how landscape heterogeneity governs stream water concentration discharge behavior in carbonate terrains konza prairie usa abstract mounting evidence suggests ecosystem changes that alter subsurface water fluxes and carbon dioxide concentrations in carbonate terrains may drive measurable changes in chemical weathering rates stream water chemistry and flow path evolution on human timescales we test this idea by exploring if the encroachment of woody vegetation into grasslands in a carbonate terrain landscape at the konza prairie ks usa has resulted in differences in landscape stream connectivity and thus the behavior of stream water solutes woody encroachment up to 60 cover at konza has been observed on watersheds particularly those that experience a fire return interval of four years or greater we focus on three headwater catchments two grassland and one woody encroached and a downstream confluence and analyze stream water discharge and chemistry major anions cations and dissolved nutrients measured from 2015 to 2016 we observe that the woody encroached watershed exhibits a greater area normalized solute flux and greater degree of chemodynamic behavior for most geogenic species compared to the less encroached grassland watersheds the downstream confluence exhibits the most chemostatic behavior for these same solutes compared to the low order watersheds we interpret the chemodynamic behavior of the woody encroached watersheds to arise from a greater diversity of flow paths and solute sources that contribute to this stream end member mixing analysis emma supports this hypothesis but also indicates a possible missing end member which we interpret to be solutes likely derived from clay weathering along limestone mudstone boundaries we invoke differences in rooting systems between grass and woody species to explain the differences in flow paths and solute generation between these headwater sites given that they sit adjacent to each other dissect the same nearly horizontal dip 0 1 0 21 nw lithologic units and experience the same climate if these processes hold true at other sites then the globally observed encroachment of woody vegetation into grasslands may deepen flow paths and enhance chemical weathering fluxes from ecosystems and over long time periods alter the trajectory of soil development and landscape evolution

sources of weathering derived solutes in two granitic catchments with contrasting forest growth chemical weathering is one of the controlling factors for landform evolution here we present deductions about the location and rate of chemical weathering within catchments based on chemical observations of soil water groundwater springs and streams in two granitic catchments with contrasting forest growth conditions forested and non vegetated and soil development the two catchments are located in the tanakami mountains of central japan and share the same climate in both catchments sio2 and na are the dominant weathering derived solutes in the first order stream using hydrological evidence the contribution to the sio2 and na fluxes from soil and bedrock were partitioned despite the difference in mean soil depth net fluxes of sio2 and na from the soil profile do not differ much between the two catchments suggesting low levels of easily weatherable minerals in the forest soil net sio2 and na fluxes from bedrock are about three times greater in the forested catchment than in the bare catchment and these differences contribute largely to the difference in net fluxes from the catchments net fluxes of sio2 and na from the forested catchment are about twice those from the bare catchment part of this increase may be related to the greater proton production in forested catchment consequently about 60 to 70 of the net sio2 and na fluxes from the non vegetated catchment and 70 to 90 from the forested catchment are derived from bedrock suggesting that the contribution of bedrock to the export of these weathering products increased with forest growth and soil formation copyright 2004 john wiley sons ltd

