Basin Dynamics and Basin Groups of the South China Sea

As an important transition domain between the thinnest continental crust and the initial oceanic crust, the ocean–continent transition zone (OCT) preserves a wealth of information on the processes of lithospheric extension and breakup. The northern margin of the South China Sea (SCS) is a non‐typical, magma‐poor passive continental margin with a particular structural pattern and sedimentary formation. The OCT in the northern margin of the SCS was developed by a series of continental rifting and seafloor spreading. Based on several multi‐channel seismic reflection profiles, crustal‐scale structural profiles extracted from gravity data and ocean‐bottom seismometers (OBS) data, this paper studies the deep crustal structures, deformation and geodynamics of the OCT to further understand the structural patterns and tectonic process from the lithospheric extension to its breakup. The OCT of the northern margin of the SCS is characterized by a crustal thinning and high‐velocity layer (HVL) in the lower crust. The OCT has three structural units: rift depression, volcanic zone and tilted fault blocks. The HVL is mainly limited in the eastern portion of the northern SCS. The HVL is distributed essentially within the OCT but does not clearly develop everywhere in the OCT. We propose a hybrid model of rifting to fit characteristics of the northern margin of the SCS. A crustal‐scale largely symmetric process predominated at the initial rifting stage. The basin‐controlling faults subsequently penetrated the entire crust, resulting in asymmetric tectonic evolution. Then, the OCT occupied this asymmetric location. Copyright © 2016 John Wiley & Sons, Ltd.

Section: Evolution Of the Northern Scsmentioning

confidence: 99%

Final breakup of continental block and opening of oceanic lithosphere: insights from deep crustal structure and tectonic evolution of the ocean–continent transition zone in the northern South China Sea

Guo

Zhao

et al. 2016

“…It is located at the junction of the Tethyan Tectonic Domain and the Western Pacific Tectonic Domain (He et al, 2008;Li et al, 2012). It is located at the junction of the Tethyan Tectonic Domain and the Western Pacific Tectonic Domain (He et al, 2008;Li et al, 2012).…”

Section: Geological Settingmentioning

confidence: 99%

Magma emplacement: an important trigger leading to slope failures in deep‐water areas of northern continental margin of South China Sea

Lin

et al. 2016

Submarine slope failures are considered as a serious geo‐hazard because they can rupture undersea pipelines, and seafloor engineering facilities can be subverted by destroying the seabed stability. Submarine slope failures are widely developed in deep‐water areas of the northern continental margin of the South China Sea, yet the mechanisms involved in their generation remain poorly known. Observations have proposed that slope instability can be due either to decomposition of gas hydrate or to magma emplacement. Here, we present new high‐resolution 2D seismic data from the deep‐water areas of the northern continental margin of the South China Sea to reveal an extensive and intimate relationship between magma emplacement and slope failures. This paper shows four landslides on the Dongsha, Shenhu, Xisha and Qiongdongnan slopes that occurred at different locations of the northern continental slope of the South China Sea. There are seismic evidences that magmatic rocks commonly developed and migrated upwards to the overlying layers and they caused these layers to uplift as a dome and possibly decreased their strength and predisposition to failure. The data reveal in detail how magma emplacement influenced slope stability and the seismic reflection features of this type of submarine landslides. The findings illustrate the importance of magma emplacement resulting in slope instability. This paper proposes that magma emplacement is a basic and critical trigger leading to slope failures in the deep‐water areas of the northern continental margin of the South China Sea and establishes genetic models for this important trigger. Copyright © 2016 John Wiley & Sons, Ltd.

“…(a) Simplified structural map of Southeast Asia and location of the study area within the South China Sea (Modified from Li et al, ; Pubellier & Morley, ). (b) Shaded bathymetric map for the northern margin of the South China Sea obtained from previous studies (Guo et al, ), showing features of scarps annotated in red dotted lines and the location of the three canyon zones depicted in the black boxes and the extent of the studied region: (1) Xisha Canyon‐Xs C; (2) Shenhu Canyon‐ Sh C; (3) Taiwan Canyon‐ Tw C; (c) the depth of water in the canyon zones and three locations of seismic profiles in Figure .…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of submarine canyon formation on the northern continental slope of the South China Sea

Hui

Guo

et al. 2018

Self Cite

Submarine canyons are common features on the northern South China Sea (SCS) continental slope. Three main submarine canyon systems were observed by multi‐beam investigation and evaluated by a pre‐existing sedimentary dataset. They include the Xisha Canyon Zone, Shenhu Canyon Zone, and Taiwan Canyon Zone on the northern SCS continental slope which developed from the middle Miocene to the present‐day. Previous analysis implied that an enriched oil‐gas accumulation formed under this region with distinct gravity anomalies or active tectonic activity. Previous interpretation and geodynamics studies have revealed the detailed sedimentary records and the coupled tectonic‐sedimentary processes. However, the timing and mechanism of formation of the canyons on the northern SCS slope are still poorly constrained and vigorously debated, especially the differences among three submarine canyons from west to east that requires allowances for a variety of conflicting datasets. Here, we adopt the high‐resolution multi‐beam relief map and seismic profiles from these three canyon systems to estimate if the SCS slope controlled geometric segmentation and differentiation of canyon formation mechanisms and times. For this purpose, we ascertained that these canyons were initially controlled by the NE‐ to NW‐trending faults as a better constraint on the sediment flow direction. All the submarine canyons in the northern SCS slope extend in a range from NE‐/N–S‐ to NW‐ and E–W‐trending directions associated with the SCS oceanic spreading and the subsequent subduction‐related deformation along the Manila Trench. Furthermore, the present‐day morphology of these canyons implies a remarkable tectonic jump from west to east in the SCS continental slope and a north‐westward recession of the continental slope. Apart from the neo‐tectonic faults, the sea‐level fluctuation, gas hydrate disassociation, sediment source, and transportation channel also yielded dynamic processes and preservation for the submarine canyons. We finally propose a coupling model of the sedimentary and tectonic processes and confirm the spatial and temporal evolution of mechanisms of these canyons.