The Andes of western Argentina record spatiotemporal variations in morphology, basin geometry, and structural style that correspond with changes in crustal inheritance and convergent margin dynamics. Above the modern Pampean flat‐slab subduction segment (27–33°S), retroarc shortening generated a fold‐thrust belt and intraforeland basement uplifts that converge north of ∼29°S, providing opportunities to explore the effects of varied deformation and subduction regimes on synorogenic sedimentation. We integrate new detrital zircon U‐Pb and apatite (U‐Th)/He analyses with sequentially restored, flexurally balanced cross sections and thermokinematic models at ∼28.5–30°S to link deformation with resulting uplift, erosion, and basin accumulation histories. Tectonic subsidence, topographic evolution, and thermochronometric cooling records point to (a) shortening and distal foreland basin accumulation at ∼18–16 Ma, (b) thrust belt migration, changes in sediment provenance, and enhanced flexural subsidence from ∼16 to 9 Ma, (c) intraforeland basement deformation, local flexure, and drainage reorganization at ∼12–7 Ma, and (d) out‐of‐sequence shortening and exhumation of foreland basin fill by ∼8–2 Ma. Thrust belt kinematics and the reactivation of basement heterogeneities strongly controlled tectonic load configurations and subsidence patterns. Geo/thermochronological data and model results resolve increased shortening and combined thrust belt and intraforeland basement loading in response to ridge collision and Neogene shallowing of the subducted oceanic slab. Finally, this study demonstrates the utility of integrated flexural thermokinematic and erosion modeling for evaluating the geometries, rates, and potential drivers of retroarc deformation and foreland basin evolution during changes in subduction.
Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach: Thermokinematic Modeling North Central Andes
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Abstract -
The impacts of the interdecadal variability of the Pacific and the Atlantic Oceans on precipitation over the Central Andes during the austral summer (December-January-February, DJF) are investigated for the 1921–2010 period based on monthly gridded precipitation data and low-pass filtered time series of the Niño 4 index (IN4), the Niño 1 + 2 index with Niño 3.4 index removed (IN1+2 * ), Atlantic Multidecadal Oscillation (AMO), and Interdecadal Pacific Oscillation (IPO) indices, and the three first rotated principal components of the interdecadal component of the sea surface temperature (SST) anomalies over the Atlantic Ocean. A rotated empirical orthogonal function (REOF) analysis of precipitation in the Central Andes (10°S–30°S) yields two leading modes, RPC1 and RPC2, which represent 40.4% and 18.6% of the total variance, respectively. REOF1 features a precipitation dipole between the northern Bolivian and the Chilean Altiplano. REOF2 also features a precipitation dipole, with highest negative loading over the southern Peruvian Andes. The REOF1 positive phase is associated with moisture transport from the lowlands toward the Bolivian Altiplano, induced by upper-level easterly wind anomalies over the Central Andes. At the same time conditions tend to be dry over the southern Peruvian Andes. The positive phase of REOF2 is related to weakened moisture transport, induced by upper-level westerly wind anomalies over Peru. The IPO warm phase induces significant dry anomalies over the Bolivian Altiplano, albeit weaker than during the IN4 warm phase, via upper-level westerly wind anomalies over the Central Andes. No significant relationship was found between Central Andean precipitation and the AMO on interdecadal timescales.more » « less
