Bias Corrected Estimation of Paleointensity (BiCEP): An improved
methodology for obtaining paleointensity estimates
Abstract
The assumptions of paleointensity experiments are violated in many
natural and archaeological materials, leading to Arai plots which do not
appear linear and yield inaccurate paleointensity estimates, leading to
bias in the result. Recently, paleomagnetists have adopted sets of
“selection criteria” that exclude specimens with non linear Arai plots
from the analysis, but there is little consensus in the paleomagnetic
community on which set to use. In this paper, we present a statistical
method we call Bias Corrected Estimation of Paleointensity (BiCEP),
which assumes that the paleointensity recorded by each specimen is
biased away from a true answer by an amount that is dependent a single
metric of nonlinearity (the curvature parameter
$\vec{k}$) on the Arai plot. We can use this
empirical relationship to estimate the recorded paleointensity for a
specimen where $\vec{k}=0$, i.e., a perfectly
straight line. We apply the BiCEP method to a collection of 30 sites for
which the true value of the original field is well constrained. Our
method returns accurate estimates of paleointensity, with a higher level
of accuracy and precision than the strict CCRIT selection criteria, and
with higher accuracy and similar precision to the modified PICRIT03
criteria. The BiCEP method has a significant advantage over using these
selection criteria because it achieves these accurate results without
excluding large numbers of specimens from the analysis.