Origin of transform faults in back‐arc basins: examples from Western Pacific marginal seas

Abstract

Transform faults in back‐arc basins are the key to revealing the evolution of marginal seas. Four marginal basins in the Western Pacific, i.e. the South China Sea (SCS), Okinawa Trough (OT), West Philippine Basin (WPB) and Shikoku‐Parece Vela Basin (SPVB), were studied to redefine the strikes and spatial distribution of transform faults or fracture zones. Based on high‐resolution tectonomorphology, gravity and magnetic anomalies, pattern of magnetic lineations, seismic profiles, geometry of basins and palaeomagnetic data, together with analyses of regional geological setting, plate reconstruction and geodynamic analysis, this paper suggests that all the transform faults in the four marginal basins are in general NNE‐trending. Moreover, by comparing with the contemporary structural framework of the East Asian Continental Margin, we propose new models concerning marginal seas spreading and have revised the previous Cenozoic plate reconstruction models related to the East Asian Continental Margin and the Western Pacific marginal seas. There are three possible origins of these NNE‐trending transform faults. 1. Inheriting the orientation of the strike‐slip faults at the rifting continental margin (e.g. the SCS and OT). The real strike of transform faults should not be NW but NNE. The large‐scale NNE‐trending dextral strike‐slip faults distributed in the continental shelf of the SCS control a series of pull‐apart basins of the SCS. Due to a higher degree of pull‐apart, oceanic crust began to open. Then they evolved into the NNE‐trending transform faults in the SCS and could also be regarded as a natural extension of the NNE‐trending strike‐slip faults in the South China Block (SCB). The geodynamic mechanism of the OT is similar to that of the SCS. Consequently, transform faults of the OT should also be NNE‐trending, which is not perpendicular to the spreading axis but instead displays oblique spreading. 2. Izu‐Bonin‐Mariana (IBM) Trench retreat to the NNE and NE. Subduction rollback to the NE and NNE produced the NE‐ and NNE‐striking horizontal tensile stress, resulting in the rifting of the Kyushu‐Palau Ridge (KPR), controlling the spreading of the SPVB and forming the NE‐ and NNE‐trending transform faults. This also involves oblique spreading. 3. The later overall rotation of the Philippine Sea Plate (PSP). Since 25 Ma, the WPB has rotated clockwise about 40°. Therefore the NW‐ and NNW‐trending transform faults that formed at the later spreading stage have rotated to be the near‐N–S‐ or NNE‐striking faults. These transform faults are almost perpendicular to the spreading axis. Copyright © 2016 John Wiley & Sons, Ltd.

Mesozoic magmatic activity and tectonic evolution in the southern East China Sea Continental Shelf Basin: Thermo‐mechanical modelling

“…The third boundary conditions may be more consistent with the real Mesozoic evolution of the ECSCSB (Figure 7). Li, Yu, et al (2013) and Zhang et al (2016) Plate. Thus, we think that the extension of the basin has relationship with the subduction retreat of the Izanagi Plate on the two-dimensional model, and extension is one of the factors for evolution of the basin.…”

“…Li, Yu, et al () and Zhang et al () analysed the temporal and spatial distribution of magmatic rocks around 160 Ma in East China. It was found that the Andean‐type continental margin developed a large number of plutons, such as Dandong, Guojialing, and South China.…”

“…The crust of the ECSCSB is considered as a typical continental crust by previous studies (Li, Yu, et al, 2013;Xu, Hao, Li, & Liu, 2008;Zhang et al, 2016, Figure 2). The crust is mainly composed of sedimentary cover and granitic rocks without basaltic rocks.…”

Geological interpretation of volcanism and segmentation of the Mariana back‐arc spreading center between 12.7°N and 18.3°N

“…These observations suggest that the cross-arc chains follow long-lived basement structures, inherited from or even pre-dating successive back-arc opening episodes [Fryer and Hussong, 1982;Fryer, 1995]. Zhang et al [2016] considered that transform faults in the South China Sea, Okinawa Trough, West Philippine Basin, and Shikoku-Parece Vela basins are similarly inherited structures, the highly oblique orientation of which reflects complex plate convergence and rotation. Thus, the segmentation of the Mariana back-arc spreading center may be controlled by an early fabric in the arc crust, with all of the major and minor offsets associated with a major E-W or NE-SW trending structures at the regional scale (Figure 15b).…”

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

“…However, the NSCSM had been convergent through the Mesozoic era under multi‐source stress fields due to closures of the Tethys and Paleo‐Pacific oceans among the Indo‐Australian, Eurasian, and Paleo‐Pacific plates. The NE‐trending dextral strike‐slip faults inherited and propagated from the Late Mesozoic faults with the same strike direction in South China, which mainly consist of a series of horse‐tail‐like secondary splay faults in plan view (Hui et al, , ; Li et al, ; Wang et al, ; Zhang et al, ). The Meso‐Cenozoic basins in the northern SCS continental margin are partially exposed to reveal a chessboard pattern in a NE‐oriented distribution due to the NE‐trending dextral strike‐slip faulting which dominate over the E–W‐ and NW‐trending faults (Li et al, ; Figure ).…”