Cenozoic rifted lacustrine basins in east China display three main basin types: (1) basins with steeply dipping boundary fault, whose hanging walls tilt along pivot points; (2) basins with listric boundary faults, whose hanging walls bend along flexural bending points; and (3) basins formed by earlier extensional rifting with later strike-slip movement superimposed. The sequence development is intimately linked to the tectonic movements in the area, where second-order sequences are regionally correlatable from basin to basin and relate to the large-scale tectonic movements in the region. Third-order sequences are related to local tectonic activity and are correlatable within basins, between subbasins, and sometimes, between neighboring basins. Detailed sequence-stratigraphic analysis and mapping of depositional systems demonstrate that sand-body distribution patterns are related to sequence-stratigraphic frameworks. For the three kinds of basins, the positions of pivot point zones, flexural bend zones, and strike-slip faults plus the syndepositional faults all control the distribution of depositional systems, systems tract, and sand bodies. These controlling factors can be attributed to different structural and stratigraphic features that change the accommodation. Structural elements include boundary faults, syndepositional faults, and abrupt changes in dip. Stratigraphic controls include preexisting surfaces with local channelization, paleobathymetric lows, and onlap onto clinoform slopes. The lowstand sand bodies deposited at the downdip end of these controlling factors constitute the current and future exploration targets for conventional reservoirs.

Three‐dimensional seismic and well data from the deepwater Xisha Trough are used to investigate the rift structure and sediment infill of a region formed adjacently to the initial oceanic ridge of the South China Sea (SCS). The high‐quality data permitted a detailed analysis of features such as (1) detachment faults soling out at the Moho, (2) rotated and thinned continental blocks covered by thick sediment, and (3) changes in the location of basin depocenters resulting from detachment faulting. During the continental rifting phase (Eocene to earliest Oligocene), faulting was broadly distributed in the Xisha Trough and resulted in the generation of isolated grabens/half grabens filled by proximal sediment sources. During continental breakup in the Northwest Ocean Sector of SCS (Oligocene), extension became restricted to a narrow region where highly tilted continental blocks and thin crust were formed. Sediment was, at that time, fed to distal depocenters, which are presently bounded by listric faults rooted in a basal detachment. Later in a second stage (early Miocene), synchronously with continental breakup in the Southwest Ocean Sector of the SCS, the study area was blanketed by thick sediment. During the two continental breakup events, the hyperextended Xisha Trough was affected by closely spaced, small‐scale faults rather than large basement‐related structures. Our study highlights the effect of continental breakup as a way to broaden sediment influx from multiple sources into deepwater basins. As a corollary, this work recognizes two distinct breakup sequences in the Xisha Trough and concludes on their geodynamic significance to the SCS.

At rifted continental margins, it has been widely reported that the amount of extension measured from faulting is less than the one observed from crustal and lithospheric thinning, referred to as “extension discrepancy.” Here, we use observations from high‐resolution seismic reflection data over the Baiyun Rift to explore the discrepancy between upper and whole crustal thinning factors when the crust of the Northern South China Sea margin thinned from 30 to <10 km. We first restore the rift system of the Baiyun Rift in the absence of post‐rift sediments and water loading. Subsequently, we calculate thinning factors based on fault geometries and crustal thickness ratios to compare the deformation of the upper and whole crust. Our results show (1) in the eastern and western basins, upper crustal thinning factors exceed that of whole crust, showing an inverse discrepancy and (2) upper crustal faulting was sufficient to explain the whole crustal thinning in a narrow area of the basin center, indicating no extension discrepancy. The inverse discrepancy in the western basin results from relatively weak ductile shearing in the lower crust, while in the eastern basin, it is caused by intense sequential detachment faulting in the upper crust. Moreover, lower crust exhumation may trigger magma underplating, which further decreases whole crustal thinning factors. Overall, the hyper‐thinning process of the continental crust beneath the Baiyun Rift is dominated by sequential detachment faulting and is characterized by upper crustal thinning factors equaling or significantly exceeding whole crustal thinning factors.