This black shale is a kind of black sedimentary rock formed 540 million years ago (early Cambrian period). In the early Cambrian period, a large number of lower-grade organisms bloomed and died in huge numbers due to a lack of oxygen. Then the rock was formed by deposition for a long time. Stratoid and lenticular stone coal appeared at the bottom of the black shale and the black shale layer contains vanadium, uranium and other trace elements, which is proof of the Cambrian anoxic events. After that, trilobites and other creatures appeared in considerable numbers, marking the "explosion" of life in the Cambrian period.