摘要
西宁-民和盆地上第三系十分发育,皆为中新统陆相红层。该统自下而上划分为谢家组、车头沟组、咸水河组和“临夏组”,每组分为二个岩性段。含哺乳动物化石28属37种,介形虫化石15属43种,轮藻化石7属10种及3个孢粉组合;最大出露厚度1595.85m。该统与渐新统马哈拉沟组整合接触,其上被第四系不整合覆盖。哺乳动物呈草原型鼠兔类为主→草原型鼠类与森林型长鼻类、鹿类混生→森林型长鼻类等大量出现并伴生鼠兔类→草原型三趾马动物群的群体演化特征。介形虫为古中国大陆生物区中新世常见属种,轮藻为我国第三纪常见组合;孢粉为草原—森林型组合。
Neogene System,all of which is composed of terrestrial facies red beds of Miocene Se-ries,is widespreaded over Xining-Minhe basin,occupying about 25% of the total area,with a maxi-mum recorded thicknees of 1595.85m.The red beds of Miocene series can be divided into four formations(from the bottom to the top),i.e.Xiejia,Chetogou,Xianshuihe,Linxia Formations;each formation can be subdivided into two litho-logic members.The fossils containing in Miocene Series have been identified as follows:Mammalia 28genera,37 species;Ostracodes 15 genera,43 species;Charophyte 7 genera,10 species;and 3 sporo-pollen assemblages,etc..The Miocene Series is in a conformable contact with Mahalagou Formation of Oligocene Seriesdownwards and underlies unconformably Qraternary System.The evolution trend of the Mammaliathere is manifested evidently in following sequence:grass Ochotona—as main order—grass Ochotonamixed with forest Proboscidea and Cervus—abnundant forest Probooscidea companied with Ochotonagrass Hipparion fauna.The genera and species of Ostracoda are common in the biocommunity ofPalaeo-China Continent in Miocene Epoch times.The Charophyte assemblage can be found freqently inTertiary System in China.The Sporopollen is a grass-forest assemblage.Because of abundant fossils,clear Stratigraphic sequence and contact relation,the studied area should be taken as an important placeto study the Miocene Series in Chine.
关键词
地层
第三纪
层序
化石
动物化石
Miocene Series sequence Mammalian fossil Xining-Minhe basin
