An Episode of Steep Geomagnetic Inclination 120,000 Years Ago

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Science  22 Jul 1983:
Vol. 221, Issue 4608, pp. 359-361
DOI: 10.1126/science.221.4608.359


The mean inclinations of three sections of 120,000-year-old fine-grained sediments from northern California range from 62° to 66°. These inclinations are significantly steeper than the inclination of the geocentric axial dipole at this site. Because these sediments have probably recorded an actual episode of steep inclination lasting several thousand years, they provide new insights into the significance of mean inclinations shallower than the geocentric axial dipole. Such inclinations are characteristic of fine-grained sediments younger than 35,000 years. The results raise questions about the time-averaged geomagnetic field and about the determination of plate motions from paleomagnetic data.