Uplift history of the Central and Northern Andes: A review

The elevation of the Andean Cordillera Is a crucial boundary condition for both climatic and tectonic studies, The Andes affect climate because they form the only barrier to atmospheric circulation in the Southern Hemisphere, and they intrigue geologists because they have the highest plateau on Earth formed at a noncollisional plate margin, the Altiplano-Puna. Yet, until recently, few quantitative studies of their uplift history existed. This study presents both (1) a review of the quantitative paleoclevation estimates that have been made for the Central and Colombian Andes and (2) an examination of the source and magnitude of error for each estimate. In the Central Andes, paleobotanical evidence suggests that the Altiplano-Puna had attained no more than a third of its modem elevation of 3700 m by 20 Ma and no more than half its modern elevation by 10.7 Ma. These data imply surface uplift on the order of 2300-3400 m since the late Miocene at uplift rates of 0.2-0.3 mn/yr, Paleobotanical and geomorphological data suggest a similar uplift history for the Eastern Cordillera-namely no more than half the modem elevation present by 10 Ma. No evidence exists for an exponential increase in uplift rate, as has been interpreted from fission-track data. These uplift rates mostly reflect mean surface uplift rather than rock uplift-that is, uplift of material points-because little dissection of the,western Eastern Cordillera has occurred south of lat 19 degrees S and of the Altiplano-Puna. Thus, the Central Andean Plateau appears to be young. In the Colombian Andes, paleobotanical data imply rapid uplift of the Eastern Cordillera between 2 and 5 Ma at rates on the order of 0.6-3 mm/yr, However, sonic of this uplift is likely rock uplift due to erosion-driven isostatic rebound rather than mean surface uplift.