Early Eocene southern China dominated by desert: Evidence from a palynological record of the Hengyang Basin, Hunan Province

The India–Asia collision and subsequent uplift of the Tibetan Plateau during the Cenozoic were the main drivers of Asian monsoon development and evolution. However, the climate and possible existence of a desert landscape in southern China prior to the significant uplift of the Tibetan Plateau remain uncertain, because of a lack of reliable proxies or direct geological evidence. The well–preserved early Eocene palynomorphs recovered from the Hengyang Basin, southern China, provide an ideal opportunity to address this problem. The palynological record suggests that the Hengyang Basin was dominated by xerophytic shrubs and an open forest vegetation landscape, confirming that a typical arid desert environment prevailed in the Hengyang Basin during the early Eocene. The high proportion of thermophilic and xerophytic taxa implies a hot and arid climate. The estimated mean annual precipitation (