西宁盆地谢家剖面车头沟组底部木化石的发现及其意义

The Discovery and Significance of the Fossil Woods in the Bottom of Chetougou Formation in Xiejia Section,Xining Basin

首次在西宁盆地谢家剖面车头沟组底部发现原始埋藏的钙质木化石,不仅填补了植物大化石缺失的历史,同时对研究青藏高原东北部的植物生态环境演化和构造运动具有重要意义。通过对木化石埋藏特征、层位地层岩性和沉积环境的综合分析,认为其为近水河岸生长的成年乔木化石,株距3～8m不等,形成具有一定空间结构的植物群落,后期由于附近山地的隆起和该区气候向干旱化发展,植物遭受掩埋后经过石膏的交代作用进而形成硫酸钙质化石,说明该地区气候从中新世早中期开始恶化加剧。

The original burial fossil woods excavation at the bottom of the Chetougou Formation in Xiejia section, Xining Basin, is not only the first found of the big plant fossil in the arid-semiarid region in NW China, but also greatly significant to research the evolution of plant ecological environment and even the tectonic movement in northeastern Tibetan Plateau. Through the comprehensive analysis of the buried fossil woods characteristics, rock-layer facies and sedimentary environment, we consider that they are adult trees growing near the bank of river, and spacing in the rows ranging from 3-8 meters, which formed the good plant communities with a certain spatial structure. Then, the uplift of the vicinal mountains and the development of arid climate in this area, the plants were buried and the metasomatism with plaster took place, and then formed the calcium sulfate fossil woods, which could show the climate deteriorated in the region since the early-Miocene.