Geology

Andean Origins

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Science  15 May 2009:
Vol. 324, Issue 5929, pp. 857
DOI: 10.1126/science.324_857a
CREDIT: ISTOCK IMAGES

The elevation of the Andes mountains has a tremendous influence on climate and ecology across South America, and their interaction with the atmosphere even tweaks Earth's rotation. Their past elevation and uplift history would have greatly influenced evolution and the development of ecosystems. The Andes were constructed by near-continuous subduction beneath South America for more than several hundred million years, and an uplift history might reveal or help elucidate specific tectonic events shaping the continent. Carrapa et al. compared dates from several techniques marking the original formation age and timing of rapid cooling of minerals now found in sedimentary rocks in the Central Andes. These ages reflect times of more rapid erosion of the Andes. The data are consistent with several episodes of uplift or exhumation including at about 350, 80 to 50, and 30 to 5 million years ago. Ehlers and Poulsen explored the relation between Andean uplift and paleoclimate of South America using a climate model and focusing on the past 10 million years or so. The simulations show that the lower Andes would have led to more drying of the Central Andes, but to more precipitation to the north. The magnitude of the results, while elucidating the importance of the Andes in climate, complicate the interpretation of stable isotope fossil plant data used to infer uplift history.

Geology 37, 407 (2009); Earth Planet. Sci. Lett. 281, 238 (2009).

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