Seawater Strontium Research Articles

Source tracing and chemical weathering implications of strontium in agricultural basin in Thailand during flood season: A combined hydrochemical approach and strontium isotope

87Sr/86Sr of river water are of great significance in constraining oceanic strontium (Sr) record and terrestrial climate change due to the connection of continental weathering and the adjacent ocean. This work presents the geochemical characteristics of dissolved Sr and hydrochemistry, and estimates chemical weathering rate together with elemental Sr flux during the flood season of the Mun River, the largest tributary of Mekong River. Hydrochemistry analysis indicates the dominance of Cl− and HCO3− for major anions with the average of 34.6 and 43.0 mg/L, respectively, and Na+ and Ca2+ together dominated the cationic composition with the average of 22.9 and 10.5 mg/L, respectively. The ion concentrations during flood season were lower than that in dry season, implying tremendous river runoff due to extreme rainfall. The dissolved Sr ranges 6.1–237.5 μg/L with higher contents in the upper Mun. Sr contents in flood season are lower and less fluctuated than that in dry season, whereas the divergence between up and downstream becomes larger. 87Sr/86Sr ranges 0.7100–0.7597, slightly higher than global average. Elemental molar ratio analysis partly corroborates the inference from correlation analysis, but 87Sr/86Sr does not correlate with Na/Ca, indicating additional influence except for the weathering of evaporites and silicates. Comparing to regional wastewater and rainwater, the lower reaches exhibits superimposed impact of agricultural inputs on weathering to dissolved loads, especially in downstream with more tributary convergence. Extreme rainfall during flood season and extensive agricultural production activities may interfere in altering riverine solutes. Silicate weathering rate and CO2 consumption rate are calculated as well as the yearly 87Sr in excess to the Mekong River and finally to the Pacific Ocean with a Sr flux of 1.98 × 103 tons/year, indicating significant influence on seawater strontium isotope evolution in the long run. Together with tropical climate and high-intensity precipitation, the accelerated chemical weathering process seems inevitable. Therefore, the impact of agricultural interference in the pan-Mekong River basin needs more systematic and multi-angle research to provide a comprehensive insight on better watershed management under tropical climatic conditions.

Separation of radiostrontium from seawater using various types of sorbents

The paper presents the results of separating radioactive strontium from seawater with commercially available local-produced sorbents (Modix, FD, MDM, DMM, Termoksid ZK, SRM-Sr) and the sorbent of our fabrication (MnO2–impregnated fiber) under static and dynamic conditions. Under the batch conditions, the distribution coefficients of strontium in seawater are determined. Under the flow conditions, output curves of strontium sorption at different seawater flow rates were obtained; the dynamic exchange capacity and total dynamic exchange capacity of the sorbents for strontium were calculated. The data obtained make it possible to calculate the amount of sorbent required to process a seawater sample of a given volume for determining the specific activity of strontium radionuclides in seawater.

Geologic variability of conodont strontium isotopic composition quantified by laser ablation multiple collection inductively coupled plasma mass spectrometry

