Holocene Paleointensity of the Island of Hawai `i From Glassy Volcanics

This study presents new high-quality paleointensity records and C-14 radiocarbon age determinations from the Island of Hawai'i during the Holocene. Previous studies on Hawai'i use experimental methods and statistical selection criteria that may produce inaccurate geomagnetic field strength estimates. Additional high-quality paleointensity results can be used to evaluate the existing Hawaiian data set and investigate Holocene geomagnetic field behavior. New paleointensity sites from 22 lava flows were calculated using the IZZI-Thellier laboratory technique and a strict set of selection criteria. Rapidly cooled, glassy volcanic material was collected for all sites. Isotopic age determinations range from 270 to > 10, 000 years before present (nine new C-14 ages are also presented as part of this study). The median intensity for the 22 flows is 47.5 mu T, with a median absolute deviation uncertainty of 5.6 mu T; substantially greater than the present-day field strength at Hawai'i (similar to 36 mu T). These new results are comparable to previously published data from this location and are consistent with global paleointensity models. There is no evidence of an intensity "spike" at 3,000 years before present, as seen in the Levant and elsewhere. Previously published data vary in intensity by experimental technique relative to data using glassy material and strict selection criteria. Non-Thellier-type data are biased low, a result of these techniques estimating intensity from possibly nonsingle domain magnetic carriers. Thellier-Thellier data are biased high, the reasons for which remain unclear as no cooling rate effect was demonstrated, and we were unable to reproduce the high bias with different selection criteria.