shallow marine carbon and oxygen isotope and elemental records indicate icehouse greenhouse cycles during the early jurassic 1 for much of the mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences we present a carbon and oxygen isotope and elemental record for part of the early jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the cleveland basin uk the invertebrate isotope record is supplemented with carbon isotope data from fossil wood which samples atmospheric carbon new data elucidate two major global carbon isotope events a negative excursion of 2 at the sinemurian pliensbachian boundary and a positive excursion of 2 in the late pliensbachian the sinemurian pliensbachian boundary event is similar to the slightly younger toarcian oceanic anoxic event and is characterized by deposition of relatively deepwater organic rich shale the late pliensbachian strata by contrast are characterized by shallow marine deposition oxygen isotope data imply cooling locally for both events however because deeper water conditions characterize the sinemurian pliensbachian boundary in the cleveland basin the temperature drop is likely of local significance in contrast a cool late pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions both the large scale long term and small scale short duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy isotope events and the sea level cycles are concluded to reflect processes of global significance supporting the idea of an early jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 ma

boron isotope signatures in the coastal groundwaters of french guiana 1 drinking water used by the population of french guiana comes mostly from rivers and can induce major health impacts consequently groundwaters are being studied in terms of an alternative drinking water supply in this context boron isotopes were applied to the coastal aquifers to better constrain the water rock interactions we found that the 1 1 b signatures vary between 2 98 and 49 35 o in the groundwaters and between 36 35 and 42 41 o in the river waters and that the local seawater gave a value of 40 76 o we also noted an inverse correlation between groundwater ph and 1 1 b this relationship previously demonstrated experimentally is particularly well defined in the french guiana coastal aquifer because of the wide ph range 4 18 to 7 64 naturally present in the groundwaters it would appear that the variations in 1 1 b values are linked to water rock interaction processes e g dissolution precipitation of silicates

global biogeochemical cycle of boron 1 the global boron b cycle is primarily driven by a large flux 1 44 tg b yr through the atmosphere derived from seasalt aerosols other significant sources of atmospheric boron include emissions during the combustion of biomass 0 26 0 43 tg b yr and coal which adds 0 20 tg b yr as an anthropogenic contribution these known inputs to the atmosphere cannot account for the boron removed from the atmosphere during rainfall 3 0 tg b yr and estimated dry deposition 1 3 2 7 tg b yr in addition to atmospheric deposition rock weathering is a source of boron 0 19 tg b yr for terrestrial ecosystems and humans mine about 0 31 tg b yr from the earth s crust more than 4 8 tg b yr circulates in the biogeochemical cycle of land plants and about 0 53 0 63 tg b yr is carried from land to sea by rivers the biogeochemical cycle of boron in the sea includes 4 4 tg b yr circulating in the marine biosphere and an annual loss of 0 47 tg b yr to the oceanic crust via a variety of sedimentary processes that collectively remove only a small fraction of the total annual inputs to the oceans thus with our current understanding of the global biogeochemistry of b the atmospheric budget shows outputs inputs while the marine compartments show inputs outputs despite these uncertainties it is clear that the human perturbation of the global b cycle has more than doubled the mobilization of b from the crust and contributes significantly to the b transport in rivers

boron isotope variations in nature a synthesis the large relative mass difference between the two stable isotopes of boron 10b and 11b and the high geochemical reactivity of boron lead to significant isotope fractionation by natural processes published 11b values relative to the nbs srm 951 standard span a wide range of 90 the lowest 11b values around 30 are reported for non marine evaporite minerals and certain tourmalines the most 11b enriched reservoir known to date are brines from australian salt lakes and the dead sea of israel with 11b values up to 59 dissolved boron in present day seawater has a constant world wide 11b value of 39 5 in this paper available 11b data of a variety of natural fluid and solid samples from different geological environments are compiled and some of the most relevant aspects including possible tracer applications of boron isotope geochemistry are summarized

assessing the fidelity of marine vertebrate microfossil δ18o signatures and their potential for palaeo ecological and climatic reconstructions abstract conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the palaeozoic despite the growing application in geochemically based palaeoenvironmental reconstructions the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen bearing compounds for analysis vertebrate microfossils teeth dermal denticles spines offer a potential substitute for conodonts from the middle palaeozoic vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments thus widening the scope of oxygen isotope studies on bioapatite however significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies well preserved vertebrate microfossils and co occurring conodont fossils from the upper devonian and lower carboniferous of the lennard shelf canning basin western australia were analysed using bulk gas isotope ratio mass spectrometry girms and in situ secondary ion mass spectrometry sims methodologies with the latter technique allowing investigation of specific tissues within vertebrate elements the 18oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo salinity and temperature and provide a baseline standard for comparison against vertebrate microfossil 18o values despite an absence of obvious diagenetic modification girms of vertebrate denticles yielded 18o values depleted in 18o by 2 4 relative to co occurring conodonts sims analysis of dentine tissues exhibited significant heterogeneity while hypermineralised tissues in both scales and teeth produced 18o values comparable with those of associated conodonts the susceptibility of permeable phosphatic fossil tissues to microbial activity fluid interaction and introduction of mineral precipitates post formation is demonstrated in the dentine of vertebrate microfossils which showed significant heterogeneity and consistent depletion in 18o relative to conodonts the hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations

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

geochemistry of surface and ground water in guiyang china water rock interaction and pollution in a karst hydrological system the chemical compositions of the surface ground water of guiyang the capital city of guizhou province china are dominated by ca2 mg2 hco3 andso42 which have been derived largely from chemical weathering of carbonate rocks limestone and dolomite the production of so42 has multiple origins mainly from dissolution of sulfate evaporites oxidation of sulfide minerals and organic s in the strata and anthropogenic sources most ground water is exposed to soil co2 and therefore the h2co3 which attacks minerals contains much soil c in addition the h2so4 produced as a result of the oxidation of sulfides in s rich coal seams and or organic s is believed to be associated with the chemical weathering of rocks the major anthropogenic components in the surface and ground water include k na cl so42 andno3 with cl and no3 being the main contributors to ground water pollution in guiyang and its adjacent areas the seasonal variations in concentrations of anthropogenic components demonstrate that the karst ground water system is liable to pollution by human activities the higher content of no3 in ground water compared to surface water during the summer and winter seasons indicates that the karstic ground water system is not capable of denitrification and therefore does not easily recover once contaminated with nitrates

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

element ca c and o isotope ratios in modern brachiopods species specific signals of biomineralization fossil brachiopods are of major importance for the reconstruction of palaeoenvironmental conditions particularly of the paleozoic in order to better understand signals of ancient shell materials modern analogue studies have to be conducted here we present c and o isotope data in conjunction with mg ca sr ca mn ca and fe ca data for nine modern rhynchonellid and terebratulid brachiopod species from tropical to intermediate latitudes and shallow to very deep marine settings c and o isotope signals of most species suggest formation of secondary shell layers near or in isotopic equilibrium with ambient seawater some species especially in the suborder terebratellidina show partly distinct disequilibrium signals suggesting some degree of phylogenetic control on the expression of vital effects mn ca and fe ca ratios measured in the modern species form a baseline to assess fossil preservation but also yield environmental information mg ca and sr ca ratios follow previously observed patterns with all studied brachiopod species comprising low mg calcite strong covariation of sr ca ratios with mg ca ratios is only observed in rhynchonellids and possibly one terebratulid species potentially linking the incorporation behaviour of alkaline earth metals to phylogeny sr ca show a strong negative correlation with 13c values in terebratellidinid species which exhibit major isotopic disequilibrium and also combined data from three localities for which two species were studied indicate such a negative relation the observed covariation of sr ca ratios with 13c values may therefore become a useful tool to detect 13c disequilibrium and to robustly estimate 13c values of ambient dic in deep time

