natural uranium and strontium isotope tracers of water sources and surface water groundwater interactions in arid wetlands pahranagat valley nevada usa summary near surface physical and chemical process can strongly affect dissolved ion concentrations and stable isotope compositions of water in wetland settings especially under arid climate conditions in contrast heavy radiogenic isotopes of strontium 87sr 86sr and uranium 234u 238u remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end member mixing that would otherwise be difficult to determine the utility of combined sr and u isotopes are demonstrated in this study of wetland habitats on the pahranagat national wildlife refuge which depend on supply from large volume springs north of the refuge and from small volume springs and seeps within the refuge water budgets from these sources have not been quantified previously evaporation transpiration seasonally variable surface flow and water management practices complicate the use of conventional methods for determining source contributions and mixing relations in contrast 87sr 86sr and 234u 238u remain unfractionated under these conditions and compositions at a given site remain constant differences in sr and u isotopic signatures between individual sites can be related by simple two or three component mixing models results indicate that surface flow constituting the refuge s irrigation source consists of a 65 25 10 mixture of water from two distinct regionally sourced carbonate aquifer springs and groundwater from locally sourced volcanic aquifers within the refuge contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices

radiogenic and stable sr isotope ratios 87 sr 86 sr δ 88 86 sr as tracers of riverine cation sources and biogeochemical cycling in the milford sound region of fiordland new zealand this study reports radiogenic sr isotope ratios 87sr 86sr stable sr isotope ratios 88 86sr and major ion concentrations for river rock sediment soil and plant samples collected from the cleddau and hollyford catchments in the milford sound region of fiordland new zealand the catchments primarily drain gabbro but some tributaries access limestone and volcanogenic sediments the goal of the study was to understand controls on riverine 88 86sr values in a landscape with multiple factors that may influence chemical weathering including dense vegetation high rainfall and abundant freshly eroded holocene fluvio glacial and landslide debris rivers draining gabbro have higher 88 86sr values than bedrock by as much as 0 14 and the 88 86sr values strongly correlate with molar ca sr ratios r2 0 69 leaching of rocks and sediment reveals no evidence for the preferential dissolution of minerals having high 88 86sr values and ca sr ratios in stream sr isotope fractionation seems unlikely because comparison against 87sr 86sr and ca sr ratios demonstrates that riverine 88 86sr values conservatively trace water mass mixing the riverine data are best explained by the input of soil water which is distinct from potential bedrock end members i e silicates and carbonates based on 88 86sr but indistinguishable in terms of ca sr and 87sr 86sr while strontium isotope fractionation during secondary mineral formation and pedogenesis is possible clay mineral formation is minor and most soils are poorly developed instead soil water 88 86sr values more likely reflect plant uptake plant samples yielded a wide range of 88 86sr values but on average they are lower than those for bedrock consistent with the expectation that plants preferentially incorporate lighter sr isotopes mass balance constraints together with 87sr 86sr ratios indicate that soil water 88 86sr values are 0 30 higher than bedrock 88 86sr values and mixing calculations show that the plant fractionated soil water pool contributes 27 of the riverine sr for tributaries accessing limestone and volcanogenic sediments ca sr and 87sr 86sr ratios appear consistent with two component mixing between silicate and carbonate weathering but 88 86sr values reveal a third contribution from soil water inputs similar to gabbro catchments the results of this study suggest that sr isotopes behave conservatively during water mass mixing and stream transport but non conservatively in soil where plant uptake can elevate soil water 88 86sr values relative to bedrock plant uptake or related biogeochemical processes such as ion exchange on organic matter surfaces also appear to modify soil water ca sr ratios many studies use 87sr 86sr and ca sr ratios to apportion riverine solutes between silicate and carbonate weathering but ca sr ratios may be non conservative in densely vegetated areas the stable sr isotope tracer shows promise for resolving riverine cation sources as well as effects from biological cycling

effect of calcite precipitation on stable strontium isotopic compositions insights from riverine and pool waters in a karst cave abstract radiogenic and stable sr isotope ratios 87 sr 86 sr 88 86 sr serve as potential tracers for evaluation of weathering sources and associated physicochemical processes in terrestrial environments despite carbonate weathering sourcing two thirds of the total continental sr flux to the ocean however few attempts have been aimed at studying stable sr isotope fractionation in carbonate dominated aquifers here we present a monthly resolved monitoring dataset of major ion concentrations and sr isotope ratios for karst riverine and pool waters at the luofang cave in the central china to understand the potential controls responsible for water 88 86 sr compositions under various climatic conditions with the exception of some pool waters in the dry period significantly heavier 88 86 sr were detected in the riverine and pool waters 0 20 to 0 42 compared to bedrock 88 86 sr 0 24 to 0 28 which can t be interpreted solely by lithology a sequential leaching experiment of the local soils suggests limited stable sr isotope fractionation during incongruent silicate mineral dissolution local plant utilization and biological activity in the soil overlying the cave are possible processes for causing the observed heavier 88 86 sr in cave water however air partial pressure of co 2 in cave monitoring water ph and sr isotopic mass balance calculations suggest that plant utilization is unlikely to be the primary control on the heavier water 88 86 sr on the other hand significant stable sr isotope fractionation was found between the cave dripping waters and calcite precipitates and the 88 86 sr car aq was estimated to be 0 15 0 07 2sd precipitation of secondary calcites might be a potential process responsible for the heavier 88 86 sr in the waters the negative correlation between 88 86 sr and sr na ratios in the cave waters is consistent with a scenario of preferential incorporation of the light sr isotope by solid phase furthermore by combining the calcite saturation states and water ph our results suggest that calcite precipitation is the most likely process controlling 88 86 sr compositions in cave water we demonstrate that secondary calcite precipitation in carbonate dominated catchments could be important in controlling the riverine water 88 86 sr compositions

stable sr isotope sr ca mg ca li ca and mg li ratios in the scleractinian cold water coral lophelia pertusa the aragonitic skeletons of scleractinian cold water corals can serve as valuable archives in paleoceanographic studies the potential of 88 86sr sr ca mg ca li ca and mg li ratios of the cold water coral lophelia pertusa to record intermediate water mass properties has been investigated here we used samples from several locations along the european continental margin spanning a large temperature range from 6 to 14 c stable strontium isotope measurements were carried out with the recently developed double spike tims technique and our results differ from those obtained with less precise methods in contrast to the strong positive relationship with temperature of previous studies our results suggest that 88 86sr measured in scleractinian cold water corals is not controlled by seawater temperature but reflects the sr isotopic composition of seawater with an offset of 88 86sr 0 196 as found in previous studies the elemental ratios sr ca li ca and mg li measured in corals are significantly related to water temperature and do not correlate with salinity moreover sr ca ratios in l pertusa display the expected inverse correlation with temperature however the variance in the sr ca data severely limits the accuracy of paleotemperature estimates the li ca and mg ca ratios reveal other influences besides temperature such as ph and or growth or calcification rate however corresponding mg li ratios in l pertusa are more tightly related to temperature as they remove these secondary effects in particular the mg li ratio in l pertusa may serve as a new promising paleotemperature proxy for intermediate water masses our dataset represents the most extensive geochemical examination of l pertusa to date revealing a temperature sensitivity of 0 015 mol mmol c for mg li however using this temperature dependence and the precision of 5 3 2sd only temperature variations larger than 1 5 c can be resolved with 95 confidence

characterising the stable δ88 86sr and radiogenic 87sr 86sr isotopic composition of strontium in rainwater rainwater plays a major role in determining the transfer of elements and pollutants to soils and hydrological catchments with compositional variations reflecting the extent of mixing between marine sea salt terrestrial dust and vegetation and anthropogenic aerosols while the radiogenic strontium isotope system 87sr 86sr is often used to help constrain the different sources of atmospheric sr the degree of variability in the stable strontium isotope system 88 86sr remains unresolved in order to determine how atmospheric sr affects the 88 86sr composition of water entering the hydrological cycle this study analysed a suite of rainwater samples collected over the course of a year in central paris rainwater 88 86sr compositions were found to range from 0 13 to 0 32 with 87sr 86sr ratios varying between 0 70796 and 0 71093 no seasonality was observed in 88 86sr whereas 87sr 86sr ratios were observed to be generally more radiogenic in the summer and less radiogenic in the winter strontium enrichment factors significantly above seawater implied a predominantly terrestrial non sea salt origin of sr in rainwater with the 88 86sr and 87sr 86sr composition of this terrestrial fraction consistent with a mixture of sr derived from carbonate dust and agricultural fertiliser evidence for a 0 1 decrease in the 88 86sr composition of the river seine as it passes through paris suggests that anthropogenic pollutants may contribute to significant regional variations in the composition of sr in the hydrological cycle together these results demonstrate that there is significant potential for both temporal and spatial variations in the 88 86sr and 87sr 86sr composition of rainwater that need to be taken into consideration when studying 88 86sr variations in localised catchments

