吉隆盆地中中新世以来孢粉组合及古环境演化

Palynological assemblages and paleoenvironmental evolution in the Gyirong Basin since Middle Miocene

喜马拉雅造山带是印度与欧亚大陆碰撞的产物,其形成和演化历史一直以来都是地球科学和生命科学研究的焦点。山脉北坡沿藏南拆离断层分布的晚新生代河湖相沉积盆地记录了造山带演化和古环境信息。本研究对喜马拉雅中段吉隆盆地旦增竹康组、沃马组和贡巴组开展孢粉学分析,借此探讨盆地沉积地层的时代、喜马拉雅隆升过程及其环境效应。依据孢粉组合将盆地内的旦增竹康组的沉积时代修订为中中新世。此外,该孢粉组合还指示吉隆盆地植被从中中新世的针阔叶混交林转变为晚中新世的疏林草地,在晚中新世晚期至上新世演化为高山草甸,并在早更新世形成现今的高山灌丛和草甸。吉隆盆地自中中新世开始沉积以来古高程就与现今较为接近,在旦增竹康组和沃马组沉积期间,海拔抬升并不显著。

The formation and evolution of the Himalaya orogeny,resulted from the collision between the Indian and Eurasian plates,has long captivated researchers in earth and life sciences.Late Cenozoic fluvio-lacustrine sedimentary basins,distributed along the Southern Tibet Detachment System on the northern slope of the Himalaya,have documented the evolution of the orogeny and paleoenvironmental changes.This study presents palynological analysis on the Danzengzhukang Formation,Woma Formation and Gongba Formation in the Gyirong Basin in the central Himalaya,to explore the sedimentary stratigraphy of the basin and the processes of Himalaya uplift and environmental effects.Based on palynological analysis,the deposition age of the Danzengzhukang Formation is revised to the Middle Miocene.Palynological assemblages reveal that since Middle Miocene,vegetation in the Gyirong Basin has transitioned from a mixed coniferous and broad-leaved forest to sparse woodlands and grasslands in Late Miocene.Subsequently,during the late Late Miocene and Pliocene,it evolved into alpine meadows,eventually forming the present-day alpine shrub and meadow vegetation since the Early Pleistocene.Paleoelevation analysis results indicate that the elevation of the Gyirong Basin has remained relatively similar to the present elevation since Middle Miocene,with no significant uplift during the deposition of the Danzengzhukang Formation and Woma Formation.