slag remains from the na slupi site prague czech republic evidence for early medieval non ferrous metal smelting archaeological investigation of the na slupi site in the central part of prague the capital of the czech republic and located in the vicinity of vysehrad castle has demonstrated the presence of early medieval 12th century large scale smelting of non ferrous metals this study is focused on the investigation of smelting remains pb rich red and black slags using a combination of geochemical and mineralogical methods in order to understand the technologies and processes used at this site glassy red slags are composed of high temperature ca k and pb rich silicates wollastonite larnite kalsilite melilite and pb bearing glass and are associated with less abundant litharge fragments red slag impregnated furnace walls composed of litharge massicot pbo and cu2pbo2 they indicate that the cupellation process in small furnaces rather than in crucibles open vessels was used for ag refining at the studied site the black slags found in much lower quantity at this site are composed of maghemite fayalite clinopyroxene melilite and glass and are s poor we believe that they correspond to waste products from the first stage of ag purification prior to final cupellation where slagging additives such as fe rich material silica sand or ashes could be added to remove impurities the pb isotopic composition of both types of slags is similar to the isotopic signature of pb zn ores from the vicinity of cracow poland and supports the hypothesis that pb was probably traded between prague and poland in the 12th century and used for refining precious metals in metallurgical workshops

ediacaran δ13c chemostratigraphy of south china abstract we report new 13 c chemostratigraphic data of the ediacaran system in south china using litho and biostratigraphic markers as independent calibrators we combine new and previously published 13 c data to construct a composite 13 c profile for the ediacaran system in south china the composite curve shows in chronostratigraphic order 1 a negative 13 c excursion en1 in the doushantuo cap carbonate that overlies the ghaub age nantuo diamictite 2 a pronounced positive 13 c excursion ep1 in the lower doushantuo formation where doushantuo type acanthomorphic acritarchs red algae and animal embryos first appear 3 a mild negative 13 c excursion en2 in the middle doushantuo formation 4 a positive 13 c excursion ep2 in the upper doushantuo formation where doushantuo type acanthomorphic acritarchs micrometazoans and stem group florideophyte red algae become abundant and diverse 5 a pronounced negative 13 c excursion en3 near the uppermost doushantuo formation 6 a strongly positive 13 c excursion up to 6 3 pdb ep3 in the lower dengying formation 7 a stable 13 c plateau ca 2 5 pdb ei in the middle and upper dengying formation where abundant vendotaenid algae macroscopic ediacaran fossils biomineralized animal tubes and mostly horizontal animal traces occur and 8 a 10 negative 13 c excursion en4 immediately below the ediacaran cambrian boundary the general pattern of this composite 13 c curve is robust despite a considerable amount of variation among the 13 c profiles of different sections this composite 13 c curve provides a first order chemostratigraphic framework for the subdivision and correlation of the ediacaran system in south china

is mid late paleozoic ocean water chemistry coupled with epeiric seawater isotope records isotopes of epeiric sea carbonates are used to construct seawater records for modeling global changes in paleozoic ocean chemistry climate and for intercontinental correlation we present for the first time geochemical results of paleozoic brachiopods biogenic low mg calcite blmc from open ocean permian carboniferous seamounts of japan situated in the tropical mid panthalassic ocean strontium isotope values of blmc from the panthalassic and paleotethys oceans are coupled with those of coeval specimens from epeiric seas of north america europe and russia p 0 393 but not with those of epeiric sea whole rocks matrix aragonite calcite mac p 0 029 and conodonts biogenic apatite ba p 0 031 oxygen isotope values of blmc from the panthalassic and paleotethys exhibit mixed results with studies of counterparts from epeiric seas p 0 596 reflecting overprinting of local environmental conditions on global trends carbon isotope values of blmc and mac from the panthalassic and paleotethys oceans are generally dissimilar to those of coeval material from epeiric seas of north america europe and russia p 0 001 and 0 002 respectively factors such as water mass stratification evaporation dilution depth temperature carbon burial and or oxidation variations and syndepositional diagenesis within the local environment probably influenced the chemistry of the fauna and accumulating sediments this decoupling of carbon and oxygen isotope values from the open ocean with those from epeiric seas makes questionable the use of isotope results from epeiric seas for international correlation constructing global seawater records determining fluxes in the global carbon cycle and for modeling climate changes and subsequently atmospheric carbon dioxide levels

isotopic records of brachiopod shells from the russian platform evidence for the onset of mid carboniferous glaciation we performed isotopic analyses of carboniferous brachiopod shells from the russian platform to examine global and regional environmental change along the western and eastern margins of laurussia during the formation of pangea and specifically to examine the isotopic evidence for the onset of mid carboniferous glaciation shell preservation was evaluated from shell microstructure cathodoluminescence trace element content and isotopic comparison with matrix material most interior nonluminescent nl prismatic shell appears to be chemically well preserved as indicated by low to undetectable si al fe and mn contents with minor exception nl shell 13c and 18o values are higher than those of corresponding cements and matrix the 13c record for the russian platform clearly shows a 3 increase from 2 4 0 7 to 5 5 0 6 in the serpukhovian or early bashkirian this shift was first reported by popp et al popp b n anderson t f sandberg p a 1986 brachiopods as indicators of original isotopic compositions in some paleozoic limestones geol soc am bull 97 1262 1269 but had not been documented for a single region widespread occurrence of high 13c values in the late carboniferous support the interpretation of popp et al with regard to this shift as a record of increased burial of organic carbon north american sections show a mid carboniferous 13c shift of only 1 5 we hypothesize that the reduced 13c shift reflects enhanced upwelling on the epicontinental seas of north america after the closing of the seaway between laurussia and gondwana the 18o record for the russian platform shows a 1 8 increase in the mid carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level as a first approximation ice volume calculations suggest that 0 7 of the mid carboniferous 18o shift is due to changes in seawater 18o and 1 1 is due to 5 c cooling concurrent positive 13c and 18o shifts provide evidence for a relationship between mid carboniferous glaciation and burial of organic carbon presumably through changes in atmospheric co2 levels

underground renewal time and mixing of the main mineral waters of tunisia a multi tracer study bottled waters are increasingly popular in tunisia most of them come from groundwaters thus raising the question of the long term availability of the mineral groundwater resources water collected from production springs or wells of eleven mineral waters of tunisia among the main commercial brands were analyzed for tritium 3h helium 3 sf6 cfcs and carbon 14 tracer tracer plots indicate that all of the groundwaters of our data set are a mixture of modern rainwater with older groundwater flow waters that are beyond the time scale of the transient tracers 14c data suggest that the age of these old waters which constitute the main water reservoir is of the order of radiocarbon half life or more most of the studied sites have groundwater renewal times in the range 50 150 years for the sites where tracer concentrations are the most diluted by old waters this value logically increase to several centuries

