Differences in sedimentary filling and its controlling factors in rift lacustrine basins, East China: A case study from Qikou and Nanpu sags

摘要

The rift lacustrine basin is characterized by a variety of sediment sources, multiple sedimentary systems, and complex filling, and its sediment supply is largely influenced by climate change. The sedimentary filling and its controlling factors have always been the focuses in basin analysis. This paper first reviews the recent advancement in rift lacustrine basin investigations with an emphasis on the structural controlling on lacustrine configuration, accommodation, and directly structural controlling on basin filling characteristics. The paleogeography resulted from spatial configuration of structural styles, and the sediment supplies synergically determine the types and distribution of depositional systems. The sedimentary filling characteristics of the fourth-order sequence record the evolution of cyclic climate. The case studies are followed on the basis of the sedimentary filling analysis in typical Nanpu sag and Qikou sag in Huanghua rift lacustrine basins in East China. The comparison of sedimentary fillings within sequence stratigraphic frameworks in the two sags shows the different episodic tectonic activities, and their resulting structural frameworks mainly controlled the different sequence stratigraphic developments, their internal architectures, and depositional systems distribution. Qikou sag has more complicate sedimentary filling controlled by episodic activities of boundary and intrabasin secondary faults and sediment supplies. Based on the studies from our own and the formers, we suggest that the sedimentary filling study in rift lacustrine basin should be under the guidance of sequence stratigraphy, use high resolution seismic and all available geological data, combine tectonic evolution and structural styles to build the sequence framework, and then reconstruct the paleo-structure and paleogeography. Studying the relationship between paleogeography and paleosedimentary filling can favor the understanding of the characteristics of sedimentary systems development and help in predicting the potential reservoir distribution. The result of this work can be applied directly to the exploration of energy resources.