New evidence of the emergence of East Asian monsoon in the early Palaeogene: A palynology perspective from central China

Abstract Earlier palaeoenvironmental reconstructions implied that East Asia climates were dominated by a zonal climate pattern during the Eocene, with an almost latitudinal arid/semiarid band around ~ 30° N paleolatitudes. However, this long-standing model has recently been challenged by growing multidisciplinary evidence. Some previous studies indicated that the middle part of what is now China had was characterized by climatic fluctuations between humid and relatively dry during the Early Eocene, akin to present East Asian monsoon regimes (EAM). Therefore, whether the EAM existed in the Early Eocene has been under much attention and debate in the scientific community. Using palynological assemblages in the Tantou Basin, central China, we quantitatively reconstructed climate changes from the Late Palaeocene to the Early Eocene to better understand climate change in East Asia. The palynological assemblages revealed that the coniferous and broad-leaved mixed forest in this area received no less than 800 mm of annual precipitation and experienced a climate change process from warm and wet to relitively cool and dry. According to palaeoclimate change curves, sudden climate change occurred in the Early Eocene, with mean annual temperature and MAP decreasing by 5.1 ℃ and 214.8 mm, respectively to become very similar to the present climate which controlled by monsoon climate. So, we inferred that this significant climate change during the Early Eocene may signal the emergence of the EAM in East Asia.