late holocene atmospheric lead deposition in the peruvian and bolivian andes the analysis of lead pb in lake sediment cores is a useful method to reconstruct local histories of pb pollution here we use pb concentration profiles from lake sediments to reconstruct local trajectories of pre colonial smelting from three metallurgical centres in the south american andes the morococha mining district peru the bolivian altiplano around lake titicaca and the silver mining centre of potosi bolivia the earliest evidence for pb enrichment from smelting is on the altiplano beginning ad 400 coincident with the rise of the pre incan tiwanaku and wari empires coeval with the collapse of these empires ad 1000 there is a dramatic decrease in pb pollution on the altiplano suggesting metallurgical activity was closely tied to the tiwanaku state in contrast metallurgy at morococha peru and potosi bolivia began ad 1000 1200 likely as the result of the diaspora generated by the collapses of tiwanaku and wari the independent chronologies of these records suggest asynchronous metallurgical activity between mining centres and local scale control of mineral resources following inca conquest of the andes ad 1450 strong increases in pb are noted at all three study sites suggesting an increase in silver production to meet inca imperial demand following hispanic conquest ad 1532 large increases in pb pollution are noted at morococha and potosi only to be superseded by industrial development the records presented here have implications for the reconstruction of andean prehistory and demonstrate the sensitivity of lake sediment geochemistry to pre colonial smelting activity the technique has much potential for exploring the timing and magnitude of pre industrial metallurgy in the new world

residence time mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone this study aims at establishing groundwater residence times identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression a multi tracer approach major ions sio2 br ba sr2 18o 2h 13c 3h ne ar combined with a groundwater residence time determination using cfcs and sf6 allows defining the global setting of the study site a typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model terrigenic sf6 excesses have been detected and quantified which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally the use of cfcs and sf6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

geochemistry of modern brachiopods applications and implications for oceanography and paleoceanography abstract modern rhynchonellida terebratulida thecideida and a few inarticulated brachiopods were collected live or soon after death at 30 locations from depths of 2 3940 m from the equator to high latitudes covering the atlantic pacific indian caribbean and mediterranean oceans seas well preserved fibers of the secondary layer combined with sr 450 1928 mg kg mn 1 199 mg kg and fe 1 610 mg kg contents confirm with few exceptions the excellent preservation of the modern brachiopod material evaluation of the stable isotope compositions was conducted on 276 specimens and on 374 published samples for a total database of 650 samples from 80 locations it revealed that oxygen isotope incorporation into shell calcite secondary layer of modern articulated brachiopods in most cases occurs in equilibrium with the ambient water and as such reflects surrounding environmental conditions thecideida as a group shallow water and low latitude incorporate oxygen isotopes 3 04 to 0 35 into shell calcite in equilibrium with their ambient water a large majority of genera and species of the terebratulida shallow water and low mid latitude also incorporate oxygen 2 30 to 3 48 into shell calcite in isotopic equilibrium with their surrounding water in contrast equilibrium incorporation of oxygen isotopes into shell calcite by the rhynchonellida is uncertain but a vital effect probably applies to the craniida the question of equilibrium disequilibrium incorporation of carbon isotopes into shell calcite of modern brachiopods remains unresolved at this time isotope compositions range up to 4 5 5 6 and 1 5 for 13 c and up to 5 5 5 9 and 0 3 for 18 o for shallow water low mid and high latitude brachiopods respectively strontium isotopes of modern brachiopods as expected show no significant variation with location latitude water depth temperature salinity and general water conditions once local habitat and ecological influences of fossil brachiopods from similar latitudes are considered their isotopic elemental values should be valuable diagenetic indicators and important oceanographic chemostratigraphic proxies

natural cf4 and sf6 on earth the occurrence of cf4 and sf6 in natural fluorites caf2 is reported contents are found to be typically 200 2000 ppt mass for cf4 and 50 100 ppt mass for sf6 cf4 and sf6 were also detected in granites where fluorite is an accessory mineral cf4 and sf6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt mole and up to 0 01 ppt mole respectively the article also discusses how natural sf6 may cause interference in hydrological tracer studies

high resolution chemostratigraphy of the cambrian ordovician gssp enhanced global correlation tool abstract the green point formation of the cow head group in western newfoundland canada represents the global stratotype section and point gssp for the cambrian ordovician boundary on laurentia the formation consists of the martin point lower and the broom point upper members which constitute a thick 170 m deep subtidal to slope marine carbonate sequence preservation of the micritic carbonates of the green point formation was evaluated by multiple petrographic and geochemical screening tools the 13 c and 18 o values of near primary micrites range from 4 7 to 1 7 vpdb and from 8 7 to 5 5 vpdb respectively with no significant correlation r 2 0 002 similarly the 13 c values show no significant correlation with mn sr ratios or total ree contents which suggest that the investigated carbonates retain their near primary 13 c signatures that can be utilized to construct a high resolution carbon isotope profile for the gssp the 13 c carb profile about the gssp trends generally positive into bed 22 of the green point formation the top of the c intermedius zone marks the onset of a negative 13 c carb shift to about 6 0 culminating in the upper part of the zone subsequently the 13 c carb profile trends positive with a double switch back about the boundary point and then continues on to the highest value in the uppermost part of bed 23 in addition the ce ce values approximately between 0 8 and 1 0 through the gssp suggest generally dysoxic waters before during and immediately after the boundary the high resolution chemostratigraphic results curve and trends covering the gssp should facilitate correlation of the cambrian ordovician boundary sections sequences from other locations

evidence for crustal degassing of cf4 and sf6 in mojave desert groundwaters dissolved tetrafluoromethane cf4 and sulfur hexafluoride sf6 concentrations were measured in groundwater samples from the eastern morongo basin emb and mojave river basin mrb located in the southern mojave desert california both cf4 and sf6 are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the mojave desert these observations provide the first in situ evidence for a flux of cf4 from the lithosphere a gradual basin wide enhancement in dissolved cf4 and sf6 concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium dissolved cf4 and sf6 concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the emb and mrb through the underlying basement the crustal flux of cf4 but not of sf6 is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity when fluxes of cf4 and sf6 into mojave desert groundwaters are extrapolated to the global scale they are consistent within large uncertainties with the fluxes required to sustain the preindustrial atmospheric abundances of cf4 and sf6

