Claudia B. Prezzi

New evidence of clockwise vertical axis rotations south of the Arica elbow (Argentine Puna)

Abstract The Central Andes show a pronounced bend at 18°S. This bend is called the Arica elbow. The existence of counterclockwise vertical axis rotations north of the Arica elbow and clockwise rotations to the south has been determined from palaeomagnetic data. Various authors have proposed different mechanisms to explain this, but whether rotations are local or regional and whether the Arica elbow is a primary or secondary feature of the Central Andes remains controversial. In order to contribute to the palaeomagnetic data available for the Argentine Puna, 102 oriented cores were obtained from Cenozoic rocks cropping out in the Bajo de las Siete Curvas area of the southern Argentine Puna. Different demagnetization techniques were applied. Pretectonic remanent magnetizations were isolated, and indicate the existence of a clockwise vertical axis rotation of approximately 7°–18°. Taking into account the presence of a major thrust fault to the west of the studied area, this rotation could be considered to be of local character, induced by a Miocene-Pliocene compression.