Conodont microfossils record seawater strontium isotope values (87Sr/86Sr), permitting chemostratigraphic correlation for tectonic and climatic reconstructions of the Paleozoic and early Mesozoic (541–201 Ma). Laser ablation multiple collection inductively coupled plasma mass spectrometry (LA MC-ICP-MS) can provide rapid, high spatial resolution 87Sr/86Sr analysis of conodont bioapatite but has not been validated by comparison with solution analysis. Validation of LA MC-ICP-MS should be completed in order to use the conodont 87Sr/86Sr values for age-correlations and environmental interpretations. Here, for the first time, we compare solution and LA MC-ICP-MS 87Sr/86Sr analyses of Carboniferous-age conodonts. Furthermore, we use quadrupole LA ICP-MS to determine concentrations of trace elements potentially responsible for isobaric interferences. Using increased mass resolving power (m/∆m = ~7500) and analyzing conodont tissue with low 85Rb/88Sr (< 0.001), we find laser ablation copacetic with solution 87Sr/86Sr values. The two-standard-deviation of these LA 87Sr/86Sr ratios (average 2SD = 0.00105) are within the two-standard-error uncertainty of solution measurements (average 2SE = 0.00001) on conodonts from the same stratigraphic level. The LA measurements are at a higher spatial resolution and on average 0.00015 higher than solution measurements. Uncertainty of the mean calculations, made on duplicate LA MC-ICP-MS analyses of individual conodonts from the same stratigraphic level, exhibit 87Sr/86Sr variability beyond the precision of reference materials (2SE = 0.00001). This finding suggests that solution 87Sr/86Sr values determined by dissolving multiple conodonts are homogenizing the conodont 87Sr/86Sr signal. As such, the precision of these solution measurements does not capture the geologic variability of conodont 87Sr/86Sr within a stratigraphic level, which may originate from differential diagenetic alteration. Conodont 87Sr/86Sr measurements that do not account for this variability are at risk of false calibrations with the paleo-seawater 87Sr/86Sr curve, which has implications for the timing of geologic events and reconstructions of paleo-environmental changes.

A record of the δ44/40Ca and [Sr] of seawater over the last 100 million years from fossil elasmobranch tooth enamel

The global geochemical cycles of calcium and strontium in seawater link the chemical composition of the oceans to the global carbon cycle and Earth's climate through the precipitation, diagenetic alteration, and sedimentary recycling of marine carbonate minerals. Here we present a record of calcium isotopic composition and [Sr] of seawater over the last 100 million years using measurements from modern and fossil shark teeth. Although there is significant variability in modern elasmobranch tooth enamel associated with physiology and diet, our record suggests a first-order increase in the average calcium isotopic composition of seawater by 0.5‰ and a decline in Sr/Ca ratios of ∼40% over the last 100 million years. These observations are in agreement with trends seen in other archives. We propose that the observed changes in both the calcium isotopic composition and Sr concentration of seawater can be explained by changes in the partitioning of the global carbonate sink associated with the development of a deep-sea carbonate reservoir in the mid-Mesozoic.

Decontamination of seawater from 137Cs and 90Sr radionuclides using inorganic sorbents

In this work, we have studied sorption of 137Сs and 90Sr radionuclides from seawater under batch conditions by ferrocyanide sorbents based on hydrated titanium and zirconium dioxides (Т-35, NPF-HTD), clinoptilolite and glauconite (NPF-GL, NPF-CL) natural aluminosilicates, zirconium phosphate (T-3A), modified hydrated titanium dioxide (T-3K) as well as by manganese dioxide based on hydrated titanium dioxide (MD-HTD). Isotherms of sorption and dependences of cesium distribution coefficients on salt content and calcium concentration were obtained. Distribution coefficients of cesium and strontium were calculated. Stability of spent sorbents against radionuclides leaching was studied in from the point of view of their further treatment.The NPF-GL and NPF-HTD sorbents are recommended for treatment of seawater-based liquid radioactive waste with various salinity; these sorbents possess high distribution coefficients of cesium 104 and 105 ml/g even at the salinity of waste as high as 100 g L−1. Distribution coefficients of strontium from seawater were (1.0–1.9)·102 ml/g for all sorbents that is conditioned by the presence of colloidal species of strontium (34 ± 7%) in the simulated seawater. Capacities of the sorbents for strontium varied within 200–310 mg/g. The sorbents strongly retain adsorbed radionuclides: the total percentage of leaching for 28 days was 4.4%, 2.2% and 3.1% for 137Cs leaching from the NPF-HTD, T-35 and T-3A sorbents respectively and 10.7% for 90Sr leaching from the NPF-CL sorbent.

