A Tertiary volcanic rocks from the Patagonian plateau, Argentina
Résumé
The Patagonian plateau basalts are a sequence of flat-lying Late Cretaceous through Tertiary basaltic and andesitic rocks exposed east of the Andes in dissected mesetas of Chilean and Argentine Patagonia. The plateau basalts cover a total area of 120,000 km2 between 40°S and 52°S. These igneous rocks rest on generally flatlying older Mesozoic silicic volcanic or sedimentary rocks. Of major importance to the paleomagnetic investigation is the lack of significant tectonic disturbance of this portion of Patagonia from Late Cretaceous to present. 12 sites (107 cores) have been sampled in the Tertiary (Paleocene to Miocene) volcanic rocks between 43°S and 46°S in latitude and between 68°W and 70°W in longitude. Rocks are usually very fresh but, as they outcrop generally on top of the mesas, few hundred meters above the Plateau, remagnetization by lightning strikes is a major problem of the paleomagnetic analysis. Paleomagnetic, rock magnetic and paleointensity results will be presented.