A thermochronometric view into an ancient landscape: Tectonic setting, development, and inversion of the Paleozoic eastern Paganzo basin, Argentina

Abstract

In this study, we utilize multiple thermochronometric methods, including apatite and zircon fi ssion track, (U-Th)/He, and zircon U-Pb, to evaluate the cooling history and provenance of sedimentary strata of the late Carboniferous to Late Permian eastern Paganzo basin and adjacent basement rocks (Argentina). The strata in the study area represent a long-lived, composite basin system that is interpreted to have experienced multiple periods of deformation, and to have received sediment from a number of different source terranes. These strata are well exposed in the Sierra de Chepes of west-central Argentina. New thermochronometric data and fi eld observations, together with published data from the surrounding mountains, allow us to reconstruct: (1) the cooling history of the underlying basement rocks and the highlands surrounding the basin, (2) the thermal history of the source areas that provided sediment to the basin, and (3) the timing of structural inversion of the basin. Our data suggest that parts of the Sierra de Chepes were rapidly exhumed in Late Devonian-Carboniferous times; these exhuming areas supplied sediment to the adjacent basin. In contrast, the overlying red-bed strata originated from a slowly exhuming region located farther east or north of the basin within the Pampean orogenic belt or the Famatinian belt, respectively. Burial by latest Carboniferous and younger strata and an elevated geothermal gradient resulted in heating of the underlying Upper Carboniferous strata and underlying granitoid basement to temperatures between 80 °C and 140 °C. During Triassic time, the eastern Paganzo basin was structurally inverted; this event was marked by rapid cooling and may be related to regional extension and the development of rift basins to the west. The basement and the Upper Paleozoic strata of the eastern Paganzo basin in the study area have remained below 50 °C since latest Jurassic-Early Cretaceous times and are characterized by very slow cooling. Results of this study provide a thermochronometric view along an ~330 m.y. path defi ning the geologic evolution of the eastern Paganzo basin and the upper crust of west-central Argentina.

Exhumation history and landscape evolution of the Sierra de San Luis (Sierras Pampeanas, Argentina) - new insights from low - temperature thermochronological data

“…These depocenters were part of the eastern Paganzo basin, which contains basement-derived clasts with provenance mainly from the east, indicating surface uplift of the easternmost Sierras Pampeanas to some extent during basin development (López-Gamundí et al, 1994;Chernicoff and Zappettini, 2007). A similar situation with a Carboniferous landscape carved into older rocks and covered or filled by fluvial sediments was documented in the Sierra de Chepes (La Rioja province) by Enkelmann et al, 2014).…”

“…On the other hand, recent thermochronological studies in other regions of the Sierras Pampeanas near the Sierra de San Luis indicate that exhumation and cooling associated with uplift since the Cenozoic was considerably small (Löbens et al, 2011;Bense et al, 2013;Enkelmann et al, 2014).…”

“…1; Enkelmann et al, 2014), whereas coeval fault activity was recognized for the Sierras de Córdoba (Whitmeyer, 2008) and the Sierra de Comechingones (Löbens et al, 2011) based on Ar/Ar pseudotachyllite and K-Ar fault gouge data, respectively. Permian exhumation and deformation, in turn, is also recorded in other areas of the Sierras Pampeanas (Coughlin et al, 1998;Bense et al, 2013Bense et al, , 2014Sato et al, 2015).…”

“…Thermochronological data which allow a quantitative evaluation of cooling and exhumation of the basement blocks are still scarce in the southeastern Sierras Pampeanas (Jordan et al, 1989;Coughlin et al, 1998;Löbens et al, 2011Löbens et al, , 2013aBense et al, 2013, Dávila andCarter, 2013;Richardson et al, 2013;Enkelmann et al, 2014;Collo et al, 2015). Hence, the evolution of these ranges since the late Paleozoic is still a matter of ongoing debate (e.g., Jordan et al, 1989;Carignano, 1999;Löbens et al, 2011;Dávila and Carter, 2013;Enkelmann et al, 2014;Rabassa et al, 2014).…”

“…Hence, the evolution of these ranges since the late Paleozoic is still a matter of ongoing debate (e.g., Jordan et al, 1989;Carignano, 1999;Löbens et al, 2011;Dávila and Carter, 2013;Enkelmann et al, 2014;Rabassa et al, 2014).…”