摘要
昆2井是柴达木盆地北部昆特依凹陷区潜伏Ⅰ号构造上的第一口勘探井,为了建立该地区地层层序,对该井的岩屑及岩芯样品进行了系统的微体古生物学研究,仅在下干柴沟组发现少量轮藻化石和零星的介形类化石。下干柴沟组下段出现的轮藻类Gyrogona qianjiangica和Lamprothamnium? brevis是我国中始新世最常见的化石。该层段的轮藻类可命名为Gyrogona qianjiangica-Lamprothamniumcurta-L. brevis组合,时代为中、晚始新世。本文以Gyrogona qianjiangica分布的顶、底界作为昆2井下干柴沟组下段的标志,划分结果与其它轮藻及介形类化石的对比结果基本一致。氯离子含量分布显示,轮藻类化石产出的下干柴沟组是整个地层剖面中含盐度最低的沉积阶段,表明下干柴沟组沉积时期,该地区处于水域比较广阔的淡水湖泊环境,但在个别层段出现咸化环境,产出以喜盐的Austrocypris为代表的介形类化石。
Well Kun 2 is the first exploration well in the Burial Structure Ⅰof the Kunteyi Depression on the northern margin of the Qaidam Basin. A systematic micropaleontology study on cuttings and rock core of the well has been done to build the stratigraphic sequence for the area, but only a few eharophytes and sporadic ostracod fossils were found from the lower Ganchaigou Formation. Gyrogona qianjiangica and Lamprothamnium？ brevis which appear in the lower member of the Lower Ganehaigou Formation are the most familiar Middle Eocene charophyte fossils in China. These charophytes in the section is included in the Gyrogona qianjiangica-Lamprothamnium curta-L. ？ brevis Assemblage of the Middle and Late Eocene. The distribution boundary of Gyrogona qianjiangica is considered as the same as for the lower member of the Lower Ganchaigou Formation, consistent with the correlation by other charophyte and ostracod fossils. The low contents of chloric ion show that the Lower Ganchaigou Formation, indicative of the lowest salinity stage, suggest that the area was a capacious fresh water lake in the sedimentary period of Lower Ganchaigou Formation. However, many halophilous ostracod fossils such as Austrocyprls were found in some section, and indicate salt water environments.
出处
《微体古生物学报》
CSCD
北大核心
2007年第1期82-88,共7页
Acta Micropalaeontologica Sinica
基金
中国科学院科技支青工程项目"构造岩性油气藏预测技术及其在柴西南地区的应用"(编号:2006-06)资助。
关键词
轮藻组合
介形类
始新统
下干柴沟组
柴达木盆地
charophyte assemblage, ostracodes, Eocene, Lower Ganchaigou Formation, Qaidam Basin
