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1. Miocene Construction of the High Andes Recorded by Exhumation of the Frontal Cordillera, La Ramada Massif of Western Argentina (32°S)

   Howlett, C J; Ronemus, C B; Carrapa, B; DeCelles, P G (January 2025, Tectonics)

   Abstract The Frontal Cordillera is a first‐order geologic feature of the southern central Andes, hosting the highest hinterland topography above the modern Pampean flat‐slab segment. The timing of Frontal Cordillera exhumation is important for testing models of Andean tectonics, yet large latitudinal gaps exist between structural and thermochronological constraints for the region. We conducted a thermochronometric study using a 4.4 km age‐elevation transect along the northeast ridge of Cerro Mercedario, the highest peak in the La Ramada massif at ∼32°S. Zircon (U‐Th)/He dates indicate partial resetting, supporting a limited magnitude of exhumation in even the most extreme Andean topography. Single grain apatite (U‐Th‐Sm)/He dates range from 8.5 ± 0.9 to 35.8 ± 3.6 Ma, with median dates of ∼10.5 to ∼15.7 Ma with increasing elevation. Integrated with geologic mapping and thermal history modeling, these data suggest Early to Middle Miocene exhumation along the Santa Cruz and Espinacito faults concomitant with uplift of the La Ramada massif. New apatite helium data from the Cordillera del Tigre segment of the Frontal Cordillera are partially reset and preferred modeling interpretations suggest exhumation ca. 11–9 Ma, coeval with shortening in the eastward adjacent Precordillera. These data add to accumulating regional evidence for out‐of‐sequence deformation during the Miocene, consistent with internal (hinterland) growth of a subcritical orogenic wedge contemporaneous with surface uplift and crustal thickening in the south‐central Andes. 

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2. Exhumation and incision of the eastern Central Andes, southern Peru: Low-temperature thermochronology observations

   https://doi.org/10.1016/j.epsl.2023.118299  

   Falkowski, Sarah; Ehlers, Todd A; McQuarrie, Nadine; Glover, Chloë O; Perez, Nicholas D; Buford_Parks, Victoria M (October 2023, Earth and Planetary Science Letters)

   Quantifying the impacts of past changes in tectonics or climate on mountain topography has proven challenging. The incision of the eastern Central Andean Plateau has been interpreted as both a result of deformation-related uplift and erosion and climate-driven erosion. Here, we contribute >100 new apatite and zircon (U-Th)/He and fission-track dates from 51 new and eight previous bedrock samples. These samples were combined with previous thermochronometer data from three ∼190-km-long and ∼200-km-apart across-strike transects along the eastern margin of the Andean Plateau in southern Peru. We discuss age-distance, age-elevation, and inverse thermal history model results along these transects to constrain the timing and extent of recent canyon incision compared to the region’s long-term (∼40 Myrs) exhumation history. Results indicate that, along the plateau flank, long-term, deformation-related exhumation is superimposed by a regional, synchronous canyon incision-related signal since ∼4–3 Ma. This incision is traceable from at least the Abancay Deflection in southern Peru to southern Bolivia along the eastern Central Andes. Based on the regional and synchronous character of canyon incision across areas with different deformation histories and exhumation magnitude, we suggest that paleoclimate change was a significant contributor to incision. However, structural processes resulting in surface uplift, erosion, and exhumation continued post-mid Miocene and contributed to the observed exhumation magnitude. 

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3. Geodynamic and Climatic Forcing on Late‐Cenozoic Exhumation of the Southern Patagonian Andes (Fitz Roy and Torres del Paine massifs)

   https://doi.org/10.1029/2023TC007914  

   Muller, Veleda_A P; Sue, Christian; Valla, Pierre G; Sternai, Pietro; Simon‐Labric, Thibaud; Gautheron, Cécile; Cuffey, Kurt M; Grujic, Djordje; Bernet, Matthias; Martinod, Joseph; et al (July 2024, Tectonics)

   Abstract High‐relief glacial valleys shape the modern topography of the Southern Patagonian Andes, but their formation remains poorly understood. Two Miocene plutonic complexes in the Andean retroarc, the Fitz Roy (49°S) and Torres del Paine (51°S) massifs, were emplaced between 16.9–16.4 Ma and 12.6–12.4 Ma, respectively. Subduction of oceanic ridge segments initiated ca. 16 Ma at 54°S, leading to northward opening of a slab window with associated mantle upwelling. The onset of major glaciations caused drastic topographic changes since ca. 7 Ma. To constrain the respective contributions of tectonic‐mantle dynamics and fluvio‐glacial erosion to rock exhumation and landscape evolution, we perform inverse thermal modeling of a new data set of zircon and apatite (U‐Th)/He from the two massifs, complemented by apatite⁴He/³He data for Torres del Paine. Our results show rapid rock exhumation recorded only in the Fitz Roy massif between 10 and 8 Ma, which we ascribe to local mantle upwelling forcing surface uplift and intensified erosion around 49°S. Both massifs record a pulse of rock exhumation between 7 and 4 Ma, which we interpret as enhanced erosion during the beginning of Patagonian glaciations. After a period of erosional and tectonic quiescence in the Pliocene, increased rock exhumation since 3–2 Ma is interpreted as the result of alpine glacial valley carving promoted by reinforced glacial‐interglacial cycles. This study highlights that glacial erosion was the main driver to rock exhumation in the Patagonian retroarc since 7 Ma, but that mantle upwelling might be a driving force to rock exhumation as well. 

