Collaborative Research: Non-equilibrium Topography and Crustal-scale Imbrication in an Arc-continent Collision, Taiwan

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This project, in collaboration with scientists from Taiwan, will study of the deformation, exhumation, and landscape evolution of the Central Range of Taiwan with focus on recently recognized patches of low relief at high elevations that straddle the crest of the range and stand in stark contrast to the steep and rugged topography predicted for an orogenic system considered to have reached steady-state topography. The research team will test the idea that these areas of low relief are uplifted remnants of a relict landscape that formed prior to a recent transient acceleration in rock uplift rate and that the acceleration in uplift was driven by crustal-scale imbrication as suggested by preliminary interpretations of seismic tomographic analyses. To test these linked hypotheses, the team will carry out three related lines of research: 1) geomorphology and cosmogenic analyses (detailed analysis of the topography; detailed field mapping of fluvial terraces; and determination of erosion rates for the areas of low relief primarily using 10Be); 2) field-based and crustal-scale kinematic analyses (documentation of the spatial distribution, relative age, and orientation of outcrop-scale faults and kinematics; determination of the dominant deformation mechanisms; and inversion of fault earthquake data for the shape and orientation of the strain ellipsoid); 3) thermochronometry studies. The integrated dataset from this study has the potential to transform understanding of the crustal deformation and landscape evolution of one of the type examples of an active, arc-continent collision.Taiwan represents one of the most active tectonic environments on Earth. The island marks the collision between the Luzon volcanic arc and the passive margin of Asia and for decades the collision has motivated geodynamic models to explain the evolution of many mountain belts around the world. The paradigm for Taiwan is that the obliquity between the northeast-southwest trending passive margin and the north-south trending volcanic arc has led to steady southward propagation of the mountain belt and a time-for-space equivalence so that cross sections of the belt can be treated as time slices for different stages in a characteristic evolution. Moreover, the relatively constant width of the orogen has led numerous workers to argue for a topographic steady state where the influx of material is balanced by erosion. This project aims to examine the idea that the mountain belt is punctuated by episodic events that perturb the steady state system.This project is supported by the Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.