viscous accretionary prisms viscoelastic relaxation of the makran accretionary prism following the 2013 baluchistan pakistan earthquake

automated fault model discretization for inversions for coseismic slip distributions 1 geoscientists increasingly rely on coseismic slip distributions inferred from geodetic observations to drive sophisticated models of the seismic cycle to date little work has been done on optimizing the parameterization of these fault models so that they reflect the resolving power of observed surface displacements the locations of noisy surface displacement observations are often widely scattered far from features we wish to analyze in the subsurface and result in highly variable model resolution with depth the few attempts to produce variably discretized fault planes are arduously constructed by hand and may not correctly reflect the ability of the data to resolve slip features motivated by the increasing size of geodetic data pools and the need for distributed slip models that accurately represent features the data can resolve we present a fully automated algorithm that iteratively adjusts the sizes of dislocations in a fault model we use the concept of smoothing scales derived from the model resolution matrix to resize dislocations so that each dislocation is sized appropriately given the area over which slip in that region of the fault would be smoothed we present a series of synthetic tests that utilize both sparse and dense data sets and we compare our variably discretized inversions to traditional regularly discretized inversions we also use our approach to invert for slip from geodetic observations of the 2004 mw 6 0 parkfield california earthquake and the 1995 mw 8 1 antofagasta chile earthquake

determination of 88sr 86sr mass dependent isotopic fractionation and radiogenic isotope variation of 87sr 86sr in the neoproterozoic doushantuo formation abstract we measured both mass dependent isotope fractionation of 88sr 88sr 86sr and radiogenic isotopic variation of sr 87sr 86sr for the neoproterozoic doushantuo formation that deposited as a cap carbonate immediately above the marinoan related nantuo tillite the 88sr and 87sr 86sr compositions showed three remarkable characteristics 1 high radiogenic 87sr 86sr values and gradual decrease in the 87sr 86sr ratios 2 anomalously low 88sr values at the lower part cap carbonate and 3 a clear correlation between 87sr 86sr and 88sr values these isotopic signatures can be explained by assuming an extreme greenhouse condition after the marinoan glaciation surface seawater mixed with a large amount of freshwater from continental crusts with high 87sr 86sr and lighter 88sr ratios was formed during the extreme global warming after the glacial event high atmospheric co2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87sr 86sr and lighter 88sr ratios subsequently the mixing of the underlying seawater with unradiogenic sr isotope compositions and normal 88sr ratios probably caused gradual decrease of the 87sr 86sr ratios of the seawater and deposition of carbonate with normal 88sr ratios the combination of 87sr 86sr and 88sr isotope systematics gives us new insights on the surface evolution after the snowball earth

stable strontium isotopes δ88 86sr in cold water corals a new proxy for reconstruction of intermediate ocean water temperatures abstract zooxanthellate scleractinian corals are known as archives for temporal variations of climate variables such as sea surface temperature salinity or productivity the use of azooxanthellate cold water corals as potential archives for intermediate water mass properties and climate variability was tested recently however the correlation of established proxies such as 18o and 13c with temperature is difficult since there is no direct temperature equation applicable as in shallow water corals other temperature proxies such as sr ca mg ca and u ca are influenced by the complex microstructure of the aragonite skeleton the rate of calcification and other vital effects observed for coral species for the first time we show that the stable strontium isotope ratio 88 86sr incorporated in the skeletons of the cold water coral species lophelia pertusa portrays the ambient seawater temperature the temperature sensitivity from live samples collected along the european continental margin covering a temperature range from 6 to 10 c is 0 026 0 003 c 2 standard error which is a sensitivity similar to the tropical shallow water coral record of pavona clavata this indicates a similar fractionation process of strontium for both zooxanthellate and azooxanthellate corals for coral aragonite the 88 86sr ratio may serve as a new paleo temperature proxy and introduces new perspectives in paleoceanography with respect to intermediate water dynamics

evidence for stable sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern taiwan abstract radiogenic sr isotopes 87 sr 86 sr are robust for provenance identification in hydrology affected mainly by the age of background lithologies and the degree of chemical weathering however there is limited knowledge concerning the fractionation mechanism of stable sr isotopes 88 sr 86 sr in rivers in this study river water was collected on a weekly to monthly basis throughout dry and wet seasons furthermore to study the variations of radiogenic and stable sr isotopes during intense weathering a major flooding event 2000 mm precipitation in three days typhoon morakot water was captured within a small drainage catchment system 161 km 2 along the hou ku river in southwestern taiwan for a better constraint on the end member compositions bedload sediments suspended particles and several host rocks were sampled for a systematic investigation the carbonate and silicate phases of these solids were chemically separated dissolved major elements indicate that the watersheds were predominated by silicate weathering stable sr isotopes show no significant variation 88 sr 0 24 0 31 temporally and spatially with an average of 0 28 additionally all solids showed lower 88 sr values than the river water while the host rocks had higher 88 sr values 88 sr 0 20 0 26 than the residual weathering products 88 sr 0 08 0 22 indicating preferential leaching of heavy sr into the hydrosphere and leaving light sr in the residual solids results of laboratory acid leaching experiments reveal that dissolution of high 88 sr value minerals occurred at an early stage of weathering the variation of weathering intensity does not alter stable sr isotopes in silicate weathering dominated river water which contains higher stable sr isotopes than the associated sediments the silicatic sedimentary rocks preferentially released higher stable sr isotopes into the hydrosphere during chemical weathering thus leaving lower stable sr isotopes in the residual solids

88sr 86sr fractionation in inorganic aragonite and in corals conflicting results have been reported for the stable sr isotope fractionation specifically with respect to the influence of temperature in an experimental study we have investigated the stable sr isotope systematics for inorganically precipitated and biogenic coral aragonite natural and laboratory cultured inorganic aragonite precipitation experiments were performed from natural seawater using the co2 diffusion technique the experiments were performed at different temperatures and different carbonate ion concentrations 88sr 86sr of the inorganic aragonite precipitated in the experiments are 0 2 lighter than seawater but showed no correlation to the water temperature or to co32 concentration similar observations are made in different coral species cladocora caespitosa porites sp and acropora sp with identical fractionation from the bulk solution and no correlation to temperature or co32 concentration the lack of 88sr 86sr variability in corals at different environmental parameters and the similarity to the 88sr 86sr fractionation in inorganic aragonite may indicate a similar sr incorporation mechanism in corals skeleton and inorganic aragonite and therefore the previously proposed rayleigh based multi element model gaetani et al 2011 cannot explain the process of sr incorporation in the coral skeletal material it is proposed that the relatively constant 88sr 86sr fractionation in aragonite can be used for paleo reconstruction of seawater 88sr 86sr composition the seawater 88sr 86sr ratio reconstruction can be further used in calcite samples to reconstruct paleo precipitation rates

