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.