Late Jurassic back‐arc extension in the Neuquén Basin (37°S): Insights from structural, sedimentological and provenance analyses

Abstract

The Middle Jurassic–Early Cretaceous evolution of the Neuquén Basin is traditionally attributed to a long phase of thermal subsidence. However, recent works have challenged this model. In view of this, we study the Late Jurassic Tordillo Formation, a non‐marine depositional unit that marks a shift to regional regression across the basin. Previous studies propose different causes for this regression, including the growth of the magmatic arc in the west, uplift in the south or extension in the north. We studied the Tordillo Formation in sections located at an intermediate position in the Neuquén Basin, in order to understand the tectonic processes active during sedimentation. We present evidence of normal faulting within the Tordillo Formation and the base of the overlying Vaca Muerta Formation. Some of these faults can be attributed as syndepositional. We characterize the Tordillo Formation as part of a distal fan‐playa lake depositional system with a contemporaneous western magmatic arc as the main source of sediment. When compared to the Late Triassic–Early Jurassic NE to NNE‐oriented rifting, which marks the opening of the Neuquén Basin, the Late Jurassic extension shows a switch in stress orientation; the latter is orthogonal to the north‐trending subduction zone. We interpret this change as a renewed phase of back‐arc extension induced by slab rollback along with minor distributed intraplate extension prior to opening of the South Atlantic Ocean.

The classical Cuevas River section revisited: an update to the style and timing of deformation of the Aconcagua region based on new geological, structural and geochronological data (32°50′S)

“…During the past two decades, the Late Jurassic has been reinterpreted as a stage of extensional deformation in the Aconcagua region (Giambiagi et al, 2003a;Vicente and Leanza, 2009;Acevedo et al, 2020;Mardones et al, 2021), in line with what is being described in other nearby sectors (Mescua et al, 2008; Frontiers in Earth Science frontiersin.org Martos et al, 2020;Acevedo et al, 2022). In this sense, the new observations presented in this work combined with the various sedimentological profiles available for the Tordillo and Río Damas formations in the area, allowed the reconstruction of the Upper Jurassic extensional architecture along the Cuevas river section (Figure 14).…”

The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S

“…Between the Middle Jurassic and the Early Cretaceous, sedimentation was mostly controlled by thermal subsidence, and the first widespread marine transgressions occurred. Some authors show evidence of an extensional pulse during the Late Jurassic (Acevedo et al, 2020(Acevedo et al, , 2022Martos et al, 2020;Mescua et al, 2008;Sruoga et al, 2011) and even flexural subsidence caused by the magmatic arc load was proposed to explain the significant thickness increase toward the western margin for some intervals of this period (Spalletti, 2013). The sea-level changes and the magmatic-arc dynamics controlled the successive marine transgressions and regressions into the basin from the proto-Pacific Ocean until the late Early Cretaceous (Spalletti, 2013).…”