Browsing by Author "Lowenstein, TK"

Now showing 1 - 9 of 9
  • No Thumbnail Available
    Item
    Ca-SO4 crossover points in Phanerozoic seawater: evidence from fluid inclusions in halite
    (American Geophysical Union (AGU), 2021-12-15) Weldeghebriel, MF; Lowenstein, TK; García-Veigas, J; Cendón, DI
    The major ion (Mg2+, Ca2+, Na+, K+, SO42-, Cl-, HCO3-) chemistry of seawater has varied in the Phanerozoic and Neoproterozoic. Transitions between SO4-rich and Ca-rich seas, here called “Ca2+- SO42- crossover points” are of great biogeochemical interest because of their coincidence with shifts in seawater Mg2+/Ca2+ ratio and the mineralogies of potash evaporites. Crossover periods occurred four times over the past 550 Myr, when seawater chemistry shifted from Ca-rich to SO4-rich or vice versa. Here, chemical analyses of 2,466 fluid inclusions in marine halite define paleoseawater [Ca2+] and [SO42-] over the past 550 Myr, with emphasis on Ca2+- SO42- crossover periods. Three types of brine chemistries are recognized from [SO42-] and [Ca2+] concentrations: (1) SO4-rich (SO4>>Ca): inclusions with measurable SO42- (7-993 mmol/kg H2O, here termed mmolal) and low Ca2+ (<91 mmolal) (Late Neoproterozoic, Permian, Triassic, and Late Cenozoic); (2) Ca2+-rich (Ca >>SO4): inclusions with measurable Ca2+ (150-2000 mmolal) and very low SO42-, below detection (Cambrian, Silurian, Devonian, Mississippian, Pennsylvanian, Jurassic, and Cretaceous); (3) crossover periods (SO4≈Ca): inclusions have measurable but low concentrations of both Ca2+ (10-120 mmolal) and SO42- (10-210 mmolal) (Late Triassic to Early Jurassic, Eocene to Oligocene). The Late Pennsylvanian Paradox Formation represents a second type of crossover period. In that case, fluid inclusions vary from Ca2+-rich (3-670 mmolal) to SO4-rich (6-590 mmolal).The fourth transition from SO4-rich to Ca-rich seawater occurred during the Terminal Proterozoic to the Early Cambrian (ca. 544-515 Ma) (Brennan et al., 2004). Salts predicted to precipitate during evaporation of crossover periods, for example Eocene and Oligocene seawater are calcite, gypsum, halite, polyhalite, sylvite, carnallite, kieserite, and bischofite. The four crossover points parallel major transitions in: (1) Mg2+/ Ca2+ ratio of seawater; (2) aragonite and calcite seas; (3) MgSO4 and KCl potash evaporites; and (4) icehouse and greenhouse climates, suggesting a link between the composition of seawater, marine potash evaporites, carbonate mineralogy, and climate.
  • No Thumbnail Available
    Item
    [Ca2+] and [SO2- 4] in Phanerozoic and terminal Proterozoic seawater from fluid inclusions in halite: the significance of Ca-SO4 crossover points
    (Elsevier, 2022-09-15) Weldeghebrial, MF; Lowenstein, TK; García-Veigas, J; Cendón, DI
    Chemical analyses of 2,618 (1,640 new and 978 published) fluid inclusions in marine halite were used to define paleoseawater [Ca2+] and [SO2- 4] over the past 550 million years (Myr). Three types of fluid inclusion brine chemistries were recognized based on measured [Ca2+] and [SO2- 4]: (1) SO4-rich with [SO2- 4] ≫ [Ca2+]; (2) Ca-rich with [Ca2+] ≫ [SO2- 4]; and (3) Ca-SO4 crossover points with [Ca2+] ≈ [SO2- 4]. The SO4-rich and Ca-rich fluid inclusion chemistries oscillated twice in the terminal Proterozoic and Phanerozoic. Transitions between SO4-rich and Ca-rich seas, here called "Ca2+ -SO2- 4 crossover points” occurred four times: terminal Proterozoic–Early Cambrian (544–515 Ma), Late Pennsylvanian (309–305 Ma), Triassic–Jurassic boundary (∼200 Ma), and Eocene–Oligocene (36–34 Ma). New fluid inclusion analyses using laser ablation-inductively coupled plasma-mass spectrometry better defined the [Ca2+] and [SO2- 4] in seawater at the Late Pennsylvanian and Eocene–Oligocene crossover points and the timing of the Triassic–Jurassic crossover point. Crossover points coincide with shifts in seawater Mg2+/Ca2+ ratios, the mineralogies of marine non-skeletal carbonates and shell building organisms (aragonite vs. calcite) and potash evaporites (MgSO4 vs. KCl types). Phanerozoic and terminal Proterozoic trends in seawater [Ca2+] and [SO2- 4] also coincide with supercontinent breakup, dispersal, and assembly cycles, greenhouse–icehouse climates, and modeled atmospheric ρCO2. Paleoseawater [Ca2+] and [SO2- 4] were calculated from the fluid inclusion data using the assumption that the [Ca2+] × [SO2- 4] ranged from 150 to 450 mmolal2, which is 0.5–1.5 times the [Ca2+] = 11 × [SO2- 4] = 29 product in modern seawater (319 mmolal2). Two additional end-member scenarios, independent of the [Ca2+] × [SO2- 4] = 150–450 mmolal2 assumption, were tested using constraints from fluid inclusion [Ca] and [SO4]: (1) constant [SO2- 4] = 29 mmolal as in modern seawater, and variable [Ca2+], and (2) constant [Ca2+] = 11 mmolal as in modern seawater and variable [SO2- 4]. Mg2+/Ca2+ ratios calculated from the three scenarios were compared to independent data on the Mg2+/Ca2+ ratios from skeletal carbonates (echinoderms and corals) and mid-ocean ridge flank calcite veins. Constant [Ca2+] of 11 mmolal is unlikely because this relatively low concentration generated unreasonably low seawater [SO2- 4] during most of the past 550 Myr and high Mg2+/Ca2+ ratios compared to independent data. Constant [SO2- 4] of 29 mmolal produced unreasonably high seawater [Ca2+] and lower Mg2+/Ca2+ ratios than those derived from fluid inclusions, echinoderms, corals, and calcite veins. Variable [Ca2+] and [SO2- 4] showed the best agreement with the Mg2+/Ca2+ ratios derived from fluid inclusions, echinoderms, corals, and calcite veins. © 2022 Elsevier B.V.
  • No Thumbnail Available
    Item
    Combined LA-ICP-MS and cryo-SEM-EDS: an improved technique for quantitative analysis of major, minor, and trace elements in fluid inclusions in halite
    (Elsevier B. V., 2020-09-30) Weldeghebriel, MF; Lowenstein, TK; García-Veigas, J; Collins, D; Sendula, E; Bodnar, RJ; Graney, JR; Cendón, DI; Lensky, NG; Mor, Z; Sirota, I
    Quantitative multi-element analyses of single fluid inclusions in halite and other sedimentary minerals can provide information on the origin and chemical evolution of ancient surface waters on Earth. Integrated laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and cryogenic-scanning electron microscopy-energy dispersive spectroscopy (cryo-SEM-EDS) were used here for the quantitative analysis of fluid inclusions in halite. Single phase fluid inclusions in modern and ancient halite were analyzed using a 193 nm ArF excimer laser ablation system coupled with a quadrupole mass spectrometer to test a new calibration technique using magnesium (Mg) as an internal standard. Mg concentrations obtained by cryo-SEM-EDS analyses of fluid inclusions were used to convert LA-ICP-MS concentration ratios into absolute elemental concentrations. Mg concentrations of ancient fluid inclusions from cryo-SEM-EDS analyses were reproducible to better than 5% relative standard deviation (RSD). Comparison between the chemical composition of modern Dead Sea brine measured using ICP-OES (optical emission spectroscopy) and the composition of fluid inclusions in Dead Sea halite formed from those brines, shows that fluid inclusions in halite faithfully record the chemistry of the brines from which they precipitated. Overall LA-ICP-MS analytical precision for major ions K, Ca, S in SO4 (above 50 mmol/kg H2O) is better than 10% RSD and accuracies range from 2% to 21%. Mean concentrations of Li, B, Sr, Rb and Ba agree within 7% of their expected values and are reproducible within 15%, whereas Cs concentrations above detection limit are typically reproducible to within 15 to 25% RSD. For trace elements in seawater, such as U and Mo, quantitative analyses in fluid inclusions are achieved at concentrations above 20 nmol/kg H2O. The results from this study confirm that the precision and accuracy of major and minor elemental analysis is improved with Mg as an internal standard instead of Na and Cl used in previous studies. Controlled, optimized ablation of >30 μm fluid inclusions in halite improved the accuracy and precision and reduced the overall limit of detection (LOD) by one order of magnitude compared to previous studies. Wide ranges of LODs, between 0.7 nmol/kg H2O and 10 mmol/kg H2O, reflect variations in inclusion volume and elemental concentrations. Analytical accuracies obtained for major elements demonstrate that cryo-SEM-EDS and LA-ICP-MS are complementary microbeam techniques for chemical analysis of individual fluid inclusions in halite. © 2021 Elsevier B.V.
