Late Pleistocene fans and terraces in the Majes valley, southern Peru, and their relation to climatic variations |
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| Authors: | Damian Steffen Fritz Schlunegger Frank Preusser |
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| Institution: | 1. Institute of Geological Sciences, Universit?t Bern, Bern, Switzerland
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| Abstract: | This study investigates the connection between sediment aggradation, erosion and climate in a desert environment of the Majes
valley, southern Peru. Luminescence dating of terraces and fans shows that sediment aggradation correlates with wet time intervals
on the Altiplano, suggesting a climatic influence on the aggradation–degradation cycles. Major periods of aggradation occurred
between ~110–100, ~60–50 and 12–8 ka. More precipitation in the Majes catchment resulted in increased erosion and transportation
of sediment from the hillslopes into the trunk river. As a result, the sediment loads exceeded the transport capacity of the
Majes River and aggradation started in the lower reaches where the river gradient is less. Depletion of the hillslope sediment
reservoirs caused a relative increase in the capacity of the trunk river to entrain and transport sediment, resulting in erosion
of the previously deposited sediment. Consequently, although climate change may initiate a phase of sediment accumulation,
degradation can be triggered by an autocyclic negative feedback and does not have to be driven by climatic change. |
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