crustal thickness variations in southern california from los angeles region seismic experiment passive phase teleseismic travel times the goal of the 1993 los angeles region seismic experiment larse93 passive phase was to collect waveform data from local and distant earthquakes to study lower crust and upper mantle structural features in southern california particularly under the san gabriel mountains and san andreas fault during larse93 approximately 88 stations were deployed in a 175 km long linear array across the los angeles basin san gabriel mountains and mojave desert northeast of los angeles during the four weeks of continuous recording teleseismic events recorded at each site provided a wide range of ray path backazimuths the teleseismic events included a number of intermediate magnitude earthquakes with epicenters in the aleutian island kamchatka kuril island mid atlantic ridge solomon island japan fiji island and chile regions this experiment was followed by larse94 which involved land refraction and deep crustal seismic reflection profiles from offshore and onshore explosion sources we have used the joint data sets in this study to distinguish upper crustal features from adjacent lower crustal and upper mantle structures p wave travel times were determined from 17 teleseisms and upper crustal residual signatures were removed by incorporating larse94 upper crustal velocity model results within each backazimuth range the resulting relative traveltime residuals increase from negative values 0 5 sec average recorded in the northern san gabriel valley southern san gabriel mountain foothills to positive values 0 2 sec average in the central and northern san gabriel mountains the residual patterns display variations for different backazimuths and incidence angles but show almost no lateral spatial shift of maximum or minimum residual along the array indicating that the dominant source of the residual pattern is shallow 50 km the patterns of residuals require a sharp lateral gradient in shallow velocities between the northern san gabriel valley located in the northernmost los angeles basin and the san gabriel mountains over a distance of less than 50 km most of the residual pattern can be explained by laterally varying crustal thickness and a high velocity anomaly in the upper mantle in our model of moho depth variations the northern san gabriel valley to the southwest of the array is underlain by thinned continental crust crustal thickness increases laterally by 12 km over a distance of less than 50 km into the san gabriel mountains this conclusion is supported by widespread surface evidence for rift style volcanism and crustal extension in southern california crustal rocks

isotopic composition 13c 14c 2h and geochemistry of aquatic humic substances from groundwater abstract aquatic humic substances from eight confined and unconfined aquifer aquitard groundwater systems were analyzed for their stable carbon radiocarbon deuterium and elemental contents fractionation of groundwater dissolved organic carbon doc showed that humic substances are an important part of the organic solute load in all groundwaters groundwater humates are distinct from other terrestrial humates and are characterized by low oxygen 36 and high carbon 53 contents elemental data from water table wells suggests this characteristic oxygen depletion is mainly a result of biochemical processes that occur in the vadose zone the stable carbon isotopic composition of groundwater humates range between 31 and 24 pdb with ann average of 26 and reflect their terrestrial origins the deuterium values of groundwater humate vary widely and are mainly a reflection of 2 h h variability in the continental water cycle radiocarbon analyses suggest a predominant soil zone origin for most groundwater humates although some groundwater systems are influenced to varying degrees by buried peat or coal soluble humate 14 c mean residence times of up to several hundred years in the vadose zone before recharging to groundwater are due to the mixing of young and old organic carbon sources rather than advective residence times

water movement through a thick unsaturated zone underlying an intermittent stream in the western mojave desert southern california usa previous studies indicated that small amounts of recharge occur as infiltration of intermittent streamflow in washes in the upper mojave river basin in the western mojave desert near victorville california these washes flow only a few days each year after large storms to reach the water table water must pass through an unsaturated zone that is more than 130 m thick results of this study done in 1994 1998 show that infiltration to depths below the root zone did not occur at control sites away from the wash at these sites volumetric water contents were as low as 0 01 and water potentials measured as the combination of solute and matric potentials using a water activity meter were as negative as 14 000 kpa water vapor movement was controlled by highly negative solute potentials associated with the accumulation of soluble salts in the unsaturated zone highly negative matric potentials above and below the zone of maximum solute accumulation result from movement of water vapor toward the highly negative solute potentials at that depth the 18o and d delta oxygen 18 and delta deuterium isotopic composition of water in coarse grained deposits plots along a rayleigh distillation line consistent with removal of water in coarse grained layers by vapor transport beneath oro grande wash water moved to depths below the root zone and presumably to the water table about 130 m below land surface underneath oro grande wash volumetric water contents were as high as 0 27 and water potentials measured as matric potential using tensiometers were between 1 8 and 50 kpa on the basis of tritium data water requires at least 180 260 years to infiltrate to the water table clay layers impede the downward movement of water seasonal changes in water vapor composition underneath the wash are consistent with the rapid infiltration of a small quantity of water to great depths and subsequent equilibration of vapor with water in the surrounding material it may be possible to supplement natural recharge from the wash with imported water recharge to the wash may be advantageous because the unsaturated zone is not as dry as most areas in the desert and concentrations of soluble salts are generally lower underneath the wash

chemical diagenesis of a multicomponent carbonate system 2 stable isotopes abstract this study examines the oxygen and carbon isotopic distribution in the brachiopods crinoids rugose corals and matrix cement from the mississippian burlington limestone iowa and missouri and the silurian read bay formation arctic canada the isotopic data can be reconciled with textural and trace element observations only if the 18o content of ancient oceans differed from that of the present oceans this postulated secular variation in the 18o content of seawater requires a separate evaluation of the mississippian and silurian carbonate components examination of the 18o content of the least altered low mg calcite fossil components of the two formations suggests that the 18o of mississippian seawater was on average about 1 5 lighter and that of silurian seawater was about 5 5 lighter than the 18o of present day ocean water the average diagenetic shift in 18o for the read bay formation which stabilized in a partly closed diagenetic phreatic meteoric system is about 1 for the original low mg calcite and about 2 for the original high mg calcite and aragonite components conversely for the burlington limestone which stabilized in an open diagenetic phreatic meteoric system the average diagenetic shift in 18o is about 3 for the original low mg calcite and about 4 f r the original high mg calcite components the 13c values of the originally low mg calcite or high mg calcite with less than 7 mole mgco3 brachiopods and rugose corals the originally high mg calcite crinoids and the originally aragonite lime mud of the burlington limestone and read bay formation are bimodally distributed this bimodal 13c distribution is independent of geologic age inferred original mineralogy of the component degree of diagenetic alteration and the type of diagenetic meteoric system with components from both the read bay formation and burlington limestone contributing to both 13c groups the mode of the light 13c group is 0 25 and for the heavy 13c group it is 3 25 pdb both 13c groups also show a decrease in 13c of about 1 with increasing diagenetic alteration stabilization

carbon oxygen and strontium isotopes in paleozoic carbonate components an evaluation of original seawater chemistry proxies abstract brachiopods trilobites cements and whole rock matrix material were evaluated for their reliability as proxies of original seawater carbon oxygen and strontium isotope chemistry in this process coeval material was evaluated from individual horizons of formations spanning the permian to cambrian unaltered shells of low mg calcite articulated brachiopods retain original seawater oxygen carbon and strontium isotope compositions as old as late ordovician assessments of older specimens are hampered by a lack of suitable material coeval brachiopod whole rock sets a definitive assessment of cement marine chemistry is difficult due to the paucity of material but despite this caveat cements hold some promise for retaining original carbon and possibly strontium isotope seawater values in contrast the potential of whole rock material as a proxy of original seawater chemistry is quite complex in some but not all instances the carbon isotopic composition of whole rock after detailed scrutiny and evaluation appears to represent an original seawater chemistry signal in a few instances their oxygen isotope compositions reflect original seawater values unlike the stable isotope compositions the strontium isotopes of all studied whole rock material permian to upper cambrian appear not to reflect original seawater chemistry values thus the potential for retaining original seawater isotope chemistry and serving as specific proxies in order of decreasing reliability are 1 unaltered low mg calcite brachiopods c o and sr isotopes 2 pristine marine cements c and sr isotopes and 3 whole rock material c isotopes carbon oxygen and strontium isotope compositions of ordovician trilobites mirror those of coeval unaltered brachiopods cambrian trilobites hold significant promise as an important proxy of original seawater isotope chemistry but further studies are needed to ascertain their full potential the survey of isotopes in some ordovician and cambrian intermediate low mg calcite trilobites demonstrates their potential as an important proxy of original seawater chemistry

