Archaeomagnetic intensity results from California and Ecuador: evaluation of regional data

We present new archaeointensity data for southeastern California (∼33°N, ∼115°W, 50–1500 yr BP) and northwestern South America (Ecuador, 2.4°S, 80.7°W, 4000–5000 yr BP). These results represent the only data from California, as well as the oldest archaeointensity data now available in northwestern South America. In comparing our results to previously published data for the southwestern United States and northwestern South America, we note that significant scatter in the existing data makes comparisons and interpretations difficult. We undertake an analysis of the sources of data scatter (including age uncertainty, experimental errors, cooling rate differences, magnetic anisotropy, and field distortion) and evaluate the effects of scatter and error on the smoothed archaeointensity record. By making corrections where possible and eliminating questionable data, scatter is significantly reduced, especially in South America, but is far from eliminated. However, we believe the long-period fluctuations in intensity can be resolved, and differences between the Southwestern and South American records can be identified. The Southwest data are distinguished from the South American data by much higher virtual axial dipole moment values from ∼0–600 yr BP and by a broad low between ∼1000–1500 yr BP. Comparisons to global paleofield models reveal disagreements between the models and the archaeointensity data in these two regions, underscoring the need for additional intensity data to constrain the models in much of the world.