南海珠江口盆地F2井中新世钙质超微化石生物地层及沉积环境

MIOCENE CALCAREOUS NANNOFOSSIL STRATIGRAPHY AND PALAEOENVIRONMENT OF WELL F2 IN THE PEARL RIVER MOUTH BASIN

提要本次工作对南海北部珠江口盆地F2井824~1 715 m井段90个样品进行了钙质超微化石分析,共鉴定10属34种。在上部824~1 095 m井段,钙质超微化石较为丰富;而中部和下部1 095~1 715 m井段,化石丰度相对较低或未发现化石。根据钙质超微化石标志性物种的存在,对该井的生物地层进行了详细划分,识别出NN11、NN10、NN9、NN8、NN7、NN6、NN5、NN4等8个钙质超微化石带,将824~1 715 m的地层时代划分为中新世。通过钙质超微化石的总丰度、分异度以及特征性环境指示种的丰度变化,F2井从早中新世至晚中新世经历了三个主要的沉积环境演化阶段,分别为浅海内陆架-滨海、滨海和浅海内陆架-中陆架。

This study presents a comprehensive analysis of calcareous nannofossils from the Miocene strata of Well F2 in the Lufeng Sag,Pearl River Mouth Basin,located in the northern South China Sea.A total of 90 samples were examined from the 824 to 1715-meter depth interval,yielding a diverse assemblage of 10 genera and 34 species.Nannofossils are notably abundant in the upper section of the well(824~1095 m),with a decrease in abundance or complete absence in the lower part(1095~1715 m).Eight calcareous nannofossil zones,namely NN11,NN10,NN9,NN8,NN7,NN6,NN5 and NN4,were identified based on the presence of marker species,confirming a Miocene stratigraphic age.This study further investigates the depositional and palaeoenvironmental history by examining the abundance,diversity,and assemblage characteristics of the nannofossils.From the early Miocene to the late Miocene,well F2 experienced three stages of depositional environment evolution:inner shelf-coastal,coastal,and inner–middle shelf environments.