Очистка морской воды от радионуклидов цезия и стронция

The article deals with the study of sorption (under batch conditions) of cesium and strontium radionuclides from sea water with ferrocyanidic sorbents based on hydrated titanium and zirconium dioxides (Т-35, NPF-HTD), glauconite and clinoptilolite natural aluminum silicates (NPF-G, NPF-C), zirconium phosphate (Т-3А), modified hydrated zirconium dioxide (Т-3К), and manganese dioxide based on hydrated titanium dioxide (MD-HTD). We have obtained the sorption isotherms, defined the cesium and strontium distribution coefficients. Dependences of the cesium distribution coefficient by the sorbents in seawater saline content have been obtained. The authors recommend NPF-G and NPF-HTD sorbents for treatment of liquid radioactive waste based on seawater with various salt content. Coefficients of the cesium distribution between solid and liquid phases were 1,0∙105 and 1,0∙104 mg/l, respectively, even at solutions with the salt content of 100 g/l. In the process of strontium sorption from seawater, the strontium distribution coefficients do not exceed 1,9·102 ml/g, this is connected with big proportion (34±7 %) of stable colloidal forms of strontium in the simulated seawater.

The Origin of Carbonate Veins Within the Sedimentary Cover and Igneous Rocks of the Cocos Ridge: Results From IODP Hole U1414A.

Carbonate veins in the igneous basement and in the lithified sedimentary cover of the Cocos Ridge at International Ocean Discovery Program (IODP) Hole 344‐U1414A reveal the hydrologic system and fluid‐rock interactions. IODP Hole 344‐U1414A was drilled on the northern flank of the Cocos Ridge and is situated 1 km seaward from the Middle America Trench offshore Costa Rica. Isotopic and elemental compositions were analyzed to constrain the fluid source of the carbonate veins and to reveal the thermal history of Hole 344‐U1414A. The formation temperatures (oxygen isotope thermometer) of the carbonate veins in the lithified sedimentary rocks range from 70 to 92 °C and in the basalt from 32 to 82 °C. 87Sr/86Sr ratios of the veins in the altered Cocos Ridge basalt range between 0.707307 and 0.708729. The higher ratios are similar to seawater strontium ratios in the Neogene. 87Sr/86Sr ratios lower 0.7084 indicate exchange of Sr with the igneous host rock. The calcite veins hosted by the sedimentary rocks are showing more primitive 87Sr/86Sr ratios <0.706396. The isotopic compositions indicate seawater, modified into a hydrothermal fluid by subsequent heating, as the main fluid source. Low‐temperature alteration and the presence of a high‐temperature fluid resulted in different carbonate precipitates forming up to several cm thick veins. The geochemical data combined with age data of the sedimentary rocks suggest intraplate seamount volcanism in the area between the Galapagos hot spot and the Cocos Island as an additional heating source, after the formation of the Cocos Ridge at the Galapagos hot spot.

Demonstration of Seawater Strontium (Sr(II)) Extraction and Enrichment by a Biosorption Technique through Continuous Column Operation

Alginate beads are promising strontium (Sr(II)) adsorbents because of their high Sr(II) adsorption capacity and cost-effectiveness. This study analyzed the selective adsorption by alginate beads in the column operation mode to recover and enrich Sr(II) from seawater. Alginate beads of 2–8 wt % were prepared and bead size was varied to optimize the column module. All beads expanded 10–20% in seawater because of its high ion content, but decreased slightly in 0.1 M HCl, which was used in the eluent but did not cause bead destruction after reaction for 14 days. In the batch adsorption experiment, 8 wt % alginate beads showed a maximum Sr(II) uptake from seawater of 147.3 mg/dm3, a concentration 25-fold higher than the Sr(II) concentration (≈ 6.1 mg/L) in seawater. Using a continuous Sr(II) adsorption column system, Sr(II) adsorption equilibrium was achieved at 12 h with a 50–100 mL/min flow rate. Elution from this column yielded an eluent containing 24.3 mg/L of Sr(II). Three consecutive elutions with pH con...

