论南海中、南部表层沉积物中的钙质超微化石

Characteristics of the Calcareous Nannofossil in the Sea-bottom Sediments of the Center and Southern South China Sea

本文共分析了南海中南部8°～12°N,108°40′～114°E范围内175个表层沉积物样品。通过对比研究钙质超微化石丰度变化和分布特征,对影响该区表层沉积中钙质超微化石丰度和绝对属种丰度变化的因素进行了探讨。随着水深由浅至深逐渐增大,本区钙质超微化石丰度和绝对属种的丰度均有从低到高、然后再降低的变化趋势。丰度急剧减少的区间为水深2700～2800 m。钙质超微化石分布可分为四个不同的区域:陆架区、陆坡区、岛礁区和深海盆区,各区域的钙质超微化石的丰度和属种数都有很大区别。影响表层沉积物中钙质超微化石的丰度变化和分布特征的主要因素有深水碳酸钙溶解作用、陆源物质稀释作用、浮游生物生产率和岛礁区环境变化。由于从湄公河搬运而来的陆源物质的稀释作用,陆架区钙质超微化石丰度相对较低;因海水深度和环境适宜,浮游生物的生产率高,陆坡区钙质超微化石的丰度高,属种数也高;岛礁区钙质超微化石丰度达到极大值,但是其属种数与陆坡区相比却低得多;海盆深水区钙质超微化石丰度低值与深海碳酸盐溶解作用有关。

This study is based on the analysis of 175 samples obtained from the sea-bottom sediments in8°～12°N,108°40′～114°E, the center and southern of the South China Sea. A preliminary acquaintanceship and discussion of calcareous nannofossil abundance, main genera and species, distribution, and their controlling factors is presented in this paper. The abundance of calcareous nannofossil and the dominant species numbers increase and then decrease with the change of water depth from shallow to deep. In the depth of 2700-2800m, the nannofossil abundance decreases rapidly. There is a great differentiation of the abundance and species numbers of calcareous nannofossil in the shelf, slope, coral reefs area and deep-water basin and the main factors impacting the nannofossil abundance, distribution, and so on are carbonate dissolution, dilution by terrigenous material, plankton productivity and the environment of coral reefs. The lower content of calcareous nannofossil and genera and species in shelf are induced by the dilution of the terrigenous material transported by Meigong River. Contrast, the higher content of calcareous nannofossil and genera and species in slope and coral reefs area are resulted from the high plankton productivity and good environment. However, the highest content of calcareous nannofossil occurs in coral reefs area but its genera and species numbers are fewer than in slope. The carbonate dissolution is responsible for the lowest content of nannofossil abundance in deepwater basin.