Figure 1. Stereographic projection showing the mean paleopole position and its A₉₅ from this study and the published paleopole position and its A₉₅ for Mongolia, Norway, Turkey, and Antarctica.

4 Results

4.1 Effect of a k-cutoff

A widely used filter to establish site-mean directions that represent spot readings of the paleomagnetic field is to check for high within-site scatter by means of a k-cutoff. Sites with low kvalues are interpreted as either remagnetized or not representative of a spot reading and are therefore discarded (Figure S1). We analyze the effect of the k-cutoff size on between-site scatter using the mean paleopole of a dataset (Figure 2) and its N, A₉₅, K, and S (Figure 3). The pole positions do not significantly change when applying a k-cutoff (Figure 2). When a low k \(\mathbf{\geq}\)10 cutoff is applied, the number of sites remaining in the dataset decreases by approximately 15-30% (Figure 3a), omitting sites with near-random direction distributions. Increasing the cutoff size beyond 20, the decay in sites decreases. The A₉₅ increases with increasing k-cutoff due to a decrease in N (Figure 3b). As expected, discarding sites with high within-site scatter leads to a higher K and lower S, although the effects are small (Figure 3c, d), except in the dataset from Norway where K rises from 30 to 70. No major improvement becomes apparent in any of the variables at the commonly used cutoff sizes of 50 and 100. Importantly, although the application of a k-cutoff may subtly decrease S and increase K, the decrease in N leads to an increase of the A₉₅, and thus to a decrease in precision of the paleopole when a k-cutoff is applied, whereas the pole position remains approximately the same.