Goedynamic Interpretations from Paleomagnetic Data of Late Paleozoic Rocks in the Southern Andes

  1. John W. Hillhouse
  1. Augusto E. Rapalini,
  2. Juan F. Vilas,
  3. Maria L. Bobbio and
  4. Daniel A. Valencio

Published Online: 18 MAR 2013

DOI: 10.1029/GM050p0041

Deep Structure and Past Kinematics of Accreted Terranes

Deep Structure and Past Kinematics of Accreted Terranes

How to Cite

Rapalini, A. E., Vilas, J. F., Bobbio, M. L. and Valencio, D. A. (1989) Goedynamic Interpretations from Paleomagnetic Data of Late Paleozoic Rocks in the Southern Andes, in Deep Structure and Past Kinematics of Accreted Terranes (ed J. W. Hillhouse), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM050p0041

Author Information

  1. Laboratorio de Paleomagnetismo, Departamento de Ciencias Geologicas, Facultad de Cs. Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon 2, 1428, Buenos Aires, Argentina

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780875904542

Online ISBN: 9781118666609

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Keywords:

  • Geology, Structural—Congresses;
  • Geodynamics—Congresses;
  • Earth—Crust—Congresses

Summary

Paleomagnetic data for three Late Paleozoic formations from the Argentine Andes are reported. These formations are: the Majaditas Formation, exposed at 31.8°S 69.4°W (Precordillera) assigned to the Middle Carboniferous; the Portezuelo del Cenizo Formation, exposed at 32.1°S 69.5°W (Cordillera Frontal) with a radiometric age of 275±10 Ma (Early Permian) and the Choiyoi Formation, exposed at 39.1°S 70.5°W (Cordillera Principal), assigned to the Permo-Triassic. The directions of the stable remanent magnetization (srm) isolated for the rocks of these formations were submitted to tilt tests. In every case these tests indicated that the srm isolated was acquired before the strata were tilted.

The paleomagnetic poles (PP) computed for the three formations (Majaditas Fm.: 200°E 42°S, A95 = 8°; Portezuelo del Cenizo Fm.: 212°E 30°S, A95 = 7°; Choiyoi Fm.: 232°E 21°S, A95=8°) are not coincident with those for coeval rocks exposed in stable areas of South America. This is interpreted in terms of two different hypotheses. The first suggests that the sampling areas of these formations are situated in crustal blocks that suffered different large clockwise rotations around vertical axes during the Mesozoic or Cenozoic. The other suggests that these rocks together with the Late Carboniferous Yalguaraz Formation, exposed in Cordillera Frontal, were part of a displaced terrane—the limits of which are not yet defined— that was accreted to the western edge of South America prior to the Early Triassic.