East vergent structure of Backbone Range: Insights from A-Lan-Yi area and sandbox modeling

Abstract:

Southern Taiwan, including Pingtung peninsula and Taitung, is the incipient oblique collision zone of Eurasian plate and Philippine Sea plate. The Luzon volcanic arc converged toward Taiwan Island and formed Hengchun Ridge south offshore Taiwan. Thus, Taiwan mountain belt developed from north to south as the Backbone Range, so that we can infer the incipient feature structure from the topography and outcrop study of southern Taiwan.

Our field survey of this study concentrated at the southeast coastline of Taiwan, also known as A-Lan-Yi Trail. According to previous study, the deformational structures such as faults and folds are consistent with regional kinematic processes, and the preserved transpression structure is the most important evidence of incipient collision. In this study, we use the sedimentary sequences of study area to trace the regional tectonics from north to south. Discovered structures in this area show the similar kinematic history as the eastern flank of Backbone Range, so that we suggest they are at the same series of a tectonic event.

To complete the regional structure mapping in this accessible area, besides the field geological data, we also applied the LiDAR-derived DTM which is a 3D visualization technology to improve our topography information. In addition, we use the sandbox modeling to demonstrate the development of structures in the eastern flank of Backbone Range. After combining the results of field observation and regional structure mapping, this study provides a strong evidence of backthrusting and backfolding deformation during the incipient oblique collision stage.