海平面变化在湖南西部桑植地区栖霞组富有机碳沉积物形成中的作用

湖南西部桑植地区中二叠统栖霞组地层旋回性明显，有机质也呈周期性变化.研究其有机质聚集堆积控制因素将有助于理解海平面变化在富有机碳沉积物形成过程中的作用.选择其中一个旋回作为研究目的层段，通过黄铁矿形态以及地球化学参数有机碳TOC、硫同位素、DOP以及微量元素的研究发现，初级生产力参数Ba、Ni、Cu和Zn的变化与TOC含量的变化一致，有机质聚集堆积主要受海洋表层初级生产力的控制，底部水体氧化还原条件与初级生产力有关.有机质的堆积最终归因于高频相对海平面变化，海平面快速上升带来丰富的营养物质，提高海洋表层生物生产力，海底有机质的分解消耗大量氧气，氧需求量的增加形成底部水体贫氧-厌氧环境. 

Role of Sea Level Fluctuation on the Formation of Organic-Carbon-Rich Sediments in the Chihsian Formation in Sangzhi Area, Western Hunan Province

The Middle Permian Chihsian Formation in Sangzhi area in western Hunan Province shows remarkable cyclicity, where organic matter cycles also occurred. The study of origin of organic matter accumulation in the Chihsian Formation helps understand the role of sea level fluctuation on the formation of organic-carbon-rich sediments. Using a cycle as the study interval, based on the study of pyrite morphology and geochemical parameters, such as TOC, δ34S, DOP and trace elements, we find out that the variation of ocean surface water primary productivity parameters, such as Ba, Ni, Cu and Zn, are consistent with TOC contents, suggesting organic matter accumulation was controlled by primary productivity. The redox condition in bottom water is related to primary productivity. The ultimate origin for the organic matter accumulation should be the high-frequency sea level fluctuation. Rapid sea level rising brought rich nutrients, flourishing surface water biologic productivity. The decomposition of organic matter from dead body demanded more oxygen concentration, resulting in dysoxic-anoxic environment in bottom water.