New Paleointensity Data From Aniakchak Volcano, Alaska, USA

Abstract

This study presents the first set of Holocene, high‐quality absolute paleointensity data from Alaska, USA. Existing paleointensity data for the Holocene are generally located at mid‐northern latitudes in North America, Europe, the Middle East, and eastern Asia. Relatively few data are from the Alaska region. IZZI‐modified paleointensity experiments were conducted on glassy volcanic materials from Aniakchak volcano, a mid‐ to high‐latitude composite volcano on the Alaska‐Aleutian arc. The CCRIT selection criteria were applied to the paleointensity results. A total of 30 specimens from six samples with estimated ages ranging from 1931 CE to 2,300 years before present passed all selection criteria. The sample‐mean paleointensities ranged from 49.5 to 68.0 microTesla (μT). The sample‐mean paleointensity results are comparable to modeled intensities, however all except for one sample‐mean paleointensity are lower than those predicted by geomagnetic field models. The paleointensity estimate for the historical 1931 CE eruption was about 15 μT greater than the expected field strength. This overestimate may result from unrecognized alteration or non‐ideal remanence carriers in this sample. Further evaluation of samples from the 1931 CE eruption using a Bayesian estimation method resulted in a paleointensity estimate that encompasses the historical field strength within uncertainty. These new paleointensity results are a valuable contribution to the mid‐ to high‐northern latitude paleomagnetic data set. Incorporation of these data into future geomagnetic field models will improve the predictions of geomagnetic field behavior in the Alaska region.