quantitative analysis of intraspecific variations in the carbon and oxygen isotope compositions of the modern cool temperate brachiopod terebratulina crossei abstract this study unravels intraspecific variations in the carbon isotope 13 c and oxygen isotope 18 o compositions of shells of the modern cool temperate brachiopod terebratulina crossei collected at a water depth of 70 m in otsuchi bay northeastern honshu japan brachiopod shells have been used as proxies of the 13 c values of dissolved inorganic carbon dic 13 c dic and seawater temperature 18 o 18 o sw values to reconstruct the evolution of phanerozoic oceans to identify more reliable shell portions as the proxies we conducted a rigorous time series comparison of 13 c and 18 o values between the brachiopod shells and calcite precipitated in isotopic equilibrium with ambient seawater equilibrium calcite 13 c ec and 18 o ec values respectively samples were collected from the outer and inner surfaces of the secondary shell layer along the maximum growth axis ontogenetic series and inner series samples respectively the ontogenetic series 13 c values which showed regular annual and irregular non annual cycles partly fell in but were mostly less than the range of the 13 c ec values the 13 c cycles were often associated with one or two minor negative peaks the peaks were likely resulted from an increased incorporation of respiration derived 12 c due to elevated metabolic activity during spawning the ontogenetic series 18 o values showed distinct seasonal variations and were mostly within the range of 18 o ec values the amplitude of the 18 o profiles was relatively large during the younger fast growth stage and decreased during the senescent slow growth stage the inner series 13 c and 18 o values of individual shells varied within narrow ranges the inner series 13 c values were close to the minimum 13 c ec values the inner series 18 o values were in the upper range of the 18 o ec values kinetic isotope fractionation effects were evident but its degree varied among different shells we identified the shell portions reliably recording past ocean environments the best estimates of annual average 13 c dic values were obtained from ontogenetic series 13 c values near the anterior shell edge and from inner series 13 c values those of the annual average seawater temperature were obtained from ontogenetic series 18 o values from the entire transect and from the fast growth stage

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

the geochemistry of boron and its isotopes in groundwaters from marine and non marine sandstone aquifers abstract the geological evolution of b in two uk sandstone aquifers is followed from precipitation chemistry through to groundwaters in both the unconfined and confined zones measurements have been made of major element geochemistry b concentrations and b isotopic ratios the isotopic measurements were carried out using icp ms following a simple preconcentration step isotopic measurements of rainfall show a bimodal distribution and it is suggested that enriched signatures are characteristic of atlantic air over britain and depleted signatures representative of continental air in the marine lower greensand aquifer dissolution of glauconite results in the mobilisation of b and a correlation with so 4 suggests that this dissolution is related to the oxidation of pyrite which appears to be the so 4 forming reaction in the aquifer in the non marine hastings beds isotopic ratios and a correlation with hco 3 suggest that b is associated with the dissolution of ferroan carbonates in both aquifers the geochemical evolution of b is complex and more information is needed on the behaviour of b isotopes during evapotranspiration and groundwater recharge

anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries the case of the podstenjsek spring slovenia anomalous behaviour of specific electrical conductivity sec was observed at a karst spring in slovenia during 26 high flow events in an 18 month monitoring period a conceptual model explaining this anomalous sec variability is presented and reproduced by numerical modelling and the practical relevance for source protection zoning is discussed after storm rainfall discharge increases rapidly which is typical for karst springs sec displays a first maximum during the rising limb of the spring hydrograph followed by a minimum indicating the arrival of freshly infiltrated water often confirmed by increased levels of total organic carbon toc the anomalous behaviour starts after this sec minimum when sec rises again and remains elevated during the entire high flow period typically 20 40 s cm above the baseflow value this is explained by variable catchment boundaries when the water level in the aquifer rises the catchment expands incorporating zones of groundwater with higher sec caused by higher unsaturated zone thickness and subtle lithologic changes this conceptual model has been checked by numerical investigations a generalized finite difference model including high conductivity cells representing the conduit network discrete continuum approach was set up to simulate the observed behaviour of the karst system the model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and sec during high flow periods the observed behaviour is relevant for groundwater source protection zoning which requires reliable delineation of catchment areas anomalous behaviour of sec can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions copyright 2011 john wiley sons ltd

geochemistry of campanian maastrichtian brachiopods from the rordal 1 core denmark differential responses to environmental change and diagenesis abstract past marine environmental conditions can be reconstructed from geochemical signatures of both benthic and planktic organisms and particularly brachiopods have been extensively used for this purpose however it is seldom possible to investigate the links between environmental conditions and shell geochemistry in monospecific records over extended periods of time here we present geochemical data from the 100 m thick brachiopod rich upper campanian upper maastrichtian chalk 73 8 68 6 ma of the rordal 1 drill core northern denmark two species that lived attached to small substrate argyrotheca bronnii roemer and gisilina jasmundi steinich and one secondarily free living species magas chitoniformis schlotheim have been studied for element concentrations as well as c and o isotope signatures each species has a unique chemical signature with m chitoniformis showing lowest mg and mn concentrations a bronnii the highest mn concentrations and g jasmundi the highest sr concentrations all three species display decreasing mg ca ratios throughout the studied interval and distinct mn enrichments in the campanian maastrichtian boundary cmb interval in the campanian part of the succession the three species are slightly enriched in 13 c median 13 c values of 0 0 to 0 5 and 18 o median 18 o values of 0 3 to 0 6 with respect to coeval chalk in the course of the maastrichtian the two attached species acquire progressively lighter isotopic compositions with a bronnii reaching 13 c and 18 o values 1 0 lower than coeval chalk the secondarily free living species m chitoniformis on the other hand becomes isotopically heavier and reaches 13 c and 18 o enrichments of 1 0 at the top of the core the observed differences between the species illustrate species specific signatures of biomineralisation diagenesis and response to environmental change this geochemical complexity illustrates that a comprehensive geochemistry based picture of the late cretaceous chalk sea can only be painted using detailed multi species and multi proxy datasets

use of stable oxygen isotope determinations from brachiopod shells in palaeoenvironmental reconstruction abstract stable oxygen isotope analyses were obtained from fossil brachiopod shells from a shallow marine deposit of upper pleistocene age approximately 80 ka in new zealand as part of a palaeoenvironmental investigation bulk analyses of entire shells of calloria inconspicua yielded highly variable results a range of 2 30 rendering these data of limited use as palaeoenvironmental proxies attempts to obtain consistent oxygen isotope values by removing areas of the brachiopod shell thought to be prone to oxygen isotope disequilibrium effects vital effects revealed that the matching anterior portions of ventral and dorsal valves from the same individual which were secreted at the same time also yielded different oxygen isotope ratios the dorsal valve 18o values were higher and less variable than those obtained from the ventral valve of the same individual the investigation was then extended to living representatives of the same species from a similar shallow water habitat from the south island of new zealand the pattern of dorsal valves yielding higher and less variable oxygen isotope values than matching areas of the ventral valves was repeated in seven out of eight individuals investigated although there was considerable variation in the absolute values from specimen to specimen contrary to common practice therefore it seems that in this species it is the much thinner and lighter dorsal valve that provides a more consistent isotopic measurement if converted into absolute temperature estimates the dorsal valve measurements correspond to a temperature midway between the mean and maximum annual temperature experienced by this species in its present day habitat which may make it acceptable as a palaeoenvironmental indicator the high level of variation between individuals including an inferred temperature from one ventral valve above the mean maximum temperature experienced indicates that a range of individuals needs to be investigated in any palaeoenvironmental investigation to avoid misleading interpretations however intra and inter specimen variation in isotopic composition may provide valuable palaeobiological information on growth rates metabolism and possibly also pathological conditions in the past