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4. Post-Laramide Extension and Erosion in the Madison and Gallatin Ranges of Southwest Montana from Apatite (U-Th-Sm)/He Thermochronometry

   https://doi.org/10.2113/2026/lithosphere_2025_149  

   Weeks, Chloë; Stanley, Jessica R; Tremblay, Marissa M (February 2026, Lithosphere)

   Abstract Since the end of the Laramide Orogeny (~50 Ma), southwest Montana has experienced complex tectonic, climatic, volcanic, and mantle dynamic processes that have left an imprint on the landscape. Here, we examine the impact of post-orogenic and recent hotspot-related processes on the landscape by quantifying the Cenozoic exhumation history of the Madison and Gallatin Ranges, located on the northern flank of the Yellowstone hotspot (YSH) in southwest Montana. We apply the apatite (U-Th-Sm)/He (AHe) thermochronometer to Cretaceous and Paleogene intrusions from three transects to constrain the Cenozoic cooling history. We also present three new zircon U-Pb crystallization ages. AHe dates from 16 samples produced dates ranging from 67 ± 8.3 Ma to 6.2 ± 0.76 Ma. Most dates are between 45 and 20 Ma and younger than their crystallization age. Samples from the elevation transect with the largest relief display a positive relationship between AHe date and elevation, and thermal history modeling shows a phase of exhumation from ~30–23 Ma. AHe dates in the Madison Range young as they approach the Madison Fault, the range-bounding normal fault, and we ascribe most of the exhumation in the Madison Range to extension and tectonic exhumation due to footwall uplift. We interpret the ~30–23 Ma cooling to represent fault initiation and a phase of Oligocene extension that shows that post-orogenic extensional faulting and collapse propagated into the Laramide domain at that time. Late Miocene AHe dates near the fault represent a renewed phase of motion in the Miocene to recent, though our data lack the resolution to constrain the specific timing. Erosional exhumation due to YSH-driven regional uplift appears to be minimal. 

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5. Eocene exhumation of the High Andes at ~30°S differentiated by detrital multimethod U-Pb-He thermochronology

   https://doi.org/10.1130/G52272.1  

   Fosdick, Julie C; Stevens_Goddard, Andrea L; Mackaman-Lofland, Chelsea; Lossada, Ana C; Rodríguez, María Pía; Carrapa, Barbara (June 2024, Geology)

   Abstract The southern Central Andes (~25–40°S) exhibit a complex tectonic history, crucial for understanding orogenic processes in subduction-related orogens, yet debate on the timing and mechanisms of early Cenozoic topographic growth persists. We present double-dated detrital zircon U-Pb and (U-Th)/He thermochronology data from the early Oligocene–Miocene Bermejo Basin at ~30°S to investigate source unroofing during development of the High Andes. (U-Th)/He results yield dates of ca. 565–16 Ma (n = 73), with distinct detrital modes that indicate a mixing of sediment sources characterized by variable cooling and exhumation histories. We employ a novel approach for modeling detrital thermochronology data that leverages the shared basin subsidence history of multiple detrital modes to resolve provenance and source unroofing histories. Results from the lower Oligocene Vallecito Formation (northwestern Argentina) reveal that detritus was sourced from Permian–Triassic Choiyoi Group rocks that underwent rapid late Eocene cooling, indicated by short lag time (2–5 m.y.) between source cooling and deposition. Our findings are consistent with bedrock studies of Eocene exhumation in the High Andes and establish source-to-basin connectivity during this time. Other detrital modes with pre-Cenozoic cooling histories were derived from Carboniferous Elqui-Colangüil and Choiyoi Group rocks or recycled from Paleozoic basins. We propose that an early Oligocene drainage divide in the High Andes was located west of the Punilla–La Plata fault, an active thrust front at ~30°S. These findings challenge Paleogene neutral stress-state models for the Andes and underscore the importance of improved knowledge of erosion and deformation histories for refining models of Andean orogenesis. 

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