites were monitored for 3 years preclearing and 2 years postclearing at five drip sites beneath and seven drip sites not beneath the surface cleared of brush physical and chemical drip water parameters exhibit preclearing and postclearing variability postclearing drip rate characteristics reflect an initial interval of anomalously heavy rainfall then a longer dry period drip water 87sr 86sr values do not exhibit preclearing to postclearing variation at sites beneath the cleared area and indicate no change in postclearing water residence time significant decreases in postclearing cave air co2 are observed at seven of nine drip sites in the cave beneath the clearing decreases in cave air co2 influence calcite growth which impacts postclearing drip water mg ca and sr ca decreases in cave air co2 immediately following brush clearing suggest that a significant portion of soil co2 respiration is from tree root respiration rather than from soil microbial activity seasonal calcite growth patterns linked to cave air co2 also exhibit variability postclearing and suggest that cave mineral deposits may record historical changes in vegetative cover

regional controls on the geochemical evolution of saline groundwaters in the edwards aquifer central texas geochemical and isotopic parameters are used to evaluate models for the evolution of saline groundwaters in the edwards aquifer which lies on the northwestern margin of the gulf of mexico sedimentary basin saline groundwaters termed badwaters range in salinity from 1000 to 12 500 mg l 1 total dissolved solids models for badwater evolution must account for complexities owing to 1 the range in compositions of saline basinal fluids that may migrate into the edwards aquifer from its down dip section and from underlying hydrostratigraphic units 2 the range of depositional diagenetic and mineralogic variations in the hist aquifer rocks 3 volcanic and intrusive igneous rocks that locally crosscut the aquifer 4 extensive faulting which in places juxtaposes edwards aquifer units with adjacent hydrostratigraphic units calcium mg na so4 cl and hco3 variations define six badwater hydrochemical facies strontium isotope values of freshwaters 87sr86sr 0 7077 0 7086 badwaters 0 7076 0 7094 and brines from aquifer rocks down dip 0 7078 0 7097 are nearly all higher than the range of most edwards aquifer rocks 0 7074 0 7077 and volcanic and intrusive igneous rocks that crosscut the aquifer 0 7032 0 7055 argillaceous carbonate rocks that underlie the edwards aquifer are likely sources of sr with high 87sr86sr values transitions between the hydrochemical facies in some locations correspond to changes in depositional environments in aquifer rocks and to changes in the intensity of faulting through the aquifer major element mineral saturation state and srca 87sr86sr variations in badwaters of the westernmost aquifer region indicate that incongruent dissolution of gypsum and recrystallization of calcite control the geochemical evolution of these badwaters srca na cl 87sr86sr variations in badwaters of extensively faulted areas to the east of the westernmost aquifer region are consistent with fluid mixing processes involving at least five endmember fluids including 1 saline groundwaters from two underlying hydrostratigraphic units 2 two endmember brines from down dip edwadrs aquifer equivalent units and 3 freashwaters that have interacted extensively with aquifer rocks the compositions of badwaters from the northeasternmost region reflect fluid mixing between freshwaters and saline groundwaters from underlying hydrostratigraphic units

a conceptual model for groundwater circulation using isotopes and geochemical tracers coupled with hydrodynamics a case study of the lez karst system france abstract geochemical and isotopic tracers 18o 2h 87sr 86sr and 13ctdic were used to constrain origins and chemical evolution of groundwater in a mediterranean karst system the lez spring is the main perennial outlet of this karst system and supplies the metropolitan area of montpellier southern france with drinking water groundwater samples were collected at the lez spring and surrounding springs and wells under different hydrodynamic conditions during two hydrological years from june 2008 until may 2010 the results show that multiple hydrological compartments interact through an important network of fractures and faults they notably reveal connections between the main jurassic limestone aquifer and the overlying cretaceous valanginian compartment and between the surface and deep levels of the karst system isotopic tracers provided information about atmospheric recharge origins lithological signatures and chemical evolution of waters long residence time groundwaters issued from deep layers have a triassic hydrochemical fingerprinting being enriched in 13ctdic and characterized by high concentrations in cl as well as high sr ca mg ca and 87sr 86sr ratios evidences suggest that these waters mix with waters from the lower layers of the main jurassic aquifer constitute an intermediate storage compartment prone to rise through piston flow mechanism a two end member hydrograph separation based on ec tds was used to determine the proportion of the deep compartment s contribution to the lez spring outflow on average over the study period the main aquifer compartment and the deep aquifer compartment are estimated to contribute 92 6 and 7 4 of groundwater flow at the lez spring respectively