δ18o and δ13c variability in brachiopods from modern shelf sediments and its utility for understanding complex oceanography southern australian shelf abstract the 18o and 13c values of brachiopod shell calcite are commonly used as proxies for ancient environmental marine conditions and secular changes in ancient ocean chemistry the variability of 18o and 13c across modern shelf settings is however not well documented this study presents 18o and 13c data from 407 holocene 5000 yr bp and living brachiopods collected from 220 sites across 3000 km along australia s southern shelf the largest cool water carbonate shelf in the modern world significant isotopic variability is present in separate specimens at individual sites and across the entire region individual specimens analyzed at multiple shell positions have an isotopic range of values up to 1 3 and 1 9 for 18o and 13c respectively multiple brachiopods at a single site have values that vary as much as 2 1 for 18o and 1 8 for 13c regional variability ranges on the order of 3 6 and 3 4 for 18o and 13c respectively the distribution of intrasite variability can be divided into areas of high and low variability areas characterized by low variability occur in zones of relatively consistent shelf water conditions high variability zones usually correspond to areas of seasonal upwelling onto the shelf and this aspect is interpreted to be the main cause of isotopic variability upwelling waters are cold leading to higher 18o values and are commonly rich in respired dissolved inorganic carbon dic and nutrients promoting active phytoplankton growth and leading to variable 13c values the extensive spatial coverage across this vast latitude parallel region provides a valuable baseline illustrating the isotopic range that could occur in a single layer in the rock record furthermore changes in isotopic signatures measured across stratigraphy might not necessarily reflect secular changes in ocean chemistry but instead could be recording local changes in shelf circulation and upwelling intensity

geological sources of boron and fluoride anomalies in silurian ordovician aquifer system estonia the objective of this study was to examine the possible natural sources of fluorides and boron in silurian ordovician s o aquifer system as the anomaly of these elements has been distinguished in groundwater of western estonia water rock interactions such as dissolution and leaching of the host rock are considered to be the main source of high fluoride and boron concentrations in groundwater altogether 91 rock samples were analysed to determine if high f and b levels in groundwater could be attributed to certain aquifer forming rock types fluorine and boron contents in limestones and dolomites vary from 100 to 500 mg kg and 5 to 20 mg kg reaching up to 1 000 and 150 mg kg in marlstones respectively k bentonites altered volcanic ash beds are rich in fluorine 400 4 500 mg kg and boron 50 1 000 mg kg thus clay rich sediments providing ion exchange and adsorption sites for f and b are the probable sources of both elements in s o aquifer system in western estonia

assessing the biomineralization processes in the shell layers of modern brachiopods from oxygen isotopic composition and elemental ratios implications for their use as paleoenvironmental proxies abstract fossil brachiopod shells are often used as valuable archives to reconstruct paleoenvironmental conditions in deep time however biomineralization processes can impact their fidelity as geochemical proxies brachiopod shells comprise an outer primary layer a secondary fibrous layer and sometimes a tertiary columnar layer therefore it is essential to assess the potential effects of the biomineralization processes in each of the different shell microstructures of modern brachiopods this study analyses the oxygen isotopic composition together with li ca na ca mg ca and sr ca data at high spatial 20 50 m resolution in seven modern brachiopod species focusing on differences between the primary secondary and tertiary layers in all studied species 18o values of the outer primary layer are consistently out of equilibrium with seawater also this shell layer is enriched in li na mg and sr contrary to the primary layer the innermost secondary layer is near or at oxygen isotopic and elemental equilibrium with ambient seawater the columnar tertiary shell layer if present has the least variable and the heaviest oxygen isotopic composition within the range of equilibrium values with seawater this tertiary layer however is depleted in minor and trace elements relative to the other shell layers thus the tertiary layer is more suitable for oxygen isotopic studies whereas the innermost secondary layer of the most mature parts of the shell is the best target in two layered shells while we do not observe any clear interspecific relationships between mg ca and sr ca ratios on one hand and environmental parameters such as temperature salinity and ph on the other hand there is a positive interspecific relationship between na ca and salinity and a negative interspecific relationship between li ca and temperature suggesting their potential use as proxies of physicochemical parameters of seawater

geochemistry of the brachiopod hemithiris psittacea from the canadian arctic implications for high latitude palaeoclimate studies abstract fossil shell material from high palaeo latitudes is increasingly studied for environmental forcings specific to these latitudes and as sensitive archives of climate change however more detailed studies of modern analogues are necessary for putting findings into global and high latitude perspectives here we present 13 c and 18 o values as well as mg sr na mn and fe contents for the rhynchonellide brachiopod hemithiris psittacea from friday harbor u s a and twenty five sites from canada ranging in latitude from 48 to 71 n median mn ca ratios are below 0 1 mmol mol and fe ca ratios are below 0 3 mmol mol with no strong correlation between ratios and no apparent geographical relationship mg ca and sr ca ratios vary within relatively narrow limits and yield median ratios of 3 7 mmol mol and 1 13 mmol mol na ca ratios vary widely amongst the sites with median values ranging from 9 to 20 mmol mol relatively uniform median 13 c values of 1 8 0 6 2 sd n 25 are observed for the canadian sites whereas at friday harbor the signature of 13 c depletion in local dic is imprinted in the shell calcite median 18 o values of 0 5 to 2 7 are more variable than carbon isotope signatures and point to precipitation of shell material in seawater diluted by variable amounts of freshwater and affected by seasonal sea ice our results imply that robust elemental patterns and carbon isotope signatures of high latitude brachiopod fossils can be expected for most palaeogeographic situations in contrast 18 o signatures of shell material from high latitude marginal seas particularly during glacial periods would yield unreasonably high seawater temperature estimates unless the oxygen isotopic composition of the ambient water is accurately accounted for in palaeotemperature calculations

natural versus anthropogenic sources in the surface and groundwater dissolved load of the dommel river meuse basin constraints by boron and strontium isotopes and gadolinium anomaly summary the river dommel a tributary of the meuse river drains an area of intensive agriculture livestock farming maize and grassland over 50 of the basin and a dense population of about 600 000 people representing 20 of the total area the combined human activities in the dommel catchment lead to a large amount of dissolved elements and compounds released in surface and groundwaters the aim of this study was to discriminate the natural including infiltration of meuse water versus anthropogenic sources of the dissolved load and to identify the various pollution sources such as agriculture industrial activity and wastewater treatment plants using geochemical tools including major and trace elements sr and b isotopes and rare earth elements ree for that purpose a same day geochemical snapshot picture of the entire basin was combined with monthly monitoring in strategic points the major and trace elements analyses allowed discriminating the main pollution sources affecting the basin i e point versus diffuse sources strontium isotopes helped to identify each tributary and to calculate mixing proportions combining these calculations with the sr isotopic data obtained from the snapshot sampling campaign during a low flow period shows that meuse water infiltration represents 25 of the total dommel discharge boron isotopes used for assessing the amount of water affected by anthropogenic input cannot discriminate between the two main anthropogenic inputs i e urban wastewater and the zinc smelter effluent as they have similar 11 b values finally the ree and especially the use of gd anomalies gd demonstrated the generalized impact of urban wastewater on the streams of the dommel basin the coupled use of different geochemical tracers sr and b isotopes together with gd in addition to the standard major element analyses led to discriminating the various anthropogenic components influencing the dommel basin water quality with these tools it also became possible to assess the complex water circulation and exchanges between water compartments including the major role of meuse water through the bocholt herenthals canal

analytical 1d dual porosity equivalent solutions to 3d discrete single continuum models application to karstic spring hydrograph modelling abstract one dimensional analytical porosity weighted solutions of the dual porosity model are derived providing insights on how to relate exchange and storage coefficients to the volumetric density of the high permeability medium it is shown that porosity weighted storage and exchange coefficients are needed when handling highly heterogeneous systems such as karstic aquifers using equivalent dual porosity models the sensitivity of these coefficients is illustrated by means of numerical experiments with theoretical karst systems the presented 1d dual porosity analytical model is used to reproduce the hydraulic responses of reference 3d karst aquifers modelled by a discrete single continuum approach under various stress conditions simulation results show the relations between the dual porosity model coefficients and the structural features of the discrete single continuum model the calibration of the equivalent 1d analytical dual porosity model on reference hydraulic responses confirms the dependence of the exchange coefficient with the karstic network density the use of the analytical model could also point out some fundamental structural properties of the karstic network that rule the shape of the hydraulic responses such as density and connectivity

