PALEOMAGNETISM OF A SEQUENCE OF UPPER PALEOZOIC LOWER MESOZOIC RED BEDS FROM ARGENTINA

Palaeomagnetic data from 101 hand samples collected in a rock sequence of about 300m of red beds and igneous rocks of the La Colina Formation (Late Palaeozoic) and Amaná‐Talampaya Formation (Early Triassic) exposed in north‐western Argentina (30° S 67° W) are given. Samples were submitted to thermal, chemical and AC cleaning. After cleaning, the majority of La Colina Formation samples showed reversed polarity and yielded a palaeomagnetic pole at 49° S 343° E (α95=5°), which is consistent with the K‐Ar age (295 ± 5 Myr, Late Carboniferous) of a basaltic lava flow situated in the middle of La Colina rock succession. These rocks also recorded a normal polarity event (which we have correlated with the latest normal polarity event of the Debal'tseva Zone at the base of the Kiaman Magnetic Interval) and two excursions of the geomagnetic field. After treatment, the samples from the Amaná‐Talampaya Formation showed normal and reversed polarity and revealed frequent reversals and excursions of the geomagnetic field suggesting an Illawarra Zone age (post Kiaman, Late Tatarian‐Early Scyntian and younger). Copyright © 1979, Wiley Blackwell. All rights reserved