Transform fault system: A microplate-based perspective on transform faults

Transform faults are one of the three main types of plate boundaries recognized in plate tectonics theory. However, various interpretations of their original definition have led to confusion in the literature. This paper presents a comprehensive review of this issue and introduces new concepts, including the transform fault system and continental margin−type transform faults. A transform fault system consists of geometrically or kinematically linked tectonic units along a transform fault. By integrating this concept with microplate tectonics, the evolution and mechanisms of 20 typical transform fault systems are analyzed in detail. From a kinematic perspective, most transform faults are passively controlled at their terminations by tectonic features, such as mid-ocean ridges, subduction zones, collisional zones, and rift zones. They serve as key features for distinguishing between the regimes of plate tectonics and mobile lids. A tectonic system without transform faults cannot be qualified as a plate tectonic regime, as both globally networked subduction zones and mid-ocean ridges can also exist within a mobile lid tectonic regime. However, the global linkage of all tectonic boundaries is impossible in both regimes due to strain localization and fault adjustments. Finally, we redefine transform faults as nearly vertical accommodation faults whose displacement abruptly terminates at one or both ends between plates. This redefinition emphasizes how variations in displacement continuity, motion changes, and kinematic adjustments regulate shear, accretion, or subduction between interacting plates.