application of major and trace elements as well as boron isotopes for tracing hydrochemical processes the case of trifilia coastal karst aquifer greece the trifilia karst aquifer presents a complex hydrochemical character due to the intricate geochemical processes that take place in the area their discernment was achieved by using the chemical analyses of major trace elements and boron isotopes major ion composition indicates mixing between seawater and freshwater is occurring five hydrochemical zones corresponding to five respective groundwater types were distinguished in which the chemical composition of groundwater is influenced mainly due to the different salinization grade of the aquifer the relatively increased temperature of the aquifer indicates the presence of hydrothermal waters boron isotopes and trace elements indicate that the intruding seawater has been hydrothermally altered as it is shown by the 11b depleted signature and the increased concentrations of li and sr trace elements analyses showed that the groundwater is enriched in various metallic elements which derive from the solid hydrocarbons bitumens contained in the carbonate sediments of the tripolis zone the concentration of these trace elements depends on the redox environment thus in reductive conditions as mn co and nh4 concentrations are high in oxidized conditions the v se mo tl and u concentration increases while ni is not redox sensitive and present high concentration in both environments

hydrogeochemical characteristics of surface water and groundwater in the karst basin southwest china groundwater is a very significant water source used for irrigation and drinking purposes in the karst region and therefore understanding the hydrogeochemistry of karst water is extremely important surface water and groundwater were collected and major chemical compositions and environmental isotopes in the water were measured in order to reveal the geochemical processes affecting water quality in the gaoping karst basin southwest china dominated by ca 2 mg 2 hco 3 and so 4 2 the groundwater is typically characterized by ca mg hco 3 type in a shallow aquifer and ca mg so 4 type in a deeper aquifer dissolution of dolomite aquifer with gypsiferous rocks and dedolomitization in karst aquifers are important processes for chemical compositions of water in the study basin and produce water with increased mg 2 ca 2 and so 4 2 concentrations and also increased tds in surface water and groundwater mg 2 ca 2 molar ratios in groundwater decrease slightly due to dedolomitization while the mixing of discharge of groundwater with high mg 2 ca 2 ratios may be responsible for mg 2 ca 2 ratios obviously increasing in surface water and mg 2 ca 2 ratios in both surface water and groundwater finally tending to a constant in combination with environmental isotopic analyses the major mechanism responsible for the water chemistry and its geochemical evolution in the study basin can be revealed as being mainly from the water rock interaction in karst aquifers the agricultural irrigation and its infiltration the mixing of surface water and groundwater and the water movement along faults and joints in the karst basin

interaction between shallow and deep aquifers in the tivoli plain central italy enhanced by groundwater extraction a multi isotope approach and geochemical modeling abstract in the tivoli plain rome central italy the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using isotopic and chemical tracers a conceptual model of the groundwater flowpaths has been developed and verified by geochemical modeling a combined hydrogeochemical and isotopic investigation using ion relationships such as dic cl ca ca mg so 4 so 4 hco 3 and environmental isotopes 18 o 2 h 87 sr 86 sr 34 s and 13 c was carried out in order to determine the sources of recharge of the aquifer the origin of solutes and the mixing processes in groundwater of tivoli plain multivariate statistical methods such as principal component analysis and cluster analyses have confirmed the existence of different geochemical facies and the role of mixing in the chemical composition of the groundwater results indicate that the hydrochemistry of groundwater is characterized by mixing between end members coming directly from carbonate recharge areas and to groundwater circulating in a deeply buried meso cenozoic carbonate sequence the travertine aquifer is fed by both flow systems but a local contribution by direct input in the plain has also been recognized the stable isotope data 18 o 2 h 13 c and 34 s supports the flow system conceptual model inferred from the geochemical data and represents key data to quantify the geochemical mixing in the different groundwaters of the plain the results of numerical modeling phreeqc are consistent with the flowpaths derived from the hydrogeochemical conceptual model the inverse models performed generated the main geochemical processes occurring in the groundwater flow system which also included mixing geochemical and isotope modeling demonstrate an increasing influence of groundwater from the deeply buried aquifer in the travertine aquifer enhanced by lowering of the travertine aquifer water table due to quarry pumping

isotope and minor element geochemistry of high arsenic groundwater from hangjinhouqi the hetao plain inner mongolia abstract high as groundwater is widely distributed in the northwestern hetao plain an arid region with slow groundwater flow arsenic concentration in groundwater ranges from 1 to 1000 g l most water samples have elevated salinities with cl and or hco 3 as the dominant anions and na as the dominant cation high concentrations of as in shallow aquifers are associated with strongly reducing conditions as evidenced by high concentrations of dissolved organic c doc nh 4 dissolved sulfide arsenite and dissolved ch 4 and relatively low concentrations of no 3 and so 4 2 results of the hydrochemical and h and o isotope geochemical studies indicate that evapotranspiration is an important process controlling the enrichment of na and cl as well as trace elements such as as b f and br in groundwater in na hco 3 dominated groundwaters as b and f were enriched decades of irrigation using yellow river water has resulted in elevation of the groundwater level which has accelerated salt accumulation in shallow groundwater and surface soil in addition irrigation is responsible for the release of some components from aquifer materials and mixing with saline groundwaters as indicated by minor element and isotope geochemical data used to trace groundwater flow paths sr isotope composition also indicates that bedrock weathering is one of the primary sources of as in groundwater in the study area

brachiopod taxa and shell portions reliably recording past ocean environments toward establishing a robust paleoceanographic proxy 1 fossils of rhynchonelliform brachiopods marine invertebrates constitute 70 of the samples used for delineating a well known phanerozoic trend in oxygen isotope composition 18o of low mg calcite shells the trend represents secular variations in temperature and or 18o of ancient seawater however the use of brachiopods as a paleoceanographic proxy is based on the presupposition that the shell calcite is precipitated in isotopic equilibrium with ambient seawater here we show that high resolution time series of the shell 18o values along the maximum growth axes of two long lived cool water brachiopods are identical to greater than or less than those of calcite precipitated in isotopic equilibrium with ambient seawater depending on the difference in shell growth rates coupled with 18o data from subtropical and warm temperate brachiopod species examined in our previous studies we provide a sound framework illustrating which taxa and shell portions reliably recorded past ocean environments

evidence of deep water inflow in a tectonic window of the northern apennines italy water samples from the river network and from some shallow and brackish springs located in a tectonic window of the northern apennines of italy were studied in the frame of a comprehensive hydrogeological investigation in order to better understand the origin and the mixing processes between the two water types noticed also in previous studies ca hco3 and na cl a sampling campaign covering the drought period during year 2010 was planned to gather electric conductivity temperature and redox potential data along the river network and on groundwater occurrences located inside the tectonic structure additionally eight water samples were collected for hydrochemical major anions and cations na k ca2 mg2 hco3 cl so4 2 and trace ion btot and isotopic 18o 2h 3h analyses and compared with other eighteen samples from shallow and brackish springs collected near the study site during the period 2005 2012 moreover river discharge and water balance estimations were carried out results confirmed the presence of old na cl water with salinity progressively increasing up to 5 5 g l 1 at the northern termination of the tectonic window these values are in agreement with the ions contents of the most mineralized spring macognano spring salinity of 7 6 g l 1 which has been considered as having the deepest and longest flow path stable isotopes and trace ions contents are consistent with rainfall and snowmelt water mixed with brines associated with a hydrocarbon reservoir hosted at depth considering as end member the more mineralized na cl water a cumulate inflow in the range of 12 9 5 9 l s 1 has been estimated this aliquot is released into the river network with different mixing proportions by the groundwater occurrences discharging from the autochthonous flysch unit

