Oligocene–Miocene age of aridity in the Atacama Desert revealed by exposure dating of erosion-sensitive landforms
- 1Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
- 2Departamento de Ciencias Geológicas, Facultad de Ingeniería y Ciencias Geológicas, Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta, Chile
- 3Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
Abstract
The age of onset of hyperaridity in the Atacama Desert, Chile, which is needed to validate geological and climatological concepts, has been heretofore uncertain. Measurement of cosmogenic 21Ne in clasts from erosion-sensitive sediment surfaces in northern Chile shows that these surfaces have been barely affected by erosion since 25 Ma. Surface exposure ages of sediment clasts give replicate values at 25, 20, and 14 Ma and individual values at 37 and 9 Ma. Predominantly hyperarid conditions are required to preserve these oldest continuously exposed surfaces on Earth. Our findings are compatible with the hypothesis that the onset of aridity in the Atacama Desert could be the reason for, rather than the consequence of, uplift of the high Andes.
Footnotes
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↵GSA Data Repository item 2005053, Table DR1 and Figure DR1, cosmogenic isotope data and images of the study area, is available online at www.geosociety.org/pubs/ft2005.htm, or on request from editinggeosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301– 9140, USA.
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- Accepted 17 December 2004.
- Received 13 September 2004.
- Revision received 17 December 2004.
- Geological Society of America
