The erosion of mountain belts controls their topographic and structural evolution1,2,3 and is the main source of sediment delivered to the oceans4 Mountain erosion rates have been estimated from current relief and precipitation, but a more complete evaluation of the controls on erosion rates requires detailed measurements across a range of timescales Here we report erosion rates in the Taiwan mountains estimated from modern river sediment loads, Holocene river incision and thermochronometry on a million-year scale Estimated erosion rates within the actively deforming mountains are high (3–6 mm yr-1) on all timescales, but the pattern of erosion has changed over time in response to the migration of localized tectonic deformation Modern, decadal-scale erosion rates correlate with historical seismicity and storm-driven runoff variability The highest erosion rates are found where rapid deformation, high storm frequency and weak substrates coincide, despite low topographic relief

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Links between erosion, runoff variability and seismicity in the Taiwan orogen

Along-strike variations of morphotectonic features in the Western Foothills of Taiwan: tectonic implications based on stream-gradient and hypsometric analysis

Neotectonic regime on the passive continental margin of the northern South China Sea

The Taiwan mountain belt provides a key example for analyzing the relation between morphology and tectonics in an active compressional environment. There is a striking geometrical relationship between the location of salients and reentrants of the mountain belt and the presence of major crustal inhomogeneities such as structural highs in the foreland basin. Major along-strike variations of structural styles occur in range-front rock units of the fold-thrust belt. Stream-gradient and hypsometric analysis has been carried out to highlight the along-strike variations of morphotectonic features and to illustrate the relative activities in different tectonic regimes of the Western Foothills. The normalized stream length-gradient index (SL index) and the Hack profile are two of the stream-gradient indices that effectively reflect the tectonic uplift in a region. De-trending and residual analysis of the hypsometric integral (HI) eliminates the spatial dependency of small drainage basins, and the residual hypsometric integral corresponds to differential uplift activity. Integration of stream-gradient indices and hypsometry provides more robust tectonic interpretation. Five morphotectonic provinces have been identified in the Western Foothills based on stream-gradient indices and hypsometry. Each province is bounded by a series of N140°E-trending transfer fault zones, either inherited from the Eurasian passive margin and/or newly formed in the sedimentary cover in response to the presence of basement highs within the foreland basin (the Peikang and Kuanyin highs). The morphotectonic features as well as deformation styles vary within each province. A high uplift but low shortening rate typifies the crustal deformation style in the transpressional regime north of the Peikang Basement High. On the contrary, a low uplift but high shortening rate characterizes the crustal deformation style in the transtensional regime south of the Peikang Basement High. The higher geomorphic indices suggest that greater tectonic activity occurs in central than in southwestern Taiwan. This inference is also supported by the coseismic deformation of the 1999 Chi-Chi earthquake.

Along-Strike Variations of Morphotectonic Features in the Western Foothills of Taiwan : Tectonic Implications Based on Stream-Gradient and Hypsometric Analysis

http://www.meas.ncsu.edu/sealevel/publications/Liu_et_al_08_MG_TaiwanStrait_Sediment.pdf

P.M. Liew

Papers

Quaternary transfer faulting in the Taiwan Foothills: evidence from a multisource approach

Holocene tectonic uplift deduced from elevated shorelines, eastern Coastal Range of Taiwan

Marine deposits of late glacial times exposed by tectonic uplift on the east coast of Taiwan