Pollen-based Miocene vegetation history from the Fotan Formation, SE China and its palaeoclimatic and palaeoenvironmental significances

The Middle Miocene Zhangpu biota (similar to 14.7 Ma)-from the Fotan Formation in the Zhangpu area, southeastern China-indicates that the rainforest had reached at least 24.2 degrees N at that time. In this study, pollen analysis was carried out in six outcrop sections of this formation in the Zhangpu area. Based on the succession of palynoflora, three developmental stages of vegetation were recognized. From the late Early Miocene to the Middle Miocene Climatic Optimum (MMCO) (the first stage), the vegetation underwent frequent disturbances associated with the volcanic activities, in which two sub-stages are recognizable. During the earlier sub-stage (late Early Miocene), the vegetation was similar to the modern subtropical evergreen broad-leaved forest and exhibited a warming trend; then during the later sub-stage (MMCO), the tropical forest developed with the appearance of diverse tropical and subtropical taxa. The second stage, which was also within the MMCO, should be an intermission of volcanic eruptions, during which the tropical forest, especially the tropical montane rain forest, steadily developed without disruptions. And during the third stage (Middle to Late Miocene), the altitudinal vegetation belts of tropical montane rain forest significantly lowered which was accompanied by the occurrence of drought-tolerant taxa, implying the significant climatic cooling and moisture reduction. The above evolutionary phases of the vegetation in the Zhangpu area show a close relationship with the Miocene global climatic variations, which might be the main driving force of the vegetation changes in the southeast coast area of China during that period.