PERSISTENT FEATURES OF POLARITY TRANSITION RECORDS FROM WESTERN NORTH-AMERICA

We report on a high resolution transition record from Searles Valley, California that appears not to be hampered by problems of smoothing or recording breakdown, and, unlike many other sedimentary records, defi nes a path unconfined in longitude. A prominent feature of the record is the steady oscillation of the pole along a swath stretching from we st Africa across north Eurasia to the northwest Pacific. The endpoints of the swath are associated with a change between steady and rapid fi eld variation, consistent with results for an older transition from a nearby volcanic record. The transition culminates with poles migrating from west Africa to South America, midway between the two earlier-pro posed longitudinal bands. This path indicates the reversing field has either a wider spectrum of behavior than recently suggested or is desc ribed by a more complicated field geometry than one dominated by an eq uatorial dipole or strong low-order nondipole component. From a compar ison with existing records from the same general geographic area, we a ddress the significance of the swath, the lack of longitudinal confine ment, patterns of steady and rapid field changes, and the temporal per sistence of these features in relation to the geometry of the reversin g field.