Geosciences / Miocene Slănic Tuff, Eastern Carpathians, Romania, in the context of Badenian salinity crisis

New geochronological investigations for the Slănic Formation, correlated with previous bio- and lithostratigaphical information, allow for a better succession of events for the Middle Miocene, including the absolute age of the Badenian salinity crisis in the bend sector of the Eastern Carpathians. Within the green Slănic Tuff, white tuff layers were in evidence. The main element distribution of the white and green tuffs indicates a dacitic composition, with higher SiO2 content for the white tuff. The white tuff has a distinct mineralogical composition with quartz, plagioclase, biotite and clinoptilolite. From such a tuff layer a biotite concentrate gives a 40Ar/39Ar age of 13.7 0.2 Ma. As above these tuff layers discrete levels of gypsum occur, the age documents the beginning of the restrictive circulation and formation of evaporites in this sector of Carpathians during Badenian times.(VLID)251000

Multiple isotope tracers from Permian-Triassic hydrated sulfates: Implications for fluid-mineral interaction

Isotopic compositions of water of crystallization and sulfate anionic group in gypsum and polyhalite were used as tracers for events related to their formation and subsequent evolution, as for example origin of crystallization water and extent of thermal overprint. For this purpose, gypsum and polyhalite from the Permo-Triassic evaporites of the Eastern Alps, were analysed for isotope composition of sulfate anionic group (δ34S and δ18OSO4) and water of crystallization (δD and δ18O). For comparison, water of crystallisation of polyhalite samples of similar age from New Mexico (USA), Kłodawa (Poland) and Hattberg, Hesse (Germany) were also investigated. Estimated δ18O and δD values of polyhalite formation brines vary from 14.4 to 3.4‰ and 42.5 to −6.1‰, respectively. Gypsum formation brines show different δ18O and δD values, from −5.7 to −15‰ and −30.9 to −88.8‰, respectively. The measured δ18OSO4 values of sulfate group are compatible with a thermal overprint at 100°–200°C for both minerals. The thermal overprint documented for the Eastern Alps led to gypsum but not to polyhalite dehydration. The isotopic composition of water of crystallization suggests that polyhalite is preserving the isotopic signature of an enriched brine. During a subsequent event, anhydrite rehydrated to gypsum, with the isotopic composition of water of crystallisation indicating lower (δD and δ18O) values than the present-day meteoric water ones. Due to their distinct mineral structure and, as a result, different temperature of dehydratation, gypsum and polyhalite record different histories following precipitation in an evaporative system

Lateglacial-Middle Holocene Stable Isotope Records in Two Coeval Stalagmites from the Bihor Mountains, NW Romania

Oxygen and carbon stable isotope records of two stalagmites from NW Romania provide a continuous climatic record between 14.8 and 5.6 ka BP. The chronology is established by 21 TIMS uranium series ages. Uncertainties in the isotope chronology range between ±20 and ±100 yr. The d18 O values are positively correlated with temperature, whereas d13 C fluctuations suggest changes in soil CO2 production. Lateglacial deposition of both stalagmites started at ~14.8 ka BP. The d18 O records subsequently show a slow decline in temperatures until 12.6 ka BP. Three warmer periods with increased soil productivity occurred at 14.5-13.9 ka BP, 13.6-13.2 ka BP, and 12.9-12.6 ka BP. Lower d18 O and high d13 C values between 12.6 and 11.4 (11.7) ka BP indicate a cold and dry climate during the Younger Dryas (GS-1). During the Early Holocene, three short cold intervals are marked on the d18 O profiles at 11.0-10.6, 10.5-10.2 and 9.4-9.1 ka BP. For the remainder of the Holocene sequence, the d18 O records show less variation between 9 and 7.8 ka BP and gradual warming from 7.6-5.6 ka BP. The speleothem records correlate with the Greenland ice core records and with other proxies throughout Europe and the North Atlantic region

Lateglacial-Middle Holocene Stable Isotope Records in Two Coeval Stalagmites from the Bihor Mountains, NW Romania

Oxygen and carbon stable isotope records of two stalagmites from NW Romania provide a continuous climatic record between 14.8 and 5.6 ka BP. The chronology is established by 21 TIMS uranium series ages. Uncertainties in the isotope chronology range between ±20 and ±100 yr. The d18 O values are positively correlated with temperature, whereas d13 C fluctuations suggest changes in soil CO2 production. Lateglacial deposition of both stalagmites started at ~14.8 ka BP. The d18 O records subsequently show a slow decline in temperatures until 12.6 ka BP. Three warmer periods with increased soil productivity occurred at 14.5-13.9 ka BP, 13.6-13.2 ka BP, and 12.9-12.6 ka BP. Lower d18 O and high d13 C values between 12.6 and 11.4 (11.7) ka BP indicate a cold and dry climate during the Younger Dryas (GS-1). During the Early Holocene, three short cold intervals are marked on the d18 O profiles at 11.0-10.6, 10.5-10.2 and 9.4-9.1 ka BP. For the remainder of the Holocene sequence, the d18 O records show less variation between 9 and 7.8 ka BP and gradual warming from 7.6-5.6 ka BP. The speleothem records correlate with the Greenland ice core records and with other proxies throughout Europe and the North Atlantic region

Ecophysiology of the hydrothermal vent snail Ifremeria nautilei and barnacle Eochionelasmus ohtai manusensis , Manus Basin, Papua New Guinea: Insights from shell mineralogy and stable isotope geochemistry

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Geographic variations in the slope of the δ2H–δ18O meteoric water line over Europe: A record of increasing continentality

International audienceδ2H and δ18O values of precipitations follow an empirical linear relationship at the global scale that is called the Global Meteoric Water Line (GMWL) and characterized by a slope of 8. However, Local Meteoric Water Lines (LMWLs) may have different slopes S depending on their geographic situation. Monthly δ2H and δ18O of precipitation have been compiled from European International Atomic Energy Agency (IAEA) stations. Those data allowed the calculation of the slopes S of the δ2H–δ18O LMWL determined for each station. S increases with longitude ϕ from c. 5 (Portugal) to c. 9 (Russia) – they are positively correlated with relative humidity (RH), negatively with temperature and positively with the mean intra-annual amplitude of temperatures, which is a proxy of continentality. Slopes of 5–6, recorded in SW Europe, reflect mean RH (70–75%) and sea surface temperatures (c. 25°C) of the Central Atlantic Ocean where the main flux of moisture is formed before being transported by the westerlies. In addition, falling water droplets within an air column with a high RH (>80%) and low temperature are expected to escape sub-cloud evaporation. Therefore, slopes with values close to 9 are considered to reflect isotopic equilibrium conditions during the condensation of water vapour in clouds