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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 317-18
Presentation Time: 9:00 AM-6:30 PM

EVOLUTION OF THE NEOGENE CACHEUTA BASIN: A RECORD OF OROGENIC EXHUMATION AND BASIN INVERSION IN THE SOUTH CENTRAL ANDES


BUELOW, Ellen, Department of Geology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92116, SURIANO, Julieta, Igeba (UBA-CONICET), Instituto de Geociencias Básicas Ambientales y Aplicadas, Ciudad Universitaria Pabellón II, Intendente Güiraldes 2160, Ciudad Autónoma de Buenos Aires, CP:C1428EHA, Argentina, MAHONEY, J. Brian, Department of Geology, Univ. of Wisconsin-Eau Claire, 105 Garfield Ave, Eau Claire, WI 54702, KIMBROUGH, David L., Department of Geological Sciences, San Diego State University, San Diego, CA 92182, GIAMBIAGI, Laura B., Instituto Argentino de Niviología Glaciología y Ciencias Ambientales, CCT, Parque San Martin s/n, Mendoza, 5500, Argentina and MESCUA, José F., Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, CCT Mendoza, CONICET, Av. Ruiz Leal s/n, Parque General San Martín, Mendoza, 5500, Argentina, buelowek0215@gmail.com

The Cachueta basin, east of Mendoza, Argentina, records a detailed history of rapid exhumation of the Andean orogenic system at 33°S. The integration of sedimentologic, stratigraphic, geochronologic, and thermochronologic studies constrains the pattern of orogenic exhumation.

The Cacheuta basin can be subdivided into five distinct lithofacies [Mariño, La Pilona, Tobas Angostura, Río de los Pozos, and Magotes] that reflect episodic sediment flux produced during orogenic exhumation. Provenance analysis identifies clastic detritus derived from the Cordillera Costal (Jura-Cretaceous zircon), Cordillera Principal (distinctive Jurassic conglomerate, Cretaceous fossiliferous limestone, and Tertiary hornblende andesite clasts), Cordillera Frontal (PermoTriassic clasts and detrital zircon) and the Precordillera (Devonian to late Paleozoic meta-sedimentary detritus). The dramatic influx of coarse clastic debris at the Mariño/Pilona contact reflect major changes in provenance related to eastward propagation of the fold and thrust belt beginning at ~16 Ma.

Detrital U/Pb and (U-Th)/He analyses constrains the pattern of basin subsidence and exhumation. Initial basin subsidence is constrained by a ca. 19.2 Ma U/Pb age from a volcanic tuff near the base of the succession. Coeval U/Pb zircon and (U-Th)/He apatite ages in strata younger than 9.9 Ma constrain the timing of basal sedimentation and associated volcanism. Conversely, strata older 9.9 Ma contain maximum depositional U/Pb zircon ages of 19.2 to 9.9 Ma, and (U-Th)/He apatite ages of 5-8 Ma, which are interpreted to reflect basin inversion.

Session No. 317--Booth# 456

Stratigraphy (Posters)
Wednesday, 4 November 2015: 9:00 AM-6:30 PM
Exhibit Hall (Baltimore Convention Center)
Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.803
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