coprecipitation and isotopic fractionation of boron in modern biogenic carbonates abstract the abundances and isotopic composition of boron in modern biogenic calcareous skeletons from the gulf of elat israel the great barrier reef australia and in deep sea sediments have been examined by negative thermal ionization mass spectrometry the selected species foraminifera pteropoda corals gastropoda and pelecypoda yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals the boron content of the biogenic skeletons is independent of mineralogical composition and is probably related to biological vital effects the 11 b values of the carbonates range from 14 2 to 32 2 relative to nbs srm 951 and overlap with the 11 b values of modern deep sea carbonate sediments 11 b 8 9 to 26 2 the variations of 11 b may be controlled by isotopic exchange of boron species in which 10 b is preferentially partitioned into the tetrahedral species and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates carbonates with low 11 b values 15 may indicate preferential incorporation of tetrahedral species whereas the higher 11 b values 30 may indicate 1 1 uptake of both boron species assuming equilibrium with seawater 2 2 preferential incorporation of b oh 4 from in situ high ph internal fluids of organisms that are isolated from seawater the b content and 11 b values of deep sea sediments foraminifera tests and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition as a result of enrichment of b in corals a substantially higher biogenic sink of 6 4 0 9 10 10 g yr is calculated for carbonates this is only slightly lower than the sink for desorbable b in marine sediments 10 10 10 g yr and approximately half that of altered oceanic crust 14 10 10 g yr thus carbonates are an important sink for b in the oceans being 20 of the total sinks the preferential incorporation of 10 b into calcium carbonate results in oceanic 11 b enrichment estimated as 1 2 0 3 10 12 per mil g yr the boron isotope composition of authigenic well preserved carbonate skeletons may provide a useful tool to record secular boron isotope variations in seawater at various times in the geological record the potential use of boron isotope geochemistry in skeletons as a tracer for palaeoenvironments is demonstrated in ostracoda and foraminifera from the gulf of carpentaria australia the 11 b values of glacial age buried skeletons 4 0 and 4 9 respectively are lower than that of their modern equivalents 17 6 and 13 3 respectively this may reflect a terrestrial boron isotope signature of the water in the gulf during the late quaternary when it was isolated from the ocean

factors which determine the hydrogeochemical behaviour of karstic springs a case study from the betic cordilleras spain the cabra alcaide karstic massif situated in the south of spain constitutes an important part of the so called natural park of the subbetic sierras this aquifer system is drained by various springs which supply a population of some 100 000 inhabitants the feed areas of these springs show very different characteristics with respect to their geological structure size of the drainage area thickness of the vadose zone elevation and degree of karstification in addition the carbonate rocks lie over a clayey substratum which contains large masses of intercalated evaporites due to these conditions the hydrochemical composition of the springs is relatively variable in this study a hydrogeochemical characterization of the aquifer in both space and time is undertaken and the factors that determine it are discussed to achieve this 19 monthly samples were taken from the 6 most significant springs of the hydrogeological system the commencement of sampling coincided with the transition from a period of several years of severe drought and a very wet two year period which amplified considerably the hydrochemical and hydrodynamic response of the springs to the recharge identification of hydrogeochemical processes was performed by studying hydrographs the temporal evolution of physico chemical parameters ionic ratios mainly mg ca and by means of simple and multivariate statistical analyses the saturation status was established using the wateqf program and the mass transfer was quantified using phreeqc with the exception of the epikarstic subsystem i e the zarza spring the majority of the results indicate that the aquifer exhibits a diffuse flow model in which piston flow phenomena are seen closely linked to the most intense precipitation along the direction of flow hydrochemical trends are seen as the water type changes from ca hco3 to ca mg hco3 at the same time enrichment in some ions derived from the dissolution of evaporitic minerals of the impermeable substratum and dedolomitization processes occur in this way almost 90 of the water samples were oversaturated in calcite the majority of cases being a consequence of the dissolution of the gypsum of the substratum only in the epikarstic springs can it be considered that the oversaturation in calcite is due to loss of co2 from the emerging groundwater it is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution of the karstic springs moreover the use of both approaches permits a more accurate establishment of the degree of aquifer karstification which in turn needs to be known in order to assess its vulnerability to contamination and to protect recharge zones

trace elements rees and stable isotopes b sr in gas groundwater sao paulo state brazil this investigation was carried out in the guarani aquifer system gas following a transect in sao paulo state brazil and involved the analysis of trace elements rees and stable isotopes b sr in both rainwater and groundwater samples the latter sampled from tube wells drilled in 10 cities the brazilian code for mineral waters bcmw has been adopted for classifying the groundwaters according to their temperature and was useful for identifying the major trends of the hydrochemical data three water categories are identified 38 c the hyperthermal waters exhibited geostatic pressures 250 bar whereas the cold hypothermal waters values 100 bar rees concentrations were higher at the monitoring point bcs bernardino de campos dissolved strontium in the groundwater behaves like other alkaline earth metals calcium and barium in samples collected along the studied transect the hyperthermal waters tended to exhibit similar 87sr 86sr ratios between 0 7088 and 0 7099 approximately corresponding to the value of ca 0 709 for seawater sr isotopic ratio at the end of the proterozoic the cold and hypothermal waters exhibited lower b contents than the hyperthermal waters the 11b ranged from 8 1 to 12 0 where the 11b values in cold hypothermal waters were characteristically positive in clear distinction to the negative 11b signatures found in hyperthermal waters

brachiopod geochemical records from across the carboniferous seas of north america evidence for salinity gradients stratification and circulation patterns abstract stable isotopic analyses of 100 well preserved carboniferous brachiopod shells representing two time slices from across north america reveal systematic regional changes in environmental conditions for both of the time slices studied the chesterian latest mississippian and the virgilian latest pennsylvanian 18o and 13c show a stepwise decrease moving across the continent from modern day west to east higher 18o in the west reflects greater water depths less freshwater input and more direct upwelling influence from cool open marine waters than in the east modelling based on these regional isotopic data indicates salinity reductions on the order of 1 4 psu in the appalachian basin relative to the midcontinent basin for the virgilian time interval over a range of reasonable thermal gradient and 18ofw assumptions the magnitude of this gradient is similar to those of modern day hudson bay and the panama bight which exhibit permanent haloclines driven by freshwater discharge considering existing paleoecological evidence for freshening the lack of more dramatic benthic freshening suggests that the depth of a regional halocline was shallower than the depths inhabited by thick shelled stenotopic brachiopods although other lines of evidence are necessary to verify the strength of the halocline estimated 18o temperatures for appalachian basin brachiopods are 3 5 c cooler than those of coeval conodonts due to either slightly warmer fresher surface waters or uncertainty in the phosphate 18o paleothermometer despite discrepancies in calculated temperatures the magnitude of the regional isotopic gradient derived from brachiopod and conodont proxies is similar after making appropriate glacioisotopic and water depth corrections a decreasing 13c trend toward the east southern paleolatitude likely reflects greater restriction and terrestrial influence near the sea s tropical shoreline trace element trends are less consistent and are affected by species and metabolism erratic variations in mg ca concentrations even among pristine samples of the same genera with similar 18o values and unrealistic mg ca derived temperatures justify continued caution in applying existing mg ca thermometer equations to paleozoic brachiopods

