Spatiotemporal evolution of Paleogene palynoflora in China and its implication for development of the extensional basins in East China

The delta O-18 values of marine benthic foraminifera indicate a long-term cooling through the middle and late Eocene around the globe. During the same time period, the India-Asia plate collision and the Pacific-Asia plate convergence must have significantly affected East Asia, especially East China. In this context, the evolving pattern of vegetation in East Asia and its controlling factor remains uncertain. In this study, 19 published Paleogene pollen records with independent age control in China were compiled and analyzed. The results indicate that the tropical and subtropical taxa and their percentages increased from the Late Paleocene to the Early Eocene, implying a warming trend in East Asia. From the Middle to the Late Eocene, the tropical and subtropical taxa and their percentages decreased continuously, showing a stepwise cooling. The most dramatic changes in vegetation occurred from the Late Eocene to the Early Oligocene in China, which is characterized by universal increase in coniferous pollen. This evolution trend of palynoflora in China appears well consistent with the delta O-18 curve of marine benthic foraminifera, revealing that global climate made a major contribution to changes in East-Asian vegetation during the Paleogene. It is noteworthy that from the Late Paleocene to the Early Oligocene East China was always wetter than West China so that broadleaf trees could bloom and develop continuously in East China. Influenced by the India-Asia plate collision and the Pacific-Asia plate convergence, the extensional basins in East China developed significantly during the Paleogene, and provided favorable locations and adequate moisture for the continuous development of broadleaf trees in East China. (c) 2012 Elsevier B.V. All rights reserved.