Abstract

Measurements of the magnetic susceptibility and the intensity and direction of remanent magnetization were made on 325 2.5-cm cylindrical cores prepared from 189 samples of the felsites, granites, and diabases exposed in the Ironton, Fredericktown, and Coldwater quadrangles, Missouri. These measurements show, first, that the directions of remanent magnetization, although quite variable, are significantly different from the direction of the present geomagnetic field in southeast Missouri and, second, that partial demagnetization in an ac field of 300 to 700 oe greatly improves the initial scatter of the remanent magnetization vector by diminishing the anomalous components of viscous and isothermal remanent magnetization shown by many samples. The paleomagnetic data from five rock units indicate a Precambrian geomagnetic pole in the vicinity of 150°W and 5°N.

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