No monsoon-dominated climate in northern subtropical Asia before 35 Ma

Different from the ITCZ-driven global tropical monsoon, the development of a monsoon-dominated climate within previously subtropical arid Asia has conventionally been regarded as marking the onset of a modern-like monsoon over East Asia. This monsoon has increasingly been reported as having appeared in the Eocene or older and linking with different forcings. Here we present robust climatic records from well-dated fluviolacustrine sediments from the eastern central Tibetan Plateau which demonstrate that such a monsoon was not established in the northern subtropical area (∼32-33oN) until at least ∼35 Ma, rather a Mediterranean-type-like climate toward drier prevailed. Numerical modelling supports that neither the existence of an Andes-like Gangdese Mts. along Tibet southern margin, nor an elevated south-central Tibet, nor an increased atmospheric CO2 concentration, were sufficient to drive the expansion of the Asian tropical monsoon northward to ∼32oN in Asia in the Eocene. •The Paleogene succession on the eastern central Tibetan Plateau was determined at ∼53–35 Ma.•Asian monsoon did not expand to northern subtropical East Asia before 35 Ma.•Forcing factor for late Eocene monsoon could not enhance monsoon to expand to northern subtropics.