Revised Middle–Upper Jurassic strontium isotope stratigraphy

A study is conducted to supplement the uppermost Lower Jurassic–lowermost Cretaceous marine strontium isotope dataset and to present new statistical fits of the Middle–Late Jurassic seawater strontium isotope curve based on a numerical time scale and a detailed biostratigraphical zonal scheme. The use of the stratigraphical scheme allows reduction of dating errors related to uncertainty of numerical age determinations. The presented correlation charts enable direct calibration between strontium isotope stratigraphy and regional biostratigraphical frameworks. New strontium isotope data have been obtained from well-preserved Lower Bajocian, uppermost Callovian, Oxfordian, Kimmeridgian, and Upper Volgian belemnite rostra.The presented seawater 87Sr/86Sr curve is characterized by reliable 95% confidence limits (mean width of ±0.000007), which take into account precision of dating of particular data points. A decrease of seawater 87Sr/86Sr ratio, from ca. 0.70730 to ca. 0.70683, is observed throughout the Middle Aalenian–Early Oxfordian (172.1–160.8Ma ago). The steepest Phanerozoic fall of the ratio, with a rate of change of up to 0.00015 per 1Ma, is recorded in the Bajocian segment of the strontium isotope curve. The Phanerozoic minimum of the marine 87Sr/86Sr ratio occurred at the Early–Middle Oxfordian transition. The 87Sr/86Sr ratio increased starting from the Middle Oxfordian till the end of the Jurassic (160.8–145.7Ma) reaching a value of ca. 0.70720 at the Jurassic–Cretaceous transition. The Middle–earliest Late Jurassic decrease in seawater 87Sr/86Sr ratio is interpreted as a result of the increased hydrothermal activity of the seafloor during the breakup of Gondwana, and the formation of new Atlantic–Tethyan oceanic basins. The successive rise of the ratio is probably related to the decelerated hydrothermal venting of the oceanic crust although a partial increase in radiogenic strontium input from continental weathering cannot be excluded.

Unradiogenic strontium and moderate-amplitude carbon isotope variations in early Tonian seawater after the assembly of Rodinia and before the Bitter Springs Excursion

Neoproterozoic sedimentary records reveal a poorly documented, ∼150m.y. time interval, between ∼1000 and 850Ma, that limit our understanding of C and Sr isotope variations in seawater and thus operation of the biogeochemical carbon cycle, changes in surface redox state, and fluctuations in continental vs. hydrothermal fluxes to the oceans following assembly of the supercontinent Rodinia. Carbon and Sr isotope data for carbonates from the Karatau Group of the Southern Ural Mountains in Russia provides a record partially covering the younger portion of this time interval. The lower part of the Karatau Group (LKG) contains well-preserved carbonate strata of the Katav, Inzer, and Min’yar formations that are focus of this study. Pb-Pb isochron ages for carbonates from the Inzer and Min’yar formations are 844±24 and 820±77Ma, respectively, establishing an early Tonian age. Carbon isotope data for unaltered carbonates in the LKG show a range of moderately positive to negative values from −2.8 to +5.9‰, with the majority below +3.0‰. 87Sr/86Sr values range from 0.70522 to 0.70534 in the Lower Inzer Member, increasing in the overlying Upper Inzer Member and Min’yar Formation, from 0.70555 to 0.70600. The Sr isotope range of the Lower Inzer Member is similar to that typical for the 1.03–0.95Ga seawater (0.70519–0.70554), suggesting that the Sr isotope composition of seawater in the aftermath of Rodinian assembly was unradiogenic for 150m.y. This pattern indicates that supercontinent-scale orogenic events do not result in an enhanced, long-term flux of radiogenic Sr from continents once the supercontinent assembled. To account for the prolonged period characterized by unradiogenic Sr seawater composition and moderate-amplitude C isotope variations, we suggest a supercontinent configuration ringed by continental arcs and with predominantly internal runoff. In this model, accompanying supercontinent blanketing resulted in thermal perturbation in the mantle, emplacement of multiple Large Igneous Provinces, and high continental freeboard. Weathering of juvenile arcs would have provided unradiogenic Sr and a high flux of sediments to the oceans, enhancing organic carbon burial and progressive oxygenation of surface environments and contributing to instability in the biogeochemical carbon cycle. Mass anomalies induced by protracted mantle plume activity led to True Polar Wander and brought the supercontinent, covered with juvenile mafic volcanics and segmented by failed rift systems, to low latitudes thus enhancing chemical weathering, atmospheric CO2 consumption, and eventually ushering in Snowball Earth conditions. Comparison with the records for early Paleoproterozoic strata indicates that a similar sequence of events bracketed both ends of the Proterozoic, highlighting fundamental relationships among plate tectonics, mantle dynamics, biogeochemical carbon cycling, surface oxygenation, and climate change.

