ヒマラヤ山脈のテクトニクスと東アジアの古環境・古気候の変動

抄録

The Indian subcontinent and Asian continent first contacted in the late Cretaceous (about 65Ma) and strongly collided after 52 Ma that is evidenced by slowed northward motion of the Indian Subcontinent from 18-20cm/yr to 4.5cm/yr. Although the first record of uplift in Himalayan regions has been recorded during the Eocene, major uplifts of the Himalayan Range and Tibetan Plateau and the subsequent sediment supply started from the Oligocene through Miocene. Particularly, the rapid uplift stages of Himalayan-Tibetan regions have been recognized, at least, around 8Ma and the last 1Ma based on sedimentological and paleonbotanical studies of marine and terrestrial sequences. The micropaleontological studies in marine sequences revealed that the increased elevations in the Himalayan-Tibetan regions forced a strong monsoonal circulation about 8 Ma, which produced intense upwelling around the Arabian Sea and more seasonal climate changes of terrestrial sequences around the southern Asia. The hypothesis that uplift of plateaus and mountains caused large-scale climate changes during the Cenozoic is still unknown. However, an enhanced chemical weathering due to tectonic uplift in the Himalayan-Tibetan regions may be explained as the active driving force of the Cenozoic global cooling at the beginning of 50 Ma.