Onset of Convective Rainfall During Gradual Late Miocene Rise of the Central Andes
Separated About Lift The uplift history of the Andes of South America is a contentious issue, with the two main hypotheses polarizing from rapid growth between roughly 10 and 7 million years ago to more gradual elevation over most of the past 40 million years. The oxygen isotopic composition of soil carbonates has been used as a proxy for altitude and to measure the timing of uplift. Poulsen et al. (p. 490 , published online 1 April) applied a global atmospheric general circulation model to show that the oxygen isotopic composition changes seen in carbonates formed in the late Miocene were driven more by changes in the amount of precipitation than by the altitude at which the precipitation forms. Consequently, it seems that oxygen isotopes are not a reliable paleoaltimeter, and Andean uplift may not have been as precipitate as thought.