珠江口盆地荔湾凹陷W22井渐新世生物地层研究  

OLIGOCENE BIOSTRATIGRAPHY OF WELL W22 IN THE LIWAN SAG OF THE PEARL RIVER MOUTH BASIN

作　　者：玄昌姬 李前裕[3] 刘传联[3,1] XUAN Changji;LI Qianyu;LIU Chuanlian(CNOOC Ltd-Shenzhen,Shenzhen 518000,China;CNOOC Ltd-Shenhai,Shenzhen 518000,China;State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China)

机构地区：[1]中海石油(中国)有限公司深圳分公司,深圳518000 [2]中海石油深海开发有限公司,深圳518000 [3]同济大学海洋地质国家重点实验室,上海200092

出　　处：《微体古生物学报》2024年第1期45-52,共8页Acta Micropalaeontologica Sinica

基　　金：中国海洋石油集团有限公司“十四五”科技重大项目(KJGG-2022-0102);国家自然科学基金项目(41930536)资助。

摘　　要：通过对珠江口盆地荔湾凹陷超深水井W22井3 266~3 991 m井段72个样品开展有孔虫和钙质超微化石分析,讨论了该层段的地层划分并确定了其年代。研究层位含有丰富的有孔虫和钙质超微化石,详细的生物地层学分析显示其属于渐新世。其中,有孔虫分析发现3 390 m以下为早渐新世P18-P21a带沉积、3 380 m以上为晚渐新世P21b-P22带至N4带下部沉积,显示其地层年代为33-23 Ma;而钙质超微化石分析则揭示出该层位包含了自NP25带底部到NP21带的地层,下渐新统/上渐新统的沉积界限在3 390 m左右, Coccolithus formosus的末现面出现在3 841 m表明钻井3 841 m以深地层年代大于32.92 Ma,但更深地层未发现始新世钙质超微化石,表明底部年龄仍为早渐新世,但推测已经接近渐新世/始新世界限(33.89 Ma)。荔湾凹陷渐新世经历了从陆架浅海到上陆坡半深海环境的演变。Through the analysis of foraminifers and calcareous nannofossils of 72 samples from the interval of 3 266~3 991 m in Well W22 in the Liwan Sag of the Pearl River Mouth Basin, the biostratigraphic subdivision was setup and the age of the studied interval was determined. The planktonic foraminiferal and calcareous nannofossil distributions showed that the age of studied section was Oligocene. The early Oligocene planktonic foraminiferal zone, P18-P21a was deposited below 3 390 m;the lower part of the late Oligocene P21b-P22 zone to the bottom N4 zone was deposited above 3 380 m, with the age of 33-23 Ma. Calcareous nannofossil analysis revealed that this section contained the fossils from the bottom of the NP25 zone to the NP21 zone, with the Lower/Upper Oligocene boundary at 3 390 m. The LO Coccolithus formosus(32.92 Ma) occurred at 3 841 m, indicating that the age of the formation below 3 841 m was older than 32.92 Ma. However, no Eocene calcareous nannofossils have been found in the deeper strata, indicating that the base age is still of early Oligocene, but close to the Oligocene/Eocene boundary(33.89 Ma). The Oligocene of the Liwan Sag underwent an evolution from a shallow shelf to a semi-abyssal environment on the upper slope.

关 键 词：有孔虫 钙质超微化石 生物地层 渐新世 荔湾凹陷 

分 类 号：P618.13[天文地球—矿床学]