柴达木盆地三湖坳陷肥胖真星介(Eucypris in flata)向东南扩展200km的控制因素  

THE INVASION SOUTHEASTWARD OF EUCYPRIS INFLATA BY 200KM IN THE SAN HU DEPRESSION OF THE QAIDAM BASIN,NW CHINA AND ITS CONTROL FACTORS

作　　者：孙镇城[1] 孙乃达[1] 乔子真[2] 曹丽[2] 路艳丽[2] 张海泉[2] 景民昌[1] 

机构地区：[1]中国石油大学(北京)资源与信息学院,北京102200 [2]青海油田公司石油勘探开发研究院,敦煌736202

出　　处：《微体古生物学报》2008年第2期113-124,共12页Acta Micropalaeontologica Sinica

摘　　要：距今200万年以前,柴达木盆地三湖坳陷为富含介形类、腹足类等水生生物群的淡水—半咸水湖泊。距今约200万年以来,柴达木盆地马海—大红沟凸起的隆升,阻挡了祁连山水系进入三湖坳陷的北斜坡地区。由于该区湖水急剧咸化,多盐—高盐水介形类肥胖真星介(Eucypris inflata)从柴达木盆地西部向东南舌进200km,替代了该地区原先丰富的淡水—微咸水介形类动物群。然而,肥胖真星介未能进入达布逊湖以东和三湖以南的富含淡水—半咸水介形类高分异度种群区。距今约150万年以来,湖水进一步咸化,介形类动物群无法在高度咸化的水体中生存,肥胖真星介在北斜坡地区绝迹。此时的沉积物中频繁出现石膏晶片和石膏层。论文展示了构造活动控制生物群分布的实例。柴达木盆地生物成因天然气起源于富含淡—半咸水介形类动物群的湖相泥岩——烃源岩。地质勘探家的首要任务是圈定生物成因气源岩区。淡水—半咸水介形类动物群分布范围的圈定对生物成因天然气勘探具有重要作用。Before 2 Ma B P, San Hu Depression was a fresh-brackish lake in Qaidam Basin with abundant ostraeoda and gastropoda. Since 2 Ma B P, the Mahai-Dahonggou Uplift has risen and blocked the water system entering the Northern Slope area of the San Hu Depression from the Qi Lian Mountains, which resulted in a quick salting of lake water. The polyhaline-hyperhaline water Ostracoda Eucypris inflata migrated 200 km to the southeast from the west of the Qaidam Basin and replaced the original abundant fresh-brackish Ostracoda fauna in this region. However, Eucypris inflata was not able to migrate to the areas east of the Dabusun Lake or south of the San Hu, where the fresh-brackish Ostracoda fauna had high species diversity. Since 1.5 Ma B P, the lake water had turned more salty, Ostracoda fauna could not live in the highly salted water and Eucypris inflata vanished in the Northern Slope area, where the gypsumtwin and gypseum bed are often appeared in the deposition. This paper shows an example of how tectonic activities control the distribution of the fauna. The biogenic gas in the Qaidam Basin was originated from a lacustrine mud source bed with rich in fresh-brackish Ostracoda fauna. Defining the distribution of fresh-brackish ostracoda aquatic fauna plays an important role in searching for biogenie gas.

关 键 词：介形类 盐湖 生物气 天然气勘探 柴达木盆地 

分 类 号：P618.13[天文地球—矿床学]