The controlling effect of chair-shaped slope break landforms on sedimentation in continental faulted basins: A case study in the Xilinhaolai area, Baiyinchagan depression, Erlian Basin, China

Abstract

To reveal the geomorphic characteristics of the gentle slope zone in a continental faulted basin and its control on sedimentary systems, we have performed the geomorphic units division and comprehensive analysis of seismic facies, well-log facies, and core facies in the Xilinhaolai area in the western area of the Baiyinchagan depression, North China. The results find that the gentle slope in the Xilinhaolai area developed a chair-shaped slope break, which includes four geomorphic segments: steep slope of the depression margin (SSDM), shallow-water gentle slope (SWGS), deepwater steep slope (DWSS), and depression center. The chair-shaped slope break controlled the distribution of the sand body by controlling the water depth and hydrodynamic type of sedimentation. The SSDM was a favorable place for the deposition of beach bars. It has become a good oil reservoir not only because of its shallow burial and good physical properties but also because of the location configured with stepped faults. On the SWGS, the active river current and lake waves caused the deposition of large-scale braided river deltas and shoal bars, which are already the main oil and gas areas discovered in the Xilinhaolai area. On the DWSS, a large-scale slump turbidite fan developed and became a very favorable oil and gas reservoir near the oil and gas source rock. The slumped turbidite fans on the DWSS and the shoal bar on the SSDM are potentially favorable reservoirs for future oil exploration.