fast ground water mixing and basal recharge in an unconfined alluvial aquifer konza lter site northeastern kansas abstract ground water chemistry and water levels at three levels in a well nest were monitored biweekly for two and a half years in a shallow unconfined floodplain aquifer in order to study the dynamics of such shallow aquifers the aquifer in northeastern kansas consists of high porosity low hydraulic conductivity fine grained sediments dominated by silt and bounded by fractured limestone and shale bedrock results show that the aquifer underwent chemical stratification followed by homogenization three times during the study period the length of time between maximum stratification and complete homogenization was 3 5 months the chemical parameters most useful for demonstrating the mixing trends were dissolved nitrate and sulfate higher nitrate concentrations were typical of unsaturated zone water and were sourced from fertilizer applied to the cultivated fields on the floodplain variations in sulfate concentrations are attributed to dissolution of rare gypsum in limestone bedrock and variable evapoconcentration in the unsaturated zone the mixing of three chemically different waters entrained unsaturated zone water water entering the base of the floodplain aquifer and water in residence before each mixing event was simulated the resident water component for each mixing event was a fixed composition based on measured water chemistry in the intermediate part of the aquifer the entrained water composition was calculated using a measured composition of the shallow part of the aquifer and measurements of soil water content in the unsaturated zone the incoming basal water composition and the fractions of each mixing component were fitted to match the measured chemistry at the three levels in the aquifer a conceptual model for this site explains 1 rapid water level rises 2 water chemistry changes at all levels in the aquifer coincident with the water level rises 3 low measured hydraulic conductivity of the valley fill and apparent lack of preferential flow pathways 4 minuscule amounts of unsaturated zone recharge and 5 dissolved oxygen peaks in the saturated zone lagging water level peaks we postulate that rainfall enters fractures in bedrock adjacent to the floodplain this recharge water moves rapidly through the fractured bedrock into the base of the floodplain aquifer the recharge event through the bedrock causes a rapid rise in water level in the floodplain aquifer and the chemistry of the deepest water in the floodplain aquifer changes at that time the rising water also entrains slow moving nitrate rich unsaturated zone water altering the chemistry of water in the shallow part of the aquifer vertical chemical stratification in the aquifer is thus created by the change in water chemistry in the upper and lower parts of the saturated zone as the water level begins to decline the aquifer undergoes mixing that eventually results in homogeneous water chemistry the rise in water level from the recharge event also displaces gas from the unsaturated zone that is then replaced as the water level declines following the recharge event this new oxygen rich vadose zone air equilibrates rapidly with saturated zone water resulting in a dissolved oxygen pulse in the ground water that peaks one half to 2 months after the water level peak this oxygen pulse subsequently declines over a period of 2 6 months

watershed scale chemical weathering in a merokarst terrain northeastern kansas usa abstract carbonate weathering in the merokarst landscape at the konza prairie near manhattan ks is governed by kinetically rapid reaction rates similar to other carbonate settings the geology of the site consists of repeating couplets of shale and limestone mantled by pleistocene loess on which most soils are built the headwater stream that is the subject of this study is intermittent and well connected to the secondary porosity in the limestone aquifers such that the water chemistry is groundwater dominated despite increasing in situ weathering rates shown by increasing solute concentrations long term 21 of 24 years decline in stream water discharge has reduced chemical denudation the current chemical denudation rate is 0 02 mm yr 1 limestone bedrock thickness 26 6 m is 38 of total bedrock thickness 70 m the present landscape would have taken 1 4 million years to dissolve at current weathering rates despite paleogeographic reconstructions suggesting exposure for the past 260 ma estimates of the time to erode younger strata using current physical and chemical denudation rates are 80 159 ma still much less than the age of the rocks an alternate source of material dust is proposed that may slow limestone weathering which in turn protects shales from physical erosion thereby slowing landscape evolution

depositional environments of the pennsylvanian pottsville formation in the black warrior basin of alabama abstract the pennsylvanian pottsville formation of the black warrior basin in alabama comprises as much as 3000 m of shale sandstone and coal the boundary between the informal units of the lower pottsville and the upper pottsville is the base of the black creek coal group in the middle part of the section lower pottsville strata include orthoquartzitic sandstone shale and coal interpreted as having been deposited in a barrier back barrier setting upper pottsville strata consist of lithic arenite shale coal and minor amounts of orthoquartzite and are interpreted as representing a lateral gradation from lower delta plain to barrier bar previous studies indicated northward sediment dispersal the change in sedimentation patterns in the middle part of the pottsville suggests introduct on into the basin of sediments from an eastern source during pottsville deposition

ecosystem controlled soil rock pco2 and carbonate weathering constraints by temperature and soil water content carbonate dissolution in soil groundwater systems depends dominantly on ph temperature and the saturation state of the solution with respect to abundant minerals the ph of the solution is in general controlled by partial pressure of co2 pco 2 produced by ecosystem respiration which is controlled by temperature and water availability in order to better understand the control of land temperature on carbonate weathering a database of published spring water hydrogeochemistry was built and analysed assuming that spring water is in equilibrium with the soil water rock atmosphere the soil pco 2 can be back calculated based on a database of spring water chemistry the average soil rock co2 was calculated by an inverse model framework and a strong relationship with temperature was observed the identified relationship suggests a temperature control on carbonate weathering as a result of variations in soil rock pco 2 which is itself controlled by ecosystem respiration processes the findings are relevant for global scale analysis of carbonate weathering and carbon fluxes to the ocean because concentration of weathering products from the soil rock system into the river system in humid high temperature regions are suggested to be larger than in low temperature regions furthermore results suggest that in specific spring samples the hydrochemical evolution of rain water percolating through the soil rock complex can best be described by an open system with pco 2 controlled by the ecosystem abundance of evaporites and pyrite sources influence significantly the chemistry of spring water and corrections must be taken into account in order to implement the inverse model framework presented in this study annual surface temperature and soil water content were identified as suitable variables to develop the parameterization of soil rock pco 2 mechanistically consistent with soil respiration rate findings