brachiopod fabric classes and biogeochemistry implications for the reconstruction and interpretation of seawater carbon isotope curves and records abstract shell calcite of modern and ancient brachiopods is an important proxy in reconstructing oceanographic conditions of seawater our investigation reveals significant magnesium and carbon isotope relationships between two classes of ancient brachiopods brachiopods of the extinct class strophomenata constructed two or three layer shells with a primary layer of randomized granular calcite a secondary layer of cross bladed laminar calcite and at times a tertiary layer of large prismatic calcite contemporaneous but extant rhynchonellata also have two or three layer shells but their secondary layer consists of calcite fibers instead of cross bladed laminar calcite furthermore inter crystalline space is limited in between the fibers of the secondary layer of the rhynchonellata but higher in the laminar secondary layer of strophomenata 18 o values of the two classes of brachiopods from the same stratigraphic interval of the lopingian nesen formation of north iran show a considerable overlap with no significant difference p 0 263 in contrast carbon isotope values are significantly different p 0 001 between contemporaneous strophomenata mean 2 18 and rhynchonellata mean 4 13 an evaluation of literature data of permian asselian and carboniferous visean and serpukhovian strophomenata mean 2 32 n 59 and rhynchonellata mean 4 94 n 105 confirms a similar differentiation in their carbon isotope values its higher magnesium contents suggest that the strophomenata probably secreted shell calcite at a faster rate than their coeval rhynchonellata this process may account for the 13 c differentiation observed between specimens of these two brachiopod classes however the different amount and composition of the organic matter of the strophomenata may also play a role in shaping their more negative carbon isotope signature thus the class of brachiopod and their associated different fabric must be adjusted for in their 13 c results and taken into consideration during the reconstruction of paleozoic global 13 c carbonate based seawater curves invariably in some earlier studies undetected impacts imposed by the class fabric on 13 c may account for some of the variation or trends documented in deep time seawater 13 c curves reconstructed with brachiopod populations from north america europe and russia

carbon isotope composition in modern brachiopod calcite a case of equilibrium with seawater abstract we examined a large number of modern shallow water articulated brachiopods representing the orders terebratulida rhynchonellida thecideida and one inarticulated brachiopod of the order craniida from polar to tropical regions for their carbon isotope compositions based on our detailed investigation we recommend avoiding fast growth areas such as the youngest shell increments in addition the primary layer and transition zone calcites of brachiopods must be avoided because they are in carbon and oxygen isotope disequilibrium with ambient seawater after adjusting isotope compositions for the mg effect we observed no significant difference p 0 05 in 13 c values between dorsal and ventral valves of our articulated brachiopods using the calcite bicarbonate enrichment factor e in conjunction with 13 c values of dissolved inorganic carbon of habitat seawater we conclude that modern shallow water articulated and some inarticulated brachiopods incorporate oxygen brand et al 2013 and carbon isotopes into shell calcite of secondary and or tertiary layers in apparent equilibrium with ambient seawater within the general concept of equilibrium incorporation with seawater shell 13 c values are an excellent recorder of local global seawater environments and water mass circulation thus application of the mg effect permits brachiopods to be an extremely powerful archive and 13 c values more precise proxy and tracer of past changes in marine productivity evolution of seawater carbon chemistry and variation in the global carbon cycle

groundwater residence time downgradient of trench no 22 at the chernobyl pilot site constraints on hydrogeological aquifer functioning following the explosion of reactor 4 at the chernobyl power plant in northern ukraine in 1986 contaminated soil and vegetation were buried in shallow trenches dug directly on site in an aeolian sand deposit these trenches are sources of radionuclide rn pollution the objective of the present study is to provide constraints for the chernobyl flow and rn transport models by characterising groundwater residence time a radiochronometer 3h 3he method t1 2 12 3 a and anthropogenic tracers including cfc and sf6 are investigated along with the water mass natural tracers na cl 18o and 2h the groundwater is stratified as evidenced by na and cl concentrations and stable isotopes 18o 2h in the upper aeolian layer the na cl relationship corresponds to evapotranspiration of precipitation while in the underlying alluvial layer an increase in na and cl with depth suggests both water rock interactions and mixing processes the 3h 3he and cfc apparent groundwater ages increase with depth ranging from recent 1 3 a at a 2 m depth below the groundwater table to much higher apparent ages of 50 60 a at 27 m depth below the groundwater table discrepancies in 3h 3he and cfc apparent ages 20 25 a and 3 10 a respectively were observed during the 2008 campaign at an intermediate depth immediately below the aeolian alluvial sand limit which were attributed to the complex water transfer processes extremely high sf6 concentrations well above equilibrium with the atmosphere and up to 1112 pptv are attributed to significant contamination of the soils following the nuclear reactor explosion in 1986 the sf6 concentration vs the apparent groundwater ages agrees with this interpretation as the high sf6 concentrations are all more recent than 1985 the persistence of the sf6 concentration suggests that sf6 was introduced in the soil atmosphere and slowly integrated in the groundwater moving along the hydraulic gradient the apparent age distribution in the lumped parameter models suggests an exponential or piston flow model in the upper geological section followed by more pronounced mixing processes in the lower section

deciphering kinetic metabolic and environmental controls on stable isotope fractionations between seawater and the shell of terebratalia transversa brachiopoda this study presents carbon and oxygen stable isotope data obtained from high resolution sampling 500 m of the brachiopod terebratalia transversa from the san juan islands washington state usa the aim of this study is to unravel the respective effects of physiological and environmental controls on the stable isotopic composition of brachiopod shell calcite based on an sem study of the shell a three dimensional sampling was performed in order to investigate carbon and oxygen isotope variations along isochrons and ontogenetic transects the primary as well as the outer part of the secondary shell layer display large and variable isotopic offsets as high as 7 for 13c and 6 for 18o relative to expected equilibrium values the significant positive correlations between 18o and 13c values indicate that the isotopic compositions of these shell domains are mainly controlled by kinetic isotope fractionation effects the ontogenetic 13c and 18o variations can be used to establish a growth curve of the studied specimen whose age is estimated close to 8 years the extent of apparent o 18 disequilibrium observed in this study is about as large as any yet measured in any organism which makes this brachiopod an interesting and important case the carbon and oxygen isotope compositions increase from the outer towards the inner part of the secondary layer where they reach values of 0 0 8 and 0 8 to 0 2 respectively corresponding calculated temperatures are between 12 and 13 8 c and fall in the range of seawater temperatures recorded off the san juan islands 7 13 c these results suggest that the calcite fibres were secreted more and more slowly during the thickening of the shell throughout the animal s life finally approximating isotopic equilibrium this study illustrates that the stable isotopic composition of the modern brachiopod t transversa is predominantly influenced by kinetic fractionation and to a minor degree by metabolic effects except for the innermost part of the shell the measured isotope ratios do not reflect environmental conditions during shell precipitation it remains to be tested by comparable studies whether other modern brachiopod species or even fossil brachiopods reflect comparable fractionation effects these results point out the need for re examination of paleozoic oceanographic conditions