Tropical weathering of the Taconic orogeny as a driver for Ordovician cooling

Research Article| June 09, 2017 Tropical weathering of the Taconic orogeny as a driver for Ordovician cooling Nicholas L. Swanson-Hysell; Nicholas L. Swanson-Hysell 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720-4767, USA Search for other works by this author on: GSW Google Scholar Francis A. Macdonald Francis A. Macdonald 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Nicholas L. Swanson-Hysell 1Department of Earth and Planetary Science, University of California, Berkeley, California 94720-4767, USA Francis A. Macdonald 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA Publisher: Geological Society of America Received: 23 Jan 2017 Revision Received: 11 Apr 2017 Accepted: 19 Apr 2017 First Online: 23 Jun 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2017 Geological Society of America Geology (2017) 45 (8): 719–722. https://doi.org/10.1130/G38985.1 Article history Received: 23 Jan 2017 Revision Received: 11 Apr 2017 Accepted: 19 Apr 2017 First Online: 23 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Nicholas L. Swanson-Hysell, Francis A. Macdonald; Tropical weathering of the Taconic orogeny as a driver for Ordovician cooling. Geology 2017;; 45 (8): 719–722. doi: https://doi.org/10.1130/G38985.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Earth’s climate cooled through the Ordovician Period leading up to the Hirnantian glaciation. Increased weatherability of silicate rocks associated with topography generated on the Appalachian margin during the Taconic orogeny has been proposed as a mechanism for Ordovician cooling. However, paleogeographic reconstructions typically place the Appalachian margin within the arid subtropics, outside of the warm and wet tropics where chemical weathering rates are highest. In this study, we reanalyze the paleomagnetic database and conclude that Ordovician constraints from cratonic Laurentia are not robust. Instead, we use paleomagnetic data from well-dated volcanic rocks in the accreting terranes to constrain Laurentia’s position given that the Appalachian margin was at, or equatorward of, the paleolatitude of these terranes. To satisfy these allochthonous data, Laurentia must have moved toward the equator during the Ordovician such that the Appalachian margin was within 10° of the equator by 465 Ma. This movement into the tropics coincided with the collision and exhumation of the Taconic arc system, recorded by a shift in neodymium isotope data from shale on the Appalachian margin to more juvenile values. This inflection in detrital neodymium isotope values precedes a major downturn in global seawater strontium isotopic values by more than one million years, as would be predicted from a change in weathering input and the relatively long residence time of strontium in the ocean. These data are consistent with an increase in global weatherability associated with the tropical weathering of mafic and ultramafic lithologies exhumed during the Taconic arc-continent collision. A Taconic related increase in weatherability is a viable mechanism for lowering atmospheric CO2 levels through silicate weathering contributing to long-term Ordovician cooling. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Participation in proficiency test for tritium strontium and caesium isotopes in seawater 2015 (IAEA-RML-2015-02)

