Mesozoic subduction-accretion zone in northeastern south china sea inferred from geophysical interpretations

Abstract

A segment of Mesozoic subduction-accretion zone was inferred across the northeastern South China Sea at approximately NE45° orientation. Basic evidence includes the following: A belt of peek gross horizontal Bouguer gravity gradient (PGHGBA) is comparable in size and intensity to that of the Manila subduction-accretion zone. A belt of high positive magnetic anomalies appears to the north and sub-parallel to the PGHGBA, representing the volcanic arc associated to the subduction zone. The PGHGBA crosses obliquely both Cenozoic structures and present seafloor topography, indicating a pre-Cenozoic age. The segment is offset left-laterally by NW-running strike-slip faults, in concord with the Mesozoic stress field of South China. In addition, the existence of the subduction zone is supported by wide-angle seismic data obtained in different years by different institutions. At approximate localities, a north-dipping ramp of Moho surface is indicated by records of ocean-bottom seismometers, and a strong reflector about 8 km beneath the Moho reflector is indicated by both OBS and long-cable seismic records. The identification of a segment of Mesozoic subduction zone in NE South China Sea fills nicely the gap of the Great Late Mesozoic Circum SE Asia Subduction-acrretion Zone, which extended from Sumatra, Java, SE Kalimantan to N Palawan, and from Taiwan, Ryukyu to SW Japan.

Structural inversion in the northern South China Sea continental margin and its tectonic implications

“…Seismic reflections are correlated with well data from MZ-1-1 (Hao et al 2001;Yan and Liu 2004;Yan et al 2014;Fig. 3) and interpretations of nearby seismic profiles by Zhou et al (1995Zhou et al ( , 2006Zhou et al ( , 2008 and Zhu et al (1999). Drilling and logging data of well MZ-1-1 were acquired by industrial standards and are provided by TCPOC.…”

“…The beginning of the drift phase, oriented north-south, is marked by a major breakup unconformity (BUU; Zhu et al 1999;Zhou et al 2006;Wang and Li 2009; Table 1). Marine magnetic anomalies in the SCS were identified to be from anomalies 11 to 5d (Taylor and Hayes 1983).…”

“…The published seismic profiles from the northern SCS (Zhou et al 1995(Zhou et al , 2006(Zhou et al , 2008 indicate that the Mesozoic basement and the Cenozoic sediment and formation were separated by seismic reflection T g (~66 Ma; Table 1). For the geological evolution of the SCS margin in the Cenozoic, the seismic reflector T 7 (~30 Ma) separated the syn-rift stage from the post-rift stage around the middle Oligocene.…”

RETRACTED ARTICLE: Mesozoic deformation in the Chaoshan Depression of the Pearl River Mouth Basin, northern South China Sea

“…As one part of the Pearl River Mouth basin, Chaoshan Depression is proved to be quite different from its neighbors by containing very thick Mesozoic sediments and a thin Cenozoic layer (Li et al 2008a, b). According to the widespread distribution of the subduction related granites onland and in Dongsha area as well as the associated compressive deformation, scientists believed that there once existed a late Mesozoic subduction zone along the southeastern China continental margin (Jahn et al 1976;Hilde et al 1977;Hamilton 1979;Zhou and Li 2000;Zhou et al 2006Zhou et al , 2008, and Zhou et al (2006Zhou et al ( , 2008 suggested that the Chaoshan Depression used to sit at the forearc of the subduction system. The 2D Velocity and Density Structure of the Mesozoic Sediments also show that there is a huge fault dipping toward north at the south of the Chaoshan Depression, which is deduced to be related to the Mesozoic subduction (Ruan et al 2009).…”

Transtensional tectonism and its effects on the distribution of sandbodies in the Paleogene Baiyun Sag, Pearl River Mouth Basin, China

“…1 The Paleogene tectonic units of the Pearl river Mouth basin (adapted after Pang et al 2005). I Panyu Low Uplift, II Yunkai Low Uplift, III Dongsha Uplift, IV Baiyun Sag, V Huizhou Sag, VI Xingning Sag, 1 city, 2 boundary of Pearl River Mouth Basin, 3 boundary of first-order tectonic unit, 4 boundary of second-order tectonic unit, 5 NW-strike fault magnetic data and the faults distribution, Chen et al (2005) and Zhou et al (2006) concluded that the Pearl River Mouth Basin was located to the north of the Mesozoic Western Pacific Plate subduction zone, and that the regional stress field vitally transformed from left-lateral transpression to right-lateral transtension in the Late Cretaceous.…”