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

the mg ca temperature relationship in brachiopod shells calibrating a potential palaeoseasonality proxy brachiopods are long lived long ranging extant organisms of which some groups precipitate a relatively diagenetically stable low magnesium calcite shell previous work has suggested that the incorporation of mg into brachiopod calcite may be controlled by temperature brand et al 2013 here we build upon this work by using laser ablation sampling to de ne the intra shell variations in two modern brachiopod species terebratulina retusa linnaeus 1758 and liothyrella neozelanica thomson 1918 we studied three t retusa shells collected live from the firth of lorne scotland which witnessed annual temperature variations on the order of 7 c in addition to four l neozelanica shells which were dredged from a water depth transect 168 1488 m off the north coast of new zealand the comparison of intra shell mg ca profiles with shell ad18o confirms a temperature control on brachiopod mg ca and supports the use of brachiopod mg ca as a palaeoseasonality indicator our preliminary temperature calibrations are mg ca 1 76 0 27 e 0 16 0 03 t r2 0 75 for t retusa and mg ca 0 49 1 27 e 0 2 0 11 t r2 0 32 for l neozelanica errors are 95 confidence intervals

relationship of pyroclastic volcanism and lake water acidification to jehol biota mass mortality events early cretaceous northeastern china abstract geochemical analysis of the 14 4 m thick lacustrine succession of the lower cretaceous yixian formation jehol group has yielded new insights concerning vertebrate mass mortality events in the lake sihetun volcanic caldera in western liaoning province northeastern china that produced the jehol biota fossil lagerstatten the long term evolution of the caldera system resulted in a shift from felsic to mafic magma chemistry accompanied by a reduced frequency of pyroclastic eruptions declining hydrothermal activity and lower lacustrine productivity the basal tetrapod beds exhibit strong hydrothermal influence as indicated by enrichments of boron b certain alkalis rb cs rare earth elements rees yttrium y and many metals e g co cr cu ge mo ni sb u v and w and by strongly negative molybdenum isotope compositions 98mo to 2 50 that may record large fractionations between molybdate and thiomolybdate species in the sihetun caldera hydrothermal system in contrast the overlying fish beds and non fossiliferous beds have an elemental and mo isotopic composition similar to calc alkaline basalts 98mo 0 29 0 04 in the surrounding watershed suggesting weathering of yixian formation volcanic rocks as the major source of sediment during its

carbon and oxygen isotopic composition of a guam coral and their relationships to environmental variables in the western pacific we examine the high resolution 32 samples year carbon and oxygen isotopic composition 13ccoral and 18ocoral in a coral core porites lobata from double reef guam over the years 1980 2000 the 13ccoral shows clear seasonal variations with mean seasonal amplitude of 1 89 which roughly corresponds with seasonal variations in solar radiation the seasonal amplitude of 18ocoral variations are small 0 23 0 57 but they are significantly correlated with sea surface temperature sst and salinity sss the 18ocoral and sst are more strongly correlated during el nino southern oscillation enso warm phases r 0 81 p 28 c and lower values of 18osw at guam these differences in oceanic parameters result from movements of the western pacific warm pool wpwp during the different phases of enso anomalies in 18osw inferred from the 18ocoral and instrumental sst are consistent with sss anomalies for the years 1980 2000 these 18osw anomalies may reflect changes in sss and evaporation precipitation due to movements of the wpwp this detailed analysis of a coral from guam suggests that it may contain an excellent archive of past enso events

isotope stratigraphy of the european carboniferous proxy signals for ocean chemistry climate and tectonics abstract carboniferous brachiopods from western europe and the former ussr have been utilized as carriers of isotopic proxy signals for paleoceanography and paleoclimatology during the assemblage of pangea this is of particular interest because this time interval coincides with the transition from greenhouse to icehouse conditions the 18 o values 3 ma running means show an overall 18 o increase from about 7 1 to 3 1 during the carboniferous the rise in the 18 o is stepwise with major shifts in the mid tournaisian and at the visean serpukhovian transition the comparable 13 c record shows a tournaisian peak at 5 a visean oscillation at about 2 5 1 a serpukhovian rise of more than 3 a plateau around 5 during the bashkirian and moscovian a 4 drop during the kasimovian and another rise of about 3 during the gzhelian the 87 sr 86 sr record shows an early carboniferous decline from 0 7083 to a mid visean minimum of 0 7077 followed by a rapid serpukhovian rise to a bashkirian and moscovian plateau at 0 7087 and a slight decline during the kasimovian and gzhelian the covariance of isotopic trends and the coincidence with geological phenomena indicates that the long term variations in ocean chemistry and climate may be coupled to the tectonic evolution of the earth system the namurian witnesses the onset of hercynian orogeny initiation of the main phase of carboniferous glaciation formation of the extensive coal deposits and the rise in 87 sr 86 sr 13 c and 18 o all this suggests that a tectonically controlled climate change resulting in cooling and increased carbon storage in the organic reservoir was the major triggering factor for all the above phenomena the late carboniferous glacial episode was interrupted by a warm interval in the stephanian the carbon and oxygen isotope data indicate that this episode may have been restricted to the early kasimovian a proposition at odds with the poorly dated record of glacial deposits that are interpreted as indicating a warm climate for the entire stephanian in addition the pattern of short lived peaks in 13 c and 18 o in the tournaisian and possibly visean may be interpreted as a reflection of short lived glacial episodes a proposition consistent with geologic records

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

on elevated fluoride and boron concentrations in groundwaters associated with the lake saint martin impact structure manitoba abstract hydrogeological investigations conducted by the geological survey of canada in the lake saint martin region of manitoba have confirmed earlier reports of naturally elevated f and b concentrations in local groundwaters fluoride and b concentrations are highly correlated r 2 0 905 and reach 15 1 mg l and 8 5 mg l respectively virtually all groundwaters with f concentrations greater than the drinking water limit of 1 5 mg l are from wells within the lake saint martin impact structure a 208 ma complex crater 23 km in diameter underlying a large part of the study area the high f groundwaters can be classified into two groups according to their anionic and isotopic compositions group i samples consist of na mixed anion groundwaters with cl greater than 100 mg l and highly depleted 18 o compositions indicative of recharge under much cooler climatic conditions than at present samples belonging to this group exhibit a striking relationship to crater morphology and are found in an arcuate belt within the southern rim of the impact structure group ii high f samples consist of na hco 3 so 4 groundwaters with little cl and less depleted 18 o compositions samples belonging to this group are associated with groundwaters recharged locally on a low ridge within the impact structure this paper traces the probable source of high f groundwaters to phosphatic pellets in shales of the winnipeg formation a regional basal clastic unit which sub crops at shallow depth beneath the crater rim as a result of more than 200 m of structural uplift associated with the impact event this extensive aquifer is known elsewhere in southern manitoba for its naturally softened groundwaters and locally elevated f concentrations group i groundwaters are interpreted as discharge from the winnipeg formation where it abuts against crater fill deposits group ii high f groundwaters are interpreted as modern recharge from within the impact structure displacing group i groundwaters thus elevated f and b concentrations observed in groundwaters of the lake saint martin area represent the geochemical signature of upwelling from a deep regional aquifer the previously unsuspected discharge zone occurs within an isolated sub crop of the aquifer formed as a result of structural uplift caused by the impact event

boron isotope systematics of marine sediments abstract boron contents and boron isotopic compositions were determined for modern and ancient permian to miocene marine sediments including pelagic clay calcareous ooze siliceous ooze and neritic clay sediments 11b values of modern marine sediments range from 6 6 to 4 8 isotopic variation is controlled by the simple mixing of four major constituents detritus of continental origin marine smectite biogenic carbonates and biogenic silica detritus of continental origin with an average 11b value of 13 to 8 is the low 11b end member constituent of marine sediments and its boron is largely controlled by the concentration of illite which originates from wind or fluvial transport marine smectite biogenic carbonate and biogenic silica on the other hand represent the high 11b end members with 11b values of 2 3 to 9 2 8 0 to 26 2 and 2 1 to 4 5 respectively these high 11b values are the result of the equilibrium uptake of boron from seawater spatial variations in boron isotopes in the pacific sediments are essentially due to the distribution of the above four constituents although ancient argillaceous sediments shale and slate have boron contents that are identical with those of modern equivalents boron contents of limestone and chert are distinctly lower than those of modern calcareous and siliceous oozes ancient marine sediments have systematically lower 11b values 17 0 to 5 6 than those of the modern sediments the lower 11b values can be caused by diagenesis which induces 1 preferential removal of high 11b boron in calcium carbonate and silica during recrystallization and 2 boron isotopic exchange in the course of the smectite illite transition the observed boron isotopic compositions of ancient argillaceous sediments are distinctly different from those of fresh and altered morb therefore boron isotope systematics will be useful in identifying components from the descending oceanic slab involved in the formation of island arc magma and in investigating mantle crust recycling through subduction processes

