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During the formation and evolution of the South China Sea, a series of multiscale submarine geomorphologies have been produced in the continental margin. The obvious submarine canyons and channels are widely distributed in the continental shelf and slope of the South China Sea. In the Taixinan Basin, several submarine canyons and channels termed as the Taixinan canyon‐channel system (TCCS) are distributed between the active and passive continental margins. Based on acquired ship‐borne multi‐beam bathymetry data in this study and the global GEBCO 2023 bathymetric dataset, we identify and define nine submarine canyons and seven submarine channels in the Taixinan Basin. The TCCS consists of the Dongsha, Taiwan, Jiulong, West Penghu, Penghu, Kaoping, Shoushan, Kaohsiung and the Fangliao canyons and submarine channels. The detailed geomorphological features of different submarine canyons and channels within the TCCS are analysed and summarized using multi‐beam bathymetry data and seismic reflection profiles across canyons. Based on the slope variations of the continental margin and the effects of turbidity currents and bottom currents on canyon, we propose a three‐stage evolutionary model of the TCCS. In the initial formation stage of canyon, the initial erosional grooves were created by tectonic activity on the continental slope and it represents the foundation of submarine canyons. During the growth and development stage, the submarine canyons are further evolved and the canyons began to deepen and widen from the continental slope to the deep‐water areas. It shows the weak erosion and sediment infilling within the canyons in this stage. On the northern continental slope of the South China Sea, continuous transportation and erosion of sediments led to the initial formation of grooves and it becomes the embryonic stage of submarine channels. The present stage of the TCCS was formed when the initial grooves on the continental slope have further developed and rebuilt under the erosion by the turbidity current and the scouring by the bottom current. In the last stage, the intense erosion by the turbidity current is supported by sediment waves around the submarine canyons and the migration of canyons is suggested by the cyclic steps formed within some canyons. [ABSTRACT FROM AUTHOR]

The northern South China Sea continental margin is the key or critical segment of the Ocean-Continent Connection Zone (OCCZ) of the Great South China Block' the junction between the Tethyan and the (Paleo-) Pacific dynamic systems' and the interaction area between the Indian Ocean and the Pacific Ocean. However' due to the low-degree geophysical exploration in the past' the regional tectonic background' processes and mechanism of the transition between the Tethyan and the Pacific tectonic domains are unclear. Based on the latest large number of seismic profiles' we focus on the Cenozoic basin structure in the continental margin of the northern South China Sea and try to reveal the Mesozoic basement structures of the northern South China Sea continental margin, with the aim of exploring the pre-Cenozoic tectonic evolution and the Cenozoic opening, spreading, ridge fossil and closure of the South China Sea oceanic basin, so as to serve the accurate oil and gas exploration in this area at the same time. The seismic interpretation of the Pearl River Mouth Basin and the field structural investigation of the South China continental margin show that the OCCZ of the South China Block has experienced three processes: Mesozoic Indosinian collisional orogeny, Early Yanshanian accretionary orogeny and Late Yanshanian transpressive orogeny. During the Cenozoic era, it experienced the dispersive extension into basins under the control of NW-SE-directed normal extension in the early stage, the dextral pull-apart into basins under the control of NE-NNE-trending strike-slip faults in the middle stage, and the sinistral pull-apart into basins under the control of NW-WNW strike-slip faults in the late stage. In general, the transition process from the Tethyan to the Pacific tectonic systems can be subdivided into four stages: the transition from the Paleo-Tethyan to the Neo-Tethyan tectonic systems, the transition from the Neo-Tethyan to the Paleo-Pacific tectonic systems, the transition from the Neo-Tethyan to the Pacific tectonic systems, and the transition from the Paleo-Pacific to the Pacific tectonic systems. The tectonic transition of the East Asian OCCZ reflects the long-term mechanism of the Earth plate dynamic system driving the plate superconvergence in East Asia, in particular of the importance of the deep or submarine "Triple Poles", the Southeast Asian U-shape subduction system, the Pacific LLSVP and the African LLSVP. More importantly, the Southeast Asian U-shape subduction system is also one of the important dynamic engines of the Earth plate motion. [ABSTRACT FROM AUTHOR]

