Continental drift process revealed by high precision seismic survey in the central basin of the South China Sea

doi:10.13745/j.esf.sf.2022.6.10-en

Abstract

Abstract:

The formation and evolution of the South China Sea has been widely studied. More than five genetic models have been proposed. The current popular model is seafloor spreading, but it is difficult to reasonably explain the mid-ocean ridge jumping in South China Sea and the continental fragments found in the central basin of the South China Sea. First, based on two high precision seismic exploration sections in the central basin of the South China Sea, a new tectonic geological interpretation of the two seismic exploration sections was given on the basis of in-depth analysis of the layered structure of the oceanic crust. Then, through the formation process of extensional tectonics, the model of continental drift driven by mantle upwelling and continental crust gravity slip was developed. Finally, the formation and evolution process of the South China Sea was deeply studied. The results show that the formation of the South China Sea is a “tectonic extrusion + active drift” model. Tectonic extrusion is a large-scale passive extrusion of the microcontinents in the southeast margin of Eurasia plate caused by the India-Eurasia collision, while active drift is the active drift of the microcontinents after extrusion. The residual seismic reflection in the central basin of the South China Sea is a phenomenon of seafloor spreading caused by active drift of microcontinents. Furthermore, the geotectonic evolution of the microcontinents surrounding South China Sea was restored. The proposed new model can reasonably explain the phenomenon of mid-ocean ridge jumping in the South China Sea and the genetic mechanism of continental debris. The proposed new continent drift model provides a new dynamic model for plate movement.

Key words: central basin of South China Sea, genesis of South China Sea, high precision seismic exploration, dynamic mechanism, continental drift

CLC Number:

LIANG Guanghe. Continental drift process revealed by high precision seismic survey in the central basin of the South China Sea[J]. Earth Science Frontiers, 2023, 30(5): 430-449.

Figures/Tables 12

Fig.1 Tectonic background of the South China Sea and its surrounding areas. Adapted after [2]. BBWB—Beibu Bay Basin; LP—Leizhou Peninsula; MOR—Mid-ocean ridge; NPCT—North Palawan microblock; PRMB—Pearl River Mouth Basin; SSC—Huangyan Seamount chain; SWTB—Southwest Taiwan Basin.

Fig.2 Two seismic profiles in South China Sea. Modified after [7]. a is the profile position map; b is the N4-3 seismic exploration profile; c is the N3-2 seismic exploration profile.

Fig.3 Physical characteristics of ocean crust stratification. Modified after [37].

Fig.4 Geological interpretation of the N4-3 seismic exploration profile in the South China Sea. a is a simple geological interpretation of N4-3, adapted from [7]; b is the latest geological interpretation of N4-3.

Fig.5 Geological interpretation of N3-2. a is the seismic exploration profile of N3-2; b is the latest geological interpretation of N3-2.

Fig.6 Schematic diagram of extensional structure and gravity slip formed by mantle upwelling. a—Mantle upwelling causes extensional structure; b—Mantle upwelling causes gravity slip; c—After the continental block gravity slip, the depressurization behind it caused mantle melting upwelling and gravity slip again.

Fig.7 Schematic diagram of the new continent drift model, demonstrating the process is driven by mantle upwelling and gravitational slip

Fig.8 The “extrusion + drift” model of South China Sea

Fig.9 The Spreading process of the Continental margin of the South China Sea. Modified after [1].

Fig.10 One-direction continents drift model of South China Sea. a—The state of south China Continental margin and paleo SCS during 65 Ma; b—The state of 35 Ma; c—The current state of the South China Sea.

Fig.11 Schematic diagram of continental drift through N4-3 profile. a—Geological interpretation map of N4-3; b—The initial state of continental drift in this profile; c—Intermediate state of continental drift in this profile.

Fig.12 Schematic diagram of tectonic evolution in the South China Sea

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