干旱区生态环境知识资源中心

Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic Be-10 and Ne-21, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at similar to 19, similar to 14, similar to 9.5 Ma; large scale fluvial modification of the landscape had ceased by similar to 2-3 Ma. The presence of clasts that record pre-Miocene exposure ages (similar to 28 Ma and similar to 34 Ma) require stagnant landscape development during the Oligocene. Our data implies an early onset of (hyper-) aridity in the core region of the Atacama Desert, interrupted by wetter but probably still arid periods. The apparent conflict with interpretation that favour a later onset of (hyper-) aridity can be reconciled when the climatic gradients within the Atacama Desert are considered.