dust impure calcite and phytoliths modeled alternative sources of chemical weathering solutes in shallow groundwater abstract in highly reactive carbonate terrains that constitute more than one fifth of critical zone landscapes quantifying bedrock weathering processes may require understanding the realities of carbonate mineral impurity on solubility biotically produced minerals as an integral part of leaky biogeochemical cycles and dust deposited minerals as important high surface area first contact solute sources the potential impact of these processes has not been thoroughly investigated as groundwater solutes are mostly thought to be sourced from chemical reactions with soil and bedrock although dust is often viewed as an important delivery mechanism of nutrients to other ecosystems including those in mountain and tropical settings we present results of computer and hand calculated manual inverse modeling of two years of stream water chemistry spanning a dry and a wet year for a groundwater fed headwater stream at the konza tallgrass prairie long term ecological research site in northeastern kansas weathering of the limestone and shale bedrock at the site provide a possible source of solutes to the groundwater fed stream but our modeling suggests an alternate source considering the pathway of groundwater recharge likely encounters highly reactive phases before encountering bedrock we used the mineralogy and geochemistry of local dust collected previously estimates of a possible chemical composition of phytolith containing potassium and an impure calcite representing measured limestone bedrock chemistry to show that chemical reactions with the current dust flux are adequate to account for the groundwater chemistry average annual amounts were about 1 380 kg ha 1 yr 1 dust dissolved 2 80 kg ha 1 yr 1 bedrock carbonate dissolved and 3 320 kg ha 1 yr 1 phytoliths precipitated small amounts of cation exchange were also required to balance the models there were only small differences between the computer and manual inverse models both methods resulted in up to 4 6 times more mass of dust dissolved than bedrock we suggest that dust weathering may be a process that occurs widely considering the ubiquitous dust flux in continental regions significance of research solutes in groundwater and in streams fed by groundwater are thought to be mostly derived from aquifer bedrock and soil water recharging the aquifer this paradigm may fail for landscapes that have been subaerially exposed for 10 s to 100 s of millions of years in terrains where relatively rapid dissolution of minerals dominates such as carbonate mineral dominated rocks like limestone here we test whether dust having high surface area and being the first inorganic solid encountered by meteoric precipitation could provide enough solutes water to reduce the amount of bedrock that dissolves extending the timeframe of landscape evolution we found through inverse modeling with phreeqc that dust can provide 4 6 times as much mass to stream water in merokarst than calcite and that the mass of dust dissolved was the same order of magnitude as local dust deposition these results give permissive evidence that dust is important to understanding groundwater chemistry

hydrogeology of thin limestones the konza prairie long term ecological research site northeastern kansas abstract the konza prairie research natural area and national science foundation long term ecological research lter site is a dissected tallgrass prairie upland located in northeastern kansas it is underlain by nearly horizontal alternating thin limestones and shales of permian age and by discontinuous quaternary alluvium shallow aquifers which interact with surface water in this region are an important steady source of water to the biota because of sporadic precipitation this study provides a summary of the shallow hydrogeology in a typical watershed on the konza prairie including an overview of directions of ground water movement inferred from water level data and of ground water chemistry measurements made every 4 to 6 weeks for over 2 5 years provide information on spatial and temporal variability in water chemistry and in directions of ground water flow during the end of a drought first year during a period of average rainfall second year and through a period of exceptionally high summer rainfall third year well yields from the limestones each cut by the ephemeral stream draining the watershed are variable and depend upon secondary porosity development potential for vertical flow is downward in all units and lateral flow directions are sometimes toward and sometimes away from the stream in addition water levels are sometimes above and sometimes below the tops of the aquifers indicating that aquifers behave sometimes as confined and sometimes as unconfined aquifers the stratigraphically and topographically lowest unit monitored morrill limestone is the highest yield aquifer and appears to be hydraulically linked to the stream the uppermost unit studied upper eiss limestone has water chemistry and well yield somewhat similar to the morrill although there is insufficient well control to establish that it too is closely linked to the stream the middle unit lower eiss limestone is characterized by lower hydraulic conductivity steady water chemistry and higher total dissolved solids than the upper and lower units despite the differing hydraulic behavior of the limestones concentration ranges of the major elements in water samples from the aquifers overlap with the exception of consistently higher dissolved magnesium in the lower eiss limestone water variability in hardness alkalinity and sulfate the principal components of the dissolved solids do not clearly distinguish between high and low permeability aquifers or parts of aquifers occasional easily identified sulfate spikes are the result of dissolution of pockets of gypsum or anhydrite in the limestones relatively long term progressive depression of sulfate concentrations is probably the result of steady recharge during relatively long et periods and is a good indicator of flushing of the aquifers even though water levels are not elevated calcium and alkalinity variations at this site reflect variations in recharge as modified by seasonal variations in below ground p co 2 calcium magnesium ratios are not constant indicating that either there is a non carbonate mineral source for magnesium or that more than one carbonate mineral with different magnesium contents contributes calcium to the water the time series sampling used in this study revealed information about the complicated chemical and hydraulic response of these shallow thin limestone aquifers to variable recharge