A proficiency test (PT) exercise has proposed by the International Atomic Energy Agency (IAEA) in the frame of the IAEA Technical Cooperation project RAS/7/021 “Marine benchmark study on the possible impact of the Fukushima radioactive releases in the Asia-Pacific Region for Caesium Determination in Sea Water” since 2012. In 2015 the exercise was referred to Proficiency Test for Tritium, Strontium and Caesium Isotopes in Seawater 2015 (IAEA-RML-2015-02) to analyse3H, 134Cs, 137Cs and90Sr in a seawater sample. OAP was one of the 17 laboratories from 15 countries from Asia-Pacific Region who joined the PT exercise. The aim of our participation was to validate our analytical performance for the accurate determination of radionuclides in seawater by developed methods of radiochemical analysis. OAP submitted results determining the concentration for the three elements i.e. 134Cs, 137Cs and90Sr in seawater to the IAEA. A critical review was made to check suitability of our methodology and the criteria for the accuracy, precision and trueness of our data. The results of both 134Cs and 137Cs passed all criteria which were assigned “Accepted” statuses. Whereas 90Sr analysis did not pass the accuracy test therefore it was considered as “Not accepted” Our results and all other participant results with critical comments were published in the IAEA proficiency test report.

Quantifying the Cenozoic marine diatom deposition history: links to the C and Si cycles

Abstract. Marine planktonic diatoms are, today, among the world's main primary producers as well as the main organic carbon exporter to the deep sea despite the fact that they were a very minor component of the plankton at the beginning of the Cenozoic. They are also the main silica exporter to the deep sea, thus balancing global chemical weathering. This study reviews their global Cenozoic depositional pattern in order to understand the modality and the context of their rise to dominance, but also to understand how diatom evolution affected the Cenozoic functioning of the ocean's biological pump. After two short-lived major abundance peaks near the Eocene–Oligocene boundary and in the late Oligocene, diatom abundance in sediments shifted in the middle Miocene to globally higher values which have largely persisted to the modern day. These quantitative findings provide support for the hypothesis according to which diatoms, through their ecological role in the ocean's biological carbon pump, have contributed to the Cenozoic changes in atmospheric carbon dioxide pressure and consequently to changes in the global climate state. Additionally, correlations between diatom abundance peaks and shifts in seawater strontium and osmium isotopic composition hint at a strong control of the silicate weathering on diatom deposition.

Large igneous provinces and organic carbon burial: Controls on global temperature and continental weathering during the Early Cretaceous

There is an abundance of evidence for short intervals of cold climatic conditions during the Early Cretaceous. However, the lack of a high-resolution, long-term Early Cretaceous paleotemperature record hampers a full-scale synthesis of these putative “cold snap” episodes, as well as a more holistic approach to Early Cretaceous climate changes. We present an extended compilation of belemnite-based oxygen, carbon and strontium isotope records covering the Berriasian–middle Albian from the Vocontian Basin (SE France). This dataset clearly demonstrates three intervals of cold climatic conditions during the Early Cretaceous (late Valanginian–earliest Hauterivian, late early Aptian, latest Aptian–earliest Albian). Each of these intervals is associated with rapid and high amplitude sea-level fluctuations, supporting the hypothesis of transient growth of polar ice caps during the Early Cretaceous. As evidenced by positive carbon isotope excursions, each cold episode is associated with enhanced burial of organic matter on a global scale. Moreover, there is a relatively good match between the timing and size of large igneous province eruptions and the amplitude of Early Cretaceous warming episodes. Altogether, these observations confirm the instrumental role of atmospheric CO2 variations in driving Early Cretaceous climate change. From a long-term perspective, the coupling of global paleotemperature and seawater strontium isotopic ratio during the Early Cretaceous is best explained by temperature-controlled changes of continental crust weathering rates.

Strontium and oxygen isotopic profiles through 3 km of hydrothermally altered oceanic crust in the Reykjanes Geothermal System, Iceland

