Summary.
Palaeomagnetic and sedimentological studies carried out on the bottom sediments from three lakes in western Argentina are described. At the within‐lake level, five lithological units could be broadly defined and were useful as a general guide in defining detailed correlations based on the magnetic susceptibility (k) and intensity of remanent magnetization (J). In one of the three lakes, el Trebol, it was possible to derive a closer, lithologically based, correlation and this was consistent with that based on the magnetic parameters. Inter‐lake correlation was derived from the inclination and declination patterns considered as a pair, also taking account of a set of radiocarbon age determinations to remove any ambiguities. All the individual measurements were transformed to a time‐scale prior to stacking to produce type‐curves. The records for Laguna el Trebol and Brazo de Campanario extend back to about 6000 radiocarbon years before present while Lago Morenito provides a record extending back to about 14000 radiocarbon years before present. The records exhibit variations with similar overall characteristics to those previously obtained for Europe and North America, but there appears to be no correlation with the northern hemisphere patterns on a swing to swing basis. Both clockwise and anticlockwise precession of the geomagnetic vector is evident both from spectral analysis of declination/inclination pairs and VGP paths.
Palaeomagnetic data from 182 hand samples collected in a rock sequence of about 620-m of red beds of Late Palaeozoic to Early Triassic age exposed in north-western Argentina (30.3O S 67.7" W), are given.After cleaning, the majority of the Upper Palaeozoic samples (Middle Section of Paganzo Group) show reversed polarity and yield a palaeomagnetic pole at 78" S 249" E (ag5 = 3"). They also record a polarity transition which we have correlated with the Middle Permian Quebrada del Pimiento Normal Event. The position of the palaeomagnetic pole and the K-Ar age of a basalatic sill at the base of the sequence support this correlation.Stable remanent magnetization has been isolated in the majority of samples from the Upper Section of the Paganzo Group; it is predominantly reversed and reveals three normal events and also three geomagnetic excursions suggesting an Illawarra Zone age (post Kiaman, Late Tatarian-Early Scythian). The palaeomagnetic pole of the reversely magnetized samples is located at 75" S 285" E (ass = 13").The red beds involved in this study are correlated with red beds from the Corumbatai Formation (State of Parand, Brazil) and with igneous rocks from the Quebrada del Pimiento Formation (Province of Mendoza, Argentina).The South American Middle and Upper Permian, Upper Permian-Lower Triassic, Lower, Middle and Upper Triassic and Middle Jurassic palaeomagnetic poles reflect a quasistatic period with mean pole at 82" S 244"E, (ag5 = 4") which followed the South American Late Palaeozoic polar shift.
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