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Palmer & Halls 1986
Palmer, H.C. and Halls, H.C. (1986). Paleomagnetism of the Powder Mill Group, Michigan and Wisconsin: A reassessment of the Logan Loop. Journal of Geophysical Research 91. doi: 10.1029/JB080i011p11571. issn: 0148-0227.

The apex and western arm of the 1.1-Ga Logan Loop, a prominent feature of the North American Precambrian apparent polar wander path, are defined by a large body of data from Keweenawan rocks of the Lake Superior Basin. Until now the eastern arm of this paleomagnetic feature has been largely defined by two data points from the Powder Mill Group of Michigan. A reexamination of this sequence reveals a primary reversed magnetization which plots close to the apex of the Logan Loop. Data from the Mellen Complex in Wisconsin, together with our data from the Powder Mill Group suggest that for deeply dipping volcanic units, the true direction of a prefolding reversed magnetization is snot obtained by simple structural rotation about presently observed strike. Reversely magnetized sites from localities where the Powder mill volcanics have shallow dips yield a pole (146¿W, 46¿N, A95=9.2¿) on the apex of the loop A well-defined, stratigraphically continuous, normal to reversed polarity change near the base of the Powder Mill group is not confirmed. Normally magnetized flows have been found at two localities, only one of which is at the base of the lava sequence. The higher metamorphic grade of normally magnetized sites suggests that normal magnetizations within the Powder Mill Group are secondary and should not be used in definition of the eastern arm of the Logan Loop.

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Journal of Geophysical Research
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