tetrafluoromethane in the deep north pacific ocean 1 dissolved tetrafluoromethane cf4 has been measured for the first time in the north pacific ocean surface water collected during calm weather is near equilibrium with the modern atmosphere deep water isolated from atmospheric exchange for centuries is near equilibrium with the preindustrial atmosphere after accounting for an expected 5 addition of this low solubility gas due to air injection during high latitude deep water formation these results strongly suggest that dissolved cf4 is conservative in seawater and that the oceanic imprint of anthropogenic increases in atmospheric cf4 can be used as a time dependent tracer of ocean ventilation and subsurface circulation processes although the continental lithosphere is a source of natural atmospheric cf4 we find no evidence of an oceanic lithospheric cf4 input into deep pacific waters the estimated upper limit of a potential oceanic lithospheric cf4 flux to the global atmosphere is on the order of 4 of that from the continental lithosphere

intraspecific variations in carbon isotope and oxygen isotope compositions of a brachiopod basiliola lucida collected off okinawa jima southwestern japan abstract this study presents intraspecific variations in carbon isotope 13 c and oxygen isotope 18 o compositions of nine specimens of a subtropical brachiopod basiliola lucida collected west of okinawa jima ryukyu islands southwestern japan the 13 c values of samples collected along the maximum growth axis ontogenetic samples from two modern and seven older pre 1945 cal ad shells show no seasonal changes the modern shells which were collected from comparable depths have similar 13 c values that fall within the range of calcite precipitated in isotopic equilibrium with ambient seawater equilibrium calcite 13 c ec values and their mean 13 c values are 1 1 1 6 less than those from the older shells this decrease in 13 c values is similar in magnitude to the decreases in atmospheric co 2 and the oceanic dissolved inorganic carbon at the sea surface in recent years 13 c suess effect suggesting that the effect can even be detected at water depths of 200 300 m in the subtropical northwestern pacific ocean the 18 o values fluctuate within a narrow range 0 26 0 41 with no seasonal changes and they exhibit small 0 14 0 51 offsets from those of equilibrium calcite 18 o ec values a statistically significant negative linear relationship is established between seawater temperature and mean 18 o values of the nine shells but the slope 0 31 c is steeper than those of equilibrium calcite 0 23 c and other calcareous organisms 0 15 to 0 26 c the cross plots of the 13 c and 18 o values suggest that the degree of the vital effect varies among individuals in this species the 13 c and 18 o values of b lucida are potentially useful for reconstructing the 13 c and 18 o evolution of ancient oceans because both values show small intraspecific variations the former is identical to the 13 c ec values and the latter shows small within shell variations and small nearly constant offsets from the 18 o ec values

late paleozoic middle latitude gondwana environment stable isotope records from western australia abstract one hundred and twelve permian fossil brachiopod samples from two western australian basins carnarvon and canning basins have been analyzed for oxygen and carbon isotopes to study the middle paleolatitude environment in the permian all samples were thin sectioned and examined using petrography and cathodoluminescence microscopy for evaluating shell preservation a total of 249 isotopic analyses from the best preserved portion non luminescent nl of shells were found useful for inferring paleoenvironments for the carnarvon basin average 13 c values of nl shells were between 4 2 and 4 5 for the callytharra formation n 123 late sakmarian early artinskian jimba jimba calcarenite n 7 early artinskian coyrie madeline formations n 71 both late artinskian early kungurian and wandagee formation n 18 late kungurian average 13 c values of nl shells were 5 0 0 4 n 9 for the quinnanie shale cundlego formations both kungurian for the canning basin mean 13 c values of nl shells were 5 1 1 1 n 11 5 3 0 2 n 4 and 4 8 0 5 n 6 for the noonkanbah formation artinskian kungurian lightjack formation roadian capitanian and hardman formation wuchiapingian respectively within the uncertainty of the stratigraphical correlation the carbon isotope values spanning late sakmarian to kungurian in middle latitude western australia are comparable to those of coeval low latitude urals average 18 o values of nl shells were about 0 0 1 to 0 1 for the callytharra formation jimba jimba calcarenite coyrie madeline formations quinnanie shale cundlego formations noonkanbah formation and hardman formation and were 0 5 0 7 and 0 3 0 7 for the wandagee formation and lightjack formation respectively these oxygen isotope values are overall higher than the coeval values reported for low latitude regions and for eastern australia the positive oxygen isotope values are here interpreted to indicate a cool temperature and or a possibly moderately high salinity condition for the two studied basins in western australia during the permian

a method for precise measurement of argon 40 36 and krypton argon ratios in trapped air in polar ice with applications to past firn thickness and abrupt climate change in greenland and at siple dome antarctica we describe a method for measuring the 40ar 36ar ratio and the 84kr 36ar ratio in air from bubbles trapped in ice cores these ratios can provide constraints on the past thickness of the firn layer at the ice core site and on the magnitude of past rapid temperature variations when combined with measured 15n 14n both variables contribute to paleoclimatic studies and ultimately to the understanding of the controls on earth s climate the overall precision of the 40ar 36ar method 1 standard error of the mean is 0 012 for a sample analyzed in duplicate corresponding to 0 6 m in reconstructed firn thickness we use conventional dynamic isotope ratio mass spectrometry with minor modifications and special gas handling techniques designed to avoid fractionation about 100 g of ice is used for a duplicate pair of analyses an example of the technique applied to the gisp2 ice core yields an estimate of 11 3k of abrupt warming at the end of the last glacial period 15 000 years ago the krypton argon ratio can provide a diagnostic of argon leakage out of the bubbles which may happen naturally during bubble close off or artifactually if samples are warmed near the freezing point during core retrieval or storage argon leakage may fractionate the remaining 40ar 36ar ratio by 0 007 per change in 84kr 36ar introducing a possible bias in reconstructed firn thickness of about 2 m if thermal diffusion is not accounted for or 6 m if thermal diffusion effects are quantified with measured 15n 14n reproducibility of 84kr 36ar measured in air is about 0 2 1 standard error of the mean but is about 1 for ice core samples ice core samples are systematically enriched in 84kr 36ar relative to atmosphere by 5 probably reflecting preferential size dependent exclusion of the smaller argon atom during bubble entrapment recent results from the siple dome ice core reveal two climate events during the last deglaciation including an 18 m reduction in firn thickness associated with an abrupt warming at sometime between 18 and 22 kyr bp and a partial or total removal of the firn during an ablation event at 15 3 kyr bp