  • No Thumbnail Available
    Item
    Geochemical indicators in Western Mediterranean Messinian evaporites: implications for the salinity crisis
    (Elsevier B. V., 2018-09-01) García-Veigas, J; Cendón, DI; Gilbert, L; Lowenstein, TK; Artiaga, D
    The Messinian Salinity Crisis (MSC) led to deposition of one of the youngest saline giant on Earth. The increasing restriction of the connections between the Mediterranean, the Atlantic Ocean and the freshwater Paratethyan basins resulted in the deposition of massive amounts of evaporites (gypsum, anhydrite, halite and potash salts) in shallow marginal basins as well as in deep Mediterranean basins. Here we show that each gypsum unit in the circum-Mediterranean marginal basins in Sicily and Spain is characterized by a narrow range of sulfate isotopic values (δ34S ~ 23‰ and δ18O ~ 14‰ in the Lower Gypsum; δ34S ~ 23‰ and δ18O ~ 17‰ in the Upper Gypsum). Sulfate isotope compositions found in MSC evaporites from a variety of circum-Mediterranean basins are homogenously high relative to expected Late Miocene marine evaporites (δ34S ~ 22‰ and δ18O ~ 12‰). This points to a stratified Mediterranean Sea with a high-salinity, dense, and anoxic bottom water mass. An intermediate depth gypsum-saturated brine flooded marginal basins from which selenite deposits formed during the MSC Stage 1 (Primary Lower Gypsum) and MSC Stage 3 (Upper Gypsum). Messinian brines were gradually affected by biogenic redox processes and isotopically differentiated from global seawater values. The homogeneity of isotopic signatures between distant synchronous gypsum deposits further supports the deep-basin deep-water model for the Mediterranean during the entire MSC event. © 2018 Elsevier B.V.
  • No Thumbnail Available
    Item
    Late Miocene evaporite geochemistry of lorca and fortuna basins (Eastern Betics, SE Spain): evidence of restriction and continentalization
    (Wiley, 2020-09-26) García-Veigas, J; Gibert, L; Cendón, DI; Artiaga, D; Corbí, H; Soria, JM; Lowenstein, TK; Sanz, E
    The Lorca and Fortuna basins are two intramontane Neogene basins located in the eastern Betic Cordillera (SE Spain). During the Late Tortonian—Early Messinian, marine and continental evaporites precipitated in these basins as a consequence of increased marine restriction and isolation. Here we show a stratigraphic correlation between the evaporite records of these basins based on geochemical indicators. We use SO4 isotope compositions and Sr isotopic ratios in gypsum, and halite Br contents to characterize these units and to identify the marine or continental source of the waters feeding the evaporite basins. In addition, we review the available chronological information used to date these evaporites in Lorca (La Serrata Fm), including a thick saline deposit, that we correlate with the First Evaporitic Group in Fortuna (Los Baños Fm). This correlation is also supported by micropalaeontological data, giving a Late Tortonian age for this sequence. The Second Evaporitic Group, (Chicamo Fm), and the Third Evaporitic Group (Rambla Salada Fm) developed only in Fortuna during the Messinian. According to the palaeogeographical scheme presented here, the evaporites of the Lorca and Fortuna basins were formed during the Late Tortonian—Early Messinian, close to the Betic Seaway closure. Sulphate isotope compositions and Sr isotopic ratios of the Ribera Gypsum Mb, at the base of the Rambla Salada Fm (Fortuna basin), match those of the Late Messinian selenite gypsum beds in San Miguel de Salinas, in the near Bajo Segura basin (40 km to the East), and other Messinian Salinity Crisis gypsum deposits in the Mediterranean. According to these geochemical indicators and the uncertainty of the chronology of this unit, the assignment of the Rambla Salada Fm to the MSC cannot be ruled out. © 1999-2024 John Wiley & Sons, Inc or related companies.
