Search results for "Global changes"
showing 3 items of 533 documents
Experimental Constraints on the Deep Magma Feeding System at StromboliVolcano, Italy
2009
International audience; New experiments have been performed on a high-K basalt (PST-9) from Stromboli volcano, Italy, to constrain the physical conditions of golden pumice magmas at their storage level and discuss their petrogenesis. Fluid-present, H2O- and CO2-bearing, near-liquidus experiments were performed at 11508C between 100 and 400MPa and under oxidizing conditions. Glasses were analyzed by Fourier transform IR spectroscopy and their H2O and CO2 concentrations compared with those in glass inclusions.Most glass inclusions cluster near the 200MPa isobar, suggesting entrapment at a depth of ~8 km. Golden pumice magmas have viscosities of 7.9 Pa s and densities of 2.48-2.57 g/cm3. Compo…
The influence of ENSO on South Africa winter rainfall
2011
International audience; We analysed the relationship between El Niño Southern Oscillation (ENSO) and South Africa austral winter rainfall using a 682 raingauges daily rainfall database documenting the period 1950-1999. The May, June and July (MJJ) seasonal rainfall amount shows a positive correlation with the Niño3.4 index that becomes significant since the mid 70's. Wet spells properties (length, frequency and intensity) at the raingauge scale indicate that high (low) MJJ seasonal rainfall amounts recorded during El Niño (La Niña) events are the result of longer (shorter) wet spells in the Cape Town area and more (less) frequent wet spells north of 33°S. Wet spells with daily rainfall amou…
Carbon cycle and sea-water palaeotemperature evolution at the Middle-Late Jurassic transition, eastern Paris Basin (France).
2014
14 pages; International audience; A very high-resolution carbon and oxygen stable isotope analysis (bulk-carbonate) of a biostratigraphically well-constrained Callovian-Oxfordian series is provided here for the first time. The homogeneity of the clayey series and the weak diagenetic alteration allow the isotopic signal variations to be considered as primary in origin. A prominent and brief negative excursion in the δ13C curve (−2‰), occurring at the start of the Middle Callovian (Jason Zone - Obductum Subzone) and correlated regionally, suggests a possible methane release. The increasing δ13C values thereafter up to the Early Oxfordian, concomitant with a warming episode, highlight the buri…