Dynamics Analysis of the Baiyun Sag in the Pearl River Mouth Basin, North of the South China Sea

Abstract

The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub‐sags versus one low uplift. Vertically, the sedimentary architecture could be divided into three layers, i.e. the faulted layer on the bottom, the faulted‐ductile stretching layer in the middle and the draping layer on the top. The main rifting stage of the sag is supposed to be characterized by ductile extension and thinning of the crust. The special deformation pattern is probably attributed to the fact that the Baiyun sag is located in the transfer zone of the pre‐existing weak zone, which made the sag a strongly deformed area, characterized by the greatly thinned lithosphere and active magmatism. The highly rising mantle under the Baiyun sag should be an important mechanism responsible for the ductile deformation, which caused partial melting of the upper mantle. Upwelling to the upper crust and the sedimentary layers, the partial melting materials accommodated extensional strain and caused non‐faulted vertical subsidence. Magma was collected under the transfer zone after the first stage of rifting, and transferred laterally in a direction perpendicular to the extension to the ENE and WSW parts of the sag and upwelled along the NW‐trending basal faults, where WNW‐trending shear faults developed in swarms. The faulting activity and sedimentation history of the Baiyun sag may have been affected by the ocean ridge jump around 24 Ma and the cessation of sea floor spreading around 16 Ma.

RETRACTED: Structural characteristics and development model of fluid diapirs within the structural transition zone, northern South China Sea

“…However, this knowledge is mostly based on pattern inference and the description of the geometric and kinematic features of the structural transition zone is even more restricted by the lack of high‐precision 3D seismic data and the lack or even absence of targeted and systematic characterization and investigation of the genesis of the transition zone (Z. Sun et al, 2008; X. M. Sun, Zhang, et al, 2014; Xie et al, 2013, 2014, 2021; D. Zhou et al, 1995; D. Zhou et al, 2008). It is not difficult to observe that there is a good coupling relationship between the development location and distribution direction of the fluid diapir zone and the concealed structural transition zone (Figure 1c).…”

“…However, this knowledge is mostly based on pattern inference and the description of the geometric and kinematic features of the structural transition zone is even more restricted by the lack of high-precision 3D seismic data and the lack or even absence of targeted and systematic characterization and investigation of the genesis of the transition zone (Z. Sun et al, 2008;X. M. Sun, Zhang, et al, 2014;Xie et al, 2013Xie et al, , 2014Xie et al, , 2021D.…”

River mouth morphodynamics and deflection over the short term: effects on spit growth and mangrove dynamics

“…The river mouths of the Guyana coast, as with other coastal systems in the Guianas, are influenced by the deposition of mud banks from the large and small rivers in the area, including the Amazon River and other rivers (Gardel et al, 2022). The areas in front of the mouth of large river systems have been well and extensively studied and reported in the literature (e.g., Wright and Coleman, 1974;Wang and Liang, 2000;Van Maren, 2007;Zhen et al, 2008;Fagherazzi et al, 2015;Nienhuis et al, 2016;Hashimoto et al, 2021;Polizel and Burningham, 2022;Lakshmanna et al, 2023;Li et al, 2023, etc.). However, there is limited or no study of the dynamics at the mouth of small river systems.…”