Keywords: 
Arc-Continent Collision; Basin Analysis; Sedimentary Geology; Tectonic Geomorphology; Taiwan's Coastal Range

The arc-continent collision system has been considered as a primary mechanism in the growth of continental crust, which involves development of both rising eroding mountains and subsiding syn-orogenic basins. However, the rates, timescales, and structural controls on these processes remain poorly understood. In this talk, I will present three published works from my Ph.D. dissertation, which address these questions through stratigraphic and geomorphic studies in the Coastal Range of eastern Taiwan, an active arc-continent collisional orogen. The first portion focuses on long-debated origin of the Lichi Mélange and associated basin evolution in the southern Coastal Range. Results of integrated stratigraphic and lithofacies analysis reveal a polygenetic origin (sedimentary deposit overprinted by structural shears) of the Lichi Mélange. This mélange unit is interbedded with orogen-derived turbidites that accumulated on accreting island-arc basement in a retrowedge foredeep basin from ca. 4.0 to 0.8 Ma. The second portion investigates vertical crustal motions involved in creation of the modern Coastal Range. I applied high-resolution backstripping procedures to composite sections in southern and northern Coastal Range, using updated age constraints and foraminifera-based paleobathymetry. The results reveal abruptly oscillating vertical motions in the accreting arc crust, which can be interpreted by an eastward migrating flexural wave, followed by an extremely rapid uplift via transpressional deformation since 0.8-0.5 Ma. In the last part, I further conducted quantitative topographic analysis to evaluate the primary controls on the landscape patterns in the modern Coastal Range. The results show that, in this fast-eroding terrain, channel steepness and hillslope gradient are independent of uplift rate but systematically vary with bedload grain size and bedrock lithology. High flux of coarse sediment and ubiquitous mass-wasting hillslopes together dominate erosion processes and set the topographic limit of the Coastal Range. These three works collectively demonstrate a comprehensive investigation into the genesis of Taiwan’s Coastal Range, from a subsiding deep-marine sedimentary basin millions of years ago to a rapidly emerging steep mountain belt today. The results provide novel perspectives in understanding how rock cycle, crustal deformation, and topographic evolution interact in an active mountain-building zone.

Flyer: Seminar_LAI_2023