LiDAR-Based Geological Mapping of the Central Coastal Range, Taiwan: New Constraints on Fault Systems and Arc Deformation

We present a high-resolution geological reinterpretation of the central Coastal Range of Taiwan based on newly produced LiDAR-assisted geological maps integrated with targeted field verification. LiDAR-derived digital elevation models (DEMs) overcome limitations imposed by poor exposure and dense vegetation and allow systematic mapping of stratigraphic boundaries and fault geometries in this key segment of the Taiwan subduction–collision system. The new maps reveal several previously unrecognized structural features. The Tuluanshan volcanic sequence contains laterally continuous, thick shear zones expressed by aligned geomorphic lineaments and systematic topographic offsets. These shear zones demonstrate significant internal deformation of the volcanic rocks, indicating that the Tuluanshan Formation actively accommodated strain rather than behaving as a rigid volcanic block. Along the western margin of the central Coastal Range, normal faults are commonly observed and consistently occur adjacent to contractional structures. Their spatial association with a major west-verging fault suggests that extension postdated major thrusting and records post-thrust extensional deformation, potentially driven by gravitational collapse or internal reorganization of the Coastal Range wedge. LiDAR-based mapping also significantly refines the distribution of the Lichi Mélange. Mélange boundaries are sharply delineated, and exotic blocks within the Lichi Formation are systematically documented, providing new constraints on mélange formation and transport and underscoring its structural importance in the collision zone. In addition, several previously unrecognized north–south–trending thrust faults are identified, separating sedimentary basins from the Tuluanshan volcanic sequence and defining fundamental tectonic boundaries that segment deformation within the central Coastal Range. These results demonstrate the critical role of LiDAR-based geological mapping in resolving complex structural relationships and provide new constraints on deformation processes during arc–continent collision in Taiwan.