springwater provenance and flowpath evaluation in blue lake bonneville basin utah abstract water in utah and nevada is important for agriculture municipal use solute transport and ecosystem preservation large spring wetland systems occur on the playa margin of the bonneville basin including blue lake 15 km south of the bonneville salt flats on the utah nevada state border large spring systems have historically been studied as water budgets don t apparently balance from direct mountain front recharge nelson and mayo 2014 gardner and heilweil 2014 and others blue lake is no exception prior studies here have suggested discharge rates 0 04 0 05 km3 yr louderback and rhode 2009 greater than expected for modelled recharge in the surrounding mountain range 0 03 km3 yr three hypothesized recharge mechanisms for blue lake are tested mountain front recharge interbasinal groundwater flow and infiltration from historic lake bonneville remote sensing suggests that a conservative estimate of blue lake discharge constitutes 50 64 of modelled mountain front recharge flint et al 2011 major ions 18o 2h dissolved gases 14c 3he 4he ne ar kr xe and trace elements sr and 87sr 86sr isotopes comprehensively constrain recharge conditions water rock interactions flowpaths and groundwater provenance of this large spring system 14c signatures suggest that blue lake discharge has a transit time between 5 600 and 12 200 years older than that of fish springs noble gas concentrations in blue lake water suggest an elevated recharge temperature greater than 19 c and low salinity indicating a deep water table and high geothermal gradient in the recharge area 87sr 86sr ratios of playa margin springs are elevated from that of mid playa groundwaters springwaters from the adjacent mountain range and alluvial fill groundwater from the valley directly south of blue lake playa margin spring sr isotope values 0 713 0 714 are most similar to direct runoff from the deep creek range granodiorite outcrop 0 713 interbasinal groundwater flow in combination with mountain front recharge is best supported by chemical data rather than mountain front recharge alone or the slow discharge of regional aquifers recharged by lacustrine infiltration from lake bonneville

geochemistry of brachiopods oxygen and carbon isotopic records of paleozoic oceans abstract combined trace element and isotope studies of 319 brachiopods covering the ordovician to permian time span show that 13c and 18o in well preserved specimens varied during the paleozoic the overall 13c secular trend is in accord with the previously published observations but its details are obscured by vital isotopic fractionation effects at generic level nonetheless the results suggest that the negative correlation between marine 13ccarbonate and 34ssulphate deteriorates at time scales of 106 years due to the long residence time and thus slow response of so42 in the ocean for oxygen isotopes all devonian and older specimens have 18o of 4 while the well preserved permian samples have near present day 18o of about 1 pdb this isotopic dichotomy is probably not due to post depositional phenomena salinity or biogenic fractionation effects this leaves open the perennial arguments for a change in 18 o 16 o of sea water versus warmer ancient oceans the present data are difficult to explain solely by the temperature alternative the coincidence of the proposed shift in 18o with the large late paleozoic changes in marine 87 sr 86 sr 13 c 12 c 34 s 32 s and sea level stands argues for a tectonic cause and for a change in 18 o 16 o of sea water although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites whatever the precise cause or combination of causes the implications for tectonism and or paleoclimatology are of first order significance

natural fluorinated organics in fluorite and rocks results of measurements of fluorinated compounds in gasses extracted from igneous and metamorphic rocks are reported a new extraction method analogous to a pepper mill for geological samples is described it permits extraction at low temperatures and ensures a rapid transfer of extracted gases from active surfaces to cryogenic pre concentration loop values for cf4 cf3cl cf2cl2 cfcl3 chf3 sf6 and nf3 in fluorites granites basalts and other igneous and metamorphic rocks are reported it is proposed that trifluoroacetic acid tfa that was recently discovered in various environmental archives could also origin from similar geogenic sources

diagenetic evaluation of a pennsylvanian carbonate succession bird spring formation arrow canyon nevada u s a 1 brachiopod and whole rock comparison abstract diagenetic evaluation of the pennsylvanian bird spring formation arrow canyon nevada u s a involved the detailed petrographic and geochemical examination of its brachiopod and whole rock components 13 c 18 o and 87 sr 86 sr of whole rock wr statistically p 0 0001 do not agree with isotope values of coeval brachiopod low mg calcite lmc more importantly a detailed investigation of the best preserved fine grained whole rock material demonstrates that it does not universally preserve its carbon isotope values in contrast with hypothetical predictions furthermore lumped trace chemistry or stable isotope tests do not unequivocally identify brachiopod or whole rock fine to coarse grained samples that carry an original seawater signal instead diagenetic evaluation involving as many screening tests as possible on a horizon by horizon level to compensate for spatial and temporal variations is necessary to identify the sample s that carries an original seawater signature many brachiopods from the bird spring formation are blue to non luminescent and carry microstructures and trace element contents similar to those of their modern tropical counterparts concurrence of chemical results between well preserved brachiopods and whole rock if originally low mg calcite is achieved in 22 of coeval samples for 13 c blmc wr with natural limits of 0 25 in 20 of samples for 18 o blmc wr with natural limits of 0 25 and in 9 of samples for 87 sr blmc wr with global limits of 0 000025 after an adjustment for mineralogical fractionation if whole rock is considered originally aragonite the concurrence of 13 c blmc wr drops to 0 and for 18 o blmc wr it drops to 6 furthermore comparison of stable isotopes of our well preserved brachiopods with those of preserved whole rock from the literature suggests that they are significantly different p 0 0001 with results of the latter dataset being more negative by about 0 77 2 57 with mineralogical adjustment for 13 c pdb and 1 31 2 11 for 18 o pdb thus our integrated screening and comparative tests indicate that 1 an overwhelming number of the whole rock samples from the bird spring formation carry a diagenetic instead of a primary signal for both carbon and oxygen isotopes and 2 many of the biogenic low mg calcite brachiopods in this succession carry an original chemical signal suitable for the reconstruction of high resolution seawater isotope curves representative of the pennsylvanian north american epeiric sea and potentially of the global oceans

climate forced change in hudson bay seawater composition and temperature arctic canada abstract global climate change impacts marine ecosystems directly and indirectly especially in the arctic and antarctic we show the first long term 1920 2011 time series of oceanographic change in hudson bay an arctic marine ecosystem based on coupled brachiopod calcite stable and clumped isotope results long term decrease in brachiopod 13c parallels that of seawater dic in hudson bay and after considering its seasonal sea ice coverage it is similar to that of the 13c suess effect observed in the north atlantic and other regions acidification of hudson bay seawater leads warming by about 10 20 years and with intensified warming from the 1970s to 2010s closely coupled to earlier sea ice breakup post industrial warming of hudson bay is initially slow but in later years faster and of greater magnitude than of the coeval global oceans our observations for the past 90 years suggest that climate forced change contributed to an average increase of about 0 1 c and 3 6 c in sea surface water temperature of hudson bay over the first 50 and subsequent 40 years respectively this 3 7 c post industrial warming of hudson bay seawater is about six times the 0 67 c increase observed during the past 100 years in global ocean sea surface temperature which is about double the postulated increase of about 2 c for polar regions our results are consistent with the general notion that polar marine environments such as hudson bay can serve as sensitive indicators of change in climate and of change still to come for lower latitude ecosystems

