DISTINCTIVE FIELD BEHAVIOR FOLLOWING GEOMAGNETIC REVERSALS

The paleomagnetism of lava flows from Kauai (Hawaii), erupted about 4 my ago immediately following a geomagnetic reversal, reveals that the post-transitional field had several distinctive characteristics. While the directional dispersion was identical to that displayed by stable field over the past 5 my, the post-transitional field intensity was un usually high. In both these respects, the field at Kauai resembles the one recorded at 15 Ma by lava flows at Steens Mountain in SE Oregon. The two records also differ in an important way: the large intensity o scillations that immediately followed the Steens Mountain reversal are not apparent in the data from Kauai. These results suggest that while the stability of the newly established dipole may vary significantly from one reversal to the next, strong dipolar field and normal directi onal dispersion may be systematic features of the post-transitional ge odynamo. Furthermore, the results lend support to the recent suggestio n that the core remains in an unusual state for many tens of kyr follo wing a reversal.