New chondrichthyans from the Irati Formation (Early Permian,Paraná Basin), Brazil: origin,paleoenvironmental and paleogeographical considerations

Three genera, known by dorsal finspine, are reported from conglomeratic sandstone at the base of the Lower Permian (Kungurian) Irati Formation (Paraná Basin) near Rio Claro, São Paulo State, Brazil, noteworthy for the great richness of vertebrate fossils. The fossils include: (1) the previously known Sphenacanthus with the species Sphenacanthus sanpauloensis and an indeterminate species; (2) the Permian – Carboniferous genus Amelacanthus; (3) a new indeterminate Chondrichthyes. These fossils are found together with: continental, fresh-water and salt-water vertebrates. The analysis of this assemblage allows inference about the origin of Paraná Basin Chondrichthyes as well as reconstruction of the paleoenvironment and the possible geographic isolation of these fishes during the Permian in Brazil.     

The Use of Stable Sulfur, Oxygen and Hydrogen Isotope Ratios as Geochemical Tracers of Sulfates in the Podwiśniówka Acid Drainage Area (South-Central Poland)

The paper presents the results of determinations of stable S and O isotopes of dissolved sulfates and O and H stable isotopes of waters from three ponds, that is, Marczakowe Do?y acid pond, Marczakowe Do?y fish pond and Podwi?niówka acid pit pond, located in the Holy Cross Mountains (south-central Poland). The δ³⁴S_V-CDT and δ¹⁸O_V-SMOW of SO₄ ^2? in waters of three ponds (n = 14) varied from ?16.2 to ?9.5 ‰ (mean of ?13.6 ‰) and from ?8.1 to ?3.2 ‰ (mean of ?4.8 ‰), respectively. The mean δ³⁴S–SO₄ ^2? values were closer to those of pyrite (mean of ?25.4 ‰) and efflorescent sulfate salts (mean of ?25.6 ‰), recorded previously in the Podwi?niówka quarry, than to sulfates derived from other anthropogenic or soil and bedrock sources. The SO₄ ^2? ions formed by bacterially induced pyrite oxidation combined with bacterial (dissimilatory) dissolved sulfate reduction, and presumably with subordinate mineralization of carbon-bonded sulfur compounds, especially in both Marczakowe Do?y ponds. In addition, the comparison of δ¹⁸O–SO₄ ^2? and δ¹⁸O–H₂O values indicated that 75–100 % of sulfate oxygen was derived from water. Due to the largest size, the Podwi?niówka acid pit pond revealed distinct seasonal variations in both δ¹⁸O–H₂O (?9.2 to ?1.6) and δD–H₂O (?29.7 to ?71.3) values. The strong correlation coefficient (r ² = 0.99) was noted between δ¹⁸O–H₂O and δD–H₂O values, which points to atmospheric precipitation as the only source of water. The sediments of both acid ponds display different mineral inventory: the Marczakowe Do?y acid pond sediment consists of schwertmannite and goethite, whereas Podwi?niówka acid pit pond sediment is composed of quartz, illite, chlorite and kaolinite with some admixture of jarosite reflecting a more acidic environment. Geochemical modeling of two acid ponds indicated that the saturation indices of schwertmannite and nanosized ε-Fe₂O₃ (Fe³⁺ oxide polymorph) were closest to thermodynamic equilibrium state with water, varying from ?1.44 to 3.05 and from ?3.42 to 6.04, respectively. This evidence matches well with the obtained mineralogical results.     

Heat capacity,entropy, and phase equilibria of dmitryivanovite

The heat capacity (C _p ) of dmitryivanovite synthesized with a cubic press was measured in the temperature range of 5–664 K using the heat capacity option of a physical properties measurement system and a differential scanning calorimeter. The entropy of dmitryivanovite at standard temperature and pressure (STP) was calculated to be 110.1 ± 1.6 J mol⁻¹ K⁻¹ from the measured C _p data. With the help of new phase equilibrium experiments done at 1.5 GPa, the phase transition boundary between krotite and dmitryivanovite was best represented by the equation: P (GPa) = −2.1825 + 0.0025 T (K). From the temperature intercept of this phase boundary and other available thermodynamic data for krotite and dmitryivanovite, the enthalpy of formation and Gibbs free energy of formation of dmitryivanovite at STP were calculated to be −2326.7 ± 2.1 and −2,208.1 ± 2.1 kJ mol⁻¹, respectively. It is also inferred that dmitryivanovite is the stable CaAl₂O₄ phase at STP and has a wide stability field at high pressures whereas the stability field of krotite is located at high temperatures and relatively low pressures. This conclusion is consistent with natural occurrences (in Ca–Al-rich inclusions) of dmitryivanovite and krotite, where the former is interpreted as the shock metamorphic product of originally present krotite.     

