Paleomagnetism of Pleistocene lake sediments from eastern California

This research encompasses rock- and paleo-magnetism of Quaternary lake sediments from Owens and Searles Basins in eastern California. These sediments are uniquely suited to studying past climate and magnetic field behavior owing to their rapid and near continuous deposition.; The Gauss/Matuyama (G/M) transition from core KM-3, Searles Valley, CA, is defined by a swath of Virtual Geomagnetic Poles (VGPs) stretching from west Africa to the northwest Pacific. We find the same pattern present in other records from western North America that span over 10 m.y., indicating that the swath is a persistent feature of the field. This compilation of regional records also reveals that the swath extends into the southern hemisphere, outlining a region marked by an absence of VGPs (centered on the Indian Ocean). Because this pattern is offset from that seen in global compilations, we suggest that the persistent fields have a nondipolar component.; Secular Variation (SV) near the G/M boundary reveals coherent directional variations that resemble ordinary SV with periods of hundreds to thousands of years and occasional swings to shallow inclinations. Inclination-only statistics indicate that angular dispersion (S) of poles is greater than expected from models of SV for the past 5my. Normal data display higher S than reverse data, suggesting that post-transitional field directions are more 'stable' than the pre-transitional ones. Reverse directions yield {dollar}sim{dollar}2{dollar}spcirc{dollar} shallower inclinations than normal directions, consistent with the presence of standing nondipole fields that do not reverse with the dipole.; A study of core OL92 from Owens Lake, CA, yields magnetostratigraphy, proxies for climate change, and fine-scale paleomagnetic field behavior. The M/B polarity reversal is identified at the base of the section, yielding an average sedimentation rate of 40cm/1000yrs. Several excursions were identified that constrain timing throughout the core. Susceptibility measurements resolve a horizon interpreted as the onset of the Late Glacial Interstadial ({dollar}sim{dollar}12,5000yr). Correlation of long period secular variation in OL92 with a record from Nevada provides additional age control, and indicates that the field can deviate significantly from the geocentric axial dipole direction for extended periods of time ({dollar}sim{dollar}100,000yrs).