南海北部琼东南盆地BD19-2-2井中新世钙质超微生物地层及沉积环境

MIOCENE CALCAREOUS NANNOFOSSIL STRATIGRAPHY AND PALAEOENVIRONMENT OF THE BD19-2-2 WELL IN THE QIONGDONGNAN BASIN,NORTHERN SOUTH CHINA SEA

对南海北部琼东南盆地BD19-2-2井中新世地层中的钙质超微进行了定量和半定量分析,发现井段上部1800~2550m地层化石较丰富,而下部2574~3100m化石丰度及分异度明显降低;根据钙质超微化石标志种的存在,对该井的生物地层进行了划分,在1800~3100m井段地层中识别出9个钙质超微化石带或联合化石带,地层时代为早中新世至晚中新世,同时探讨了钙质超微划分下中新统-中中新统、中中新统-上中新统界线的化石标志。依据钙质超微化石总丰度、分异度及特征性环境指示种丰度的逐渐变化,确认BD19-2-2井从早中新世至晚中新世经历了4个沉积环境演化阶段,海水深度由浅变深,海水变暖。

Calcareous nannofossils in Well BD19-2-2,Qiongdongnan Basin,northern South China Sea,were analyzed in this study.Calcareous nannofossils are abundant in the upper part of the Well（1800~2550m）,whereas the lower part（2574~3100 m）is depauperate in fossils.Nine calcareous nannofossil zones or assemblage zones are recognized on the basis of index fossils.Biozonal fossils defining the lowermiddle Miocene and middle-upper Miocene boundaries are discussed.On the basis of calcareous nannofossil abundance,diversity and association,the early-late Miocene depesitional and paleoenvironmental history of the northern South China Sea is discussed in detail.