origin of a foreland dipping seismogenic zone and its basal decollement in southwestern taiwan abstract an unusual foreland dipping seismicity band has been identified at a depth between 7 and 25 km beneath the coastal plain a foreland basin in southwestern taiwan this seismogenic zone is closely associated with abrupt changes in vp vs based on our new high resolution seismic tomography rocks with high vp vs ratios of up to 1 84 were found directly above the inclined seismicity band below it the vp vs ratio dramatically drops to about 1 72 1 78 we found that this change may result from illite bearing slates transforming to muscovite bearing phyllite mica schist previous studies suggested that the frictional instability regime for illite quartz gouge and muscovite quartz gouge falls in the range of 250 500 c we calculated the isotherms based on regional heat flow data and found that the foreland dipping seismicity band can well be bounded between the 250 c and 500 c isotherms in addition in the same temperature range wet illite hydromuscovite would transform to muscovite and release water this dehydration may elevate pore pressure and facilitate the formation of an incipient decollement at the base of the seismicity band in front of the mountain belt the hypothesis that such a decollement exists is supported by the existence of a corresponding zone of low resistivity and also by the geometry of the earthquake of october 22 1999 the latter clearly shows a fault branched off the basal decollement with an angle about 45 this finding implies that the effective friction coefficient of the basal decollement is at least 23 less than that of the overlying rocks

formation of phreatic caves in an eogenetic karst aquifer by co2 enrichment at lower water tables and subsequent flooding by sea level rise formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater extensive phreatic caves also occur however in eogenetic karst aquifers where fresh and saltwater do not mix for example in the upper floridan aquifer these caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs alternatively these caves have been hypothesized to have formed at lower water tables during sea level low stands these hypotheses have not previously been tested against one another analyzing morphological data and water chemistry from caves in the suwannee river basin in north central florida and water chemistry from wells in the central florida carbonate platform indicates that phreatic caves within the suwannee river basin most likely formed at lower water tables during lower sea levels consideration of the hydrological and geochemical constraints posed by the upper floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose co2 gas into the groundwater sea level rise and a wetter climate during the mid holocene lifted the water table above the elevation of the caves and placed the caves tens of meters below the modern water table when rising water tables reached the land surface surface streams formed incision of surface streams breached the pre existing caves to form modern springs which provide access to the phreatic caves phreatic caves in the suwannee river basin are thus relict and have no causal relationship with modern surficial drainage systems neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers dissolution at water tables potentially driven by vadose co2 gas offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks copyright 2012 john wiley sons ltd

