滇西兰坪盆地上新世古环境分析

Analysis of Paleoenvironment during the Late Pliocene of Lanping Basin,Western Yunnan,China

在对滇西兰坪盆地上新世三营组化石（孢粉、树叶）和沉积分析基础上,探讨了滇西兰坪盆地上新世时期的古环境特征。三营组（N2s）沉积相主要为湖泊相,次为扇三角洲相;在纵向上主体表现为湖泊相—扇三角洲相—湖泊相—扇三角洲相的相序变化。孢粉和植物叶化石研究结果显示高山栎植物为优势种,采用共存因子分析法定量证实兰坪盆地上新世古气候总体凉爽湿润,为山地亚热带季风气候,植被具有明显垂直分带特征,与现在云南地区的植被相似。结合青藏高原隆升及周边气候环境变化推测上新世末期,青藏高原可能经历了一次强烈的构造隆升运动,局部高度可能在2 200~2 500 m。

The characteristics of paleoenvironmental during the Pliocene of Lanping basin, western Yunnan were studied based on sedimentary facies, pollen and plant fossils. The sedimentary facies of the Sanying Formation in the Lanping basin are predominated by lacustrine facied, and supplemented by deltaic facies. The sedimentary facied in longitudinal direction showed conspicuous variation, and its sedimentary facies include lacustrine, deltaic, lacus-trine ,and deltaic. The flora is absolutely dominated by Quercus sect. Heterobalanus, and the climate of the Lanping Basin in the Late Pliocene is cool and humid according to the quantitatively reconstructed by Coexistence Approach Analysis of the flora. It was moist mountain subtropical monsoon climate type, and vegetation has obvious vertical zoning characteristics. It is similar to the modem vegetation in Yunnan area. By the uplift of Qinghai-Tibet Plateau and the surrounding climate change,we speculated that the Qinghai-Tibet Plateau may have experienced an intense tectonic uplift movement in the late Pliocene, and local height may be 2 200 - 2 500 m.