The distribution of native Se is parallel with Se-rich carbonaceous strata, with local circles or strips.Selenium particles become sparse from the Permian Maokou to Wujiaping formation along the dip.

• 横向上沿着富硒碳质岩层的倾向方向，从二叠纪茅口组的碳质硅质岩层到吴家坪组的碳质页岩层，自然硒的发现由易到难。