Abstract:

The geometric architectures of depositional sequences in fault-depressions play an important role in the analysis of sequence stratigraphy.According to its geometric architectures,the Sahantala Formation of the Jurassic Cretaceous in Jirgalangtu Depression,Erlian Basin could be classified into ten seismic sequences of third grade,which in turn constitute three supersequences.The shapes of the sequences are box-like,wedge shape and sheet drape in ascending order.The sequence boundaries varied from bilateral fault^→ monoclinal fault overlap^→ marginal overlap types,correspounding respectively to the fracture subsidence,depression and filling stages of the basin.The Jirgalangtu Depression is composed of low level,water inflow and high level configurations and contains abrupt slope subaqueous fan system,prograding fan delta-turbidite fan system and marginal minor fan delta system.The combination of the three sequences includes retrograding,prograding and aggrading types.It is proposed in this paper that the geometric architectures of sequences could reveal the process of sequence dynamics,the deposition property and evolution process of the basin.