羌塘盆地达卓玛剖面古—始新世古生物群特征

Paleocene and Eocene Palaeobiocoenotic feature in the Dazhuoma section at Gangni village of Qiangtang Basin

详细研究了首次发现于羌塘盆地岗尼乡达卓玛剖面下第三系的介形虫、轮藻和保存完好的昆虫化石,建立了3个化石组合。根据这些组合面貌及其分布的主要层位,认为含有丰富生物化石的这套地层的时代应为古—早始新世。

The Dazhuoma section at Gangni village is a welldeveloped one in Qiangtang Basin. It extends along a ditch in Anduo county. Its top and base contect with the fault of Jurassic,with a total thickness of 1 986.08 m.It is composed of darkish purple, greenish grey mudstones, siltymudstone, purplish red thinbedded siltstone and greyish white, greenish grey muddygypsolite and gypsolite, being of lacustrine deposites. They contain not only abundant ostracoda, and charophyta ,but also very wellpreserved insect fossils. Three assemblages can be recognized.Ostracoda occurs mainly in the interval between bed 174 to 249 of middlelower parts of the second member. One assemblage of Sinocypris reticulataLimnocythere cf. hubeiensis is recognized and it is of Early Eocene in age.Charophyta are present mainly in 19 samples from the second member (bed 191～364). They belongs to 7 genera, 8 species and 3 cf. species. One assemblages of Lamprothamnium lanpinensisChara banyueshanensis is recognized.Most fossils in this assemblage are distributed widely in Paleocene and Lower Eocene in the eastern and southern China.The assemblage is of Paleocene and Early Eocene in ages.Insect fossils occur mainly in the lower part of the second member (bed 179～249).They are not only hyghly diversified, and also abundant in individuals.One assemblage of RicaniidaeBlattidae is recognized. It is of Paleogene in age.