The Abancay Deflection, forming the northern edge of the Altiplano in the Peruvian Andes, is a remarkable geomorphic feature marking the along-strike segmentation of the Andes. Little is known about the timing and spatial distribution of exhumation in this area. To constrain the exhumation history of the Abancay Deflection and its drivers, we present apatite (U-Th)/He and fission-track thermochronology data from samples collected along an elevation transect at Machu Picchu. Geomorphologic analysis demonstrates recent and ongoing drainage reorganization recorded by the spatial distribution of the normalized steepness index (ksn) and normalized integrated drainage area (χ) parameters. Thermochronologically derived cooling rates are converted into exhumation using regionally constrained geothermal gradients between 16° and 26°C/km. Time-temperature inversions imply steady and slow exhumation (<0.05 km/m.y.) between 20 and 4 Ma, followed by rapid exhumation (>0.9 km/m.y.) since 4 Ma. The timing of rapid exhumation, combined with the geomorphic analysis, suggests that fluvial capture of the previously endorheic Altiplano by the Urubamba River drove recent incision and exhumation. Depending on the value of the geothermal gradient used, total exhumation since 4 Ma can be explained by river incision alone or requires additional exhumation driven by tectonics, possibly associated with movement on the Apurimac fault.Supplementary material: Additional information is available at https://doi.org/10.6084/m9.figshare.c.5177343

The Central Andes contain the second-highest and widest plateau on Earth: The Altiplano. This wide morphologic domain spreading over 350-400 km of maximum width is characterized by low relief sustained by an overthickened crust of ∼60 km (Allmendinger et al., 1997;James, 1971). Andean topography building started during the Cretaceous (∼120-110 Ma; Jaillard & Soler, 1996). Tectonic, climatic, and erosional interactions affecting the Altiplano and its eastward border, the Eastern Cordillera (Figure 1), have been extensively studied in the southern Central Andes (Bolivia, Argentina;Strecker et al., 2007). The northern edge of the Altiplano, namely the Abancay Deflection (southern Peru; Dalmayrac et al., 1980;B. Gérard et al., 2021;Marocco, 1971), however, has been poorly documented, although its relief and structural organization reveals uncommon features with curved faults, deflected drainage basins and rivers, and deeply incised landforms. The Abancay Deflection occupies a part of the Altiplano to the south and the Eastern Cordillera northward (Figures 1 and 2) and is limited to the north by the Subandes. Morphologically, the Altiplano and the Eastern Cordillera acquired their respective modern mean elevation of ∼4 and ∼4.5 km before 5 Ma (Sundell et al., 2019). Although having experienced similar timing and magnitude of surface uplift, the Altiplano and the Eastern Cordillera are quite different in terms of morphology and geology. In comparison, the Eastern Cordillera presents prominent landscape relief enhanced by deep incision and much older bedrock lithologies (Paleozoic for the Eastern Cordillera vs. Meso-Cenozoic for the Altiplano; Figure 2a). The Subandes represent the most recent domain in terms of orogen building and corresponds to the eastward propagation of Andean deformation through successive fold and thrust fronts since the Abstract Located at the northern tip of the Altiplano, the Abancay Deflection marks abruptly the latitudinal segmentation of the Central Andes spreading over the Altiplano to the south and the Eastern Cordillera northward. The striking morphological contrast between the low-relief Altiplano and the high-relief Eastern Cordillera makes this area a well-suited place to determine spatiotemporal variations in surface and/or rock uplift and discuss the latest phase of the formation of the Central Andes. Here, we aim to quantify exhumation and uplift patterns in the Abancay Deflection since 40 Ma and present new apatite (U-Th)/He and fission track data from four altitudinal profiles and additional individual samples. Age-elevation relationships and thermal modeling both document that the Abancay Deflection experienced a moderate, spatially uniform, and steady exhumation at 0.2 ± 0.1 km/Myr between 40 and ∼5 Ma implying common large-scale exhumation mechanism(s). From ∼5 Ma, while the northern part of the Eastern Cordillera and the Altiplano registered similar ongoing slow exhumation, the southern part of the Eastern Cordillera experienced one order-of-magnitude of exhumation acceleratio...