Heat capacity,entropy and phase equilibria of stishovite

The low-temperature heat capacity (C _P) of stishovite (SiO₂) synthesized with a multi-anvil device was measured over the range of 5–303 K using the heat capacity option of a physical properties measurement system (PPMS) and around ambient temperature using a differential scanning calorimeter (DSC). The entropy of stishovite at standard temperature and pressure calculated from DSC-corrected PPMS data is 24.94 J mol⁻¹ K⁻¹, which is considerably smaller (by 2.86 J mol⁻¹ K⁻¹) than that determined from adiabatic calorimetry (Holm et al. in Geochimica et Cosmochimica Acta 31:2289–2307, 1967) and about 4% larger than the recently reported value (Akaogi et al. in Am Mineral 96:1325–1330, 2011). The coesite–stishovite phase transition boundary calculated using the newly determined entropy value of stishovite agrees reasonably well with the previous experimental results by Zhang et al. (Phys Chem Miner 23:1–10, 1996). The calculated phase boundary of kyanite decomposition reaction is most comparable with the experimental study by Irifune et al. (Earth Planet Sci Lett 77:245–256, 1995) at low temperatures around 1,400 K, and the calculated slope in this temperature range is mostly consistent with that determined by in situ X-ray diffraction experiments (Ono et al. in Am Mineral 92:1624–1629, 2007).     

On some aspects of peaks-over-threshold modeling of floods under nonstationarity using climate covariates

This paper discusses some aspects of flood frequency analysis using the peaks-over-threshold model with Poisson arrivals and generalized Pareto (GP) distributed peak magnitudes under nonstationarity, using climate covariates. The discussion topics were motivated by a case study on the influence of El Niño–Southern Oscillation on the flood regime in the Itajaí river basin, in Southern Brazil. The Niño3.4 (DJF) index is used as a covariate in nonstationary estimates of the Poisson and GP distributions scale parameters. Prior to the positing of parametric dependence functions, a preliminary data-driven analysis was carried out using nonparametric regression models to estimate the dependence of the parameters on the covariate. Model fits were evaluated using asymptotic likelihood ratio tests, AIC, and Q–Q plots. Results show statistically significant and complex dependence relationships with the covariate on both nonstationary parameters. The nonstationary flood hazard measure design life level (DLL) was used to compare the relative performances of stationary and nonstationary models in quantifying flood hazard over the period of records. Uncertainty analyses were carried out in every step of the application using the delta method.     

U–Pb zircon and 40Ar–39Ar K-feldspar dating of syn-sedimentary volcanism of the Neoproterozoic Maricá Formation: constraining the age of foreland basin inception and inversion in the Camaquã Basin of southern Brazil

New U–Pb zircon and ⁴⁰Ar–³⁹Ar K-feldspar data are presented for syn-sedimentary volcanogenic rocks from the Neoproterozoic Maricá Formation, located in the southern Brazilian shield. Seven (of nine) U–Pb sensitive high-resolution ion microprobe analyses of zircons from pyroclastic cobbles yield an age of 630.2±3.4 Ma (2σ), interpreted as the age of syn-sedimentary volcanism, and thus of the deposition itself. This result indicates that the Maricá Formation was deposited during the main collisional phase (640–620 Ma) of the Brasiliano II orogenic system, probably as a forebulge or back-bulge, craton-derived foreland succession. Thus, this unit is possibly correlative of younger portions of the Porongos, Brusque, Passo Feio, Abapã (Itaiacoca) and Lavalleja (Fuente del Puma) metamorphic complexes. Well-defined, step-heating ⁴⁰Ar–³⁹Ar K-feldspar plateau ages obtained from volcanogenic beds and pyroclastic cobbles of the lower and upper successions of the Maricá Formation yielded 507.3±1.8 Ma and 506.7±1.4 Ma (2σ), respectively. These data are interpreted to reflect total isotopic resetting during deep burial and thermal effects related to magmatic events. Late Middle Cambrian cooling below ca . 200 °C, probably related to uplift, is tentatively associated with intraplate effects of the Rio Doce and/or Pampean orogenies (Brasiliano III system). In the southern Brazilian shield, these intraplate stresses are possibly related to the dominantly extensional opening of a rift or a pull-apart basin, where sedimentary rocks of the Camaquã Group (Santa Bárbara and Guaritas Formations) accumulated.     

Zur geomorphologischen und geologischen Entwicklungsgeschichte der Ostabdachung der Zentralalpen in der Miozänzeit

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Der Unmittelbare Nachweis des Vindelizischen Rückens unter der Süddeutschen Molasse

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