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通过对青海省循化县积石镇羊圈贡拜村-西沟中新统-上新统实测剖面中介形类动物群的研究,在其中的35个层位样品中发现含介形类化石7属32种,并建立了两个组合:(1)Candona-Candoniella组合;(2)Ilyocypris-Candoniella-Candona组合。依据介形类组合带,将咸水河组上部时代厘定为中新世中期,而临夏组时代厘定为中新世晚期-上新世早期。根据介形类动物群在剖面上的分布规律,自下而上建立5个生态组合:(1)Candona-Can-doniella生态组合;(2)Ilyocypris errabundis-Ilyocypris dunschanensis生态组合;(3)Candona-Candoniella生态组合;(4)Ilyocypris biplicata-Candoniella生态组合;(5)Candonaoppressa-Candona exti ma生态组合。通过对介形类生态组合进行详细的生态特征分析,结合磁性年代学数据,将循化盆地14.6-5Ma的古气候划分为5个阶段:(1)14.6-9.5Ma为凉干期;(2)9.5-9.38Ma为热干期;(3)9.38-6.88Ma为冷干期;(4)6.88-6.83Ma为温干期;(5)6.83-5Ma为凉干期。
Based on the study of the Mesozoic faunas in the Gongpiyun-Gonggou-Yanggou survey section of Yangquan, Jishu, Xunhua County, Qinghai Province, in the 35 samples of these strata, 7 genera and 32 species, and established two combinations: (1) Candona-Candoniella combination; (2) Ilyocypris-Candoniella-Candona combination. Based on the Mesozoic belt, the upper age of the Xiushuihe Formation was determined as the mid-Miocene, while the Linxia Formation was determined as the late Miocene-Early Pliocene. According to the distribution pattern of the ostracods in the cross section, five ecological combinations were established from bottom to top: (1) Candona-Can-doniella ecological combination; (2) ecological combination of Ilyocypris errabundis-Ilyocypris dunschanensis; (3) Candona- Candoniella ecological combination; (4) Ilyocypris biplicata-Candoniella ecological combination; (5) Candonaoppressa-Candona exti ma ecological combination. By analyzing the ecologic characteristics of the ostracod assemblages in detail and combining with the geochronological data, the paleoclimate of 14.6-5 Ma in the Xunhua Basin is divided into five stages: (1) 14.6-9.5Ma is the dry period; (2) ) 9.5-9.38Ma for the dry period; (3) 9.38-6.88Ma for the dry period; (4) 6.88-6.83Ma for the dry period; (5) 6.83-5Ma for the dry period.