This study summarizes paleomagnetic secular variation (PSV) in five published Holocene records from Eastern North America. We have developed 100-year increment time series for the declinations and inclinations for all sites and compared their directional variability. We see evidence of ten correlatable features in both inclination and declination. We focus on the clockwise or counter-clockwise motion of paleomagnetic directions (termed circularity) in these PSV records. We have first calculated the incremental rate and direction of motion (clockwise or counter-clockwise) for each record over the last 4000-8000 years. We have separately looked for discernable looping in individual records. We estimate the loop sizes, durations, and circularity direction. We see the same pattern of circularity in both measurement techniques. There are seven intervals of oscillating circularity and looping in all five sites. Both techniques suggest a distinctive oscillating, teeter-totter like, behavior to PSV circularity that must be due to the pattern of fluid flow in the outer core. This teeter-totter behavior is unbalanced with more time spent in clockwise motion than in counter-clockwise motion. We think the teeter-totter oscillation may be due to torsional oscillation in the outer core fluid flow. The loops have a distribution of sizes and durations with smaller loops being shorter in duration and bigger loops having longer durations. All five PSV records show 5 intervals of ~102 yr significant acceleration in circularity rate and PSV rate combined with change in circularity direction. These features are broadly analogous to historic geomagnetic jerks.

Well-dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California records the depositional history of a fluctuating saline-alkaline lake in the terminal basin of the Owens River system draining the eastern Sierra Nevada. Here we establish a U-Th chronology for the ~76-m-long SLAPP-SLRS17 core collected in 2017 based on dating of evaporite minerals. 98 dated samples comprising 9 different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical and reproducibility criteria. After application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145-110 ka left the age model unconstrained over the penultimate glacial termination (Termination II). We thus established a tie point between plant wax δD values in the core and a nearby speleothem δ18O record at the beginning of the Last Interglacial. We construct a Bayesian age model allowing stratigraphy to inform sedimentation rate inflections. We find the >210 ka SLAPP-SRLS17 record contains five major units that correspond with prior work. The new dating is broadly consistent with previous efforts but provides more precise age estimates and a detailed evaluation of evaporite depositional history. We also offer a substantial revision of the age of the Bottom Mud-Mixed Layer contact, shifting it from ~130 ka to 178±3 ka. The new U-Th chronology documents the timing of mud and salt layers and lays the foundation for climate reconstructions.