The Iceland Deep Drilling Program well RN-17 was drilled 3km into a section of hydrothermally altered basaltic crust in the Reykjanes geothermal system in Iceland. The system is located on the landward extension of the Mid-Atlantic Ridge, and the circulating hydrothermal fluid is modified seawater, making Reykjanes a useful analog for mid-oceanic ridge hydrothermal systems. We have determined whole-rock Sr and O isotope compositions, and Sr isotope compositions of epidote grains from the RN-17 cuttings and RN-17B core. Whole rock oxygen isotope ratios range from −0.13 to 3.61‰ V-SMOW, and are isotopically lighter than fresh MORB (5.8±0.2‰). The concentrations of Sr in the altered basalt range from well below to well above concentrations in fresh rock, and appear to be strongly correlated with the dominant alteration mineralogy. Whole rock Sr isotope ratios ranged from 0.70329 in the least altered crystalline basalt, to 0.70609 in the most altered hyaloclastite samples; there is no correlation with depth. Sr isotope ratios in epidote grains measured by laser ablation MC-ICP-MS ranged from 0.70360 to 0.70731. Three depth intervals, at 1000m, 1350m, and 1650m depth, have distinctive isotopic signatures, where 87Sr/86Sr ratios are elevated (mean value>0.7050) relative to background levels (mean altered basalt value ~0.7042). These areas are proximal to geothermal feed zones, and the 1350m interval directly overlies the transition from dominantly extrusive to dominantly intrusive lithologies. Oxygen isotope measurements yield integrated water/rock ratios of 0.4 to 4.3, and suggest that hydrothermal fluids must have formerly had a component of meteoric water. Strontium isotopic measurements provide a more sensitive indication of seawater interaction and require significant exchange with seawater strontium. Both isotopic systems indicate that the greenschist-altered basalts were in equilibrium with hydrothermal fluids at a relatively high mean water/rock (Wt.) ratio ranging from about 0.5 to 4. These ratios are higher than estimates from ODP Hole 504B and IODP Hole 1256D, but are consistent with values inferred from vent fluids from 21° and 13°N on the East Pacific Rise (Albarède et al., 1981; Michard et al., 1984; Alt et al., 1996; Harris et al., 2015).

Biostratigraphy constraining strontium isotopic stratigraphy and its application on the Lopingian (Late Permian)

The Lopingian is one of the fastest rising periods of seawater strontium isotopic ratios (87Sr/86Sr) in earth history, and its mechanisms and increasing rates of the 87Sr/86Sr evolution were still disputed widely. These disputations among researchers were caused mainly by timeframe selection (sections’ thickness or data of radiometric ages), and different stratigraphic boundaries and un-upmost dated ages. This paper examined published 87Sr/86Sr data of the Lopingian, and projected them on timescales based on evolutionary and age constrained conodonts fossils. 87Sr/86Sr evolution vs fossil constraining timescales was re-established in this period. This research suggests: (1) 87Sr/86Sr excursion projects on fossil zones can truly support 87Sr/86Sr evolutionary pattern in the period; (2) 87Sr/86Sr evolution provides a new approach for stratigraphic research of marine carbonate sections in lieu of biostratigraphic data; (3) 87Sr/86Sr stratigraphy works on marine carbonate sections of different sedimentation rates even between different basins; (4) the 87Sr/86Sr data and its shift was dependent on samples materials and chemical treatment methods; (5) the increasing rate of marine water 87Sr/86Sr in the Late Permian is suggested as 5.4×10−5/Ma or slightly lower; (6) sedimentation age and its 87Sr/86Sr of the Lopingian marine carbonate suggested as: DPRO=259-(RS−0.70695)/5.4×10−5±1 Ma.

