Paleomagnetic study of Tres Vírgenes Volcanic Complex, Baja California, Mexico

Abstract

While the great majority of paleomagnetic studies come from Central Mexico (Trans Mexican Volcanic Belt), still few works are available from Baja California peninsula. Twelve lava and domes from the Tres Vírgenes Volcanic Complex were sampled, and 96 standard paleomagnetic cores were analyzed. Available isotope ages range from 22 ka to 300 ka. Magnetic mineralogy analysis indicates that titanium-poor titanomagnetite is the main carrier of remanent magnetization, although some sites also contain Ti-rich titanomagnetites commonly observed in recent volcanic eruptions. Nine of the studied lavas yielded normal polarity magnetization with site mean declination ranging $D=349°-28.1°$ and inclination $I=32.4°-55.4°$ as expected for the Bruhnes chron. Mean paleodirections show remarkable coincidence with previously reported data from the nearby San Quintín volcanic field. The scatter parameter of the virtual geomagnetic poles $S_B={15.12}_{13.87}^{16.60}$ agrees, under uncertainties, with the latitude-dependent G Model of paleosecular variation for the Bruhnes chron. Both Thellier double heating and Tsunakawa-Shaw absolute paleointensity methods were applied, however, the success rate was relatively low with 4 reliable values ranging from $21.46\mu Tto56.4\mu T$. One of the lava domes that we dated at 253 ± 24 ka using the U-Th systematics demonstrated the worldwide observed Calabrian Ridge 0 short-lived geomagnetic event.