the origin and migration of mud volcano fluids in taiwan evidence from hydrogen oxygen and strontium isotopic compositions abstract mud volcanoes are important gateways for deep fluids to migrate upward and provide windows for studying fluid sediment interaction at depth fluids emitted from 40 terrestrial mud volcanoes were collected in southern and eastern taiwan to study their chemical compositions including h o and sr isotopes 87sr 86sr and 88 86sr relative to seawater the mud volcano fluids are depleted in cl mg so42 and d and are elevated in b ba li and 18o possibly due to water rock interaction and clay dehydration mainly smectite to illite transformation in the source region the distribution of sr in mud volcano fluids shows patterns associated with their localities and geological settings most fluids have higher 87sr 86s than seawater indicating water rock interaction at depth the low na 87sr 86s and high ca fluids emitted from eastern taiwan imply intense interaction with igneous basement most fluids have higher sr cl and lower 88sr than seawater except mud volcanoes in the northern chu kou fault which emit low sr cl and extremely high 88sr up to 0 82 fluids we performed laboratory carbonate precipitation experiments that indicate that these high sr isotope ratios are caused by co precipitation of carbonates from high alkalinity fluids mud volcano fluids in taiwan originate at depth and their chemical compositions are controlled by the host rock degrees of water rock interaction and clay dehydration but also are masked by retrograde progresses such as carbonate precipitation during migration our results show that an approach combining water isotopes d and 18o and strontium isotopes 87sr 86sr and 88 86sr provides a robust tool for tracing fluid sources and migration pathways in accretionary prisms

ca sr and ba stable isotopes reveal the fate of soil nutrients along a tropical climosequence in hawaii abstract nutrient biolifting is an important pedogenic process in which plant roots obtain inorganic nutrients such as phosphorus p and calcium ca from minerals at depth and concentrate those nutrients at the surface here we use soil chemistry and stable isotopes of the alkaline earth elements ca strontium sr and barium ba to test the hypothesis that biolifting of p has been an important pedogenic process across a soil climosequence developed on volcanic deposits at kohala mountain hawaii the geochemical linkage between these elements is revealed as generally positive site specific relationships in soil mass gains and losses particularly for p ba and ca using the ratio of immobile elements titanium and niobium ti nb to link individual soil samples to a restricted compositional range of the chemically and isotopically diverse volcanic parent materials at sites where p is enriched in surface soils relative to abundances in deeper soils the isotope compositions of exchangeable ca sr and ba in the shallowest soil horizons 10 cm depth at those sites is consistently heavier than the volcanic parent materials the isotope compositions of exchangeable ca and sr trend toward heavier compositions with depth more gradually reflecting increasing leakiness from these soils in the order ba

tropical atlantic sst history inferred from ca isotope thermometry over the last 140ka exploring the potentials of new methods in palaeothermometry is essential to improve our understanding of past climate change here we present a refinement of the published 44 40ca temperature calibration investigating modern specimens of planktonic foraminifera globigerinoides sacculifer and apply this to sea surface temperature sst reconstructions over the last two glacial interglacial cycles reproduced measurements of modern g sacculifer collected from surface waters describe a linear relationship for the investigated temperature range 19 0 28 5 c 44 40ca 0 22 0 05 sst c 4 88 thus a change of 44 40ca of 0 22 0 05 corresponds to a relative change of 1 c the refined 44 40camodern calibration allows the determination of both relative temperature changes and absolute temperatures in the past this 44 40camodern calibration for g sacculifer has been applied to the tropical east atlantic sediment core geob1112 for which other sst proxy data are available comparison of the different data sets gives no indication for significant secondary overprinting of the 44 40ca signal long term trends in reconstructed sst correlate strongly with temperature records derived from oxygen isotopes and mg ca ratios supporting the methods validity the observed change of sst of approximately 3 c at the holocene last glacial maximum transition reveals additional evidence for the important role of the tropical atlantic in triggering global climate change based on a new independent palaeothermometer

evidence for slip partitioning and bimodal slip behavior on a single fault surface slip characteristics of the 2013 mw7 7 balochistan pakistan earthquake abstract deformation is commonly accommodated by strain partitioning on multiple independent strike slip and dip slip faults in continental settings of oblique plate convergence as a corollary individual faults tend to exhibit one sense of slip normal reverse or strike slip until whole scale changes in boundary conditions reactivate preexisting faults in a new deformation regime in this study we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike slip or a dip slip sense during independent fault slip events we use 0 5 m resolution optical imagery and sub pixel correlation analysis of the 200 km 2013 m w 7 7 balochistan pakistan earthquake to document co seismic surface slip characteristics and quaternary tectonic geomorphology along the causative hoshab fault we find that the 2013 earthquake which involved a 6 1 strike slip to dip slip ratio ruptured a structurally segmented fault quaternary geomorphic indicators of gross fault zone morphology reveal both reverse slip and strike slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike slip motion in 2013 observations of along strike variations in range front relief and geomorphic offsets suggest that the hoshab fault accommodates a substantial reverse component of fault slip in the quaternary especially along the southern section of the 2013 rupture we surmise that quaternary bimodal slip along the hoshab fault is promoted by a combination of the arcuate geometry of the hoshab fault the frictional weakness of the makran accretionary prism and time variable loading conditions from adjacent earthquakes and plate interactions

structural control on megathrust rupture and slip behavior insights from the 2016 mw 7 8 pedernales ecuador earthquake the heterogeneous seafloor topography of the nazca plate as it enters the ecuador subduction zone provides an opportunity to document the influence of seafloor roughness on slip behavior and megathrust rupture the 2016 m w 7 8 pedernales ecuador earthquake was followed by a rich and active postseismic sequence an internationally coordinated rapid response effort installed a temporary seismic network to densify coastal stations of the permanent ecuadorian national seismic network a combination of 82 onshore short and intermediate period and broadband seismic stations and six ocean bottom seismometers recorded the postseismic pedernales sequence for over a year after the mainshock a robust earthquake catalog combined with calibrated relocations for a subset of magnitude 4 earthquakes shows pronounced spatial and temporal clustering a range of slip behavior accommodates postseismic deformation including earthquakes slow slip events and earthquake swarms models of plate coupling and the consistency of earthquake clustering and slip behavior through multiple seismic cycles reveal a segmented subduction zone primarily controlled by subducted seafloor topography accreted terranes and inherited structure the 2016 pedernales mainshock triggered moderate to strong earthquakes 5 m 7 and earthquake swarms north of the mainshock rupture close to the epicenter of the 1906m w 8 8 earthquake and in the segment of the subduction zone that ruptured in 1958 in a m w 7 7 earthquake

impacts of topographic relief and crustal heterogeneity on coseismic deformation and inversions for fault geometry and slip a case study of the 2015 gorkha earthquake in the central himalayan arc

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

88 sr 86 sr fractionation and calcite accumulation rate in the sea of galilee abstract this study used the sea of galilee lake kinneret northern israel as a natural laboratory to investigate the fractionation of the stable sr isotope ratio 88 sr 86 sr during precipitation of inorganic primary calcite from the lake s water it was found that the absolute value of the 88 sr 86 sr fractionation factor 88 86 sr increases as a function of calcite accumulation rate 88 86 sr 0 05 to 0 042 log r mol m 2 d 1 where r is the accumulation rate furthermore the 87 sr 86 sr and 88 sr 86 sr ratios in the freshwater and brines that enter the lake were used to calculate the contributions of these sources to the lake sr budget the 87 sr 86 sr and 88 sr 86 sr ratios were measured in primary calcite aragonite shells of live melanopsis lake water and various water sources to the lake while the lake s 87 sr 86 sr ratios are determined by the mixture of freshwater of the jordan river and saline springs the 88 sr 86 sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation associated with the precipitation of primary calcite data analysis suggests that long term accumulation of inorganic calcite depleted in the heavy isotope 88 sr results in an increase of the 88 86 sr value of the lake water by 0 05 in contrast to the primary inorganic calcite biogenic aragonite of the melanopsis shells show a rather constant 88 sr 86 sr water caco 3 fractionation of 88 86 sr 0 21 similar 88 86 sr values were reported for the precipitation of coralline and inorganic aragonite from seawater and the precipitation of inorganic calcite from various continental waters the 88 86 sr value of inorganic calcite is modulated by the rate of carbonate precipitation as noted above and shown by precipitation experiments massive precipitation of primary calcite with a wide spread of accumulation rates occurs during the spring phytoplankton bloom in lake kinneret the bloom dictates the degree of calcite saturation in the lake and hence the stable sr isotopic composition of the precipitating calcite the correlation between 88 sr 86 sr and the calcite accumulation rate can be therefore used as a tool to reconstruct environmental and ecological variations in the historical lake by analyzing the 88 sr 86 sr ratio in the primary caco 3 recovered from the lake s sedimentary archives

