Development of the southern Eastern Cordillera, NW Argentina, constrained by apatite fission track thermochronology: From early Cretaceous extension to middle Miocene shortening

Abstract

For the Puna Plateau and Eastern Cordillera of NW Argentina, the temporal and spatial pattern of deformation and surface uplift remain poorly constrained. Analysis of completely and partially reset apatite fission track samples collected from vertical profiles along an ESE trending transect extending from the plateau interior across the southern Eastern Cordillera at ∼25°S reveals important constraints on the deformation and exhumation history of this part of the Andes. The data constrain the Neogene Andean development of the Eastern Cordillera as well as rift‐related exhumation for some of the sampled locations in the Late Jurassic/Early Cretaceous. An intervening Eocene‐Oligocene exhumation episode in the southern Eastern Cordillera was probably related to crustal shortening. Subsequent reburial of the area by Andean foreland basin strata commenced between 30 and 25 Myr. Magnitude and duration of sedimentation, revealed by thermal modeling, differ between the sample locations, pointing to an eastward propagating basin system. In the southern Eastern Cordillera, Andean deformation commenced at 22.5–21 Myr, predating both the inferred formation of significant topography by 5–7.5 Myr and preservation of sediments in the adjacent Cenozoic basins by 6.5–8 Myr. Comparing the calculated structural depth of partially reset samples suggests that newly formed west dipping reverse faults along the former Salta Rift margin accommodated most of the Neogene tectonic movement. Late Cenozoic deformation at the southern Eastern Cordillera began earlier in the west and subsequently propagated eastward. The lateral growth of the orogen is coupled with a foreland basin system developing in front of the range and then becomes subsequently compartmentalized by later emergent topography.

Middle Eocene deformation–sedimentation in the Luracatao Valley: Tracking the beginning of the foreland basin of northwestern Argentina

“…The Middle Eocene deformation-sedimentation age ascribed here to the Quebrada de los Colorados Formation is comparable to other deformational ages defined for distinct areas of northwestern Argentina (Puna and Cordillera Oriental), including the Altiplano and Cordillera Oriental of southeastern Bolivia (Horton, 2005;Ege et al, 2007) and the Atacama region of Chile (Arriagada et al, 2006). Recent thermo-chronology (AFT) studies of granite from eastern Puna and Cordillera Oriental (Haschke et al, 2005) have suggested a contractional episode during the Late Eocene-Early Oligocene (Coutand et al, 2001;Coutand et al, 2006;Deeken et al, 2006). On the other hand, Hongn et al (2007) documented a Middle Eocene deformation in the northern Calchaquí Valley (Fig.…”

“…This area recorded tectonic overprints from the Upper Neoproterozoic-Lower Paleozoic deformation affecting the basement, a widespread phenomenon in NW Argentina (Turner and Mon, 1979;Mon and Salfity, 1995) that has lasted to the present. Older structures were reactivated during subsequent deformation, especially during the Cretaceous rifting and Cenozoic Andean-shortening (Hongn and Seggiaro, 2001;Riller and Hongn, 2003;Carrera et al, 2006;Deeken et al, 2006).…”

“…According to recent work Deeken et al, 2006;Payrola Bosio et al, 2006;Hongn et al, 2007;Carrapa and DeCelles, 2008), the record of the first Andean deformational events has a very complex distribution (Fig. 9) and chronology ( Fig.…”

The effect of inherited paleotopography on exhumation of the Central Andes of NW Argentina

“…1). The Eastern Cordillera has been the site of deformation and exhumation since at least the Miocene (Coutand et al, 2001Deeken et al, 2006;Carrapa et al, 2011a). Eastward propagation of the deformation through the region in the late Cenozoic was responsible for disruption of the regional foreland basin system.…”

Geochemical, isotopic and single crystal 40Ar/39Ar age constraints on the evolution of the Cerro Galán ignimbrites

“…Contraction would facilitate squeezing out low density melt from the mush zone, which would in turn ascend to a level of neutral buoyancy higher in the crust. This uplift, which began at 6-5 Ma, occurred in an out-of-sequence order on steep east-and west-dipping reverse faults (see Deeken et al 2006). The early uplift could be linked with different phases of the Toconquis eruptions, and the younger faults further to the east to the Galán extracaldera and intracaldera ignimbrites.…”