早中新世以来南海北部陆坡古生产力的碳酸盐和生物成因Ba元素记录

通过对南海北部ODP1148站岩芯454．8mcd以上（约23．2Ma以来）的175个沉积物样品中CaCO3以及生物成因Ba含量变化的研究，并结合初期对ODP1148站岩芯分析的一些相关地球化学组成结果，探讨了碳酸盐、生物成因Ba作为海洋古生产力指标的影响因素，以及早中新世以来南海北部陆坡古生产力的变化特征。结果显示，除中新世早期（23～21．4Ma）以外，生物成因Ba与CaCO3含量和沉积速率变化有很好的相关性，反映南海北部古生产力变化波动较大。对钻孔中生物成因Ba的研究表明，在沉积埋葬以及埋葬后的保存过程中（特别是在320mcd以下）。生物成因Ba会在少氧或缺氧环境下发生还原反应而迁移，影响了它在古环境研究当中的作用。另外，结合钻孔中CaCO3含量变化的数据，在南海北部陆坡，CaCO3的溶解作用并不是很强，其沉积后保存良好，可作为研究南海北部古生产力的基础性指标。

Carbonate and biogenic Ba records of paleoproductivity since early Miocene in northern South China Sea

CaCO3 and biogenic Ba contents of 175 samples from the top 454.8 mcd （meters composite depth） Neogene sediments at ODP Site 1148 in the northern South China Sea were reported to discuss on the utility of CaCO3 and biogenic Ba paleoproductivity proxies. The results indicate a good correlation between mass accumulation rates of CaCO3 and biogenic Ba during 0 - 21.4 Ma, suggesting that both CaCO3 and biogenic Ba may be regarded as a proxy of paleoproductivity change efficiently in this region. However, the correlation is poor during 23.0 - 21.4 Ma, which may be attributed to suboxic diagenesis modification on biogenic Ba. Diagenesis may cause dissolve of biogenic Ba, which hinders the utility of biogenic Ba as paleoproductivity proxy at suboxic or anoxic environments. On the contrary, the dissolution of CaCO3 is weak and it can be well preserved in the sediment in the South China Sea. Therefore, CaCO3 is a basic proxy for pal ctivity studies in the South China Sea.