Causes of rapid uplift and exceptional topography of Gongga Shan on the eastern margin of the Tibetan Plateau

Abstract

Erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation, relief development, and crustal weakening. In many orogenic systems, it can be difficult to distinguish whether true feedbacks exist, or whether observed features are a consequence of tectonic forcing. To help elucidate these interactions, we examine Gongga Shan, a 7556 m peak on the eastern margin of the Tibetan Plateau where cosmogenic 10Be basin-wide erosion rates reach >5 mm/yr, defining a region of localized rapid erosion associated with a restraining bend in the left-lateral Xianshuihe Fault. Erosion rates are consistent with topography, thermochronometry, and geodetic data, suggesting a stable pattern of uplift and exhumation over at least the past 2–3 My. Transpression along the Xianshuihe Fault, orographically enhanced precipitation, thermally weakened crust, and substantial local relief all developed independently in the Gongga region and existed there prior to the uplift of Gongga Shan. However, only where all of these conditions are present do the observed topographic and erosional extremes exist, and their relative timing indicates that these conditions are not a consequence of rapid uplift. We conclude that their collocation at 3–4 Ma set into motion a series of feedbacks between erosion and uplift that has resulted in the exceptionally high topography and rapid erosion rates observed today.