A sequence demarcation that integrates the conventional markers of sequence boundaries and characteristics of salt rhythmite is more practical for the salt-bearing Eogene in Dongpu depression.According to this demarcation

the Eogene can be divided into 2 second-order sequences and 10 third-order sequences

ensuring the unity of salt rhythmite development and sequence growth.The saltbearing third-order sequence(low-frequency) composition displays a peculiar regularity: the horizontal distribution area of salt-bearing formation in Transgressive Systems Tract(TST) and Highstand Systems Tract(HST) is larger than that in Lowstand Systems Tract(LST).Within the high-frequency sequences

especially the subsequence units corresponding with the fifth-order sequences

salt and sandstone layers are synchronous deposits of different faces

and they form a complete unit of subsequences together with the underlying dark mudstone layers. The developing mode of high-frequency salt-bearing sequence is believed to be formed by high-stand evaporation.