INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Near pure surface uplift of the Argentine Frontal Cordillera: insights from (U-Th)/He thermochronometry and geomorphic analysis
GREGORY D. HOKE, NATHAN GRABER; JOSÉ MESCUA, LAURA GIAMBIAGI; PAUL FITZGERALD, JAMES METCALF
JOURNAL OF THE GEOLOGICAL SOCIETY
GEOLOGICAL SOC PUBL HOUSE
Lugar: Londres; Año: 2015 vol. 399 p. 383 - 383
Apatite (U-Th)/He thermochronology from paleosurface-bounded vertical transects collected in deeply incised river valleys with > 2 km of relief and geomorphic analysis are employed to examine the timing of uplift of the Frontal Cordillera and its relation to the evolution of the proximal portions of the Andean foreland between 32°S and 34°S latitude. The results of apatite (U-Th)/He (AHe) analyses are complex; however, the data show positive age-elevation trends, with higher elevation samples yielding older AHe ages than samples at lower elevation. Slope breaks occur at ~25 Ma in both profiles, separating very slow cooling and or residence within a partial retention zone (slope of ~10 m/Ma) at the highest elevations andfrom a slope of ~60-100 m/Ma cooling rate at lower elevations. The older AHe ages suggest either 1) minimal burial of the Frontal Cordillera and/or 2) significant pre-middle Miocene local relief. Geomorphic analysis of the adjacent, east-draining Río Mendoza and Río Tunuyán catchments reveals a glacial imprint to the landscape at elevations above 3000 m, including greater channel steepness and lower profile concavities developed during glacial erosion. Detailed analysis of headwall heights provides evidence of on-going rock uplift along the entire eastern flank of the Frontal Cordillera and in the eastern flank of the Principal Cordillera south of the slab dip transition.