Abstract
Sampling strategies used in paleomagnetic studies play a crucial role in
dictating the accuracy of our estimates of properties of the ancient
geomagnetic field. However, there has been little quantitative analysis
of optimal paleomagnetic sampling strategies and the community has
instead defaulted to traditional practices that vary between
laboratories. In this paper, we quantitatively evaluate the accuracy of
alternative paleomagnetic sampling strategies through numerical
experiment and an associated analytical framework. Our findings
demonstrate a strong correspondence between the accuracy of an estimated
paleopole position and the number of sites or independent readings of
the time-varying paleomagnetic field, whereas larger numbers of in-site
samples have a dwindling effect. This remains true even when a large
proportion of the sample directions are spurious. This approach can be
readily achieved in sedimentary sequences by distributing samples
stratigraphically, considering each sample as an individual reading.
However, where the number of potential independent sites is inherently
limited the collection of additional in-site samples can improve the
accuracy of the paleopole estimate (although with diminishing returns
with increasing samples per site). Where an estimate of the magnitude of
paleosecular variation is sought, multiple in-site samples should be
taken, but the optimal number is dependent on the expected fraction of
outliers. We provide both analytical formulas and a series of
interactive Jupyter notebooks allowing optimal sampling strategies to be
derived from user-informed expectations.