Spasmodic deformation in the Southwest of the Gondwana boundary, Upper Paleozoic of Ventana ranges in Argentina

GUADALUPE ARZADÚN; MARÍA BELÉN FEBBO; RENATA TOMEZZOLI; NORA NOEMÍ CESARETTI; GISELLE CHOQUE; NATALIA FORTUNATTI; JUAN MARTÍN CALVAGNO

Viena

Congreso; EGU General Assembly 2022 Meeting; 2022

European Geosciences Union

At the east of the Ventana Ranges, Buenos Aires, Argentina, outcrops the Carboniferous-PermianPillahuincó Group (Sauce Grande, Piedra Azul, Bonete and Tunas Formation). We carried out anAnisotropy of Magnetic Susceptibility (AMS) study on Sauce Grande, Piedra Azul and BoneteFormation that displays ellipsoids with constant Kmax axes trending NW-SE, parallel to the foldaxes. The Kmin axes are orientated in the NE-SW quadrants, oscillating from horizontal (base of thesequence-western) to vertical (top of the sequence-eastern) positions, showing a change fromtectonic to almost sedimentary fabric. This is in concordance with the type and direction offoliation measured in petrographic thin sections which is continuous and penetrative to the baseand spaced and less developed to the top. We integrated this study with previous TunasFormation results (Permian). Similar changes in the AMS pattern (tectonic to sedimentaryfabric), as well as other characteristics such as the paleo-environmental and sharp curvature in theapparent polar wander path of Gondwana marks a new threshold in the evolution of thebasin. Those changes along the Pillahuincó deposition indicate two different spasms in thetectonic deformation that according to the ages of the rocks are 300-290 Ma (Sauce Grande toBonete Formation deposition) and 290-276 Ma (Tunas Formation deposition). This CarboniferousPermian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpretedas the result of rearrangements of the microplates that collided previously with Gondwana, andlatitudinal movements of Gondwana toward north and Laurentia toward south to reach theTriassic Pangea.