barium isotopes in cold water corals abstract recent studies have introduced stable ba isotopes 138 134 ba as a novel tracer for ocean processes ba isotopes could potentially provide insight into the oceanic ba cycle the ocean s biological pump water mass provenance in the deep ocean changes in activity of hydrothermal vents and land sea interactions including tracing riverine inputs here we show that aragonite skeletons of various colonial and solitary cold water coral cwc taxa record the seawater sw ba isotope composition thirty six corals of eight different taxa from three oceanic regions were analysed and compared to 138 134 ba measurements of co located seawater samples sites were chosen to cover a wide range of temperature salinity ba concentrations and ba isotope compositions seawater samples at the three sites exhibit the well established anti correlation between ba concentration and 138 134 ba furthermore our data set suggests that ba ca values in cwcs are linearly correlated with dissolved ba in ambient seawater with an average partition coefficient of dcwc sw 1 8 0 4 2sd the mean isotope fractionation of ba between seawater and cwcs 138 134bacwc sw is 0 21 0 08 2sd indicating that cwc aragonite preferentially incorporates the lighter isotopes this fractionation likely does not depend on temperature or other environmental variables suggesting that aragonite cwcs could be used to trace the ba isotope composition in ambient seawater coupled ba and 138 134 ba analysis on fossil cwcs has the potential to provide new information about past changes in the local and global relationship between ba and 138 134 ba and hence about the operation of the past global oceanic ba cycle in different climate regimes

accuracy and precision of 88sr 86sr and 87sr 86sr measurements by mc icpms compromised by high barium concentrations barite baso4 is a widely distributed mineral that incorporates strontium sr during formation mass dependent fractionation of sr isotopes occurs during abiotic precipitation of barite and formation of barite associated with biological processes e g bacterial sulfide oxidation sr isotopes in barite can provide provenance information as well as potentially reconstruct sample formation conditions e g saturation state temperature biotic versus abiotic incomplete separation of ba from sr has complicated measurements of sr isotopes by mc icpms in this study we tested the effects of ba in sr sample solutions and modified extraction chromatography of sr using eichrom sr spec eichrom technologies llc usa resin to enable rapid accurate and precise measurements of 88sr 86sr and 87sr 86sr ratios from ba rich matrices sr isotope ratios of sample solutions doped with ba were statistically indistinguishable from ba free sample solutions below 1 ppm ba deviations in both 87sr 86sr and 88 86sr occurred above 1 ppm ba an updated extraction chromatography method tested with barite and ba doped seawater produces sr sample solutions containing 10 100 ppb levels of ba the practice of zr spiking for external mass discrimination correction of 88sr 86sr ratios was also evaluated and it was confirmed that variable zr levels do not have adverse effects on the accuracy and precision of 87sr 86sr ratios in the zr concentration range required to produce accurate 88 86sr values

teleseismic location techniques and their application to earthquake clusters in the south central pacific abstract improved methods for single and multiple event hypocenter determinations are developed and applied to the problem of locating earthquake clusters in the south central pacific ocean bayesian statistical methods are used to incorporate a priori information about arrival time variance into the derivation of hypocenter confidence ellipsoids permitting a more realistic calculation of critical parameters in the case where the number of stations is small the diagonal elements of certain projection operators called data importances by minster et al 1974 are used to evaluate network balance the hypocentroid of an event cluster is defined to be the average location of events within the cluster and the deviations of individual hypocenters from the hypocentroid are called cluster vectors the problem of estimating the cluster vectors can be decoupled from the problem of estimating the hypocentroid by a simple but fundamental mathematical result here termed the hypocentroidal decomposition theorem the algorithm based on this analysis appears to have many advantages over other published methods for multiple event location both in its efficient use of available information and its computational speed the application of this method to three clusters of shallow intraplate seismicity in the south central pacific designated regions a b and c demonstrates that the seismicity within each cluster is very localized the rms lengths of the cluster vectors for each group of epicenters are estimated to be only 9 6 and 12 km respectively estimates of the epicentroids are

an investigation of the accuracy of coulomb stress changes inferred from geodetic observations following subduction zone earthquakes earthquake clustering along plate boundaries suggests that earthquakes may interact and static coulomb stress change csc is commonly invoked as one possible mechanism for stress transfer between earthquakes and nearby faults previous work has addressed the precision of csc predictions that are influenced by observational noise inversion regularization and simplified modeling assumptions here we address the accuracy of csc predictions informed by geodetic observations in subduction zones where inversion model resolution is poor we conduct synthetic tests to quantify the degree to which the sign and magnitude of csc can be reliably inferred from slip distributions inverted from various geodetic observations insar gps seafloor observations we find that in an idealized subduction zone csc can only be confidently inferred for receiver faults far 10s of km from the earthquake source though this distance shortens with the addition of synthetic seafloor observations we apply this methodology to the 2010 mw8 8 maule earthquake and identify 13 aftershocks from a population of 475 documented events for which we can confidently resolve co seismic stress changes these results demonstrate that the low model resolution of fault slip inversions in subduction zones limits our ability to address fundamental questions about earthquake sources and stress interactions nonetheless our results highlight that stress change predictions are considerably more accurate after the introduction of seafloor geodetic observations additionally we show that insar observations are not required to substantially improve stress change approximations in regions where gps may be the only viable observation such as in island arcs settings

the 2017 july 20 mw 6 6 bodrum kos earthquake illuminates active faulting in the gulf of gokova sw turkey

sr stable isotope composition of earth the moon mars vesta and meteorites abstract high precision stable sr isotopic variations 88 sr 86 sr are reported in a variety of terrestrial samples martian and lunar meteorites hed undifferentiated primitive meteorites chondrules and refractory inclusions almost all the whole rock samples are isotopically indistinguishable at a 50 parts per million ppm level the exceptions are cv and co chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material five separated chondrules and one refractory inclusion from allende are isotopically light with 88 86 sr fractionations up to 1 73 whereas the matrix is enriched in the heavy isotopes 88 86 sr 0 66 the depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in sr however in that case more than 60 of the original material would be unaccounted we propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy sr from neutral sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix we conclude that cv and co chondrites are not the primary building blocks for earth and mars

the phanerozoic δ88 86sr record of seawater new constraints on past changes in oceanic carbonate fluxes the isotopic composition of phanerozoic marine sediments provides important information about changes in seawater chemistry in particular the radiogenic strontium isotope 87sr 86sr system is a powerful tool for constraining plate tectonic processes and their influence on atmospheric co2 concentrations however the 87sr 86sr isotope ratio of seawater is not sensitive to temporal changes in the marine strontium sr output flux which is primarily controlled by the burial of calcium carbonate caco3 at the ocean floor the sr budget of the phanerozoic ocean including the associated changes in the amount of caco3 burial is therefore only poorly constrained here we present the first stable isotope record of sr for phanerozoic skeletal carbonates and by inference for phanerozoic seawater 88 86srsw which we find to be sensitive to imbalances in the sr input and output fluxes this 88 86srsw record varies from 0 25 to 0 60 vs srm987 with a mean of 0 37 the fractionation factor between modern seawater and skeletal calcite 88 86srcc sw based on the analysis of 13 modern brachiopods mean 88 86sr of 0 176 0 016 2 standard deviations s d is 0 21 and was found to be independent of species water temperature and habitat location overall the phanerozoic 88 86srsw record is positively correlated with the ca isotope record 44 40casw but not with the radiogenic sr isotope record 87sr 86sr sw a new numerical modeling approach which considers both 88 86srsw and 87sr 86sr sw yields improved estimates for phanerozoic fluxes and concentrations for seawater sr the oceanic net carbonate flux of sr f sr carb varied between an output of 4 7x1010mol myr and an input of 2 3x1010mol myr with a mean of 1 6x1010mol myr on time scales in excess of 100myrs the f sr carb is proposed to have been controlled by the relative importance of calcium carbonate precipitates during the aragonite and calcite sea episodes on time scales less than 20myrs the f sr carb seems to be controlled by variable combinations of carbonate burial rate shelf carbonate weathering and recrystallization ocean acidification and ocean anoxia in particular the permian triassic transition is marked by a prominent positive 88 86srsw peak that reflects a significantly enhanced burial flux of sr and carbonate likely driven by bacterial sulfate reduction bsr and the related alkalinity production in deeper anoxic waters we also argue that the residence time of sr in the phanerozoic ocean ranged from 1myrs to 20myrs

