Atmospheric halogen and acid rains during the major Deccan episode: magnetic and mineral evidences

Environmental and climatic changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low magnetic susceptibility interval just below the Iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of palaeoenvironmental perturbations linked to paroxysmal Deccan phase-2. Results show a drastic decrease of detrital magnetite and presence of fine specular akaganeite, a hypothesized reaction product between FeCl2 from the volcanic plume with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after about 33,000 years, which is consistent with our magnetic data and the duration of the Deccan phase-2. This discovery represents an unprecedented piece of evidence of the nature and importance of the Deccan-related environmental changes

The pre-KPB interval: sedimentary record of a major Deccan Traps pulse?

The KPB crisis is one of the major biological crises that affected the Earth at Phanerozoic times. There is still an acrimonious debate on the nature and origin of this mass extinction: proponents of the idea that large bolide impacts caused most of the Phanerozoic mass extinctions are opposed to those who favoured a terrestrial origin linked to continental flood basalt eruptions of the Deccan Traps. The major limitations reside in the difficulty to date with precision the stratigraphic position of Deccan traps pulses since direct markers are still missing

Energy Resolution Performance of the CMS Electromagnetic Calorimeter

The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals

Southern Ocean deep-water carbon export enhanced by natural iron fertilization

The addition of iron to high- nutrient, low- chlorophyll regions induces phytoplankton blooms that take up carbon(1-3). Carbon export from the surface layer and, in particular, the ability of the ocean and sediments to sequester carbon for many years remains, however, poorly quantified(3). Here we report data from the CROZEX experiment(4) in the Southern Ocean, which was conducted to test the hypothesis that the observed north - south gradient in phytoplankton concentrations in the vicinity of the Crozet Islands is induced by natural iron fertilization that results in enhanced organic carbon flux to the deep ocean. We report annual particulate carbon fluxes out of the surface layer, at three kilometres below the ocean surface and to the ocean floor. We find that carbon fluxes from a highly productive, naturally iron-fertilized region of the sub- Antarctic Southern Ocean are two to three times larger than the carbon fluxes from an adjacent high-nutrient, low- chlorophyll area not fertilized by iron. Our findings support the hypothesis that increased iron supply to the glacial sub- Antarctic may have directly enhanced carbon export to the deep ocean(5). The CROZEX sequestration efficiency(6) ( the amount of carbon sequestered below the depth of winter mixing for a given iron supply) of 8,600 mol mol(-1) was 18 times greater than that of a phytoplankton bloom induced artificially by adding iron(7), but 77 times smaller than that of another bloom(8) initiated, like CROZEX, by a natural supply of iron. Large losses of purposefully added iron can explain the lower efficiency of the induced bloom(6). The discrepancy between the blooms naturally supplied with iron may result in part from an underestimate of horizontal iron supply