Paper No. 302-3
Presentation Time: 9:30 AM
LONG-TERM EROSION RATE RECORD FROM THE ANDEAN FORELAND, NW ARGENTINA
The controls of climate and tectonics on erosion rates over long timescales remain poorly understood, in part due to the difficulty of directly measuring erosion rates over millions of years. In this study we use cosmogenic 10Be to develop a 3.7 Myr long, high-resolution record of erosion rates in the northwestern Argentine Andes. Fluvial foreland sediments were collected from the Orán Group, exposed in the Río Iruya canyon. The canyon has experienced 100 m of incision in the past 100 years, which ensures minimal post-exposure cosmogenic production. We combine magnetostratigraphy and U-Pb dating of volcanic tephra to develop a precise chronologic framework with a temporal resolution of ~100 kyr from 5.5 -1.8 Ma. Reconstructed erosion rates vary by a factor of 3, and show a compelling cyclicity throughout much of the record. Preliminary results show a correlation between erosion rate and the amplitude of changes in summer insolation at 15° S, suggesting that changes in the South American Summer Monsoon may have driven erosion rates over this time period This provides preliminary support to Zhang et al. (2001)’s hypothesis that high-amplitude swings in climate drive higher overall erosion rates by creating disequilibrium landscape conditions.