the 12 november 2017 mw 7 3 ezgeleh sarpolzahab iran earthquake and active tectonics of the lurestan arc

coupled δ44 40ca δ88 86sr and 87sr 86sr geochemistry across the end permian mass extinction event abstract we report high resolution high precision 44 40ca 88 86sr and 87sr 86sr records spanning the permian triassic boundary ptb from the meishan and dajiang carbonate successions in south china the goal of the study was to understand the behavior of ca and sr isotopes during a time period in earth history characterized by severe biological and environmental perturbations including a major mass extinction flood basalt volcanism ocean acidification and sea level fluctuations dajiang displays negative 44 40ca and 88 86sr excursions and invariant 87sr 86sr ratios in the

characterizing nutrient pathways in quebec canada vineyards insight from stable and radiogenic strontium isotopes abstract soils are a crucial interface of earth s critical zone responsible for the biogeochemical cycling of mineral nutrients while the sources of essential nutrients such as ca and sr in plants have been widely studied the processes by which these nutrients are transferred from the soil to the plants is less clear we present new evidence for systematic nutrient fractionation between soils grapes and wines from five vineyards from the quebec terroir canada using the novel stable sr 88 86sr isotope system we coupled this approach with traditional radiogenic 87sr 86sr measurements on the same samples bulk soils labile fraction of these soils whole grapes and wines from five vineyards from the quebec terroir canada to ensure that variations in 88 86sr values were provoked by processes involved in sr transfer instead of mixing between different sources the 88 86sr values generally decrease from the bulk to the labile fractions of the soils to the grapes a decrease in the difference between the soil fractions 88 86srbulk labile with increasing 88 86sr values in the labile fraction is interpreted to reflect increasing pedogenic mineral precipitation and higher soil fertility the depleted 88 86sr values of the grapes are consistent with a preferential uptake of lighter isotopes by plants this effect is magnified in soils showing higher secondary mineral precipitation an increase in the 88 86sr values from the grapes to the wines reflects the separation of the skin seeds and the juice pulp enriched in 88sr in the winemaking process this mixing relationship is supported by a correlation between the sr concentrations and the 88 86sr values of the wines and grapes these findings suggest promising new applications of stable sr isotopes values for studying soil fertility and the impact of nutrient availability for plant growth in agricultural ecosystems as well as the impact of the maceration processes in the production of wine the overall similarity of 87sr 86sr ratios of the labile soil fractions grapes and wines from the same vineyard support the hypothesis of a same sr source from the soil solution to its transfer to the grape and wine and confirm the potential of the 87sr 86sr ratios as a proxy for geographic provenance of wine however slightly lower 87sr 86sr ratios in the grape pulps by 0 00040 on average compared to the skins and seeds suggest that the sources of nutrients available for plant uptake vary during the vegetative cycle the grape seeds and skins formed in the early growth cycle are characterized by rapid growth due to enhanced rhizosphere activity enhanced mineral dissolution providing higher nutrient levels the enhanced mineral solubility results in higher 87sr 86sr ratios in the skin and seeds derived from enhanced dissolution of 87sr enriched silicate minerals in contrast the pulp develops later in the growth cycle when rhizosphere activity and mineral solubility is reduced resulting in a lesser contribution from silicate minerals and thus reflect a higher proportion of dissolved carbonate contributing to the lower 87sr 86sr ratios of the pulps

sr isotopes in natural waters applications to source characterisation and water rock interaction in contrasting landscapes strontium isotopes 87sr 86sr are routinely measured in hydrochemical studies to determine sources and mixing relationships they have proved particularly useful in determining weathering processes and quantifying end member mixing processes a number of routine case studies are presented which highlight that sr isotopes represent a powerful tool in the geochemists toolbox helping to constrain weathering reactions weathering rates flow pathways and mixing scenarios differences in methodologies for determining the weathering component in natural environments inherent differences in weathering rates of different minerals and mineral heterogeneity often cause difficulties in defining the weathering component of different catchments or aquifer systems nevertheless sr isotopes are useful when combined with other hydrochemical data to constrain models of water rock interaction and mixing as well as geochemical processes such as ion exchange this paper presents a summary of recent work by the authors in constraining the sources of waters and weathering processes in surface catchments and aquifers and indicates cases where sr isotopes alone are insufficient to solve hydrological problems

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

enrichment of 88 sr in continental waters due to calcium carbonate precipitation abstract 88 86sr data published over the last few years suggest that continental waters are enriched with 88sr as compared to the rocks in their drainage basins in an attempt to understand this phenomenon this study established the fractionation in the 88sr 86sr ratio during precipitation of continental carbonates i e carbonates precipitated on land from surface pedogenic or ground waters and evaluated the contribution of this process to the 88sr enrichment in rivers for this stable and radiogenic sr isotopes 88sr 87sr and 86sr were measured in calcite samples and their precipitating waters collected in various continental environments such as soil cave streams and groundwater the results indicate that continental carbonates are 88sr depleted relative to their precipitating waters placing them as one of the most 88sr depleted reservoirs on earth the average difference in 88 86sr values between waters and solid caco3 tufas or speleothems that they precipitate is carb water 0 218 0 014 1sd an even larger fractionation e carb water 0 285 0 02 was measured in groundwater with particularly high carbonate alkalinity and high carbonate precipitation rate that depleted 65 of the sr in the groundwater resulting in substantial 88sr enrichment in the residual dissolved sr sr 88 86 0 656 results also suggest that pedogenic carbonate precipitation in soil profile removes 50 85 of the sr from the recharging soil water thereby increasing the 88 86sr value of the soil water from 0 18 to 0 3 0 6 similar 88sr enrichment was observed in drip water from a karst cave a maximum removal flux of sr into continental carbonates of about 20 gmol sr y 1 is required to yield the reported 88sr enrichment in global rivers sr 88 86 0 32 relative to their rock sources when using the fractionation factor derived in this study carb water 0 218 and the published 88 86sr composition of marine carbonates of 0 16 this surprisingly large flux requires that 40 of the originally weathered sr should co precipitate with continental carbonates this calculation may suggest that caco3 precipitation is a significant mechanism in the continental sr cycle it is possible however that other mechanisms such as sr uptake by plants or incongruent weathering of silicates could also contribute to the riverine 88sr enrichment alternatively the average 88 86sr value of marine carbonate rock sections undergoing weathering is higher than suggested in current literature it is concluded that additional 88 86sr data on marine carbonate rock sections should be collected to resolve the enigma of the high value of riverine 88 86sr

continued obliquity pacing of east asian summer precipitation after the mid pleistocene transition abstract records from natural archives show that the strength of the east asian summer monsoon easm strongly depends on the orbital configuration of the earth however the dominant orbital cycles driving easm have been found to be spatially different speleothem stable oxygen isotopic records from southern china which are believed to reflect large scale changes in the asian monsoon system are dominated by climatic precession cycles further north on the chinese loess plateau clp loess and paleosol sequences which are argued to be controlled by monsoon intensity are in pace with global ice volume changes dominated by obliquity and after the mid pleistocene transition by 100 kyr cycles to understand these critical discrepancies here we apply a novel proxy based on the trace metal compositions of pedogenic carbonate in the eolian deposits on the clp to reconstruct summer precipitation over the last 1 5 million years our reconstructions show that summer precipitation on the clp is dominantly forced by obliquity not in pace with the ice volume imprinted loess paleosol sequences before and after the mid pleistocene transition or with the precession paced speleothem oxygen isotopic records coupled with climate model results we suggest that the obliquity driven variations of summer precipitation may originate from the gradient of boreal insolation that modulates the thermal contrast between the asian continent and surrounding oceans

radiogenic and stable strontium isotopes in provenance studies a review and first results on archaeological wood from shipwrecks abstract different approaches are used to study wood provenance but most of them are based on tracers in wood that are generally controlled by climatic factors the strontium isotopic ratio 87 sr 86 sr in trees and soils is related to the signature of the local bedrock despite being used in diverse archaeological studies sr isotopes have rarely been used to trace the provenance of archaeological wood and especially wood from shipwrecks in addition recent analytical advances have allowed the detection of mass dependent fractionation of sr isotopes during biogeochemical processes as reflected in the variation of 88 86 sr values between different environmental materials the 88 86 sr values could be used in conjunction with the 87 sr 86 sr isotope ratio to improve constraints on the sources of sr in the archaeological materials being studied this paper discusses the potential and limitations of using both of these sr isotope ratios to trace the provenance of wood from shipwrecks we review the 87 sr 86 sr and 88 86 sr variations in rocks waters soils plants and other living organisms and discuss how to determine the local sr isotopic signature of potential sites we also compile a list of known wood post mortem modifications in seawater possible implications in terms of the modification of the original sr isotope ratios of wood during storage in seawater are illustrated through preliminary observations this paper points out some limitations and perspectives for using sr isotopes in provenancing wood from shipwrecks and suggests future research to test and apply this approach for tracing the origin of archaeological wood

