The University of Chicago Press, The Journal of Geology, 2(112), p. 127-144, 2004
DOI: 10.1086/381654
Full text: Unavailable
River?borne quartz carries a cosmogenic nuclide memory that is a function of the catchment?wide erosion rate. This record may be preserved in fluvial deposits such as river terraces. If the age of a terrace is independently known and transport time in the river system is relatively short, then the upstream erosion rate at the time of terrace deposition can be determined. We have used cosmogenic nuclides to date river terraces in the lower Meuse catchment, the Netherlands, and to obtain a 1.3 Ma record of paleoerosion rates in a 104?km2 drainage basin comprising the Ardennes Mountains. Paleoerosion rates were uniform within the range of 25?35 mm/ka from 1.3 to 0.7 Ma. After 0.7 Ma, erosion rates have increased progressively to Late Pleistocene values of around 80 mm/ka. Around 0.7 Ma, both climatic and tectonic boundary conditions changed. The amplitude and duration of climate cycles increased significantly, resulting in long periods of sustained low temperatures in the Meuse catchment. In addition, an episode of magmatic underplating and mafic volcanism in the nearby Eifel caused up to 250 m of surface uplift in the Meuse catchment. The main streams in the region have responded to the perturbation at 0.7 Ma within a few 105 yr. Our data indicate that the catchment?wide response time is much longer. Further investigations are required to attribute the observed increase in paleoerosion rates to one or the other mechanism discussed.