silver lining evidence for inka silver refining in northern chile prehistoric silver purification using lead cupellation has been documented in multiple places throughout the andes but direct evidence of the inka use of this technology has remained elusive in this study we use x ray fluorescence scanning electron microscopy and electron microprobe analysis to document direct evidence of inka period ad 1400 1532 silver purification using lead cupellation in the tarapaca valley of northern chile local metalworkers used wind driven huayra furnaces to produce pure lead metal sustaining temperatures of ca 900 1100 c to smelt lead bearing ores that may have included galena the lead metal was then used in open vessel cupellation of silver bearing ores some of which may have been cupriferous and derived from the nearby inka mines at huantajaya phase analyses of the slagged interiors of bowl shaped ceramic vessels used for cupellation indicate that the metalworkers maintained the oxidizing environment and temperatures between 800 and 1100 c requisite for cupellation we argue that the inka introduced this technique to tarapaca metalworkers the absence of finished silver artifacts in local valley contexts suggests that the refined silver was removed from the valley for use elsewhere in the empire

shell structure patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells this study investigates 13c and 18o variations in the shells of modern brachiopods representing all extant groups of calcite precipitating brachiopods collected live from 8 locations sem examinations determined the ultrastructural characteristics of each species prior to isotope analyses 13c and 18o analyses of shell carbonate were carried out with samples representing disparate morphological features and ultrastructural shell layers of both ventral and dorsal valves generally 18o values from the fibrous secondary or prismatic tertiary shell layers of the articulated terebratulida and rhynchonellida species were in oxygen isotopic equilibrium with ambient seawater isotopic temperatures extrapolated from these values are close to measured annual mean seawater temperatures 18o values were relatively unaffected by shell specialisation the only exception was antarctic species liothyrella uva which did not have a complete tertiary shell layer typical of this genus and had 18o values of the innermost layer strongly correlated with 13c and mostly not in oxygen isotopic equilibrium with ambient seawater with the exception of the rhynchonellid notosaria nigricans the outer primary layer material was depleted in 13c and 18o and highly variable inclusion of this material even as part of a whole shell sample could lead to misinterpretation of seawater temperature therefore only fossil secondary layer material should be used the anomalous articulated thecideidine brachiopod thecidellina barretti is composed of mainly primary shell material and was not in oxygen isotope equilibrium 18o values from the laminar secondary layer material of the inarticulated craniida are highly variable therefore these species are not recommended for use as palaeoenvironmental proxies this study suggests caution when employing fossil brachiopod shells with similar ultrastructures to modern craniid and thecideidine brachiopods the carbon isotope composition is highly variable in all of the brachiopods studied analysis of samples from specialised regions of the secondary shell layer show a pattern of depletion in 13c relative to non specialised secondary material the carbon isotope variability is independent of 18o and is repeated in most of the articulated species regardless of geographical location this is possibly a vital effect produced by metabolic prioritisation

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

charcoal taphonomy and significance in geology botany and archaeology abstract charcoal occurs in the natural environment as either a result of wildfire or volcanic processes in addition people may make charcoal either for domestic or industrial use charcoal may be used as a fuel for domestic heating and cooking through a range of industrial uses such as iron smelting more recently the charcoalification process has been used to make biochar that is relatively inert and promotes atmospheric co 2 reduction with such a wide range of uses research has been published in a broad range of journals and often whole areas of study are unfamiliar to other charcoal researchers here we review a range of charcoal studies and their inter relationships we present some of the results of a major international meeting on charcoal brussels september 2008 highlighting the potential of charcoal studies as part of palaeoenvironmental investigations both in a geological and archaeological context

carbon and oxygen isotopic compositions of modern brachiopod shells from a warm temperate shelf environment sagami bay central japan this study presents carbon 13c and oxygen 18o isotopic compositions of shells of an articulated brachiopod laqueus rubellus living in a warm temperate shelf environment in japan high resolution three dimensional samplings were conducted 1 to clarify variations in the isotopic compositions within a single shell 2 to evaluate offset of the compositions from those of the calcite precipitated in isotopic equilibrium with ambient seawater equilibrium calcite and 3 to specify shell portions that reflect the isotopic compositions of ambient seawater the 13c and 18o values of samples from the secondary shell layer which constitutes the main body of the brachiopod shell are in and or out of those of the equilibrium calcite the isotopic compositions of samples from the outermost part of the secondary shell layer outer surface of the secondary shell layer correlated well with growth rates positive correlations are recognized between the 13c and 18o values of these samples which can be ascribed to a kinetic fractionation effect although limited data on 13c of total dissolved inorganic carbon dic and 18o of seawater at the brachiopod sample site enable only approximate estimates of the 13c and 18o of the equilibrium calcite they are comparable with those of the brachiopod shell the 18o values of samples from the outermost part of the secondary layer along a growth axis of laqueus rubellus are a reliable environmental proxy because they mostly fall in the 18o range for the equilibrium calcite although samples from the inner series of l rubellus are depleted partially enriched in 13c 18o by 0 8 0 3 relative to the equilibrium calcite both isotopic variations are quite small therefore the isotopic compositions in this series would also be useful if the offsets are corrected this study clearly illustrates that although the 13c and 18o of modern brachiopod shells are influenced by the kinetic fractionation effect appropriate selection of species and shell portions reflecting the isotopic compositions of ambient seawater enables the reconstruction of secular variations in 13c or 18o in the oceans throughout geologic time

groundwater sources and geochemical processes in a crystalline fault aquifer the origin of water flowing in faults and fractures at great depth is poorly known in crystalline media this paper describes a field study designed to characterize the geochemical compartmentalization of adeep aquifer system constituted by a graben structure where a permeable fault zone was identified analysesof the major chemical elements trace elements dissolved gases and stable water isotopes reveal theorigin of dissolved components for each permeable domain and provide information on various watersources involved during different seasonal regimes the geochemical response induced by performinga pumping test in the fault zone is examined in order to quantify mixing processes and contributionof different permeable domains to the flow reactive processes enhanced by the pumped fluxes are alsoidentified and discussed the fault zone presents different geochemical responses related to changes in hydraulic regime theyare interpreted as different water sources related to various permeable structures within the aquifer during the low water regime results suggest mixing of recent water with a clear contribution of olderwater of inter glacial origin recharge temperature around 7 c suggesting the involvement of watertrapped in a local low permeability matrix domain or the contribution of large scale circulation loops during the high water level period due to inversion of the hydraulic gradient between the major permeablefault zone and its surrounding domains modern water predominantly flows down to the deep bedrockand ensures recharge at a local scale within the graben pumping in a permeable fault zone induces hydraulic connections with storage reservoirs the overlaidregolith domain ensures part of the flow rate for long term pumping around 20 in the present case during late time pumping orthogonal fluxes coming from the fractured domains surrounding the majorfault zone are dominant storage in the connected fracture network within the graben structure mainlyensures the main part of the flow rate 80 in the present case reactive processes are induced by mixingof water from different sources and transfer conditions a specific approach is applied to quantify thereaction rate involved along the pumping time autotrophic denitrification coupled with iron mineralsoxidation is highlighted and water rock interaction is clearly enhanced by the flux changes induced bypumping

tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere observations in groundwaters along the san andreas fault abstract tetrafluoromethane cf 4 concentrations were measured in 14 groundwater samples from the cuyama valley mil potrero and cuddy valley aquifers along the big bend section of the san andreas fault system safs in california to assess whether tectonic activity in this region is a significant source of crustal cf 4 to the atmosphere dissolved cf 4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge c r e 30 fmol kg 1 h 2 o indicating subsurface addition of cf 4 to these groundwaters groundwaters in the cuyama valley contain small cf 4 excesses 0 1 9 times c r e which may be attributed to an in situ release from weathering and a minor addition of deep crustal cf 4 introduced to the shallow groundwater through nearby faults cf 4 excesses in groundwaters within 200 m of the safs are larger 10 980 times c r e and indicate the presence of a deep crustal flux of cf 4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the safs extrapolating cf 4 flux rates observed in this study to the full extent of the safs 1300 km 20 100 km suggests that the safs potentially emits 0 3 1 10 1 kg cf 4 yr 1 to the earth s surface for comparison the chemical weathering of 7 5 10 4 km 2 of granitic rock in california is estimated to release 0 019 3 2 10 1 kg cf 4 yr 1 tectonic activity is likely an important and potentially the dominant driver of natural emissions of cf 4 to the atmosphere variations in preindustrial atmospheric cf 4 as observed in paleo archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity including changes driven by variations in continental ice cover during glacial interglacial transitions

δ18o and δ13c values of modern brachiopod shells abstract researchers have not rigorously tested the hypothesis that calcite from modern brachiopod shells is precipitated in oxygen isotope equilibrium with ambient seawater isotopic variability at the intraspecimen and intertaxon levels has not been examined without such data for modern brachiopods similar data from ancient brachiopods cannot be accurately interpreted in this study a survey is made of 18 o and 13 c values of terebratulid rhynchonellid thecideidine and craniacean brachiopods from antarctica the bay of fundy curacao japan new zealand norway puget sound palau sicily and south africa this suite of samples provides a wide range of taxonomic levels temperatures salinities and depositional environments for evaluating the degree of isotopic equilibrium attained during precipitation of brachiopod calcite new data indicate that modem brachiopod calcite is not always precipitated in oxygen and carbon isotope equilibrium with ambient seawater calcite from the primary layer and specialized shell structures hinge brachidium foramen interarea muscle scars are depleted in both 18 o and 13 c a characteristic of biological fractionation or vital effects often found in other calcerous marine organisms our findings suggest that these portions of the brachiopod shell should be avoided during sampling of ancient brachiopods secondary layer calcite the material most often analyzed in ancient brachiopods has higher 18 o and 13 c values which approach and sometimes correspond with predicted equilibrium values therefore secondary layer calcite is the most suitable portion of the brachiopod shell for use as an ancient seawater proxy although near equilibrium precipitation in secondary layer calcite is encouraging to those studying the isotopic composition of ancient oceans these data come with caveats large intraspecimen variability in the 18 o values of secondary layer calcite 1 in some samples limits the use of brachiopods as precise indicators of the 18 o value or temperature of ancient seawater the 18 o and 13 c values of secondary layer calcite deviate from predicted equilibrium values toward the lower values of the primary layer and specialized shell structures indicating a measurable vital effect in most cases measured 18 o values are lower than the calculated equilibrium values dictated by seasonal variations in the 18 o value and temperature of seawater ontogenetic variations in the 13 c values of secondary layer calcite have also been measured and must be assessed when interpreting ancient data modern brachiopods occur in a wide range of seawater salinities and temperatures therefore the relation between salinity and the 18 o value of seawater must be known to correctly calculate the temperature of calcite precipitation from secondary layer 18 o values errors of up to 15 c are found if ambient seawater is assumed to have a constant 18 o value e g 0 smow and the 18 o values of secondary layer calcite are used to calculate temperature coupled with vital effects and intraspecimen variability these errors can obscure the resolution of secular variations in the rock record

oxygen isotope fractionation between calcite and fluid as a function of growth rate and temperature an in situ study the 18o content of carbonates expressed as 18o is widely used in paleothermometry yet it is clear from comparison of experimental results and natural carbonate samples that chemical isotopic equilibrium is not always achieved in nature this observation underscores the importance of exploring possible effects of growth rate on isotopic fractionation which is the focus of this study in situ secondary ion mass spectrometry sims analyses of 18o were performed on single crystals of experimentally grown calcite the change in growth rate v over time within each crystal was monitored by addition of multiple rare earth element ree spikes into the fluid from which the calcite grew the values of 18o in bulk calcites and experimental fluids were measured by stable isotope ratio mass spectrometers the average sims 18o overlaps with those determined by conventional mass spectrometry within analytical uncertainty the fractionation factor expressed as 18o approaches its equilibrium value in slowly grown calcites v 0 02 nm s and decreases by 1 5 with increasing growth rate from 10 3 to 0 34 nm s here 18o 103 ln 18o and 18o 18o 16o calcite 18o 16o fluid our results provide the first in situ evidence that under equilibrium conditions 18o may be depleted in the near surface region of calcite relative to the bulk crystal lattice and that this 18o depleted zone can be captured during rapid crystal growth crystal growth rate is therefore a potentially important consideration when using 18o in natural carbonates as a proxy for ocean and terrestrial temperature

environmental and physiological influences on isotopic and elemental compositions of brachiopod shell calcite implications for the isotopic evolution of paleozoic oceans abstract brachiopods from the demissa bed middle devonian hamilton group biologically regulated the incorporation of mg sr and na into their shell calcite significant taxonomic differences in the elemental contents of three species athyris spiriferoides mediospirifer audacula and mucrospirifer mucronatus may be related to differences in calcification processes in contrast no significant difference or vital effects were observed between the isotopic values of mediospirifer audacula and athyris spiriferoides from erie 18o 0 03 p 0 949 13c 0 76 p 0 083 and genessee counties 18o 0 39 p 0 471 13c 0 06 p 0 854 this suggests that these brachiopods did not exert a biological control over their isotopic compositions and that their shell calcites reflect ambient physicochemical conditions isotopic compositions in unaltered shell calcites of brachiopods from genessee county which was close to the basin depocentre are heavy for carbon 13c x 5 01 pdb and oxygen 18o x 2 85 pdb compared to the species sampled at the basin s edge erie county 13c x 2 79 pdb 18o x 3 83 pdb there is a significant separation in isotopic values between the deeper and shallower water brachiopods of the basin 18o 0 98 p 0 0005 13c 2 22 p 0 0005 the 18o variation suggests a temperature salinity change with water depth whereas the change in 13c composition probably records an enrichment depletion of organic matter with water depth this observation has significant implications for paleozoic ocean isotopic evolution studies because many global changes in marine 18o and 13c are based on isotopic shifts of similar magnitude