Increased erosion of high-elevation land during late Cenozoic: evidence from detrital thermochronology off-shore Greenland.

Mountain regions at high altitudes show deeply incised glacial valleys that coexist with a high-standing low-relief landscape, whose origin is largely debated. Whether the plateaus contributed to sediment production during the late Cenozoic is a currently debated issue in glacial geomorphology and paleoclimatology. In this study, we used detrital apatite fission-track dating of marine sediments to trace provenance and spatial variation in focused erosion over the last 7 million years. The decomposition of age distributions into populations reveals that, moving upwards through the sections, two young populations get younger, while two older populations get progressively older. We interpreted these trends as the effect of glacial erosion on the valley floors and an increased sediment contribution from the high elevations. To test this hypothesis, we compared the measured ages with synthetic age distributions, which represented a change in the elevation of focused erosion. We conclude that the central-eastern Greenland region is the main source of sediments, and in addition to enhanced valley incision, sediments have also been sourced from progressively higher elevations since 7 Ma. The ageing trend provides an unusual case in detrital thermochronology and a strong evidence that intensified Quaternary glaciations amplify the erosional process both in valley bottoms and at high elevations.