PALEOMAGNETIC TEST OF THE LOVEJOY FLOOD BASALT HYPOTHESIS
The stable paleomagnetic directions of all but the last-erupted flow of the Lovejoy series are southeast and upward, with a mean distinct at greater than 99% confidence from the 16 Ma reference direction for its location. Moreover, the scatter of directions about the mean is unusually low, showing that the flows were erupted within a time short compared to the time scale of secular variation of the earths magnetic field, that is, within a few hundred to a few thousand years. The last-erupted flow has an intermediate direction, characteristic of a geomagnetic excursion or reversal transition. We have found this same unusual direction at other localities, showing that this flow traveled at least 50 km. Statistical analysis between localities of flows with more ordinary directions shows that several of them quite probably flowed greater distances of 100 to 200 km. Taking these paleomagnetic results together with their age and geochemistry, we concur with the proposition of Wagner and others (2000) that the Lovejoy basalt series is part of the same volcano-tectonic episode that gave rise to the Columbia River Basalt Group.