Fig. 5: ¹⁰Be-derived paleo-erosion rates from the Río Iruya and nearby Quebrada de Humahuaca from 6 Ma to 1.8 Ma.

a Paleo-erosion rates calculated for the Río Iruya catchment based on the preferred uplift regime and mean catchment production rate evolution scenario (see Supplementary Fig. 4b and Supplementary Dataset 2). Black circles indicate samples, and the blue piecewise cubic spline is interpolated between sample errors (±2σ envelope). Long-eccentricity cycles (400 kyr) are shown in the background for reference (light gray) with the modern Río Iruya catchment erosion rate (0.34 mm/yr) shown in dark gray. b Paleo-erosion rates (±1σ bars)(red) and c δD values of volcanic glass shards sampled throughout the adjacent intermontane Quebrada de Humahuaca (purple) (±1σ on age and δD values) (Fig. 3, Supplementary Fig. 3)^21,86. Data from the Humahuaca Basin document sustained surface uplift of the Humahuaca Basin and surrounding ranges in the Eastern Cordillera from ~6 Ma to 3.5 Ma resulting in the development of a significant orographic barrier along the Eastern Cordillera by 3.5 Ma. Continued orographic isolation and aridification of the basin followed, driving an order of magnitude reduction in basin denudation rates despite the presence of considerable topography. V-SMOW - Vienna standard mean ocean water.