Archeomagnetic secular variation

This investigation had two goals. The first was an attempt to verify a reported rapid increase in the intensity of the earth's magnetic field in the time period 800-1000 A.D., which was first noted by Bucha in 1970. The second was to measure intensity and magnetization direction on archeological samples between 4000 and 8000 years in age. For the first objective, potsherds from Utah Highway 95 archeological digs were used. The styles of pottery were tree ring dated 750-1100 A.D. at other sites. For the second objective, baked earth samples collected from the Sudden Shelter site in southern Utah spanning 3360-7565 B.P. were used. Pa1eointensities were determined using the double heating technique developed by Thellier (1935). The paleointensities of the potsherds confirmed the anomalous increase in intensity from 800-1000 B.C. as well as the existence of relatively short period secular variation in magnetic intensity. The directional data obtained from the Sudden Shelter samples had poor statistical precision and the mean direction was displaced from the axial dipole direction towards the present field indicating a viscous magnetization. Paleointensity data from the Sudden Shelter site was marginal. They defined a trend differing systematically from that found by Bucha (1967) in Czechoslovakia.