古海洋活性磷埋藏记录及其在氧气地球化学循环研究中的运用

在综合现代大洋活性磷循环特征的基础上,提出大洋中活性磷主要来源于有CO2 参与的地表岩石的化学风化,输入通量在很大程度上受到气候与构造等因素的控制;进入大洋之后的活性磷经光合作用而进入有机物,并通过一系列的转化环节而最终埋藏下来;从而可以根据古海洋活性磷埋藏记录,推断地质历史中不同时间尺度的全球变化情况。对比160 Ma以来的古海洋总磷和100 Ma活性磷埋藏记录可以发现:(1)总磷和活性磷的埋藏速率与长期的海平面变化明显关联,在温室气候条件下,两者基本呈正相关关系;在冰室气候条件下则为反相关关系;(2)总磷和活性磷埋藏速率的变化,能够在一定程度上指示古海洋营养条件的变化;(3)白垩纪中期大洋缺氧事件对应活性磷的埋藏峰值,表明大洋活性磷循环与大洋缺氧事件之间存在着非常密切的关系。此外还例举了古海洋活性磷埋藏记录在氧气地球化学循环研究中的运用,指出活性磷循环对大气氧含量的稳定起到重要的作用。文章最后对古海洋活性磷埋藏记录研究中存在的一些问题进行了讨论。

Burial records of reactive phosphorus in the paleocean and its application to the oxygen geochemical cycle

According to comprehensive summaries of the characteristics of reactive phosphorus cycles in the modern ocean, we propose that the reactive phosphorus in the ocean mainly come from the surface rocks that experienced chemical weathering with the participation of CO_2. The flux of reactive phosphorus into the ocean depends largely on climate and tectonic factors. Once phosphorous has entered the ocean, reactive phosphorus will be synthesized into organic matter, and then buried after a series of transformation processes. Past global changes, possibly on different time scales, can be inferred from the records of burial reactive phosphorus. By correlating the records of burial total phosphorus since 160 Ma and of reactive phosphorus since 100 Ma, we find that: (1) accumulation rates of total and reactive phosphorus could be correlated well with long-term changes in the sea-level, which showed a positive relationship in the greenhouse climate, and an inverse connection in the icehouse climate, respectively; (2) the change in the accumulation of total and reactive phosphorus could designate, to some degree, the variations of nutrient status in the paleocean; (3) oceanic anoxic events located well within the peak of accumulation rates of both the total and reactive phosphorus, indicates a close relationship between the phosphorus cycle and oceanic anoxic events. Additionally, in this paper we give an example of the application of reactive phosphorus burial records to the study of geochemical cycle of oxygen, and show the significance of phosphorus cycle in terms of the stability of atmospheric oxygen. Some problems in the study of burial records of reactive phosphorus are discussed in the last section of the paper.