ケニア地溝帯におけるヒト誕生前後の環境変遷史を如何にして解読するのか?

We are now carrying out an international project investigating the theme：“The Neogene history of environmental change in the Kenya Rift：contribution to evolution from ape to early hominid”．In this paper，we first review earth science and paleo-primatology in the East African Rift System，mainly the Kenya Rift．We then outline the main components of the project，which comprise：（1）Detailed geological mapping and stratigraphy of the Nachola-Samburu Hills，Nakali and Tugen Hills areas，where middle to latest Miocene beds yielding very important hominoid and hominid fossils are distributed．（2）Research on middle Miocene flood volcanism in the entire Kenya rift；spanning age determination，petrological and volcanological characteristics，and estimation of influence on earth- and bio- environments．（3）Radiometric ages，paleomagnetic stratigraphy and biostratigraphy of the middle to latest Miocene beds．（4）Investigation of sedimentary processes in the rift，as related to rift dynamics．（5）Deciphering the history of environmental change，using mammal fossils．（6）Comparative geochemical studies of modern lacustrine and terrestrial sediments，and sedimentary rocks deposited between 5 and 16 Ma．（7）Proposal for seismic research and drilling of 2000m ofstrata spanning 16 Ma，as representative ofthe Kenya rift basin．Geological，geochronological，paleontological and geochemical studies would be made of the drill core．（8）Deciphering the history of environmental change from 16 to 5 Ma，based on synthesis of the above research．