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

karst morphology and groundwater vulnerability of high alpine karst plateaus high alpine karst plateaus are recharge areas for major drinking water resources in the alps and many other regions well established methods for the vulnerability mapping of groundwater to contamination have not been applied to such areas yet the paper characterises this karst type and shows that two common vulnerability assessment methods cop and pi classify most of the areas with high vulnerability classes in the test site on the hochschwab plateau northern calcareous alps austria overlying layers are mostly absent not protective or even enhance point recharge where they have aquiclude character the cop method classifies 82 of the area as highly or extremely vulnerable the resulting maps are reasonable but do not differentiate vulnerabilities to the extent that the results can be used for protective measures an extension for the upper end of the vulnerability scale is presented that allows identifying ultra vulnerable areas the proposed enhancement of the conventional approach points out that infiltration conditions are of key importance for vulnerability the method accounts for karst genetical and hydrologic processes using qualitative and quantitative properties of karst depressions and sinking streams including parameters calculated from digital elevations models the method is tested on the hochschwab plateau where 1 7 of the area is delineated as ultra vulnerable this differentiation could not be reached by the cop and pi methods the resulting vulnerability map highlights spots of maximum vulnerability and the combination with a hazard map enables protective measures for a manageable area and number of sites

brachiopods as indicators of original isotopic compositions in some paleozoic limestones the original stable isotopic composition of paleozoic marine carbonate rocks is important to establish a baseline for evaluating diagenetic alteration and providing a reliable data base for modeling exogenic geochemical cycles of the elements we have compared the 18 o and 13 c values in the nonluminescent portions of brachiopods with similar published data of whole brachiopods other whole fossils and estimates of original isotopic composition of marine cements the oxygen and carbon isotopic records for each of these paleozoic components show generally good internal consistency significant discrepancies however were noted between results on the different components isotopic and trace element data presented in this study suggest that permo carboniferous whole brachiopods are little altered chemically nonetheless a more reliable but not fool proof approach for obtaining pristine isotopic values is microsampling of least altered regions based on cathodoluminescence in conjunction with staining techniques and elemental analyses the carbon and oxygen isotopic compositions of all components decrease in 18 o and 13 c in geologically older material neither temporal trend is monotonic however oxygen isotopic results suggest an important positive shift in 18 o of about 2 during the early carboniferous whereas the carbon isotope trend shows a major positive shift 2 3 during the mid carboniferous

paleoenvironmental changes in the silurian indicated by stable isotopes in brachiopod shells from gotland sweden ratios of stable carbon and oxygen isotopes in brachiopod shells more than 370 specimens esp atrypa reticularis from the silurian of gotland sweden have been analysed preservation of biological skeletal ultrastructures observed in sem micrographs and cathodoluminescence analyses indicate that usually no diagenetical alteration occurs the silurian of gotland consists of 440 m carbonate deposits spanning the late llandovery to late ludlow epochs 431 411 m y repeatedly uniform sequences of micritic limestones and marks are interrupted by complex structured reefs and adjacent platform sediments previously the alteration of facies is interpreted as the result of sea level fluctuations caused by a gradual regression with superimposed minor transgressive pulses the silurian sequence of gotland exhibits principally parallel carbon and oxygen isotope records corresponding closely to the topostratigraphic units lower values occur in periods dominated by deposition of marly sequences higher values are observed in periods dominated by reefs and extended carbonate platforms the isotope ratios are influenced by local as well as global factors the oxygen isotope ratios are interpreted to reflect paleosalinity changes due to varying freshwater input rather than changes in paleotemperature consequently the facies distribution of gotland is interpreted as resulting from changes in terrigenous input caused by different rates of continental weathering and freshwater runoff rather than by sea level fluctuations periods of arid climate and therefore anti estuarine downwelling of oxygenated surface water appear as short episodes of reef growing 1 5 m y in an epoche characterized by a tropic humid climate which causes an estuarine circulation and the upwelling of co2 rich deep water carbon isotope ratios are obviously connected to these changes in circulation by the advection of 13c rich surface water arid episodes or upwelling of 13c depleted deep water humid episodes of a silurian ocean which itself reveals generally euxinic deep water conditions due to the burial of organic carbon in black shales

chemical stabilization of low mg calcite an example of brachiopods abstract trace element study of brachiopod shells from the upper ordovician ellis bay formation anticosti island quebec canada shows that they underwent only a slight 20 diagenetic equilibration with meteoric waters despite 450 million years of postdepositional history this in contrast to large trace element repartitioning observed in their enclosing rocks attests to the relative stability of low mg calcite even within the realm of meteoric waters paleozoic brachiopods apparently exerted a biological control on the distribution of na and mg in their low mg calcitic shells preferentially incorporating the former and discriminating against the latter trace constituent

geochemical and isotopic evidences for a severe anthropogenic boron contamination a case study from castelluccio arezzo central italy abstract in 2009 a deterioration of garden plants watered with domestic wells was related to high boron concentrations up to 57 mg l measured in the shallow aquifer from the industrial area of castelluccio tuscany italy where several factories are or were using boron compounds for their industrial processes since 2012 a geochemical and isotopic survey of stream ground and waste waters and sediment samples was performed in addition monthly geochemical surveys were carried out from january to september 2013 during which concentrations of boron up to 139 mg l were measured the geochemical dataset also included raw borax and sodium boron hydride and anthropogenic materials b rich slags and muds stored in one of the local factories the latter being to the best of our knowledge analyzed for the first time in this work for bulk and leachate boron concentration and isotopic ratios the results highlighted that the high concentrations of boron found in the local shallow aquifer had unequivocally an anthropogenic source it was suggested that prolonged interaction between industrial presently stored at ground level or buried by products and waste and meteoric waters was likely the main process responsible of the groundwater contamination as supported by the analysis of the major solutes the dispersion of the contaminant could not clearly be observed downward the shallow hydrogeological circuit consequently the presence of other sources of boron in the industrial area of castelluccio cannot be excluded this would also explain the reason why no univocal results were obtained by the 11 b 10 b isotopic ratios measured in water sediment and bulk and leachate anthropogenic samples to minimize the boron contamination a hydraulic barrier should be constructed where the highest concentrations of boron were measured

within shell variations in carbon and oxygen isotope compositions of two modern brachiopods from a subtropical shelf environment off amami o shima southwestern japan 1 this study examines the fidelity of carbon 13c and oxygen 18o isotope compositions of two modern brachiopod species kikaithyris hanzawai and basiliola lucida to use as proxies of 13c values of total dissolved inorganic carbon and temperature and or 18o values of seawater respectively well preserved shells of k hanzawai and living individuals of b lucida were collected from a subtropical shelf environment off amami o shima southwestern japan some portions of the shells are in isotopic equilibrium with the ambient seawater while other portions are not the degree of disequilibrium differs between the two species and between different portions of each shell statistically significant positive correlations are recognized between the 13c and 18o values of these samples which can be ascribed to a kinetic fractionation effect far from the posterior shell edge and along the axis of shell growth the 18o values of the secondary shell layer of k hanzawai mostly fall within the expected range of equilibrium calcite the 13c values from the inner surface of the secondary shell layer in both species are relatively constant and are equivalent to or very close to equilibrium calcite therefore these portions of the shells are most suitable for collecting reliable environmental proxy data although the 13c and 18o values of modern brachiopod shells are predominantly controlled by a kinetic fractionation effect the appropriate selection of species and shell portions that reflect the isotopic composition of ambient seawater can facilitate the reconstruction of secular variations in oceanic 13c or 18o values

hydrogeological processes in a fluviokarstic area inferred from the analysis of natural hydrogeochemical tracers the case study of eastern serrania de ronda s spain in riverine karst areas surface water interacts with the groundwater flowing through carbonate aquifers understanding the interference of water fluxes in this type of environments is essential to effectively manage the groundwater resources particularly in areas where karst aquifers comprise the main source of drinking water in this research the interaction between surface water and groundwater in the turon river valley eastern serrania de ronda s spain and the functioning of sierra blanquilla karst aquifer have been characterised by means of hydrodynamic monitoring and the combined use of physical chemical parameters and natural hydrogeochemical tracers the results show connected gaining streams in the river stretches close to the permanent springs while in the surroundings of the overflow springs the river reaches behave as gaining high flow and as perched losing low flow soil natural tracers permit tracing runoff arising from the upper part of the hydrological watershed via river which interacts with the groundwater drained in the main discharge area of the aquifer furthermore the analysis of hydrogeochemical data and chemographs demonstrate that sierra blanquilla aquifer behaves as a typical conduit flow system in which the unsaturated zone predominantly participates during high flow periods while the saturated zone is more active in low flow when the groundwater inputs maintain the turon river discharge the more detailed understanding of how the hydrogeochemical characteristics of groundwater vary over time and space has direct consequences on karst spring protection and in the environmental preservation of groundwater ecodependent systems

