Significant mid-latitude aridity in the middle Miocene of East Asia

The East Asian climate history during the Neogene is a complicated and contentious issue, in particular because of its bearing on the development of the East Asian monsoon and Tibetan uplift chronology. Here we present a paleoprecipitation analysis based on mean molar tooth height (hypsodonty) of large herbivorous mammals to investigate the spatial pattern of climate zonation in East Asia during the middle Miocene. We show a generally humid and uniform situation before the late middle Miocene, replaced by a mid-latitude arid belt from the late middle Miocene, into the earlier part of the late Miocene. These findings are concordant with the global phenomena of the middle Miocene climate optimum and the subsequent cooling, and suggest that the predominant climate in East Asia for most of the Miocene was planetary rather than monsoonal. Our results support a late initiation of the East Asian summer monsoon, coincidentally with the beginning of eolian red clay deposition in the later late Miocene at 7–8 Ma.