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

evaluation of earthquake triggering during the 2005 2008 earthquake sequence on qeshm island iran 1 coseismic static coulomb stress changes may either advance or retard the timing of subsequent earthquakes on nearby faults in a manner that depends both on the relative orientations of faults within the vicinity of the primary rupture as well as on the postseismic redistribution of stress here we examine interferometric synthetic aperture radar insar data spanning two earthquakes that occurred in close temporal and spatial proximity on qeshm island in southern iran remote observations of earthquakes such as ground deformation or seismic waves allow us to infer earthquake source parameters but in general a nonunique family of solutions is consistent with the data given our understanding of data noise and the limitations of our ability to model the real earth here we explore methods for assessing and propagating insar noise through our entire analysis of the stress triggering potential between these two earthquakes we generate a range of source models for each earthquake based both on insar and seismic observations and assess whether the expected static coulomb stress change during the first earthquake is likely to have brought the second event closer to or further from failure some combinations support the hypothesis that the first earthquake brought the second fault closer to failure whereas some do not fault plane geometries that agree with insar constraints are more likely to suggest that the first earthquake increased the likelihood of the second earthquake those based on the harvard and global centroid moment tensor tend to not support triggering between the two events

phantom earthquakes and triggered aseismic creep vertical partitioning of strain during earthquake sequences in iran 1 we present evidence for significant aseismic fault slip at shallow depth above a pair of mainshock aftershock sequences in the zagros mountains of iran the two mw 5 9 earthquakes are each spanned by high quality geodetic imagery and have well recorded sequences of aftershocks that occurred beneath a salt decollement earlier studies of the geodetic data inferred that the mainshocks were located above the decollement requiring a 10 km spatial separation between aftershock cluster and earthquake centroid we find that the geodetic data simultaneously allow two slip sources of similar magnitude one within the basement collocated with aftershocks and one shallow source also equivalent to mw 6 responsible for the primary signal apparent in the geodetic imagery should this phenomenon be widespread in the zagros it would partially explain a previously noted discrepancy between observed seismic moment release in the zagros and current convergence rates between the arabian and eurasian plates

monitoring the earthquake source process in north america with the implementation of the usgs national earthquake information center prompt assessment of global earthquakes for response system pager rapid determination of earthquake moment magnitude is essential especially for earthquakes that are felt within the contiguous united states we report an implementation of moment tensor processing for application to broad seismically active areas of north america this effort focuses on the selection of regional crustal velocity models codification of data quality tests and the development of procedures for rapid computation of the seismic moment tensor we systematically apply these techniques to earthquakes with reported magnitude greater than 3 5 in continental north america that are not associated with a tectonic plate boundary using the 0 02 0 10 hz passband we can usually determine with few exceptions moment tensor solutions for earthquakes with m w as small as 3 7 the threshold is significantly influenced by the density of stations the location of the earthquake relative to the seismic stations and of course the signal to noise ratio with the existing permanent broadband stations in north america operated for rapid earthquake response the seismic moment tensor of most earthquakes that are m w 4 or larger can be routinely computed as expected the nonuniform spatial pattern of these solutions reflects the seismicity pattern however the orientation of the direction of maximum compressive stress and the predominant style of faulting is spatially coherent across large regions of the continent

reassessing the stable δ88 86sr and radiogenic 87sr 86sr strontium isotopic composition of marine inputs the stable strontium isotope system 88 86sr has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system the principal output flux of oceanic sr however in order to be able to interpret carbonate driven variations in 88 86srseawater a robust understanding of 88 86srinput is required surprisingly only a limited amount of 88 86sr data currently exists for rivers and hydrothermal fluids thus this study assesses the variability of 88 86sr and 87sr 86sr in global rivers hydrothermal fluids and porewaters as well as minor marine sr sources such as continental dust rainwater and glacial ice our analyses broadly confirm the findings of krabbenhoft et al 2010 and reveal flux weighted 88 86srriverine and 87sr 86srriverine compositions of 0 32 and 0 71299 respectively the hydrothermal fluids analysed in this study are consistent with an end member 88 86srhydrothermal composition that is the same as the oceanic crust at 0 24 although three samples that display 88 86sr compositions offset from the seawater hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive 88 86srhydrothermal to higher values porewater fluids obtained from sediment cores in the atlantic and pacific oceans have 88 86sr compositions within error of seawater 0 39 implying that the diagenetic flux of sr may not significantly affect the 88 86sr composition of seawater continental loess samples have 88 86sr compositions that are consistently lighter than or equal to terrestrial silicates with their tendency to lower values thought to reflect the preferential removal of heavier sr isotopes into solution during weathering finally rainwater and glacial ice samples have 88 86sr compositions that are also isotopically lighter than their associated water sources a factor that may be attributed to interaction with isotopically light loess and additional sr contributions from the bedrock together the principal marine inputs define flux weighted oceanic 88 86srinput and 87sr 86srinput compositions of 0 32 and 0 71161 these values are consistent with an elevated supply of riverine sr to the oceans due to increased post glacial weathering but require the enhanced weathering of exposed carbonate shelves during glacial periods or significant changes in the rate of carbonate burial to match observed changes in the 87sr 86sr ratio of seawater our results confirm that providing a diagenetically robust proxy can be found the 88 86sr and 87sr 86sr isotope systems should provide a useful proxy for investigating changes in the marine carbonate system through time

insights into combined radiogenic and stable strontium isotopes as tracers for weathering processes in subglacial environments this study reports stable and radiogenic strontium isotope behaviour in the dissolved load and suspended sediments from the subglacial outflow of the lemon creek glacier juneau ice field alaska over a single melt season in situ measurements discharge total alkalinity ph and conductivity are combined with elemental concentrations x ray diffraction xrd analysis and radiogenic strontium isotope measurements to interpret the variations observed in stable strontium isotopic ratios the stable sr isotope composition 88sr 86sr ratio expressed as 88 86sr of the dissolved load averages 0 31 0 05 and is heavier than both the suspended sediment 0 18 0 03 as well as local bedrocks 0 20 to 0 26 we attribute the enrichment of heavier isotopes in the dissolved load to the uptake of lighter sr isotopes by secondary weathering minerals driving the dissolved load to heavier values x ray diffraction xrd analysis confirms the presence of clays in the suspended sediments and thermodynamic modelling suggests the presence of iron oxy hydroxide phases although it is not possible to completely rule out the effect of dissolution of primary minerals in controlling sr isotopic compositions of the dissolved load our data indicate that the extent of secondary mineral formation likely plays a significant role the preferential weathering of minerals such as biotite consistent with the mineralogical assemblages found in the suspended sediments as well as the potential presence of radiogenic calcites from metacarbonates derived from the yukon tanana terrain may be driving the small seasonal shifts in 87sr 86sr of the dissolved load to more radiogenic compositions from 87sr 86sr dl 0 71048 to 0 710647 using the combination of stable and radiogenic strontium isotopes to investigate weathering processes shows that radiogenic sr isotopes provide information regarding weathering of primary phases while the stable sr isotope data appear to record information regarding the extent of secondary mineral formation where secondary minerals incorporate the light isotopes driving the dissolved load to heavy values