interannual and decadal variability of the western pacific sea surface condition for the years 1787 2000 reconstruction based on stable isotope record from a guam coral 1 we present a monthly resolved 213 year stable isotope time series from a coral from guam 13 n 145 e which is located on the northern edge of the western pacific warm pool oxygen isotopic composition of the coral skeleton 18ocoral shows seasonal interannual and decadal variability which documents significant oceanographic changes related to thermal and hydrologic variations in this region the 18ocoral anomaly reflects sea surface temperature sst anomaly and sea surface salinity sss anomaly with significant r values of 0 69 and 0 49 respectively which are strongly linked to oceanographic changes that occur during el nino southern oscillation enso warm and cool phases we identified 46 enso warm el nino and 53 cool phases la nina in the coral record which are consistent with those phases reconstructed by nino 3 4 sst anomaly spectral analyses of the 18ocoral anomaly record for the years 1790 1999 identified significant peaks around 3 to 7 years these results indicate that the guam coral has recorded enso periodicity the 18ocoral anomaly shows decadal variability of 15 to 45 year periodicity with significant shifts 0 2 from warmer to cooler condition and vice versa an accumulative decrease in 18ocoral time series may imply 0 75 c warming of sst and 0 23 freshening of seawater 18o corresponding to a decrease of sss by 0 85 in the northwestern tropical pacific over the last 2 centuries

paleoceanographic conditions at approximately 20 and 70 ka recorded in kikaithyris hanzawai brachiopoda shells abstract the 13c and 18o values of fossil brachiopod shells have been widely used as paleoenvironmental proxies in this study we investigated intrashell and intraspecific variations in the isotopic and minor element concentrations of well preserved shells of the brachiopod kikaithyris hanzawai yabe from the last glacial period 20 ka last glacial maximum lgm and 70 ka marine isotope stage 4 mis4 collected in the central ryukyus and used these data to estimate the paleoceanographic conditions seawater temperature concentration of dissolved inorganic carbon dic and 13c value of dic 13cdic the 13c and 18o profiles along the maximum growth axis obtained from the inner shell surface show three distinct intervals corresponding to changes in shell morphology these results suggest that the bulk isotopic compositions of brachiopods with complex shell morphologies are unsuitable for paleoenvironmental reconstructions nevertheless there exists a specific shell portion with relatively small intrashell and intraspecific variations the past seawater temperatures derived from the 18o values of this portion are consistent with the alkenone and planktic foraminiferal mg ca based past seawater temperatures reported in previous studies the past 13cdic values estimated from the 13c values of the specific shell portion are within the range of the past 13cdic values calculated from known atmospheric and oceanographic parameters the past dic concentrations reconstructed from the brachiopod based 13cdic values are lower than the present concentrations in the east china sea which can be explained by low partial pressure of co2 during the last glacial period these results indicate that the 13c and 18o values obtained from k hanzawai shells are potential paleoenvironmental indicators the intrashell and intraspecific variations in the k hanzawai shells are different for each minor element some anomalously high mn and fe concentrations in the shells are probably caused by metabolic factor s not by meteoric diagenesis this suggests that the minor element concentrations are useful but not perfect for distinguishing diagenetically altered and unaltered portions of the shells of k hanzawai in the studied succession

mechanism of regional enrichment of groundwater by boron the examples of bangladesh and michigan usa abstract in bangladesh concentrations of boron in groundwater reach 2 1 mg l 1 and are high regionally in alluvial aquifers of late pleistocene holocene age concentrations exceed 0 5 mg l 1 across approximately 6700 km 2 of the deep aquifer 150 m depth and 3000 km 2 of the shallow aquifer 1 and high values are widespread in the ne of the county these concentrations exceed the regulatory guideline values for human consumption of 0 5 mg l 1 who or 0 9 mg l 1 usa the boron has desorbed from mineral surfaces as freshwater flushing displaces saline waters from the aquifers in bangladesh desorption is driven by decreasing ionic strength the equilibrium re adjustment of mineral sorption sites to the low boron concentration in freshwater and competitive exchange with hco 3 co 3 in deep bangladesh aquifers in barisal district 250 m deep boron enrichment delineates a buried estuary marking a previous course of the ganges and or brahmaputra rivers boron enrichment is accompanied by ion exchange that depletes ca and enriches na in the flushing freshwater the patterns of enrichment and depletion indicate the direction of water quality change in terms of salinization or freshening with greater sensitivity than absolute chemical parameters

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

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

the ireviken event in the lower silurian of gotland sweden relation to similar palaeozoic and proterozoic events abstract for a long time the silurian was thought to represent a time of stable environmental conditions in the greenhouse period that followed the late ordovician glaciation during the past decade knowledge about the silurian has increased markedly and today it is known that the conditions in the silurian were much more variable than previously assumed detailed isotopic investigations have revealed several distinct positive excursions in both carbon and oxygen isotope values in low latitudes these periods of high c and o isotope values are in many cases characterised by the growth of reefs and the formation of extended carbonate platforms the sediments deposited during these excursions contain impoverished fossil assemblages especially with respect to conodonts graptolites and trilobites a conspicuous isotope excursion coincident with facies changes and a marked mass extinction is observed near the llandovery wenlock boundary this event is called the ireviken event after its type locality on the island of gotland sweden jeppsson l 1987 in palaeobiology of conodonts ellis horwood ltd chichester pp 129 145 here isotope data from nine sections at the nw coast of gotland are presented that cover the time interval of the ireviken event the 13c mean values rise from 1 4 to 4 5 and the 18o values increase from 5 6 to 5 0 the relative timing of stable isotope development extinctions and facies development is discussed it is shown that first extinctions precede the isotope excursion this indicates that extinction events and stable isotope development are only indirectly connected but might reflect the same causes other events characterised by similar relationships between positive isotope excursions mass extinctions and facies development are found in younger parts of the silurian late wenlock and ludlow in the late ordovician the late cambrian and with some reservations in the proterozoic the similarities between these events indicate analogous controlling mechanisms for the silurian climatic changes between humid and arid conditions in low latitudes were postulated in an earlier study of the authors a palaeoceanographic climatic model was postulated which is consistent with most of the sedimentological palaeontological and geochemical data here we demonstrate that this model may be applicable also for the older events

global carbon isotopic events associated with mass extinction and glaciation in the late ordovician mass extinctions and glacioeustatic sea level changes in the lower part of the hirnantian final stage of the ashgill are accompanied by shifts in marine stable isotope compositions previously published stable isotope changes have been used to identify the onset and demise of the gondwana glaciation and to suggest relationships between biotic changes and carbon cycling within the oceans however the existing isotopic data set had limitations because it was derived from ordovician low latitude settings and from carbonates or organic carbon in separate areas we report new data from ordovician high latitude carbonates and demonstrate parallel shifts in organic and carbonate 13c from baltica brachiopod shells from a high palaeolatitude periglacial setting in argentina have elevated 13c values similar to those described previously from low latitude sites the new data demonstrate that the positive hirnantian 13c excursion previously only recognised from low palaeolatitude areas was widespread and probably global in extent the poor preservation state of the brachiopods unfortunately prevented the determination of a reliable oxygen isotopic value from the same material preliminary carbon isotopic data from thermally immature organic matter from estonia provide the first indication of a synchronous shift in organic and inorganic 13c in sediments from the same basin this work provides new data of critical importance for constraining models of end ordovician palaeoceanography and climate change

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