Seismic reflection and refraction data acquired from both onshore and offshore in the South China area and on the continental shelf of the northern South China Sea passive margin provide new constraints on the P‐wave velocity structure beneath the continental shelf and contribute to constructing a continental rift evolution model. Based on the crustal thicknesses and P‐wave velocities derived from the velocity structure of the seismic profile OBS2010‐2 across the continental shelf, two distinct domains are identified: (a) the thinned/extended continental crust and (b) the transitional crust. The thinned continental crust has a thickness of 25–27 km across the Hainan Rise, decreasing to 21–23 km further south in the rift and faulted depression zone. The transitional crust is characterized by a thickness of 20–21 km. High‐velocity values (>7.0 km/s) in the lower crust of the transitional domain may indicate possible magmatic underplating during rifting. Our results show that the Cathaysia Block extends from onshore South China to offshore into the South China Sea and is bounded by the transitional crust of the continental shelf. The initial rifting of the continental margin occurred in the rift and faulted depression zone and might be explained by the upwelling of the lithosphere based on a depth‐dependent extension mechanism during the late Cretaceous or Paleocene rifting. [ABSTRACT FROM AUTHOR]

Multichannel seismic data on the continental shelf have been used to image the rift-related shallow structural units of the Pearl River Mouth Basin across the northwestern margin of the South China Sea. The Hainan Uplift, Zhu 3 Depression and Shenhu-Ansha Uplift zones are bounded by normal faults or listric-normal faults, which suggest lithospheric extension on the continental shelf. Graben structures 10-15 km wide are imaged on the Wanshan Uplift and Northern Fault Terrace from the reflection data. The thinned continental crust and anomaly rift-related crust in the depression zone and the transitional crust indicated by the wide-angle OBS velocity model dominate the crustal structure of the continental shelf in the continental margin of the South China Sea. The different total crustal stretching factors in different shallow structural units suggest that non-uniform horizontal stretching controls the crustal thinning. The total crustal stretching factor is ca. 1.4-1.6 at the coast area, ca. 1.67-1.8 in the rift-depression zone and ca. 1.7-1.75 in the transitional crustal domain. Pure-shear crustal thinning controls the crustal extension in the rift-depression zone. The high heat flow anomaly in the vicinity of the seismic lines and anomaly rift-depression velocity structure suggest that the crustal thinning on the continental shelf of the South China Sea can be produced by lateral mantle flow within the hotter regional lithospheric background. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Mesozoic Western Pacific subduction system significantly impacted the North China and South China blocks along the East Asian continental margin and influenced the tectonic, magmatic, metallogenic and geomorphic evolution of the region. However, the dynamics and impact on the zone along the East Asian ocean-continent connection zone remain debated. Here we provide a comprehensive synthesis of the state-of-the-art information from deformation analysis, magmatism, geochronology, tomography and other fields from this region. We evaluate first the pre-Yanshanian (pre-Jurassic) final assembly of blocks and the Late Triassic formation of the unified continental margin in East China. We then focus on the Jurassic and Cretaceous geological processes in the East Asian ocean-continent connection zone. The temporal and spatial evolution of structural propagation, sedimentary depocentre, age zonation and migration of magmatism, as well as the large-scale tectono-morphological inversion in the Earth surface system combined with deep processes, are probed. In the early Yanshannian Period (Early and Middle Jurassic, 200–160 Ma), the destruction of the North China Craton (NCC) was mainly affected by the westward early-stage layered rollback, and stepwise delamination and thinning of its continental lithosphere, resulting in the early Yanshanian westward migration of tectonism and magmatism. Coevally, the combined effect of the closure of the Mongal-Okhotsk Ocean to the north and the subduction of the Bangong-Co- Nujiang Ocean to the south imparted an overall compressional setting in the East Asian Ocean-Continent Connection Zone (EAOCCZ). The centres of asthenospheric upwelling and mantle extrusion at depth