strontium isotopes trace biological activity in the critical zone along a climate and vegetation gradient abstract weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock the geogenic nutrient pathway however the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter the organic nutrient cycle isotope ratios of strontium sr an element that behaves similarly to ca in ecosystems confer two types of information radiogenic sr isotopes inform as to the sources of sr and the degree of weathering while stable sr isotopes constrain partitioning between compartments of the critical zone bedrock water secondary solids and plants to date however neither the reactions nor the mass balance between compartments that fractionate sr isotopes nor the fractionation factors involved are well understood here we present geochemical budgets of sr using radiogenic and stable sr isotopes and ca sr ratios at four sites along a substantial climate and primary production gradient in the coastal mountains of chile we found that sr release through weathering is isotopically congruent and released sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool despite this the 88sr 86sr ratio of bio available sr which should reflect the ratio of dissolved sr is higher than that of rock and regolith we propose that this offset is caused by plants while 88sr 86sr in plant organs at the four study sites systematically increased from roots towards their leaves whole plant sr isotope compositions indicate preferential uptake of light sr into plants with a fractionation of up to 0 3 relative to the bio available pool despite this strong biological fractionation 88sr 86sr ratios in bio available sr do not covary with biomass production across our study sites because with greater plant growth sr is recycled more times after release by weathering an isotope neutral process rather the loss of sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio available sr organic solids thus appear to constitute a significant export path of elements released during weathering with the removal of solid plant debris reducing the recycling factor of sr and possibly that of other mineral nutrients too

strontium isotope fractionation of planktic foraminifera and inorganic calcite we have investigated the strontium isotope fractionation 88 86srcarb aq between inorganic calcite and aqueous sr2 ions by precipitation experiments at a constant temperature of 25 c and precipitation rates r ranging from 102 3 to 104 2 mol m2 h strontium isotope ratios were measured using the 87sr 84sr double spike technique it was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate view the mathml source the measured 88 86sr values are significantly correlated with previously measured 44 40ca and sr ca values of the same calcite samples 88 86srcarb aq 0 18 44 40cacarb aq 0 01 view the mathml source the slope of 88sr 86sr versus 44ca 40ca fractionation is 0 18 0 04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions but not with isotope fractionation in a diffusive boundary layer using published equilibrium 44 40cacarb aq and view the mathml source values we estimate the equilibrium isotope fractionation of strontium to be very close to zero 88 86sreq carb aq 0 01 0 06 this estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust the results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera specimens of two warm water species globigerinoides ruber and globigerinoides sacculifer were picked from the holocene section of a caribbean sediment core we found no significant difference in 88 86sr between the two species in addition g ruber specimens from marine isotope stage 2 in the same core show 88 86sr values identical to the holocene specimens the strontium isotopes of both foraminifera species are strongly fractionated 88 86srcarb aq 0 248 0 005 when compared to published data of other major marine calcifiers applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates comparable in magnitude to rates known from scleractinian reef corals this interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by kisakurek et al 2011 which was based on calcium isotopes and elemental sr ca ratios

the δ44ca temperature calibration on fossil and cultured globigerinoides sacculifer new tool for reconstruction of past sea surface temperatures we report direct 44ca temperature calibration on cultured and fossil calcite foraminifera showing that ca isotopes are potentially a new proxy for past sea surface temperatures sst samples have been analyzed using a 43ca 48ca double spike and thermal ionization mass spectrometry tims in order to avoid species dependent isotope fractionation we focused our investigations on a single foraminifera species globigerinoides sacculifer which is known to inhabit shallow euphotic waters in tropical and subtropical oceans ca isotope measurements were performed on cultured g sacculifer that grew in seawater kept at temperatures of 19 5 26 5 and 29 5 c a 44ca change of 0 24 0 02 per 1 c is defined by the weighted linear regression through reproduced 44ca data of the three temperatures 95 confidence level application of this new method to fossil g sacculifer of an equatorial east atlantic sediment core geob1112 5 46 7 s 10 45 0 w 3125 m indicates that the 44ca difference between marine isotope stage 1 mis 1 and mis 2 is 0 71 0 24 according to the current 44ca temperature calibration this value corresponds to a temperature difference between mis 1 and mis 2 of 3 0 1 0 c

the 2008 wells nevada earthquake sequence source constraints using calibrated multiple event relocation and insar abstract the 2008 wells nevada earthquake represents the largest domestic event in the contiguous united states outside of california since the october 1983 borah peak earthquake in southern idaho we present an improved catalog magnitude complete to 1 6 of the foreshock aftershock sequence supplementing the current u s geological survey preliminary determination of epicenters catalog with 1928 well located events to create this catalog both subspace and kurtosis detectors are used to obtain an initial set of earthquakes and associated locations the latter are then calibrated through the implementation of the hypocentroidal decomposition method and relocated using the bayesloc relocation technique we additionally perform a finite fault slip analysis of the mainshock using interferometric synthetic aperture radar insar observations by combining the relocated sequence with the finite fault analysis we show that the aftershocks occur primarily up dip and along the southwestern edge of the zone of maximum slip the aftershock locations illuminate areas of postmainshock strain increase aftershock depths ranging from 5 to 16 km are consistent with insar imaging which shows that the wells earthquake was a buried source with no observable near surface offset electronic supplement description of methods and figures of relocated aftershocks interferograms residuals transformations and seismic station locations

from rifted margins to foreland basins investigating provenance and sediment dispersal across desert arabia oman u a e arid arabia where chemical weathering and anthropic modifications are negligible is a huge natural laboratory for the study of sediment provenance mafic and ultramafic detritus from ophiolite belts is found along the oman mountains and on masirah island obduction orogen provenance dominant cellular serpentinite grains from residual mantle harzburgites of the sama il ophiolite contrast with gabbroic diabase and basaltic grains from igneous crustal rocks of the masirah ophiolite detritus from autochthonous basement and cover rocks is found along the arabian sea margin rift shoulder provenance transition from carbonate dominated lithic sands undissected stage to hornblende rich plagioclase arkoses dissected stage is best documented at the northern edge of the gulf of aden along the older strike slip owen basin margin only locally are feldspars hornblende and garnet derived from small outcrops of pan african basement modern eolian sands from yemen to the arabian persian gulf display marked enrichment in quartz low plagioclase feldspar ratios and depleted dense mineral assemblages with rounded epidotes hornblende garnet and ultrastables pointing to extensive recycling also fostered by quaternary changes the rub al khali and wahibah sand seas have distinct quartz feldspar ratios reflecting largely separate transport pathways dune fields fed chiefly from rift highlands in the west and south mix with orogenic detritus in the northeast carbonate dominated sands in coastal uae are mostly derived from the zagros mountains blown by northerly shamal winds across the gulf during pleistocene lowstands to reach the backbulge depozone and the foreland beyond contributions from the oman mountains reach only 5 10 of bulk sediment along their southern apron and mostly indirectly through deflation of plio pleistocene fans the sama il ophiolite supplies enstatite and diopside to the eastern uae and wahibah sands the masirah ophiolite supplies amphiboles and clinopyroxenes locally along the batain coast the composition of desert sediments faithfully mirrors tectonic history of source terranes deformation style during orogeny and unroofing level during extension bulk petrography coupled with dense mineral analysis thus represents a powerful tool to investigate not only provenance and sediment transport but also crustal dynamics and geologic evolution at continental scale

