新近纪深海大洋红层的分布分类及成因

新近纪大洋红层是一种在氧化条件下形成的红色-粉色-棕色海洋沉积物。白垩纪大洋红层研究成果众多，然而新近纪大洋红层研究缺乏系统的分析和总结。本文以新近纪大洋红层为研究对象，通过对全球大洋钻探井位资料的分析，发现39个钻井含有新近纪大洋红层。通过对不同大洋区域、不同钻井内93个红层离散样品的主量元素CaO，Al2O3和SiO2含量进行三元图投点分析，将新近纪大洋红层分为铝质和钙质大洋红层，其中绝大多数为铝质大洋红层。进一步分析了部分钻井中离散样品的磁化率变化、反射光谱一阶导数曲线、热退磁曲线和交变磁场退磁曲线变化，结果表明新近纪大洋红层的致色矿物以赤铁矿为主。12个钻井中新近纪大洋红层离散样品的低总有机碳含量和低CaCO3含量指示较低的生物生产力，此外19个钻井中红层的沉积速率平均为4 mm/ka，而非红层的沉积速率平均为85.3 mm/ka，指示红层的沉积速率相对较低。总结和分析新近纪大洋红层的以上特征，本文认为较低的有机质堆积速率为铁氧化物(赤铁矿)的形成提供了有利的氧化条件，使得沉积物中的铁氧化物在成岩阶段得以保存，最终形成全球分布的新近纪大洋红层。

Distribution, classification, and origin of Neogene deep oceanic red beds

The oceanic red beds(ORBs) are red to pink to brown marine sediment formed in oxic conditions. Previous researches mainly focused on the Cretaceous ORBs, but the systematic analysis and summary of Neogene ORBs are not comprehensive. This paper selects the ORBs in Neogene as the research object. Through re-analysis of global ocean drilling sites data, we found 39 sites contain Neogene ORBs. By using ternary diagram of the main elements CaO, Al2O3 and SiO2 content of 93 discrete samples of ORBs at different in oceans, the Neogene ORBs are divided into Al-ORBs and Ca-ORBs, most of them are Al-ORBs. Further analysis of the magnetic susceptibility changes, the first derivative curve of the reflectance spectroscopy, the thermal demagnetization curve and the and alternating field demagnetization curve of the discrete samples in sites indicate that hematite is the main mineral imparting the red color of Neogene ORBs. The low Total Organic Carbon and low CaCO3 content of ORBs in 12 sites indicates lower biological productivity. In addition, the average sedimentation rate of ORBs in 19 sites was 4 mm/ka, while the average deposition rate of non-red beds was 85.3 mm. /ka, this feature also shows that the deposition rate of the red layer is relatively low. Summarizing and analyzing the above characteristics of Neogene ORBs, this paper believes that the low organic materials accumulation rate provides favorable oxic conditions for the formation of iron oxides (hematite), so that the iron oxides can be preserved and cause coloration during the diagenesis, the global Neogene ORBs was finally formed.