Abstract

A thick sequence of orogenic strata exposed in the Coastal Range of eastern Taiwan documents uplift of at least 7.5 and 5.9 km at two anticlinal crests following marine deposition of the uppermost preserved beds at ∼1.0 Ma. The resulting mean uplift rates of 7.5 and 5.9 mm/yr are minimum values for localities that represent relative maxima in total uplift, and are consistent with previous studies that document general uplift of about 5 mm/yr in Taiwan. Despite rapid uplift, the Coastal Range is transected by the antecedent course of the Hsiukuluan River. Maintenance of this transverse drainage, rather than defeat and diversion to a ready alternate course to the sea provided by the range-bounding Longitudinal Valley, suggests that uplift has been steady over time and exemplifies a general balance between uplift and denudation rates in Taiwan. Denudation in the Coastal Range approximates the rapid present-day denudation documented in the much higher Central Range, due at least in part to less resistant rock types in the Coastal Range. Uplift of the Coastal Range is driven by the tectonic incorporation of the Luzon island arc into the Taiwan mountain belt (and thus into the Asian continental margin), probably over a west-dipping decollement hypothesized to have formed during eastward propagation of the eastern deformation front of the dominantly west-vergent orogen.

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