Paleomagnetic Record of a Geomagnetic Field Reversal from Late Miocene Mafic Intrusions, Southern Nevada
Catherine D. Ratcliff 1,
John W. Geissman 1,
Frank V. Perry 2,
Bruce M. Crowe 3, and
Peter K. Zeitler 4
1 Department of Earth and Planetary Sciences, University of New Mexico, Albuguergue, NM 87131-1116, USA.
2 Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
3 Los Alamos National Laboratory, Las Vegas, NV 89109, USA.
4 Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18105, USA.
Late Miocene (about 8.65 million years ago) mafic intrusions and lava flows along with remagnetized host rocks from Paiute Ridge, southern Nevada, provide a high-quality paleomagnetic record of a geomagnetic field reversal. These rocks yield thermoremanent magnetizations with declinations of 227° to 310° and inclinations of –7° to 49°, defining a reasonably continuous virtual geomagnetic pole path over west-central Pacific longitudes. Conductive cooling estimates for the intrusions suggest that this field transition, and mafic magmatism, lasted only a few hundred years. Because this record comes principally from intrusive rocks, rather than sediments or lavas, it is important in demonstrating the longitudinal confinement of the geomagnetic field during a reversal.
Submitted on May 19, 1994
Accepted on August 26, 1994
