鄂西地区中二叠统栖霞组下部烃源岩形成机理

中二叠统栖霞组下部烃源岩广泛发育于扬子地台台内盆地和台地边缘。多种古环境参数V/(V+Ni)、V/Cr、Cu、Ni、Zn、Hf、Nb、自生U含量和烃类百分含量的研究表明，栖霞组烃源岩周期性变化的有机质埋藏量主要受控于海洋表层初级生产力，而生产力的变化受气候引起的海平面变化的影响。海平面的上升带来丰富的营养物质，提高海洋初级生产力，导致大量有机质在海底堆积。细菌分解有机质对氧的消耗以及盆地水体循环的减弱促使底水贫氧。海平面变化是栖霞组有机质富集的最终因素。

Formation mechanism of source rocks in the lower Chihsian Formation of Middle Permian,western Hubei Province

Source rocks in the Chihsian Formation of Middle Permian were widely developed in the intraplatform subbasins and the platform margins.Multiple palaeoenvironment parameters(or proxies)，including V/(V+Ni)，V/Cr ratios，Cu，Ni，Zn，Hf，Nb and U concentrations，as well as hydrocarbon contents，suggest that the amount of organic matter，varing episodically in the Chihsian Formation，was initially associated with the primary productivity，which was in turn controlled by the climate induced sea level fluctuations.During sea level rise，increased nutrient flux could have enhnced the primary productivity and subsequent burial of organic matter onto seafloor，inducing oxygen deficient in bottom water columns，as a result of increased oxygen demands by respiration of phytonplankton and organic decaying in the basin，along with the sluggish water circulation within the basin.Sea level changes are thus considered as the ultimate drving forcing for the organic matter accumulation in Chihsian Formation.