顕生代におけるグローバル炭素循環と大気 CO&lt;sub&gt;2&lt;/sub&gt;：数値シミュレーションによるアプローチ

The global carbon cycle on a geological age consists of an inorganic carbon cycle (continental weathering and metamorphism-volcanism) and organic carbon cycle (oxidative weathering of organic carbon and organic carbon burial). The GEOCARB, one of the global carbon cycle models, calculates these geochemical carbon fluxes and atmospheric CO2 level in the period of Phanerozoic. Important parameters in the GEOCARB are those for the continental uplift, river runoff, evolution of vascular plants, weathering feedback, and CO2 degassings. Seawater strontium isotope ratio and sedimentation rate of terrigenous sediments can be used to estimate the continental uplift parameter. Regarding the vascular plant, more quantitative studies are necessary to elucidate its effect on the global carbon cycle. Concerning the degassing parameter, not only subduction volcanism but also hot spot volcanism and igneous activity in back arc basin should be considered. Runoff is dependent on continental positions and terrestrial temperature, but the interrelationship among them is not fully considered in the GEOCARB. In this respect, another type of the model, namely, the GEOCLIM, may be more appropriate. Volcanic rock weathering and climate sensitivity are also crucial in the global carbon cycle. Volcanic rock weathering might have controlled the atmospheric CO2 level in the Phanerozoic, although the value of the weathering flux has not been constrained. Regarding the climate sensitivity, a short-term feedback (Charney feedback) has been assumed in the GEOCARB. However, a long-term climate feedback, namely, the Earth System Sensitivity (ESS), should be incorporated. According to the recent version of GEOCARB (GEOCARBSULF), most influential parameters on the atmospheric CO2 are those for the climate sensitivity and vascular plants. In this model, atmospheric CO2 level in the Cenozoic is not well consistent with the results of geochemical proxies. This may be due to the insufficient estimation of degassing parameters, and/or a change in the climate sensitivity accompanied with formation of continental ice sheets in the Cenozoic.

Baseline concentrations of strontium and 90Sr in seawater from the northern Gulf

Baseline concentration of strontium and Sr-90 in Gulf is presented. The strontium concentration is much higher than reported for other oceanic waters, while the Sr-90 concentration is low at 0.7–1.0mBql−1, that represents the background level following nuclear tests and can be used as an effective tracer in case of any radioactive release in the region. The strontium concentration is primarily related to the increasing salinity off the Gulf coast.

Life history strategy diversity in the Kamchatkan Dolly Varden char Salvelinus malma (Walbaum) (Salmonidae, Salmoniformes): Ontogenetic reconstructions based on the data of X-ray fluorescence analysis of the microchemistry of recording structures

The issues related to specific traits of the life cycle and formation of the life history strategy diversity in fishes are urgent at present for optimization of the use of biological resources. Recently, the problems in the field of retrospective deciphering of the life cycle are being solved by methods of microchemical analysis of otoliths. These techniques determine the presence of marine, estuarine, or freshwater periods in the ontoge� nesis with sufficient accuracy [1–4]. These methods are based on direct dependence of accumulation of ions of elements in fish otoliths corresponding their content in the environment, e.g. the content of stron� tium in seawater is much higher than in fresh water. The efficiency of methods of “otolith microchemitry” was repeatedly confirmed in various teleostean groups [2–9]. At the same time, most methods of otolith analysis deciphering the life history strategy in fish

Strontium isotope variations in Middle Jurassic (Late Bajocian–Callovian) seawater: Implications for Earth's tectonic activity and marine environments

Strontium isotope ratios of well-preserved belemnite rostra and ammonite shells are presented from stratigraphically well-dated Upper Bajocian–Callovian sediments of the Polish Jura Chain in central Poland. Nekto-benthic belemnites show a narrow trend of changes of 87Sr/86Sr ratio that are interpreted to record secular variations in the strontium isotope composition of seawater. A new fit of the seawater strontium isotope curve for the Late Bajocian–Callovian is presented based on current and literature data. The data show a gradual decrease of seawater 87Sr/86Sr ratio throughout the Late Bajocian–earliest Middle Callovian, lowest 87Sr/86Sr ratios (0.706850) and the flat minimum of the curve were reached in the latest Middle and the Late Callovian. The Middle Jurassic decrease in seawater 87Sr/86Sr ratio is interpreted to have been a result of the increased volcanic activity of the seafloor. Studied nektonic ammonites are considered to have lived in surface or shallow near-coastal waters of the Polish Jura Chain basin and been affected by the freshwater influx. A slight enrichment of ammonite shells in 87Sr isotope is linked to a change in strontium isotope composition of the surface or near-coastal waters due to the riverine strontium input.