hydrologically driven variations in the karst related carbon sink fluxes insights from high resolution monitoring of three karst catchments in southwest china summary rainfall p discharge q water temperature ph and specific electrical conductivity ec of the three karst catchments banzhai huanghou and houzhai with different land uses and carbonate lithologies but similar subtropical monsoonal climate in guizhou province southwest china were monitored with ctdp 300 high resolution multi parameter data loggers during the period of may 2007 october 2013 in addition hco3 and calcium concentrations were titrated in the field and the other major ions determined in the laboratory once every one or two months simple linear regression models were used to link the continuous chemical data to in situ measured data to estimate the concentration of hco3 the co2 partial pressures and the calcite saturation indices on the high resolution logger data continuous karst related carbon sink fluxes csfs were also estimated with the continuous q and hco3 concentrations in each catchment area the primary goal of this study is to understand how discharge and hco3 concentration determine the csfs at the storm scale seasonal scale and annual scale and to estimate the csfs for the three studied catchments results show that the variation in runoff river discharge played a more important role in controlling the csfs than the variation in hco3 for all the karst catchments because of the chemostatic behavior of hco3 in the catchments soil coverage vegetation and bedrock lithology determined the csfs by controlling the proportion of precipitation that recharges groundwater and thus q and controlling the soil co2 productivity and thus hco3 the average csfs in the banzhai huanghou and houzhai karst catchments were 29 3 33 5 and 39 8 t co2 km 2 a 1 respectively which are 15 times higher than those csfs by silicate weathering in the silicate rock catchments with similar hydrology showing the dominant role of carbonate weathering in the rock weathering related carbon sink the interannual change in csfs was large 1 7 2 5 fold for this study depending mainly on the variations of catchment river discharge e g high flow year vs low flow year this suggests that the conventional view that pre and post anthropogenic riverine carbon fluxes are equal is problematic in that large changes in river hydrology caused by global climate and land use and land cover changes have already been documented

eustatic and autocyclic influences on deposition of the lower pennsylvanian mary lee coal zone warrior basin alabama abstract deposition of marine strata associated with the lower pennsylvanian mary lee coal zone pottsville formation was controlled by the allocyclic mechanism of eustatic sea level change the vertical stacking of marine marginal marine and terrestrial facies indicates that this interval was deposited during a single transgression regression transgression cycle ravinement surfaces and associated autochthonous macro invertebrate and trace fossil assemblages record the landward retreat of the shoreline and abrupt deepening due to rapid rise in sea level these horizons are overlain by terrigenous clastic facies either tidal sand bodies or shelf mudstones which indicate shoaling due to progradation during the subsequent filling of the generated accommodation space although marine influence including the effects of tidal currents continued during the more terrestrial phases of deposition autocyclic factors including the control of paleotopography by differential compaction of buried peat bodies were also important in determining facies distribution

the controls on the major and trace element variation of shales siltstones and sandstones of pennsylvanian permian age from uplifted continental blocks in colorado to platform sediment in kansas usa shales siltstones and sandstones of pennsylvanian permian age from near the source in colorado to those in the platform in eastern colorado and kansas have been analyzed for major elements and a number of trace elements including the rees the near source sandstones are significantly more enriched student t test at better than the 99 confidence level in sio2 and na2o concentrations and more depleted in al2o3 fe2o3 total tio2 th hf sc cr cs rees y and ni concentrations and laco and lani ratios than the near source shales and siltstones most likely due to more plagioclase and quartz and less clay minerals in the sandstones than in the shales and siltstones there are no significant differences in k2o and sr concentrations and eueu lalu lase thsc thco and crth ratios between the near source sandstones and the near source shales and siltstones samples of the molas hermosa and cutler formations near the source that were formed in different environments in the same area contain no significant difference in eueu lalu lasc thsc thco and crth ratios so a generally silicic source and not the environment of deposition was most important in producing these elemental ratios for example crth ratios of near source shales siltstones and sandstones range from 2 5 to 17 5 and eueu range from 0 48 to 0 78 which are in the range of sources of sediments derived from mainly silicic and not basic sources near source shales and siltstones contain significantly higher student t test and more varied concentrations of most elements al2o3 fe2o3 mno tio2 ba th hf ta co sc rees nb y but significantly lower concentrations of na2o and eueu than platform shales and siltstones in kansas e g la 65 7 40 and eueu 0 55 0 07 in near source shales and siltstones and la 23 7 8 7 and eueu 0 64 0 08 in platform shales and siltstones the sio2 and cao concentrations are not significantly different in platform shales and siltstones compared to the near source shales and siltstones so dilution of other minerals by quartz and calcite is not the main reason for the lower concentration of most elements in the platform relative to the near source shales and siltstones rather the lesser concentrations of most elements in clay minerals of the platform shales and siltstones can account for the lower concentration of most elements compared to corresponding near source shales and siltstones the lower concentrations of many elements in clay minerals in the platform shales and siltstones may be a result of having been derived from recycling of clay minerals from older rocks the greater homogeneity of elemental concentrations of the platform shales and siltstones compared to those in the source is also consistent with homogeneous mixing of such recycled material also there is no significant difference in thsc laco thco lani and crth ratios of the near source sedimentary rocks in colorado to the platform shales and siltstones in kansas and the latter are also consistent with derivation from mostly silicic source rocks