constraining the marine strontium budget with natural strontium isotope fractionations 87sr 86sr δ88 86sr of carbonates hydrothermal solutions and river waters we present strontium sr isotope ratios that unlike traditional 87sr 86sr data are not normalized to a fixed 88sr 86sr ratio of 8 375209 defined as 88 86sr 0 relative to nist srm 987 instead we correct for isotope fractionation during mass spectrometry with a 87sr 84sr double spike this technique yields two independent ratios for 87sr 86sr and 88sr 86sr that are reported as 87sr 86sr and 88 86sr respectively the difference between the traditional radiogenic 87sr 86sr normalized to 88sr 86sr 8 375209 and the new 87sr 86sr values reflect natural mass dependent isotope fractionation in order to constrain glacial interglacial changes in the marine sr budget we compare the isotope composition of modern seawater 87sr 86sr 88 86sr seawater and modern marine biogenic carbonates 87sr 86sr 88 86sr carbonates with the corresponding values of river waters 87sr 86sr 88 86sr river and hydrothermal solutions 87sr 86sr 88 86sr hydend in a triple isotope plot the measured 87sr 86sr 88 86sr river values of selected rivers that together account for not vert similar18 of the global sr discharge yield a sr flux weighted mean of 0 7114 8 0 315 8 the average 87sr 86sr 88 86sr hydend values for hydrothermal solutions from the atlantic ocean are 0 7045 5 0 27 3 in contrast the 87sr 86sr 88 86sr carbonates values representing the marine sr output are 0 70926 2 0 21 2 we estimate the modern sr isotope composition of the sources at 0 7106 8 0 310 8 the difference between the estimated 87sr 86sr 88 86sr input and 87sr 86sr 88 86sr output values reflects isotope disequilibrium with respect to sr inputs and outputs in contrast to the modern ocean isotope equilibrium between inputs and outputs during the last glacial maximum 10 30 ka before present can be explained by invoking three times higher sr inputs from a uniquely glacial source weathering of shelf carbonates exposed at low sea levels our data are also consistent with the weathering peak hypothesis that invokes enhanced sr inputs resulting from weathering of post glacial exposure of abundant fine grained material

calibration of stable oxygen isotope signatures in galapagos corals a 2 year 1993 1994 study was conducted in the galapagos islands ecuador to determine the relationship between 18o in skeletal carbonate and sea surface temperature sst in three species of reef building corals pavona clavus pavona gigantea and porites lobata coral samples were grown at 3 10 and 3 m depth at bartolome island champion iisland and urvina bay isabela island respectively hourly measurements of sst and sea surface salinity sss were taken at each site immediately adjacent to colonies which were stained biannually to establish the chronology of growth in addition surface waters were sampled periodically bimonthly to monthly at each site to determine variation in 18o seawater results indicate the mean annual ssts were similar between sites varying from 22 9 c at champion to 23 8 c at urvina bay comparisons of monthly sst averages between instrumental and remote sensing satellite 1 1 grid data show a high correspondence r2 ranging from 0 84 to 0 94 indicating that remote sensing data are useful for interpreting the 18o record in corals when instrumental data are lacking here 18ocoral analyses of eight specimens show that coralline aragonite is a reliable indicator of sst in galapagos in general higher resolution coral sampling year resolved more of the monthly variation in sst up to 97 at a sampling resolution of 1 4 samples per millimeter of linear skeletal growth comparisions of the 18ocoral signal among and between species at the same site showed consistent seasonal patterns of variation closely tracking sst in addition comparisons between sites were highly concordant with some differences reflecting local variation in sst seasonal patterns however were essentially the same over the entire region thus we conclude that the 18ocoral signal from coral skeletons in galapagos can be used to interpret regional changes in sst variation

controls on stable strontium isotope fractionation in coccolithophores with implications for the marine sr cycle abstract the controls on stable sr isotope fractionation into the calcite produced by the coccolithophore species emiliania huxleyi coccolithus pelagicus spp braarudii and gephyrocapsa oceanica are investigated each species has been cultured under controlled laboratory conditions at a range of temperatures 10 25 c to test the potential of 88 86 sr as a proxy for growth rate and or sea surface temperature coccolithophores are one of the most abundant pelagic calcifiers since sr substitutes to some degree for ca in their calcite coccoliths coccolithophores represent a significant output of sr from seawater potentially influencing the 88 86 sr mass balance in the modern oceans the coccoliths are investigated for their 88 86 sr sr ca and 18 o measured as function of temperature as temperature is increased all species show a negative stable sr isotopic fractionation related to a temperature controlled growth rate we infer the shift of 88 86 sr to lighter values as indicative of a kinetic control on the isotope fractionation revealing the potential of 88 86 sr as a proxy for growth rate which in these experiments is primarily dictated by temperature the results from these experiments indicate that coccolithophore calcite incorporates sr with a very light 88 86 sr isotope composition as low as 0

mg isotopic composition of carbonate insight from speleothem formation simultaneous high precision measurement of 24 mg 25 mg and 26 mg isotopic compositions were made by multiple collector inductively coupled mass spectrometry mc icp ms relative to the international standard srm980 data are presented on low mg calcite speleothems and their associated host rocks and waters from four caves one in the french alps and three in israel covering various climate conditions in addition data are presented on three dolostones and three limestones from the himalaya the overall variation is 4 13x and 2 14x in n 26 mg and n 25 mg respectively this is 35 times the uncertainty of the measurements and clearly demonstrates that the terrestrial isotopic composition of mg is not unique each speleothem shows a characteristic range of n 26 mg values that are attributed to the isotopic composition of the local water differences between the isotopic composition of mg in the water dripping from stalactites and that of the modern speleothem are interpreted as being due to mg isotopic fractionation during carbonate precipitation in the temperature range of 4 18 c the low mg calcite is enriched in light isotopes by 1 35x amu and the dependence on temperature has been found to be less than 0 02x amu c despite various geological settings the n 26 mg of the studied dolostones is 2 0 1 2x higher than the n 26 mg of the limestones all together these results suggest a strong mineralogical control and a weak temperature effect on the mg isotopic composition of carbonate a 2002 elsevier science b v all rights reserved

strontium 86 labeling experiments show spatially heterogeneous skeletal formation in the scleractinian coral porites porites this paper presents the results of an effort to label calcium carbonates formed by marine organisms with stable isotopes to obtain information about the biomineralization processes the growing skeleton of the scleractinian coral porites porites was labeled three times with enhanced abundances of sr 86 the distribution of sr 86 in the skeleton was imaged with the nanosims ion microprobe with a spatial resolution of similar to 200 nm and combined with images of the skeletal ultra structure importantly the distribution of the sr 86 label in the p porites skeleton was found to be strongly heterogeneous this constrains the physical dimensions of the hypothetical extracellular calcifying fluid ecf reservoir at the surface of the growing skeleton which is implicit in most geochemical models for coral biomineralization these new experimental capabilities allow for a much more detailed view of the growth dynamics for a wide range of marine organisms that biomineralize carbonate structures citation houlbreque f a meibom j p cuif j stolarski y marrocchi c ferrier pages i domart coulon and r b dunbar 2009 strontium 86 labeling experiments show spatially heterogeneous skeletal formation in the scleractinian coral porites porites geophys res lett 36 l04604 doi 10 1029 2008gl036782

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

seasonal changes in the radiogenic and stable strontium isotopic composition of xijiang river water implications for chemical weathering seasonal changes in strontium sr isotopic systematics in large rivers can effectively track temporal variations in regional chemical weathering and help to better constrain the sr isotopic budget of global oceans however such records are scarce here we present a year long time series of both radiogenic and stable sr isotope measurements 87sr 86sr and 88sr from river water at guiping in the middle reaches of the xijiang river south china temporal changes in chemical weathering in the drainage basin were investigated by recording seasonal changes in the composition of both sr isotopes and major ions in the river water river water 87sr 86sr values range from 0 708487 to 0 710336 with most values being 0 7092 are generally accompanied by high rb sr ratios and low ph and 13c of dissolved inorganic carbo dic and occur during periods of large river flux this indicates that the contribution to the chemistry of river water from the weathering of silicate rocks is enhanced during rainy seasons seasonal variation in river water 88sr is large from 0 147 to 0 661 with higher 88sr values generally corresponding to higher 87sr 86sr values again low 88sr values 0 3 suggest a dominant contribution from the weathering of carbonate rocks whereas the high 88sr values may represent a contribution from intensive weathering of silicate rocks using the time series data we estimated the flux weighted averages of sr concentration 87sr 86sr and 88sr for the xijiang river to be 1 00 mol l 0 70960 and 0 38 respectively the sr concentration and 87sr 86sr results are close to previous estimates while the 88sr value is amongst the highest recorded for the large rivers of the world and is close to that of seawater our results indicate that large rivers draining through tropical sub tropical regions could play an important role in regulating the stable sr isotopic budget of global oceans