A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing

Abstract

This paper reports an empirical test of a new nonheating Preisach-based protocol for determining the absolute ancient magnetic field intensity (paleointensity) using a selection of synthetic samples and a large suite of modern lavas and pyroclastic lithic samples. Generally, the Preisach paleointensity estimates compare favorably with the expected field intensities: (1) for the synthetic samples displaying single-domain-like behavior, the method returned the correct result for the known field, while multidomain samples yielded an underestimate, and (2) averaging 168 post-1850 A.D. lavas yielded a value <6% within the expected field value. These Preisach paleointensity estimates are also compared with paleointensity determinations made on the same suite of samples using standard Thellier-type heating protocols and the nonheating remanence (REM) method. The Preisach paleointensity estimates compare favorably for samples that yielded correct Thellier-type determinations, including the synthetic single-domain-like samples. In addition, the Preisach method produced estimates for cases where the Thellier-type estimates failed. A possible selection criterion was identified (median destructive field), which was found to improve the paleointensity estimates in some sample suites. For the investigated sample set the Preisach method was found to be much more accurate than the REM method. The importance of cooling rate on the Preisach paleointensity estimate is also examined.