Cenozoic Age Counterclockwise Rotation in the Northwest End of the Sierras Pampeanas, Argentina

GUTIÉRREZ, A.; MON, R.; CISTERNA, C. E.; ALTENBERGER, U.; ARNOUS, A.

Open Journal of Geology

Scientific Research Publishing Inc.

Año: 2023 vol. 13 p. 345 - 383

2161-7589

Investigations into the Andean orocline revealed a counterclockwise rotationof about 37° in the north and a clockwise rotation of about 29° in the south.This rotation would have started in the Eocene because the Nazca and SouthAmerican plates converged. The transition zone between the Puna and theSierras Pampeanas has a clockwise rotation pattern. Our new data show thatthe NE convergence of the Nazca and South American plates caused thecounterclockwise rotation around the NW end of the Sierras Pampeanas. Thetemperature rise during a magmatic activity at 13 Ma would have favored acounterclockwise rotation of the mountain blocks of about 20° on a detachment zone within 10 to 15 km of depth. These range rotations generated localstress tensors trending NE and NW, facilitating the development of valleys,basins, mineralized dikes, mineral deposits, and alluvial fans separated fromtheir origin. The Atajo fault shows both ductile and brittle characteristics. Amylonitic belt from the Sierra de Aconquija was juxtaposed on the rocks ofthe Ovejería Block and the Farallón Negro Volcanic Complex by reverse vertical displacement, and a dextral horizontal component of displacement resulted in curvatures that gave rise to pull-apart basins and step over features.The Santa Maria Valley, Campo del Arenal, Hualfín Valley, and Pipanaco saltflat most likely constituted a vast early Miocene basin rarely interrupted bylow feature relief.