Figure S1. Room-temperature mean susceptibility (kmRT) and low-temperature mean susceptibility (kmLT) of chalk samples, indicating that paramagnetic and diamagnetic minerals are the main contributors to the rock mean susceptibility (see Issachar et al., 2018 for details). (A) kmLT versus kmRT plot showing a linear correlation with a slop of 3.3. (B) kmLT/kmRTversus kmRT plot showing an average amplification factor of 4.6 ± 0.4.