mechanisms for chemostatic behavior in catchments implications for co2 consumption by mineral weathering a r t i c l e i n f o article history concentrations of weathering products in streams often show relatively little variation compared to changes in discharge both at event and annual scales in this study several hypothesized mechanisms for this chemostatic behavior were evaluated and the potential for those mechanisms to in uence relations between climate weathering uxes and co2 consumption via mineral weathering was assessed data from loch vale an alpine catchment in the colorado rocky mountains indicates that cation exchange and seasonal precipitation and dissolution of amorphous or poorly crystalline aluminosilicates are important processes that help regulate solute concentrations in the stream however those processes have no direct effect on co2 consumption in catchments hydrograph separation analyses indicate that old water stored in the subsurface over the winter accounts for about one quarter of annual stream ow and almost one half of annual uxes of na and sio2 in the stream thus ushing of old water by new water snowmelt is an important component of chemostatic behavior hydrologic ushing of subsurface materials further induces chemostatic behavior by reducing mineral saturation indices and increasing reactive mineral surface area which stimulate mineral weathering rates co2 consumption by carbonic acid mediated mineral weathering was quanti ed using mass balance calculations results indicated that silicate mineral weathering was responsible for approximately two thirds of annual co2 consumption and carbonate weathering was responsible for the remaining one third co2 consumption was strongly dependent on annual precipitation and temperature these relations were captured in a simple statistical model that accounted for 71 of the annual variation in co2 consumption via mineral weathering in loch vale published by elsevier b v

increasing shallow groundwater co2 and limestone weathering konza prairie usa in a mid continental north american grassland solute concentrations in shallow limestone hosted groundwater and adjacent surface water cycle annually and have increased steadily over the 15 year study period 1991 2005 inclusive modeled groundwater co2 verified by measurements of recent samples increased from 10 2 05 atm to 10 1 94 atm about a 20 increase from 1991 to 2005 the measured groundwater alkalinity and alkaline earth element concentrations also increased over that time period we propose that carbonate minerals dissolve in response to lowered ph that occurs during an annual carbonate mineral saturation cycle the cycle starts with low saturation during late summer and autumn when dissolved co2 is high as dissolved co2 decreases in the spring and early summer carbonates become oversaturated but oversaturation does not exceed the threshold for precipitation we propose that groundwater is a co2 sink through weathering of limestone soil generated co2 is transformed to alkalinity through dissolution of calcite or dolomite the annual cycle and long term increase in shallow groundwater co2 is similar to but greater than atmospheric co2 2008 elsevier ltd all rights reserved