lake type controls on petroleum source rock potential in nonmarine basins based on numerous empirical observations of lacustrine basin strata we propose a three fold classification of lacustrine facies associations that accounts for the most important features of lacustrine petroleum source rocks and provides a predictive framework for exploration in nonmarine basins where lacustrine facies are incompletely delineated 1 the fluvial lacustrine facies association is characterized by freshwater lacustrine mudstones interbedded with fluvial deltaic deposits commonly including coal shoreline progradation dominates basin fill resulting in the stacking of indistinctly expressed cycles up to 10 m thick in map view the deposits may be regionally widespread but laterally discontinuous and contain strong facies contrasts transported terrestrial organic matter contributes to mixed type i iii kerogens that generate waxy oil type i kerogen is hydrogen rich and oil prone type iii kerogen is hydrogen poor and mainly gas prone the luman tongue of the green river formation wyoming and the honyanchi formation junggar basin china provide examples of this facies association which is also present in the songliao basin of northeastern china the central sumatra basin and the cretaceous doba doseo basins in west central africa 2 the fluctuating profundal facies association represents a combination of progradational and aggradational basin fill and includes some of the world s richest source rocks deposits are regionally extensive in map view having relatively homogenous source facies containing oil prone type i kerogen examples include the laney member of the green river formation wyoming the lucaogou formation junggar basin china the bucomazi formation offshore west africa and the lagoa feia formation campos basin brazil 3 the evaporative facies association represents dominantly aggradational fill related to desiccation cycles in saline to hypersaline lakes and may include evaporite and eolianite deposits sublittoral organic rich mudstone facies are relatively thin but may be begin page 1034 quite rich and widespread the highest organic enrichment coincides with the deepest lake stages low input of land plant organic matter results in minimal lateral contrasts in organic content in some cases a distinctive type i s sulfur rich kerogen may generate oil at thermal maturities as low as 0 45 vitrinite reflectance equivalent examples include the wilkins peak member of the green river formation wyoming the jingjingzigou formation junggar basin china the jianghan and qaidam basins china and the blanca lila formation argentina

folding with thermal mechanical feedback a reply a unified theory of deformation at all scales is outlined processes operating during deformation and metamorphism can be coupled in the form of reaction diffusion equations solutions to these equations depend on the specific processes that dominate the dissipation of energy hobbs et al 2008 is concerned with a scale where deformation and conduction of heat dominate and this corresponds to the regional scale other papers present results for other length and time scales boudinage develops through these processes in materials where the strict biot theory predicts no boudinage the strict biot theory is applicable only at the instant of instability and provides no information on the subsequent growth of the folds analytical results for growth to large amplitudes show that only one wavelength develops and not a spectrum of wavelengths as proposed by treagus and hudleston in press and others the wavelength to thickness ratio that finally develops is strongly dependent on boundary conditions and so such ratios tell us nothing about the conditions of folding unless these boundary conditions are known the processes involved in folding with thermal mechanical feedback are identical for single and multi layer systems so that it requires little space to expand the discussion to multi layers

stratigraphic classification of ancient lakes balancing tectonic and climatic controls lakes and lake deposits present two fundamental paradoxes 1 modern lakes are vastly complicated but the rock records of lakes are relatively simple extensive observations reveal three distinct facies associations of common and widespread occurrence these are referred to here as fluvial lacustrine fluctuating profundal and evaporative facies associations 2 most explanations of modern and ancient lakes attribute their nature to climate but neither modern lake parameters lake size depth and salinity nor the character of ancient lake strata thickness extent lithology correlate with measured or inferred climatic humidity we propose that it is the relative balance of rates of potential accommodation mostly tectonic with sediment water fill mostly a function of climate that controls lake occurrence distribution and character lake basins may be termed overfilled balanced fill or underfilled depending on the balance between these rates we conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales 1 m to hundreds of meters and macroscales hundreds to thousands of meters

navier stokes flow and transport simulations using real fractures shows heavy tailing due to eddies 1 two dimensional navier stokes flow and transport simulations are conducted for a 15 cm long fracture mapped via x ray computed tomography 1 the actual fracture with irregular aperture 2 a truncated fracture where the largest aperture area is excluded from the domain 3 the truncated fracture with further thinning of other large aperture areas and 4 a fracture with uniform vertical aperture equal to the actual fracture s mean aperture are subjected to the same pressure gradient slight variations in fracture characteristics result in significantly different flow and transport behavior flux is much larger for the uniform aperture fracture compared to the actual fracture a pronounced eddy is present at the largest aperture zone of the actual fracture resulting in a power law tail absent in other cases the uniform aperture fracture has the largest effective dispersion coefficient estimated via inversion of a 1d analytical model the analytical model fit to the other cases is not as robust as in the uniform aperture case

storm response of the karstic carbonate aquifer of southcentral kentucky abstract temperature and specific conductance were continuously measured in the downstream drainage of the turnhole spring subbasin in the southcentral kentucky karst precipitation was monitored with a rain gage network in the catchment area so that the storm response of specific conductance and temperature could be examined the aquifer feeding the turnhole spring is highly karstic with much of the discharge through integrated open conduits some of which carry water from surface sinking stream catchments both temperature and specific conductance fluctuate rapidly in response to storm events the conductivity curves and to a lesser extent the temperature curves show a sharp dip that lags some hours behind the storm pulse at the onset of the dip is a complicated sequence of fine structures that is interpreted to be the inputs from conduit tributaries to the master trunk drainage system the recovery curves have an exponential form that can be fitted to produce a characteristic response time for the conduit system

