Fig. 1

Tectonic and geologic settings of Taiwan. A Plate tectonic setting showing northwest convergence between the Philippine Sea and Eurasian Plates (PSP and EUR, respectively) at ~7.8 cm/yr (yellow arrow). Gray triangle in northern Taiwan shows Ryukyu block (RYUK), which is rotating CW ~47°/Myr, red arrow, based on GPS data (Rau et al. 2008). Yellow star represents subduction reversal inflection point. B Geologic map of Taiwan (modified from Lin and Chen 2016). Units in color are discussed in the text. Note 50° change in orientation of cleavage and 48° change in orientation of late-stage veins north of the orocline C relative to veins south of the orocline D is consistent with instantaneous CW rotation of the RYUK block and suggests rotation started ~1 Ma. OT: Okinawa Trough. RA: Ryukyu Arc. LV: Longitudinal Valley. Stereonets and all subsequent nets are equal-area, lower hemisphere projections