Formation and erosional decay of peneplains in the northern Gandise belt, Tibetan Plateau, revealed by low-temperature thermochronology and cosmogenic nuclides

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Large-scale peneplains constitute the most prominent geomorphic element of the Tibetan Plateau, but little is known about their formation and subsequent evolution. By applying lowtemperature thermochronology, sediment provenance analysis, and cosmogenic nuclides we aim to (1) date the planation phase in south-central Tibet, (2) reconstruct the paleogeography and geologic setting during post-orogenic erosion and basin formation, (3) quantify the Quaternary erosion rate of the low-relief surfaces and the incision rate of rivers dissecting the peneplains, and (4) evaluate whether the peneplains were covered by ice for extended periods in the Quaternary. Our preliminary results suggest that different structural blocks have variable thermal histories. Basement rocks exposed at the peneplains cooled below apatite FT and He closure temperatures (ca. 110 and 70 °C, respectively) between 89 and 35 Ma. 10Be concentrations in granitic bedrock and grus samples yield local erosion rates of 6-12 m Ma-1, whereas catchment-wide erosion rates are only slightly higher (11-18 m Ma-1). This demonstrates that the peneplain region is extremely stable and has barely been modified by erosion in the last millions of years.