an appalachian sourced deltaic sequence northeastern alabama usa biofacies lithofacies relationships and interpreted community patterns abstract the thin sequence of lower pennsylvania rocks along sand mountain plateau coal field northeastern alabama u s a records the deposition in a deltaic coastal plain paleoenvironment along the ancient appalachian seaway the section is laterally continuous well exposed and preserves a rich macrobiota identified coexisting paleodepositional environments contain distinctive biofacies specific paleoenvironments of deposition contain unique biofacies in this late carboniferous westphalian a sequence the criteria established for the recognition of these biofacies can be utilized to assist in refined interpretations of deltaic sites in carboniferous coastal paleoenvironments identifiable biofacies include those preserved under a variety of forested wetland swamp conditions distributary and crevasse splay channels coastal bays interdistributary and lagoonal barrier sands and distal storm deposits fig 1 gastaldo et al 1989 vegetation in forested wetlands grew either in clastic substrates or peat substrates the principal biofacies preserved in clastic substrate swamps were lycophyte dominated and can be recognized by either a predominance of canopy litter or subterranean stigmarian appendages gastaldo 1986 the canopy litter that has accumulated on the forest floor was preserved under unique sedimentological conditions and reflects the ecological gradient associated with the distribution of lycophyte genera in the swamp gastaldo 1987 a monotypic assemblage of lycophytes characterized edaphically stressed sites in sites proximal to the levee a mixed assemblage of lycophytes calamiteans pteridophytes and pteridosperms is common in the absence of compressed canopy macrodetritus subterranean axes with helically arranged appendages rootlets crosscutting the bedding may be preserved macro invertebrates are restricted to traces and trails reflecting behavioral traits when conditions were conducive for their movement into these sites peat colonizing vegetation parallels that of the clastic swamp deep distributary channels contain sandstone cast and compressed aerial trunks of lycophytes and spenophytes these occur in bedload deposits along with quartz and quartzose pebbles and cobble size phyllite clasts degradation of external morphology usually precludes assignment of logs to a systematic position lower than order in shallower en echelon stacked crevasse sands occur a mixture of lycophyte calamitean and pteridosperm woody parts additionally scoriaceous fern like foliage may be found little evidence exists for macro invertebrate communities in these unstable settings coastal bays preserve in situ macro invertebrate communities as well as allochthonous macrodetritus that was derived principally from levee vegetation four phases of biofacies development can be delineated gibson and gastaldo 1987 stress tolerant inarticulate brachiopods dominate the initial transgressive phase individuals are found isolated in the siltstone commonly preserved by authigenic cementation in siderite concretions rarely are patches or clusters of individual encountered where clustering does occur it is associated with the colonization of woody plant parts transition to the molluscan dominated phase is accompanied by the establishment of a rich ichnofauna continued transgression and the development of more normal salinities under lagoonal conditions are paralleled by an increase in species richness and abundance the third biofacies phase remains molluscan dominated but the assemblages at any particular point in time are represented by monospecific genera plant macrodetritus was utilized by the macro invertebrate communities and that which is preserved is restricted to highly fragmentary unindentifiable remains the fourth biofacies phase reflects the development of lagoonal conditions this change can be recognized by macro invertebrate body and ichnofossil fauna seilacher s cruziana ichnofacies diversification an increase in the abundance of brachiopods and other invertebrates is considered to represent more open marine conditions barrier sandstone and distal storm deposits contain disarticulated epifaunal brachiopods bivalves gastropods and trilobites these stenohaline forms are concentrated in a shell lag at the base of migrating barrier sand bodies the overlying sandstone is devoid of macro invertebrate body fossils and plant macrodetritus but is characterized by the colonization of zoophycos traces

ouachita appalachian juncture a paleozoic transpressional zone in the southeastern u s a the northern margin of gondwana collided with the southern margin of the north american craton in the late paleozoic 330 265 ma near normal compressional stresses generated where the trend of the north american margin was nearly perpendicular to gondwana s plate motion vector closure direction caused extensive crustal shortening and decollement thrusting within the sedimentary section the appalachian and ouachita fold belts are the erosional remnants of this collision on the north american margin transecting the ouachita fold belt are several zones of late paleozoic transcurrent faulting the val verde ardmore anadarko and reelfoot zones they occur where the precollision margin of the north american craton was oriented oblique or parallel to the closure direct on with gondwana stresses generated within these zones during the collision were transpressional rather than simply compressional and gave rise to high angle faulting high amplitude vertical displacements and the emplacement of positive flower structures in the val verde and ardmore anadarko basins these features have proven to be major structural traps for oil and gas on the basis of seismic and well data this study identifies a zone of complex structures including positive flower structures in the subsurface paleozoic section of kemper county in east central mississippi the region is considered to be another transpressional zone analogous to the val verde ardmore anadarko and reelfoot zones the kemper county zone separates and truncates the appalachian valley and ridge fo d belt in the subsurface from the mississippi ouachita deformed belt to the west and is therefore also identified as the juncture between the ouachita and appalachian fold belt systems in the southeastern u s a

