南海北部4万年以来有机碳和碳酸盐含量变化及古海洋学意义

THE CHARACTERIZATIONS AND PALEOCEANOGRAPHIC SIGNIFICANCES OF ORGANIC AND INORGANIC CARBON IN NORTHERN SOUTH CHINA SEA DURING PAST 40 KA

  • 摘要: 南海北部陆坡的17937柱状样上部4万年来有机碳和碳酸盐的含量分布特征显示:有机碳含量总体显示出冰期高、间冰期低的特征,碳酸盐则相反。C/N元素比分布范围和二组分分析说明该站位的有机碳以海洋自生有机碳为主,全新世达80%以上。根据海洋沉积物中总有机碳含量和两类不同来源有机碳所占比例计算得出的海洋自生生物产生的有机碳含量在MIS2时期最高,说明末次冰期海洋生产力提高。冰期冬季风强化,海水混合程度加强,营养物质利用更充分以及陆源输入增多导致营养物质增加。碳酸盐含量主要受陆源物质稀释的影响,为"大西洋型"旋回。碳酸盐旋回在全新世早中期存在低碳酸钙事件,可能与该时期的强降雨冲刷所致陆源稀释作用增强、海水溶解作用增强以及海洋表层生产力的降低等综合作用相关。

     

    Abstract: The content of total organic carbon (TOC) and inorganic carbon during the past 40 ka were measured in core 17937 from the northern slope of South China Sea. The results showed that the TOC ex-hibited higher values in glacial period than in interglacial periods, but with reverse pattern for the carbon-ate content. The element ratio of C/N and two components formula analysis indicate that the TOC in the studied area is mainly from the aboriginal organisms, with a relative percent over 80G in Holocene. Calcu-lation from the TOC and the relative percent of the two kinds inputs implied TOC content of the marine or-ganisms was higher in MIS2, indicating higher marine productivity during the last glacial due to the en-hanced nutrition supply by the improved water deep-mixing by strengthened winter monsoon and increased terrigenous inputs. Carbonate content in the area was characterized by "Atlantic Style" by terrigenous sed-iment dilution and a low carbonate event was found during early-middle Holocene which may be the inte-grated result of rapid land dilution, strong carbonate dissolution and lower marine primary productivity.

     

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