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

本课题组（组长：Hisatake Okada）于1999年利用科学研究资助（No. 11691113）在法国南部开展了实地调查和抽样项目。该项目被设计为IODP（综合海洋钻探计划）的主要目标之一“极端气候下的古环境”的前期研究。团队对中白垩纪暖事件OAE1b层段进行了广泛的研究，获得了含Paquier层段的块状柱状剖面，并在OAE1b层段上部进行了多次试钻。作为法国南部中白垩世OAE层序古海洋学研究的第二个新课题（科研资助项目No. 15253007），我们计划获得OAE1a和OAE 1b层序的高质量岩心。我们聘请了一家专业公司FORACO来完成这项任务，并成功地从Barrem…More村以北10公里处的Goguel （OAE1a）层回收了6000万岩芯，从St.Andre的Killian （OAE1b）层回收了1500万岩芯。这是在这些地层中发现的第一批岩心。为了对这些岩心进行高质量的分析，我们开发了新的技术：一种用特殊类型的树脂固定整个岩心而不干扰断裂部分的技术，以及一种精确的微钻技术，以每隔一毫米的间隔获得样品。除了对整个岩心进行详细的无损分析外，还进行了各种微古生物学、地球化学和沉积学分析。通过这些分析，现在可以清楚地看到，在OAE1a事件中黑色页岩形成过程中存在两种海洋条件：一种是全水柱缺氧，对海洋生物圈造成破坏的条件；另一种是缺氧水没有达到光带，对海洋生物群造成有限影响的条件。同样明显的是，在基利安OAE1b水平事件期间，发生了四个缺氧波动周期。这种波动的原因可以归结为陆地养分供给量的变化导致初级生产水平的波动。少

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