Palaeomagnetism and K—Ar Ages of Cenozoic Basalts from Argentina

• Published in: Geophysical Journal of the Royal Astronomical Society Vol. 19; no. 2; pp. 147 - 164
• Main Authors: Valencio, D. A., Linares, E., Creer, K. M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-02-1970
• ISSN: 0956-540X; 0016-8009; 1365-246X
• DOI: 10.1111/j.1365-246X.1970.tb06038.x

Results of a combined palaeomagnetic-geochronological study made on Cenozoic basalts from the extra-Andean area of the Provinces of Mendoza and Neuquén are presented and discussed in the light of the geological stratigraphy of the area and of the normal and reversed geomagnetic polarity intervals now well established for the past 4 My. The polarities of samples which yielded older dates are compared with the time zones of normal and reversed polarity but with arbitrary (i.e. not absolute) time scales, suggested by sea-floor spreading. It is concluded that the volcanism during the Cenozoic in this area occurred in cycles. The most recent cycle occurred between the Upper Pliocene and the end of the Pleistocene in the north, centre and south of Neuquén province and in the south of Mendoza province. An older cycle extended from the Upper Miocene until the Middle Pliocene in the south and centre of Neuquén province. We have defined new boundaries, which we have called G1 and G2, between normal and reversed epochs at 5.5±0.3 My (R/N) and at 6.6±0.3 My (N/R?) respectively.