BRITTLE DEFORMATION: FAULT ANALYSIS IN TAIWAN'S EASTERN CENTRAL RANGE

Taiwan’s eastern Central Range reflects the collision between the Luzon volcanic arc and Eurasia’s passive margin. The Central Range has been undergoing rapid exhumation over the last 1 Ma at a rate of ~5-8mm/yr. We set out to document the geometry and kinematics of structures that have contributed to exhumation across the plastic-to-brittle transition. Plastic deformation is known to reflect the NW-SE shortening recorded by steeply dipping foliations with a down-dip extension. Plastic deformation is also captured in strain shadows found in the eastern Central Range’s slate belts. The fabric element that seems to record the transition between plastic and brittle strain are veins that show mutual cross-cutting relations with young metamorphic foliations. The orientation of the veins and their mineral fill suggests a NE-SW stretching direction, approximately normal to shortening. The veins share orientations with well-developed joints that appear to reflect continued extension at shallow crustal levels (<5 km). To continue on the deformation history, we specifically focus on exposed outcrop-scale faults that reflect late-stage deformation throughout Taiwan’s eastern Central Range. Recent findings suggest that relatively young faults are known to accommodate brittle deformation and also represent similar kinematics compared to earthquake focal mechanism solutions. We aim to constrain the geometry and kinematics of deformation as the metamorphic core is exhuming, and we enter the brittle regime to establish a connection between brittle structures of unknown age and contemporary earthquakes. Focal mechanism solutions and fault data express sub-horizontal NE-SW stretching and oblique normal faulting in the eastern Central Range. We suggest that oblique normal faults accommodate the NE-SW stretching direction.