Control of transfer zone over sequences and depositional system in Fushan sag, Beibuwan Basin

Key words:  Beibuwan Basin  Fushan sag  transfer zone  sequence patterns  sedimentary system

Abstract:

Based on the interpretation of the 3D seismic data, the sequence patterns and sedimentary characteristics in the sedimentary period of Liushagang formation were studied taking the transfer zone of the Fushan sag as the research project. The results show that the transfer zone developing above the Huachang in the centre of Fushan sag, plays a crucial role in adjusting the structure differences between the western and eastern areas. There are significant differences on the strike of faults and structure styles between two extensional structure systems, which develops at two lateral sides of the transfer zone respectively. The multi-level step-fault belt type of sequence pattern develops in the western area, while the gentle slope type of sequence pattern in the eastern area.The flexure slope break type of sequence pattern develops in the transfer zone with huge-scale braided channel delta in the high system tract and large-scale turbidite fan in the low system tract. Structural transfer zone, relative lake level changes and paleogeomorphy control the sequence architecture and depositional filling of the Fushan sag together, and this controlling effect varies among different system tracts to some extent.