continued to migrate eastward, driving the eastward lithospheric thinning with periodic and alternating extension and compression. The South China Block experienced a westward flat subduction during the early Yanshanian Period, resulting in the westward propagation of deformation and magmatism, followed by late two-stage delamination to induce the eastward tectono-magmatism. The difference in tectono-magmatic styles between the North China and South China blocks is a result of the different mechanisms and syles of the deep delamination processes under the superconvergence regime of the East Asian and adjacent plates. Especially delamination under North China generated the northwestward layered and fractured subcontinental lithospheric mantle, whereas under the eastern South China Block, were the oceanic lithospheric mantle of the Paleo- Pacific Plate that underwent flat subduction, or continental garnet peridotite mantle. In the middle Yanshanian Period (Late Jurassic to early Early Cretaceous, 160–125 Ma), the EAOCCZ underwent escape tectonics to form some basins related to strike slip faulting. Generally the extensional basins in the tails of the triangular-shaped escape blocks are perpendicular to the extrusion direction. The transtensional or transpressional basins are controlled by the strike slip faults distributed on both sides of the triangular block, and the flexural basins occur in front. In the late Yanshanian Period (late Early Cretaceous-Late Cretaceous, 125–65 Ma), the Paleo-Pacific (Izanagi) Plate subducted NNW-ward beneath the Eurasian continent, and the subduction angles changed gradually following eastward mantle extrusion induced by the closure of the Okhotsk Ocean to the north and Bangong-Nujiang Ocean to the south, as well as the rollback and subduction retreat of the Paleo-Pacific Plate to the east. The EAOCCZ gradually experienced lithospheric collapse and the formation of metamorphic core complexes, as well as obvious landscape reversal. During 70–45 Ma, the Izanagi-Pacific Ridge subducted beneath the EAOCCZ to induce wide uplift resulting in the formation of the Cenozoic dextral transtension-related basins. [ABSTRACT FROM AUTHOR]

Abstract Any plate has a growth process from small to large. The micro-blocks or micro-plates are sometimes the precursors of large plates. The origin, growth, aborting, extinction and residual process of micro-blocks are of great significance for the study of plate tectonics and pre-plate tectonics. The micro-block can be divided into continental, oceanic and mantle micro-blocks according to their compositions. In this paper, the micro-blocks in the global oceans have been summarized according to the following five environments: mid-ocean ridge system, subduction system, transform fault system, deep-sea intraplate system and extension-rift system. We first propose a genetic classification of micro-blocks comprising: detachment-derived, rifting-derived, transform-derived, propagation-derived, ridge jumping-derived, subduction-derived, accretion-derived, collision-derived and delamination-derived micro-blocks. The different types of micro-block boundaries such as active or fossil detachment fault, subduction zone, mid-ocean ridge, transform fault, fracture zone, transfer fault, accommodation zone, lithosphere-scale strike-slip fault, pseudofault, intra-oceanic convergent zone, overlapping spreading centre, non-transform offset, rheological crustal or mantle discontinuity, are systematically discussed for different micro-blocks. Thus, the number of triple junctions will be more than the 16 in the traditional Plate Tectonic Theory. A stability analysis of these triple junctions is the key to understanding the causes of micro-blocks. However, the micro-block has no ultimate cause, so it is unnecessary to pursue one ultimate cause or initiation of plate tectonics. These micro-blocks within oceanic basins, along oceanic margins or within the deep mantle, can not only be used to develop deep ocean fine structural analysis and plate tectonic reconstruction, but also to explain the causes of micro-blocks in some orogens. This will enrich the research of more detailed pre-orogenic or syn-orogenic evolution of orogenic belts, and even extend to the study of early Precambrian pre-plate tectonic mechanisms. The micro-block can be a transition among microplate, plate and terrane under a plate tectonic regime. It can also be formed in inter-sphere tectonic processes. It helps better our understanding of regimes of cratonic basin formation and intra-continental deformation which are the difficulties faced by the Plate Tectonics Theory. We speculate that the Micro-block Tectonics Theory is a unified tectonic theory of cross-layer, cross-phase, cross-space-time scale and cross-planet. [ABSTRACT FROM AUTHOR]