Mid-Late Miocene vegetation and environments in Southeast China: Insights from a marine palynological record in northwestern Taiwan

Taiwan Island represents the exposed accretionary prism developed by eastward subduction of South China Sea (SCS) oceanic lithosphere beneath the Philippine Sea Plate since the middle Miocene. There are many well-documented data about the biostratigraphic correlation, except for palynological studies. Here, we present a new palynological record of mid-Late Miocene deposits from the Chuhuangkeng section, Miaoli, northwestern Taiwan, which reveals a vegetation and paleoelevation reconstruction in Southeast China, during the Middle to Late Miocene, corresponding to the time interval of about 14.5-5.5 Ma. Most samples yielded well-preserved palynomorphs, and the palynological results suggest that the dominant vegetation was the mixed coniferous-broadleaved forests in the Coastal Mountains of Southeast China (CMSC) during the Mid-Late Miocene. Moreover, based on large amounts of Tsuga and Picea pollen, we hypothesized that a subalpine conifer forest then flourished in the CMSC, and the estimated maximum paleoelevation might be up to ∼3000 m above sea level (a.s.l.) during the Mid-Late Miocene, being 1000-1500 m higher than today. These findings offer a new perspective to comprehend the paleotopographic evolution of China and the source area of Taiwan's spruce forests. Additionally, the high abundance of Pinus, Tsuga, Picea pollen and fern spores also suggests an enhancement of the EASM during the Mid-Late Miocene.