3.1. Paleomagnetic Results
The samples were demagnetized generally up to 20 mT (for details see Supporting Information Figs S2) which removed the viscous remanent magnetization (VRM) component causing a change in the direction of remanent magnetization during such demagnetization for most of the samples. This soft VRM component in the samples has a mean D: 13.8° and I: 56.8° values which is close to the present day’s Earth’s magnetic field direction values for the Czech Republic (D: 4.4° and I: 66.8°) (see Supporting Information Figs S3).
The intensity of the natural remanent magnetization (NRM) of the samples varies between 8.5-34.1e-3 A/m. Median destructive field (MDF) values where samples lost half of its magnetization range between 5-8 mT for the samples. NRM intensity and MDF values of the samples are shown in Supporting Information Figs S3. The maximum angular deviation (MAD) values for Matuyama and Brunhes sections are between 0.3o-5.4o (Fig. 5a). These values for the transition section are between 0.7o-5.3o which is relatively reliable for the detection of the migration of the paleomagnetic vector from reversed to normal polarity (Fig. 5a). The trend of the MAD values increases across the transition which can also be seen in the other studies (Sagnotti et al., 2014; Okada et al., 2017) (Fig. 5b).
In this study, paleomagnetic data showed inclination values changing by approximately 90o when measuring the sediment from 12.8 to 7.1 cm depth (Fig. 6). This revealed the transition nature of the Matuyama-Brunhes magnetic reversal in Za Hajovnou cave. Below this depth, there is a Matuyama section which has inclination fluctuations between -6.3o-88.7o (Fig. 6). Inclination angle changes between 33o-65.9o for Brunhes section above transition (Fig. 6). Also, the transition from reversed to normal polarity can be seen in declination data with similar depth. It has more frequent oscillations which show ~180° change from reversed to normal polarity between 2.5-9.2 cm depth (Fig. 6b). Despite the fluctuations, the intensity values of ChRM which can depend on the concentration variation of magnetic carriers of every individual sample were decreasing for the Matuyama section from the bottom to the transition between 35.1-15 cm depth (Fig. 6). After the transition from reversed to normal polarity, these values kept increasing which can be seen in the Brunhes section between 7.1-0 cm depth (Fig. 6). Fig. 6 shows the data in comparison with other studies that consisted of various sediment types and locations around the world. The depth of the data sets was normalized considering the transition zone and differences of sedimentation rate for each study and is not given in Fig. 5, 6. Even though there are some differences in absolute values, comparisons of this data set with other studies showed that fluctuations and frequency of fluctuations in our data are consistent with other data sets and serves as a supporting argument for Matuyama-Brunhes magnetic reversal in Za Hajovnou cave (Fig. 6).