Miocene to Quaternary basin evolution at the southeastern Andean Plateau (Puna) margin (ca. 24°S lat, Northwestern Argentina)
H. Pingel, R. N. Alonso, U. Altenberger, J. Cottle and M. R. Strecker
Journal name: Basin Research
Issue: Vol 31, No 4, August 2019 pp. 808 - 826
Info: Article, PDF ( 2.48Mb )
The Andean Plateau of NW Argentina is a prominent example of a high‐elevation orogenic plateau characterized by internal drainage, arid to hyper‐arid climatic con-ditions and a compressional basin‐and‐range morphology comprising thick sedimen-tary basins. However, the development of the plateau as a geomorphic entity is not well understood. Enhanced orographic rainout along the eastern, windward plateau flank causes reduced fluvial run‐off and thus subdued surface‐process rates in the arid hinterland. Despite this, many Puna basins document a complex history of flu-vial processes that have transformed the landscape from aggrading basins with coa-lescing alluvial fans to the formation of multiple fluvial terraces that are now abandoned. Here, we present data from the San Antonio de los Cobres (SAC) area, a sub‐catchment of the Salinas Grandes Basin located on the eastern Puna Plateau bordering the externally drained Eastern Cordillera. Our data include: (a) new radio-metric U‐Pb zircon data from intercalated volcanic ash layers and detrital zircons from sedimentary key horizons; (b) sedimentary and geochemical provenance indi-cators; (c) river profile analysis; and (d) palaeo‐landscape reconstruction to assess aggradation, incision and basin connectivity. Our results suggest that the eastern Puna margin evolved from a structurally controlled intermontane basin during the Middle Miocene, similar to intermontane basins in the Mio‐Pliocene Eastern Cordillera and the broken Andean foreland. Our refined basin stratigraphy implies that sedimentation continued during the Late Mio‐Pliocene and the Quaternary, after which the SAC area was subjected to basin incision and excavation of the sedimen-tary fill. Because this incision is unrelated to baselevel changes and tectonic pro-cesses, and is similar in timing to the onset of basin fill and excavation cycles of intermontane basins in the adjacent Eastern Cordillera, we suspect a regional climatic driver, triggered by the Mid‐Pleistocene Climate Transition, caused the present‐day morphology. Our observations suggest that lateral orogenic growth, aridification of orogenic interiors, and protracted plateau sedimentation are all part of a complex process chain necessary to establish and maintain geomorphic characteristics of oro-genic plateaus in tectonically active mountain belts.