9316544 Brown The objective of this project is to investigate the behavior of the Earth's magnetic field during a transition from reversed to normal polarity. Recently a sequence of lavas yielding transitional paleomagnetic directions was discovered as part of a larger interdisciplinary study of Volcan Tatara-San Pedro in the central Chilean Andes. Subsequent radiometric dating, using both traditional K-Ar and laser 40/39 Ar techniques, has identified the rocks as being 780,000 years old, the age of the Brunhes-Matuyama (B-M) reversal. Virtual geomagnetic poles (VGPs) from these eleven flows cluster around Australia - Southeast Asia. This detailed study of a Southern Hemisphere reversal record (only the third B-M identified in volcanic rocks) will provide important data for preferred paths and clustered VGP analyses.
