Universite de Nantes, France

Flood Basalt eruptions may have played a key role in past climatic changes by releasing huge amount of volcanic gazes in the atmosphere. Continental Flood Basalt provinces consist of an accumulation of single-lava flows covering a surface of 1 Mkm (super 2) corresponding to a volume of 1Mkm (super 3) over a short-lived period that lasts about 1 Ma typically. Along fissures from tens to hundreds of km long, large amounts of gas (CO (sub 2) , SO (sub 2) , H (sub 2) 0, HF...) are injected in the upper troposphere and lower stratosphere at the vents, while the lava flows covered huge areas. We focused on the approximately 65 Ma Deccan Province degassing in sulfur. To estimate the pre-eruption sulfur concentration, we used an empiric Fe0/S ratio based on 335 samples fresh MORB glass analysis. Thus, we can predict the initial S content of Deccan Trap's magmas, ranging from 933 ppm (Neral Fm) up to 1879 ppm (Mahabaleswhar Fm). Remaining sulfur in the lavas was also measured by pyrohydrolysis and ion chromatography. The difference between these two values may represent amount (in ppm) of sulfur degassed during eruptions. Consequently, the sulfur cycle should record such a massive injection over a short geological period. Samples of Maastrichtian and Paleocene chalk from DSDP site 217 were pyrohydrolysed and the sulfur content was measured by ion chromatography. Thus, the amount of sulfur structurally substituted in carbonate (Carbonate Associated Sulfate) is known. Samples also underwent isotopic data (delta (super 13) C and delta (super 18) O) acquisition, in order to access to climatic changes recorded during this period. Large inputs of sulfur due to volcanic activity in the external cycle should lead to severe perturbations.