  • No Thumbnail Available
    Item
    Late Miocene evaporite geochemistry of Lorca and Fortuna basins (Eastern Betics, SE Spain): Evidence of restriction and continentalization
    (John Wiley & Sons, Inc., 2019-09-26) García-Veigas, J; Gilbert, L; Cendón, DI; Artiaga, D; Corbí, H; Soria, JM; Lowenstein, TK; Sanz, E
    The Lorca and Fortuna basins are two intramontane Neogene basins located in the eastern Betic Cordillera (SE Spain). During the Late Tortonian—Early Messinian, marine and continental evaporites precipitated in these basins as a consequence of increased marine restriction and isolation. Here we show a stratigraphic correlation between the evaporite records of these basins based on geochemical indicators. We use SO4 isotope compositions and Sr isotopic ratios in gypsum, and halite Br contents to characterize these units and to identify the marine or continental source of the waters feeding the evaporite basins. In addition, we review the available chronological information used to date these evaporites in Lorca (La Serrata Fm), including a thick saline deposit, that we correlate with the First Evaporitic Group in Fortuna (Los Baños Fm). This correlation is also supported by micropalaeontological data, giving a Late Tortonian age for this sequence. The Second Evaporitic Group, (Chicamo Fm), and the Third Evaporitic Group (Rambla Salada Fm) developed only in Fortuna during the Messinian. According to the palaeogeographical scheme presented here, the evaporites of the Lorca and Fortuna basins were formed during the Late Tortonian—Early Messinian, close to the Betic Seaway closure. Sulphate isotope compositions and Sr isotopic ratios of the Ribera Gypsum Mb, at the base of the Rambla Salada Fm (Fortuna basin), match those of the Late Messinian selenite gypsum beds in San Miguel de Salinas, in the near Bajo Segura basin (40 km to the East), and other Messinian Salinity Crisis gypsum deposits in the Mediterranean. According to these geochemical indicators and the uncertainty of the chronology of this unit, the assignment of the Rambla Salada Fm to the MSC cannot be ruled out. © 2019 The Authors. Basin Research © 2019 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists
  • No Thumbnail Available
    Item
    The major-ion composition of Cenozoic seawater: the past 36 million years from fluid inclusions in marine halite
    (American Journal Science, 2013-10-01) Brennan, ST; Lowenstein, TK; Cendón, DI
    Fluid inclusions from ten Cenozoic (Eocene-Miocene) marine halites are used to quantify the major-ion composition (Mg2+, Ca2+, K+, Na+, SO42-, and Cl-) of seawater over the past 36 My. Criteria used to determine a seawater origin of the halites include: (1) stratigraphic, sedimentologic, and paleontologic observations; (2) Br- in halite; (3) delta S-34 of sulfate minerals; (4) Sr-87/Sr-86 of carbonates and sulfates; and (5) fluid inclusion brine compositions and evaporation paths, which must overlap from geographically separated basins of the same age to confirm a "global" seawater chemical signal. © 2013, American Journal of Science.
