Earth’s magnetic field varies in both space and time. Characterizing and understanding those variations can help us to understand the processes in Earth’s core that generate the magnetic field. They can also help to provide constraints on planetary differentiation, inner core nucleation, and atmospheric evolution. Records of the Earth’s field can be found in rocks, marine and lake sediments, and fired archeological artifacts. Past and current work in this area has involved characterizing changes in the intensity of Earth’s magnetic field in marine sediments from the northeast Pacific Ocean, pot sherds from the American Southwest, and volcanic glass from the Juan de Fuca Ridge. A current collaboration with Jeff Gee at Scripps Institution of Oceanograpy and Mike Jackson at University of Minnesota is examining how well ignimbrites record the intensity of Earth’s magnetic field. This project is funded by the National Science Foundation Earth Science Division (NSF-EAR EAR0944067). Ongoing work at the Juan de Fuca Ridge is funded by the National Science Foundation Ocean Science Division (NSF-OCE OCE1060986).
Gee, J.S., Y. Yu, and J.A. Bowles, Paleointensity estimates from ignimbrites: an evaluation of the Bishop Tuff, Geochem. Geophys. Geosys., 11, Q03010, doi:10.1029/2009GC002834, 2010. Link to pdf.
Bowles, J., Data Report: Revised magnetostratigraphy and magnetic mineralogy of sediments from Walvis Ridge, Leg 208, In D.Kroon, J.C. Zachos, J.C., and C. Richter (Eds.), Proc. ODP, Sci. Results, 208: College Station, TX (Ocean Drilling Program), 1–24, doi:10.2973/odp.proc.sr.208.206.2006, 2006.
Bowles, J., L. Tauxe, J. Gee, D. McMillan, S. Cande, The source of tiny wiggles in Chron C5: A comparison of sedimentary relative intensity and marine magnetic anomalies, Geochem. Geophys. Geosys., 4, doi:10.1029/2002GC000489, 2003. Link to pdf.
Bowles, J., J. Gee, J. Hildebrand, L. Tauxe, Archaeomagnetic intensity results from California and Ecuador: evaluation of regional data, Earth Planet Sci. Lett., 203, 967-981, 2002.