Intrinsic Bias in Averaging Paleomagnetic Data

Abstract

The transformation of isotropically distributed geomagnetic poles to local site directions introduces slight apparent inclination shallowing if the directional average is compared to the geocentric axial dipole direction. This effect depends on site latitude and pole dispersions. For typical dispersions of poles, 063 between 10° and 20°, the average inclination will appear too shallow by about 1° to 2° for site latitudes of 10° to 60° North or South. On the other hand, when some of the scatter might be due to isotropic scatter in directions, averaging all the data in polar space, will introduce a steepening effect. For most paleomagnetic studies this intrinsic inclination bias will be small in comparison with other uncertainties, typically of the order of 5° to 10°. However, for integrated high resolution studies of specific aspects of the geomagnetic field this methodological ambiguity might bias the results, and we caution against averaging paleomagnetic data only in directional space.