  • No Thumbnail Available
    Item
    Rapid changes in major ion chemistry of seawater and the end-permian mass extinction
    (Geological Society of America, 2017-10-22) Lowenstein, TK; García-Veigas, J; Cendón, DI; Gilbert Beotas, L
    The end-Permian mass extinction is interpreted to have involved elevated global temperatures, ocean anoxia, ocean acidification, a disturbed sulfur cycle, and ocean euxinia. The same period also contains one of the largest accumulations of evaporites in the geologic record, including saline giants in the US, England, the Netherlands, Germany, Poland, Ukraine, and Russia. Here we show from fluid inclusions in marine halites that there was a major shift in seawater chemistry involving SO4and Ca which coincides with other global perturbations in seawater chemistry at the end-Permian and perhaps the mass extinction. Permian seawater, determined from the chemical compositions of fluid inclusions in marine halites from the North American Permian Basin (Kansas, Texas and New Mexico) and the Southern Permian Basin (Central Europe) shares chemical characteristics with modern seawater, including SO4 > Ca at the point of gypsum precipitation and evolution into a Mg-Na-K-SO4-Cl brine. An abrupt shift to Ca-rich fluid inclusions occurs in the Changhsingian Rustler Formation of New Mexico over 1.5 meter of stratigraphic section and in the Changhsingian Zechstein Cycle Na2 and basal Na3 Cycle of Poland. Such an abrupt shift in the major ion chemistry of seawater in two basins at about the same time is unusual because the residence times of SO4 and Ca in seawater are 10 m.y. and 1 m.y., respectively. Changes in the major ion chemistry of seawater are well known to occur over periods of 106 to 107 years, so the end-Permian seawater chemistry shift indicates some catastrophic process. The shift from sulfate-rich to calcium-rich brines coincides with a marked drop in δ34S in Zechstein and Rustler anhydrite, which suggests a link between changes in the major ion chemistry of seawater and perturbations in the sulfur cycle. These changes are interpreted to have been caused by overturn of anoxic sulfidic deep-waters from the Panthalassan superocean during the Changhsingian stage which may have coincided with the end-Permian mass extinction.
  • No Thumbnail Available
    Item
    Seafloor hydrothermal systems control seawater chemistry: evidence from fluid inclusion in halite
    (The Geological Society of America, 2019-09-24) Weldeghebriel, MF; Lowenstein, TK; Demicco, RV; Graney, JR; García-Veigas, J; Cendón, DI; Bodnar, RJ; Sendula, E
    Long-term changes in the major ion and isotopic composition of seawater coincide with icehouse-greenhouse climate fluctuations, calcite-aragonite seas, and sea level changes. However, there is disagreement over what processes controlled the changes in ocean chemistry. This study uses a new record of Li concentration in paleoseawater to explore how temporal variations in the flux of MOR hydrothermal brines, the largest source of Li to seawater, and reverse weathering of seafloor basalts (important sink) control the oceanic Li cycle on multimillion-year time scales. Here we present a 350-million-year record of seawater lithium concentrations [Li+]sw from direct measurement of primary fluid inclusions in marine halite using combined LA-ICP-MS and cryo SEM-EDS. We also present a 150 Myr forward model of [Li+]sw. From 350-0 Ma, the lithium concentration of seawater oscillated systematically, parallel to secular variations of sea level, greenhouse-icehouse climates, and major ion chemistry such as the Mg2+/Ca2+ ratio. Highest seawater Li occurred during the Cretaceous, up to one order of magnitude higher than modern [Li+]sw, which coincides with low seawater Mg2+/Ca2+ ratios, high atmospheric CO2, and Mesozoic-Early Cenozoic Greenhouse climates. Such high Li concentrations require high MOR hydrothermal activity. Conversely, Permian and Cenozoic (35-0 Ma) seawater had relatively low Li, consistent with high Mg2+/Ca2+ ratios, low atmospheric CO2, and late Paleozoic and Cenozoic icehouse periods. The forward model involves 10 Kyr time steps and variable cycling of hydrothermal fluids through the axial portion of the MOR system and variable rates of low-temperature weathering of seafloor basalts. The model agrees well with paleoseawater fluid inclusion data for Li. The same model parameters, with variable Li isotope fractionation of off-axis oceanic crust, are used to successfully model the 9‰ increase of δ7Li in seawater from 60-0 Ma. Our data and modeling suggest that seafloor hydrothermal systems exerted the dominant control on the [Li+] and δ7Li composition of Phanerozoic seawater. These data will be further used to test the long-term relationships between seafloor MOR activity, the carbon cycle, and climate. © Copyright 2019 The Geological Society of America (GSA)