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

ACEVEDO, ELIANA; FERNÁNDEZ PAZ, LUCÍA; ENCINAS, ALFONSO; HORTON, BRIAN; HERNANDO, AGUSTÍN; VALENCIA, VÏCTOR; FOLGUERA, ANDRÉS

BASIN RESEARCH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022 p. 1 - 25

0950-091X

The Middle Jurassic– Early Cretaceous evolution of the Neuquén Basin istraditionally attributed to a long phase of thermal subsidence. However, recentworks have challenged this model. In view of this, we study the Late JurassicTordillo Formation, a non- marine depositional unit that marks a shift to regionalregression across the basin. Previous studies propose different causes for thisregression, including the growth of the magmatic arc in the west, uplift in thesouth or extension in the north. We studied the Tordillo Formation in sectionslocated at an intermediate position in the Neuquén Basin, in order to understandthe tectonic processes active during sedimentation. We present evidence ofnormal faulting within the Tordillo Formation and the base of the overlying VacaMuerta Formation. Some of these faults can be attributed as syndepositional.We characterize the Tordillo Formation as part of a distal fan- playa lakedepositional system with a contemporaneous western magmatic arc as the mainsource of sediment. When compared to the Late Triassic– Early Jurassic NE toNNE- oriented rifting, which marks the opening of the Neuquén Basin, the LateJurassic extension shows a switch in stress orientation; the latter is orthogonal tothe north- trending subduction zone. We interpret this change as a renewed phaseof back- arc extension induced by slab rollback along with minor distributedintraplate extension prior to opening of the South Atlantic Ocean.