Fig. 3

Examples of coercivity component fits to IRM acquisition curves. a-c - Sample WW 2.4B from the Anisian grey limestone; d-f - Sample WW 3.3C from the Anisian grey limestone; g, h, j - Sample WW 8.18B from the Anisian grey limestone; k-m - Sample WW 7.11B from the Anisian red marly limestone; o-q - Sample WW 10.73B from the Rhaetian claystone. Component (Comp.) 1 (pink) is interpreted as hematite, Comp. 2 (green) is variably oxidized magnetite, and Comp. 3 (light blue) is the ‘skew’ component, see main text for detailed explanation. The sum of the components is marked in red; data points are the grey points. In the linear acquisition plots (LAP), i.e., a, d, g, k, o, the magnetic moment is plotted versus the logarithmic field value; in the gradient acquisition plots (GAP), i.e., b, e, h, l, p, the gradient of the LAP is plotted; in the standardized acquisition plots (SAP), i.e., c, f, j, m, q, the standardized score (z) is plotted versus the logarithmic field value. In this way of plotting deviations from cumulative log-Gaussian distributions show up as deviations from a straight line, indicating the need of additional components for a good fit