青藏高原晚新生代孢粉组合与古环境演化

对取自沱沱河盆地、通天河盆地、那曲盆地、东温泉盆地、乌郁盆地的新近纪湖相沉积与取自巴斯错、错鄂、纳木错的晚第四纪湖相沉积,进行孢粉分析;结合西宁—民和盆地、伦坡拉盆地、南木林盆地、渭河盆地的孢粉资料,分析青藏及邻区新生代晚期古植被和古环境的演化过程。发现渐新世晚期—中新世早期青藏与周边邻区的古环境发生了显著分异,导致青藏地区热带亚热带植物濒临消亡,与全球温暖气候条件和青藏地区古纬度环境不符,是青藏高原隆升的重要标志。中新世早期—第四纪晚期,青藏高原落叶阔叶林和针叶林呈现总体减少趋势和准周期性波动,与全球气候变化呈良好对应关系。第四纪晚期草本植物含量逐步增高,出现蒿—松—桦为主,针叶林、落叶阔叶林、灌木、草本植物混生的植被景观。

Late Cenozoic environmental evolution of the Qinghai-Tibet Plateau as indicated by the evolution of sporopollen assemblages

Sporopollen was analyzed for samples from Neogene lacustrine sediments of the Tuotuohe, Tongtianhe, Nagqu, East Wenquan and Oiyug basins and Late Quaternary lacustrine sediments of Bas Co, Co Ngoin and Nam Co on the Tibetan Plateau. According to these data together with the sporopollen assemblage data from the Xining-Minhe basin, Lunpola basin, Namlin basin and Weihe basin, the authors analyzed the evolution of the Late Cenozoic paleovegetations and paleoenvironment on the Qinghai-Tibet Plateau and in its adjacent regions and found that vegetation and environment differentiation occurred in the Late Oligocene-Early Miocene in the Qinghai-Tibet region and its surrounding regions, resulting in rapid decrease and gradual disappearance of tropical-subtropical plants in the Qinghai-Tibet region. Such a change of vegetation did not coincide with the global warm climate and lower paleolatitudes of the Qinghai-Tibet region in the Late Oligocene-Early Miocene, and the extinction of tropical-subtropical plants indicates that the Qinghai-Tibet Plateau was uplifted in the Early Miocene. The broad-leaf and needle-leaf plants on the plateau showed a trend of general decrease and quasi-periodical fluctuations from the Early Miocene to Late Quaternary, which corresponded well with the global climate changes. In the Late Quaternary herbaceous plants increased gradually, leading to the appearance of the vegetation landscape of mixed needle-leaf plants, broad-leaf plants, shrubs and herbaceous plants dominated by Artemisia, Pinus and Betula on the Tibetan Plateau in the Late Pleistocene and Early Holocene.