Abstract
Additional sampling in another area and reevaluation of previously rejected data have provided paleomagnetic poles for five new sites in the 85-million-year-old Cretaceous granites of the Sierra Nevada, California. The mean of these five poles and the nine poles previously reported is located at 165°W and 69°N, with the semiangle of the 95% confidence cone equal to 9.6°. This mean paleomagnetic pole differs only slightly from that previously reported for nine sites only and agrees with two Cretaceous poles from rocks in Quebec; thus it may represent a geographic pole as well. There is no systematic distribution of individual virtual poles with respect to their mean. The only ferromagnetic mineral in all these rocks is pure magnetite, which probably accounts for the large observed dispersion of NRM directions and the magnetic instability of many of the specimens. Measurements of susceptibility anisotropy indicate that only about half of the dispersion can be caused by random anisotropy and that the observed uniform anisotropy at some sites has not biased the NRM directions significantly.
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