苏北-南黄海盆地白垩纪-古近纪淡水有孔虫的发现及其意义  

Discovery and significance of Cretaceous-Paleogene freshwater foraminifera in Subei-South Yellow Sea Basin

作　　者：刘玉瑞[1] LIU Yurui(Scientific and Technical-Equipment Department,SINOPEC Jiangsu Oilfield Company,Yangzhou,Jiangsu 225009,China)

机构地区：[1]中国石化江苏油田分公司科技装备处,江苏扬州225009

出　　处：《石油实验地质》2021年第1期1-13,95,共14页Petroleum Geology & Experiment

基　　金：中国石油化工股份有限公司项目“高邮凹陷断裂体系控藏机理及有利区带研究”(P19027-3)资助。

摘　　要：前人认为苏北-南黄海盆地泰二段、阜二段和阜四段所含的有孔虫等“海相”化石为海侵带来的生物和湖水咸化的生物。但研究发现,有孔虫多不在上述层段;“海相”化石不集中出现,围岩不含膏盐;古气候、古水文不支持湖水咸化。经地层对比证实,97枚有孔虫产自4个新层系,其余3枚在阜二段。海侵源头古东海洋不存在,无海相化石,各门“海相”生物为可生活在淡水中的广盐性分子;晚白垩世-古近纪,湖侵期古气候湿润、古湖泊水深,水域无法咸化;海绿石、磷灰石和微量元素等无法区分海、陆相;不同的广盐性生物多单独繁盛,并与大量的淡水生物共生,围岩相带无膏盐。据此认为,本区各门广盐性生物为淡水古生态,有孔虫在淡水环境可生存,3期区域湖侵不存在湖水咸化现象;中国中-新生代陆相盆地大规模优质烃源岩主要是淡水湖泊沉积的,可提供极其丰富的油气资源。In previous studies,the“marine facies”fossils in the second member of Taizhou Formation and the second and fourth members of Funing Formation of the Subei-South Yellow Sea Basin were generally considered to be organisms associated with transgression and organisms that lived in saline lakes.However,after reviewing the data,this theory proved to be wrong:most of the foraminifera do not exist in the above mentioned members.The distributions of“marine facies”fossils are not concentrated,and the surrounding rocks do not contain gypsumsalt.The evidence of paleoclimate and paleohydrology is also contrary to lake salinization theory.Formation comparison results show that 97 foraminifera are from 4 new strata,and the remaining 3 are in the second member of Funing Formation.The source of transgression,the ancient East China Sea,does not exist,and there are no marine fossils here.The“marine facies”fossils found here are all euryhaline organisms that can also live in fresh water.During the Late Cretaceous-Paleocene lake invasion period,the ancient climate was humid and the ancient lake was deep,and the water could not be salinized.Glauconite,apatite and trace elements cannot be used as a criterion for distinguishing between marine and terrestrial facies.Different types of euryhaline organisms are usually flourishing separately,and coexist with a large number of freshwater organisms;meanwhile,the surrounding rocks do not contain gypsumsalt.According to the evidence above,the euryhaline organisms in this area are interpreted to live in freshwater,since foraminifera can live in a freshwater environment,and there was no water salinization in the three stages,of regional lake invasion.The large scale,high quality source rocks in Mesozoic-Cenozoic terrestrial basins in China are mainly freshwater lacustrine sediments,which can provide rich oil and gas resources.

关 键 词：有孔虫 非海相化石 淡水环境 白垩纪 古近纪 淡水烃源岩 苏北-南黄海盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探]