140 Building the South American Cordillera, Paleozoic to Recent: Insights from Geo-Thermochronology

An overview of the lithospheric development of the South American Cordillera since the Paleozoic. We invite submissions that utilize geochronology and thermochronology data for basement evolution, structural geology, basin analysis, and landscape evolution.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 304C

Flexural Modeling Indicates Northward Progression of Eastern Cordilleran Uplift in the Central Andes

Paper number: 140-1
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Abstract

Within the South American Cordillera, the central Andes are characterized by their anomalous width, highly thickened crust, and high magnitude of shortening. Arguably the defining structural event of this orogen segment occurred as contractional deformation jumped ~400 km inboard from the Western Cordillera (WC) to the Eastern Cordillera (EC, a bivergent fold-thrust belt), isolating part of the former foreland to form the Altiplano Basin (AB) in a hinterland position. The spatio-temporal progression and underlying tectonic-geodynamic drivers of this major kinematic jump remain unclear. Recent detrital zircon (DZ) work on the northern AB has suggested the EC developed progressively southward rather than forming synchronously along strike, but this has not been tested for the central and southern AB.

We present extensive new volcanic zircon and DZ maximum depositional ages from multi-km measured sections in the central and southern AB. These data provide the first regional, absolute chronostratigraphic framework for testing models of basin evolution, the progression of orogenesis, and Cordilleran geodynamics. Flexural modeling and sediment provenance analysis constrained by this new chronostratigraphy indicate EC development was asynchronous along strike, beginning earlier adjacent to the southern AB (~21°S) than the central AB (~18°S). When combined with previous work on the northern AB, the results suggest the EC originated as disconnected segments which later merged along strike into a regional fold-thrust belt. Possible mechanisms for this structural evolution include the influence of multiple flat slab segments or initial reactivation of pre-existing structures prior to linkage of new fold-thrust structures. The hinterland AB thus offers valuable insights into the early stages of retroarc orogenesis and the broadening of a classic Cordilleran orogen.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413126

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