Title
Causes of variable shortening and tectonic subsidence during Neogene changes in subduction, southern central Andes (28–30ºS)
Document Type
Conference Proceeding
Publication Date
12-17-2021
Publication Title
American Geophysical Union Meeting
Abstract
The Andes of western Argentina record along- and across-strike 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 (28–33ºS), retroarc shortening generated a fold-thrust belt and intraforeland basement uplifts that converge north of ~29ºS, providing opportunities to explore the effects of varied deformation and subduction regimes on flexural subsidence and synorogenic sedimentation. We integrate new detrital zircon U-Pb and apatite (U-Th-Sm)/He analyses with sequentially restored, flexurally balanced cross sections and thermokinematic models at ~28.5–30ºS to link deformation with resulting uplift, erosion, and basin accumulation histories. Tectonic subsidence, topographic evolution, and bedrock cooling records point to (1) shortening and distal foreland basin accumulation at ~18–16 Ma, (2) thrust belt migration, changes in sediment provenance, and intensified flexural subsidence from ~16 to 9 Ma, (3) intraforeland basement deformation, local flexure, and potential drainage reorganization at ~8–5 Ma, and (4) out-of-sequence shortening and exhumation of foreland basin fill by ~5–2 Ma. Thrust load configurations and subsidence patterns were strongly influenced by basement heterogeneities, including changes in regional lithospheric strength and reactivation of the Paleozoic Valle Fértil suture zone. Finally, geo/thermochronological data and model results resolve a southward progression of thrust belt development consistent with predictions of upper-plate deformation in response to Neogene shallowing of the subducted oceanic slab. This study demonstrates the utility of flexural thermokinematic and erosion modeling for evaluating the geometries, rates, and potential drivers of retroarc deformation and foreland basin evolution during changes in subduction.
Controlled Subject
Subduction zones
Disciplines
Dynamics and Dynamical Systems
Repository Citation
Mackaman-Lofland, C.,
Horton, B. K.,
Ketcham, R. A.,
McQuarrie, N.,
Fosdick, J. C.,
Fuentes, F.,
Constenius, K. N.,
Capaldi, T.,
Stockli, D. F.,
Alvarado, P. M.
(2021).
Causes of variable shortening and tectonic subsidence during Neogene changes in subduction, southern central Andes (28–30ºS).
American Geophysical Union Meeting