Incorporation of the Paleogene foreland into the Neogene Puna plateau: The Salar de Antofalla area, NW Argentina

40Ar/39Ar geochronology of mafic volcanism in the back-arc region of the southern Puna plateau, Argentina

“…The importance of these back-arc mafic centers as indicators of the thermal and compositional state of the mantle source has long been recognized, and the overall features of their distribution and chemical characteristics are well established (Coira et al, 1982;Knox et al, 1989;Kay et al 1994Kay et al , 1997Kay et al , 1999Kraemer et al, 1999). The relative concentration of back-arc volcanism in the southern Puna features prominently in geodynamic arguments for late Cenozoic lithospheric delamination beneath this region as a consequence of shortening and crustal thickening (Kay et al, 1994;Whitman et al, 1996).…”

“…Also, the back-arc volcanic activity is concentrated along faults and it has been suggested that magma ascent and eruption were favored by a shift in fault kinematics, from nearly-exclusive thrust faulting with NW-SE shortening through the Miocene, to an oblique-slip regime with a component of N-S extension in the late Pliocene (e.g., Coira et al, 1982;Marrett and Emerman, 1992;Marrett et al, 1994). However, two dates from 6 to 7 Ma were reported in the literature (Marrett et al, 1994;Kay et al, 1999;Kraemer et al, 1999) so clearly, the timing issue (onset and duration) needs further clarification before the volcanism can be related to tectonics and mantle processes (Kay et al, 1997). The purpose of this study was to improve the geochronological framework for back-arc mafic magmatism in the region with a program of Ar-Ar dating of wellcharacterized samples from the area between the Salar de Antofalla and the Cerro Galán caldera, where young mafic centers are most abundant.…”

Tectonics, Climate, and Landscape Evolution of the Southern Central Andes: the Argentine Puna Plateau and Adjacent Regions between 22 and 30°S

“…Our field studies and theoretical analyses indicate, however that the nature of this coupling may also vary strongly depending on the pre-orogenic geologic history. This is emphasized by the width of the present Puna Plateau and the adjacent tectonic provinces and their relation to the Cretaceous Salta Rift (e.g., Allmendinger et al 1983;Grier et al 1991;Kley and Monaldi 2002;Kley et al 2005;Mon et al 2005;) and those structures within the present plateau that were generated during a different subduction regime in Oligocene time (e.g., Kay et al 1999;Kraemer et al 1999;Carrapa et al 2005). The width of these tectonic provinces in the Central Andes is thus a first-order result of structural inheritance and tectonic conditions and may not be primarily a function of the arid climate, as envisioned by Montgomery et al (2001).…”

“…Late Oligocene sediments in this area indicate that an arid environment existed prior to and during the uplift of the Sierra de Calalaste (Adelmann 2001), and internal drainage was established in the Antofalla Basin possibly as early as late Oligocene to early-to mid-Miocene time (Kraemer et al 1999;Adelmann 2001).…”

“…These sedimentary basins are presently internally drained and contain thick sequences of continental evaporites and clastic deposits (Jordan and Alonso 1987;Alonso et al 1991). Contraction in the region of the present-day plateau and adjacent areas in the Eastern Cordillera and the northern Sierras Pampeanas has apparently contributed to the formation of closed depocenters on the present plateau and transiently closed intramontane basins within the other tectonic provinces of northwestern Argentina Alonso et al 1991;Grier et al 1991;Kraemer et al 1999;Coutand et al 2001;Marrett and Strecker 2000;Bossi et al 2001;Carrapa et al 2005). Jordan et al (1983) The Eastern Cordillera comprises a region of late Proterozoic to early Paleozoic metasedimentary and intrusive rocks (e.g., Jezek et al 1985;Omarini 1983) that were uplifted along bivergent, north-northeast striking thrust faults, which were largely responsible for the deformation of Neogene intramontane and foreland sedimentary sequences (Mon and Salfity 1995).…”