river reversals into karst springs a model for cave enlargement in eogenetic karst aquifers most conceptual models of epigenic conduit development assume that conduits sourcing karst springs form as water that is undersaturated with respect to carbonate minerals flows from recharge to discharge points this process is not possible in springs fed by distributed recharge that is transmitted through aquifer matrix porosity such as unconfined aquifers in eogenetic carbonate rocks diffusely recharged water has a long residence time within the aquifer and thus would have equilibrated with the aquifer rocks prior to discharge to the conduits the upper floridan aquifer has high matrix permeability 10 13 m 2 and many springs lack discrete inputs of undersaturated allogenic water in their recharge areas consequently another explanation for their development is necessary during flooding of the suwannee river in north central florida water highly undersaturated with respect to carbonate minerals commonly recharges the upper floridan aquifer through spring vents and solution scallops oriented away from the vents suggest most dissolution along conduit walls occurs during these flow reversals during a single flow reversal at the peacock spring cave system flood water was capable of dissolving up to 3 4 mm of the conduit wall rock dissolution occurs as flow reversals follow preexisting features that include joints and paleo water table caves lack of speleothems in conduits in the upper floridan aquifer has been used as evidence that the caves formed in the phreatic zone however flooding would dissolve any speleothems that may have formed during previous subaerial exposure conduit enlargement during flow reversals suggests that dissolution can progress in the normal upstream directions and this process may be an important driver of dissolution in any karst aquifer with outflows to surface water that are subject to flooding flow reversals would also introduce dissolved organic carbon and oxygen into the groundwater and provide important energy sources for cave ecosystems as well as altering redox chemistry of the aquifer water

the snake river plain idaho representative of a new category of volcanism studies of the volcanic geology of the snake river plain idaho and comparison with other basaltic regions suggest a new category of volcanic activity termed basaltic plains volcanism typified by the snake river plain this style of volcanism is intermediate between basaltic flood or plateau eruptions and hawaiian volcanism characteristics that are common to both hawaiian and plains volcanism are multiple lava flow units which erupt primarily from point sources formation of low shields and frequent emplacement through lava tubes or channels characteristics that are common to both flood basalts and plains volcanism are high volume flows vents aligned along rift zones and planar surfaces the recognition of plains volcanism in other areas provides a means to interpret the style of eruption and volcanic history

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

structure and eruptive mechanisms at surtsey volcano iceland glassy basalt tuff was the primary material cored in 1979 from a 181 m deep drill hole on the east tuff ring of surtsey volcano despite the fact that the hole extends 122 m below sea level all the core is similar to the exposed tephra composing the two tuff rings of the island the tuff includes abundant accretionary lapilli and tuff vesicles indicating that it was all deposited subaerially during the growth of the tuff rings repeated hydromagmatic explosion cycles began with a series of intermittent tephra finger explosions leading up to continuous uprush explosions which lasted for several minutes to several hours this nozzle like continuous activity produced eruption columns 100 250 m in diameter and 500 2000 m in height which probably quarried several hundred metres below the ground surface the continuous uprush explosion type provides a reasonable mechanism to excavate a diatreme from the top down during construction of the tuff rings concentric faults repeatedly downdropped a funnel like structure 400 800 m in diameter several hundred metres thus accounting for the presence of subaerially deposited tephra in the drill core far beneath sea level ring dykes later intruded upward along these faults and fed small lava flows heat in the surface tephra probably originated primarily from these shallow intrusions

using hydrochemical stable isotope and river water recharge data to identify groundwater flow paths in a deeply buried karst system the deeply buried river connected xishan karst aquifer xka in western beijing china has been suffering from diminishing recharge for several decades which in turn leads to the disappearing of spring water outflows and continuously lowering of groundwater level in the area thus it is important to correctly recognize the groundwater recharge and flow paths for the sustainable development of the xka to investigate these issues the hydrochemical and isotopic compositions are analysed for both surface water and groundwater samples collected over an area of about 280 km2 results show that a the river water is characterized by high na contents b the 2h and 18o values in the river water are distinctively higher than those of groundwater samples after experiencing the long time evaporative enrichment in the upstream reservoir c the sr concentrations and 87sr 86sr ratios of groundwater clearly indicated the interaction between water and carbonate minerals but excluded the water silicate interaction and d the groundwater samples in the direct recharge area of the xka have the lowest na concentrations and the 2h and 18o values based on the large differences in the na contents and 18o values of groundwater and surface water a simple two component mixing model is developed for the study area and the fractions of the river water are estimated for groundwater samples we find that the distribution pattern of the river water fractions in the xka clearly shows a change of directions in the preferential flow path of the groundwater from its source zone to the discharge area overall our results suggest that the recharged surface water can be a useful evidence for delineating the groundwater flow path in river connected karst aquifer this study improves our understanding of the heterogeneity in karst groundwater systems