Turbidite system controlled by fault interaction and linkage on a slope belt of rift basin: Zhanhua depression, Bohai Bay Basin, China

Abstract

Although the relationship between faulting and sedimentation has been extensively studied and discussed over the past decades using a variety of examples and surface and subsurface data. However, limited information is available regarding the evolutions within the interaction zones in sedimentary processes, depositional architecture and sand bodies dispersal, which are crucial for hydrocarbon exploration, specifically in deep-water sedimentary system. To investigate the effects of fault interaction and linkage on the sedimentary processes and architecture of deep-water turbidite systems and explore the impact of fault linkage patterns on the dispersal of sand bodies, 3D seismic data, cores and logging data were collected from the southern slope zone of the Zhanhua Depression, Bohai Bay Basin. The Kenxi area exhibits two typical fault-reworked geomorphologies (i.e. slope geomorphology with weak reworking and fault-trough geomorphology with strong reworking), which control the development of fan depositional architecture dominated by turbidity current and fault-confined channel depositional architecture dominated by mixed traction current and turbidity current, respectively. These turbidite systems indicate that they are connected to flood occurrence based on systematic lithofacies analysis. Nevertheless, two distinct sediment grain sizes and drainages have been formed and may be related to fault confinement and slope gradients. Additionally, we propose conceptual fault linkage models that regulate drainage and the dispersion of sand bodies, highlighting the effects of fault evolution stages and separation distance on local geomorphology. First, the region with relatively unconfined geomorphology, dominated by non-separated faults in the soft linkage stage, is where lobe deposits are more likely to have formed. The relay ramps, shaped by separated faults in the soft linkage stage, control the direction of the transportation of sediments in the proximal area. Second, the distribution of fault-confined channels is laterally confined by long extended fault-trough geomorphology formed following hard linkage by non-separated faults. The local footwall hump (i.e. local topographic high) formed in an overlapped zone by separated faults provides frontal confinement for sand bodies in the hard linkage stage. This study reveals that in addition to onshore river systems, the architecture and distribution of deep-water turbidite systems are significantly influenced by fault interaction and linkage patterns. Meanwhile, it provides a new model for facilitating the prediction of the reservoir distribution of turbidite systems in the slope zone of rift basins.