Figure 6. Effect of the number of
samples discarded per paleomagnetic site on a) paleopole position in
stereographic projection, shown without outliers discarded and with one
outlier discarded, and the b) A95, c) K, and d) S of the
acquired paleopole.
4.4 Effect of sample distribution over sites
To average between-site scatter, it is common to collect multiple sites
at a locality. The minimum number of sites recommended for determining a
paleopole varies between authors (e.g., Meert et al., 2020; Van der Voo,
1990), but as shown by Vaes et al. (2021), poles with larger N tend to
plot closer to a best estimate of the time-averaged pole. We performed
experiments varying the number of samples per site and the number of
sites, with combinations chosen such that the total amount of
paleomagnetic samples remained approximately 100. We studied the effect
on angular distance to the reference pole, A95, K, and S
(Figure 7) of the acquired paleopole. The means were calculated from
1000 runs of the specific number of samples per site and number of
sites, where the number of samples and sites was randomly selected from
the total population during each run.
The paleopole position is strongly influenced by the distribution of
samples over sites in case of Mongolia, Turkey, and Antarctica, and lies
further from the reference pole if the samples are distributed over
fewer sites (Figure 7a). There also is a major effect on the
A95. For all datasets, the A95 is by far
the smallest when it is constrained by 100 sites of n = 1, and the
highest when it is constrained by 15 sites of n=7 (Figure 7b). The
effect on K and S is small, except in the dataset from Norway (Figure
7c, d). In that dataset, K is highest and S is lowest for 15 sites with
n=7. Nonetheless, the paleopole position is far better determined when
taking many sites with few samples.