perennial flow through convergent hillslopes explains chemodynamic solute behavior in a shale headwater catchment abstract stream chemistry reflects the mixture of complex biogeochemical reactions that vary across space and time within watersheds for example streams experience changing hydrologic connectivity to heterogeneous water sources under different flow regimes however it remains unclear how seasonal flow paths link these different sources and regulate concentration discharge behavior i e changes in stream solute concentration as a function of discharge at the susquehanna shale hills critical zone observatory sshczo in central pennsylvania usa concentrations of chemostatic solutes k mg na si cl vary little across a wide range of discharge values while concentrations of chemodynamic solutes fe mn ca decrease sharply with increasing stream discharge to elucidate controls on chemodynamic solute behavior we investigated the chemistry of surface water and shallow subsurface water at the sshczo in early autumn when discharge was negligible and concentrations of chemodynamic solutes were high dissolved ions colloids and micron sized particles were extracted from hillslope soils and stream sediments to evaluate how elements were mobilized into pore waters and transported from hillslopes to the stream during the study period when flow was intermittent the stream consisted of isolated puddles that were chemically variable along the length of the channel inputs of subsurface water to the stream were limited to an area of upwelling near the stream headwaters and the water table remained over a meter below the stream bed along the rest of the channel chemodynamic elements fe and mn were preferentially mobilized from organic rich soils as a mixture of dissolved ions colloids and micron sized particles consequently subsurface water draining organic rich soils in the upper catchment was enriched in fe and mn conversely ca increased towards the catchment outlet and was primarily mobilized from stream sediments as ca2 concentrations of chemostatic solutes were relatively invariable throughout the catchment we conclude that chemodynamic behavior at sshczo is driven by seasonally variable connectivity between the stream and hillslope soils during the dry season stream water derives from a shallow perched water table interflow that upwells to generate metal rich stream headwaters high concentrations of soluble fe and mn at low discharge occur when metal rich headwaters are flushed to the catchment outlet during periodic rain events interflow during the dry season originates from water that infiltrates through organic rich swales thus metals in the stream at low flow are ultimately derived from convergent hillslopes where biological processes have concentrated and or mobilized these chemodynamic elements in contrast high concentrations of ca2 at low discharge are likely mobilized from stream sediments that contain secondary calcite precipitates we infer that chemodynamic solutes are diluted at high discharge primarily due to increased flow through planar hillslopes this study highlights how spatially heterogeneous biogeochemistry and seasonally variable flow paths regulate concentration discharge behavior within catchments

the appalachian ouachita connection paleozoic orogenic belt at the southern margin of north america late paleozoic orogenic belt structures exposed in the appalachian mountains of alabama and in the ouachita mountains of arkansas plunge from opposite directions beneath postorogenic mesozoic cenozoic strata in the mississippi embayment of the gulf coastal plain figure 1 the paleozoic stratigraphic sequence and details of structural style in the ouachita outcrops contrast strongly with those in the appalachian outcrops furthermore straight line projection of structural strike from the outcrops does not lead to a simple connection of structures beneath the coastal plain concealed by the coastal plain cover are answers to questions such as the following are the orogenic belts continuous discontinuous offset or intersecting how are along strike changes in stratigraphy and structural style expressed what is the sequence of tectonic evolution early attempts to interpret the subsurface relationships between the appalachian and ouachita structures were of necessity based on the first few scattered wells that were drilled through coastal plain strata into paleozoic rocks subsequent studies have enjoyed the availability of progressively more numerous deep wells and a growing accumulation of geophysical data various stages in the evolution of thought were outlined by king 1950 1961 1975 and by thomas 1973 1976 this review summarizes available subsurface data in a pre mesozoic paleogeologic

vadose co2 gas drives dissolution at water tables in eogenetic karst aquifers more than mixing dissolution most models of cave formation in limestone that remains near its depositional environment and has not been deeply buried i e eogenetic limestone invoke dissolution from mixing of waters that have different ionic strengths or have equilibrated with calcite at different pco2 values in eogenetic karst aquifers lacking saline water mixing of vadose and phreatic waters is thought to form caves we show here calcite dissolution in a cave in eogenetic limestone occurred due to increases in vadose co2 gas concentrations and subsequent dissolution of co2 into groundwater not by mixing dissolution we collected high resolution time series measurements 1 year of specific conductivity spc temperature meteorological data and synoptic water chemical composition from a water table cave in central florida briar cave we found spc pco2 and calcite undersaturation increased through late summer when briar cave experienced little ventilation by outside air and decreased through winter when increased ventilation lowered cave co2 g concentrations we hypothesize dissolution occurred when water flowed from aquifer regions with low pco2 into the cave which had elevated pco2 elevated pco2 would be promoted by fractures connecting the soil to the water table simple geochemical models demonstrate that changes in pco2 of less than 1 along flow paths are an order of magnitude more efficient at dissolving limestone than mixing of vadose and phreatic water we conclude that spatially or temporally variable vadose co2 g concentrations are responsible for cave formation because mixing is too slow to generate observed cave sizes in the time available for formation while this study emphasized dissolution gas exchange between the atmosphere and karst aquifer vadose zones that is facilitated by conduits likely exerts important controls on other geochemical processes in limestone critical zones by transporting oxygen deep into vadose zones creating redox boundaries that would not exist in the absence of caves copyright 2014 john wiley sons ltd