Abstract: A special biota,consisting of abundant and ender mic microfosils,is named Chinocythere-Bohaidina Biota,which has been fonud from the upper submember in the 4th member of Shahejie formation to Dongying formation in Bohaiwan basin.It is divided into two subbiota and five groups.At the base of 1st member of Shahejie formation.there is an obvious interruption between the two subbiota in the evolution process,which represents the boundary between Eocene and Oligocene.However,placing the boundary at the middle of 2nd member of Shahejie formation should be accepted according to the depositional cycle.

摘要： 渤海湾盆地沙河街组四段上亚段至东营组发育着丰富的、地方性色彩浓烈的微体古生物群——Chinocythere—Bohaidina生物群.根据特征被进一步细分为两个亚群、五个生物小群.两亚群之间在生物群体演化上存在一个明显的间断,该间断反映了始新世与渐新世的界线,其具体位置在沙一段底部.但参考沉积旋回等,其界线可划在沙二段中部.

关键词: 渤海湾盆地, 沙河街组, 东营组, 微古生物学, 始新世, 渐新世, 地质时代确定