High resolution analysis of paleoenvironment and material transport during the hot-house Earth system

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This research group (Leader : Hisatake Okada) had started in 1999 a field survey and sampling project in Southern France using the Grant-in Aid for Scientific Research (No. 11691113). The project was designed as a precursory study for one of IODP (Integrated Ocean Drilling Program)'s main target, the "Paleoenvironment under Extreme Climates". The team had studied extensively the OAE1b interval of Mid-Cretaceous Warm Event, and had obtained a massive columnar section containing Paquier interval, and also had conducted several test drilling at the upper level of OAE1b interval.In this new research project (Grant-in Aid for Scientific Research No. 15253007) designed as the second project to study the paleoceanography of Mid-Cretaceous OAE sequence in Southern France, we have planed to obtain high quality cores from OAE1a and OAE 1b intervals. We have hired a professional company FORACO for this task and have succeeded to recover a 60m core from Goguel (OAE1a) level at 10km north of Barrem … More Village and also 15m cores from Killian (OAE1b) level at St.Andre. These were the first cores ever recovered from these intervals. In order to conduct high-quality analysis for these cores, we have developed new techniques : a technique to fix the whole core by a special type of resin without any disturbance of the fractured portions and a technique of precise micro drilling to obtain samples at one mm intervals.In addition to elaborate non-destructive analysis for the whole cores, various micropaleontological, geochemical and sedimentological analysis has been conducted. As a result of these analysis it is now clear that two types of oceanic conditions existed during the formation of black shales in the OAE1a event : a condition with total water column becoming anoxic resulting a devastation to marine bioshere, and the other in which anoxic water did not reached to photic zone causing a limited effect to marine biota. It is also evident that during the Killian level of OAE1b event four cycles of anoxic fluctuations occurred. The cause of this fluctuations can be deduced to fluctuation of primary production level resulted by changing amount of terrestrial nutrient supply. Less