南海南部中布容期颗石藻化石记录及其意义

COCCOLITH RECORDS AND THEIR MEANINGS FOR THE MID-BRUNHES INTERVAL IN THE SOUTHERN SOUTH CHINA SEA

对南海南部ODP1143站750ka以来的颗石藻化石进行了属种鉴定及百分含量分析,结果显示,在480～260ka的中布容期,Florisphaera profunda百分含量降低,而Gephyrocapsa caribbeanica等桥石类繁盛。同时,这一时期的海水结构发生改变,营养跃层变浅,海水表层生产力增加。研究发现,中布容时期为地球偏心率低值时期;而偏心率值最小时,最适宜颗石藻生长。因此,可以推测这一时期颗石藻群落发生的变化在很大程度上受到地球偏心率的影响。同时,中布容期大洋碳储库发生重大变化,也可能与偏心率引起的大洋浮游植物群落变化有关。

Coceolith species and percentage analysis for the past 750 ka from ODP Site 1143 of the southern South China Sea has been carried out. The results show that in the mid-Brunhes interval （4804260 ka）, the percentage of Florisphaera profunda declined as Gephyrocapsa caribbeanica was booming. Meanwhile, the structure of the sea water has changed, the nutricline depth decreased, and the primary productivity increased. Studies show that during the mid-Brunhes interval, the eccentricity was in a low levels. As the low eccentricity favours the cocoolith growth, it can be detected that the great change in coccolith community is mainly influenced by the eccentricity. Also, the change of the ocean carbon reservoir during the mid-Brunhes interval can be the result of the eccentricity-trigged-booming of the different phytoplank ton communities.