2.2. Demagnetization Measurements
To clean the secondary magnetizations from the sedimentary samples, we applied a stepwise alternative field (AF) demagnetization method in Pruhonice Paleomagnetism Laboratory of Czech Academy of Sciences. This method was carried out using a 2G Enterprises Cryogenic Magnetometer on 44 samples divided into 3 different sequences. The first sequence was 17 samples (13_0P, 10_5P, 09_8P, 08_5P, 05_9P, 03_8P, 01_2P, 01_2M, 03_5M, 05_8M, 08_2M, 10_0M, 13_0M, 15_0M, 17_2M, 19_2M, 22_0M) where we demagnetized at 1 mT intervals between 0-49 mT and 10 mT intervals between 50-100 mT. The second sequence was 14 samples (12_0P, 07_1P, 04_2P, 01_5P, 01_0M, 02_7M, 05_6M, 08_0M, 10_5M, 12_7M, 15_4M, 17_9M, 20_1M, 22_5M) where we demagnetized at 2 mT intervals between 0-48 mT and 10 mT intervals between 50-100 mT. The third sequence was 13 samples (10_0P, 07_7M, 05_6P, 03_0P, 00_2P, 01_8M, 04_2M, 06_2M, 09_1M, 12_8M, 14_5M, 17_0M, 21_5M) and we demagnetized at 0.5 mT intervals between 0-39.5 mT and 10 mT intervals between 40-100 mT. Demagnetization data was interpreted by using Remasoft software which was written by Agico Company (Martin Chadima and Frantisek Hrouda).
Characteristic remanent magnetization (ChRM) directions and maximum angular deviation (MAD) values were determined from principal component analysis (PCA) (Kirschvink, 1980) on the Zijderveld diagram (Zijderveld, 1967). Virtual geomagnetic pole’s (VGP’s) latitudes and longitudes were calculated using PMGSC software by Randy Enkin. Table 1 shows the data of alternative field demagnetization for each sample. Examples of alternative field demagnetization results for the Matuyama and Brunhes intervals (two examples each) are shown in Fig. 4. The rest of the samples are in the Supporting Information Tables S1 and Supporting Information Figs S2. Maximum angular deviation (MAD) values of this study and other studies (Sagnotti et al., 2014; Okada et al., 2017) are shown in Fig. 5.
Table 1. Alternative field demagnetization, virtual geomagnetic pole (VGP) data, and Matuyama-Brunhes magnetic reversal scale for this study. Minus (-) values for virtual geomagnetic pole (VGP) latitudes and longitudes indicate the southern and western hemispheres. MAD: maximum angular deviation, φp: VGP latitude, λp: VGP longitude.