The natural remanent magnetization of sixty‐one lava flows from the Plio‐Pleistocene Lousetown formation was measured. The field area extends from Virginia City, Nevada, to Truckee, California, on the eastern slope of the Sierra Nevada. Geomagnetic polarity epochs and stratigraphic controls are used to determine the general extrusion sequence. The flow‐mean directions of magnetization separate into two distinct groups. Thiry‐two flows at Lousetown Creek have a D ≃ 64°, I ≃ −67°, and the remainder of the flows have more usual normal and reverse polarity directions with D ≃ 20°, I ≃ +46° (north‐seeking directions). Both sets of flows have directions of magnetization that are significantly different from an axial dipole field. It is concluded from the respective directions of magnetization that: (1) the first set of flows represents an intermediate direction of the geomagnetic field during a transition from reverse to normal polarity, and (2) the geomagnetic field deviated significantly from an axial dipole field within the late Pliocene.
Sixty-five Brunhes age lava flows from Easter Island are analyzed for secular variation statistics and mean geomagnetic field parameters. The present rotation axis is enclosed within the 95% confidence limits of the mean virtual geomagnetic pole (0 = 87.4 ø, ½ = 204.2ø; dm = 4.13 ø, dp = 2.57ø). The angular standard deviation of a subset of 51 poles is 12.8 ø with upper and lower confidence limits of' 14.8 ø and 11.3 ø. The secular variation of the young Easter Island basalts lies above a pure dipole wobble component of secular variation but below the lower limit for all proposed models. Thus it appears that the Pacific secular variation low extends into the southeast Pacific but is not as pronounced as it is around Hawaii.
The magnetic anomaly usually associated with the Olduvai geomagnetic event (1.96 million years) should probably be associated with the Gilsa event (~ 1.65 million years). The Oldu-vai event can be correlated with a con-sistently appearing minor anomalycalled W. This reassignment gives near-ly uniform spreading rates for sections of the mid-ocean ridge system consid-ere( l here.
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