The Cenozoic period can be divided into three evolution steps (Es 4 +Ek, Es 2+Es 3, Es 1+Ed), based on their characteristics of deposition and structural development.

• 其中早第三纪阶段又可依据沉积、构造发育特征分为Es4+Ek ,Es2 +Es3 和Es1+Ed 3个演化时期。