## 3 Results
### Identification of Periods in Magnetic Susceptibility Data  
Figure 5 shows the results of applying spectral methods to the magnetic susceptibility data for the Pontian deposits (Figure 2a) of the Zhelezny Rog Cape. Of the three prominent peaks on the Lomb periodogram, two peaks fall within the 95% confidence interval (Figure 5a). These peaks are located at frequencies of 0.0425 and 0.2519, corresponding to periods of 23.53 m and 3.97 m, respectively. This result is confirmed by the Fourier periodogram (Figure 5a), where the main peaks are located at frequencies of 0.0437 and 0.2519 periods of 22.88 m and 3.97 m. In contrast to the example described above (Figure 3a), the Fourier and Lomb periodograms in Figure 5a differ slightly. These differences can be explained by white noise in the original data (Figure 2a). Figure 5b shows the spectrum obtained using the REDFIT algorithm. Two peaks fall within the 95% confidence interval. They occur at frequencies of 0.0444 and 0.2525, which correspond to the periods of 22.52 m and 3.96 m. These periods coincide with the periods identified by the Fourier and Lomb periodograms. Figure 4: Function constancy exponent (construction—variance) and determination of periods. Figure 6 shows the Fourier and Lomb periodograms and the REDFIT spectrum for the magnetic susceptibility data from the Lower Maeetian deposits (Figure 2b). Only one peak of the Lomb periodogram falls within the 95% confidence interval (Figure 6a). This peak is located at a frequency of 0.1408, which corresponds to a period of 7.1 m. This result is partially confirmed by the Fourier periodogram, where the main peak is at a frequency of 0.1516 (period 6.6 m). We are inclined to believe that the differences in the periodograms can be explained by noise in the data. The REDFIT spectrum is shown in Figure 6b. In this spectrum, just one peak is located in the 95% confidence interval. It occurs at a frequency of 0.1497, corresponding to a period of 6.68 m. The similarity in the periods obtained from the Fourier periodogram and the REDFIT spectrum may indicate more white noise than red noise in the initial data. To identify periods, the developed DMA-algorithm is applied. In Figure 7, the calculated constancy values for the magnetic susceptibility data of the Pontian and Lower Maeetian deposits are shown in blue. As discussed previously, periods are considered to be the points of 'global' minima of the constancy exponent _C(f, T)_. For this reason, the calculated constancy exponents were'strongly' smoothed to obtain their global trends. The smoothed constancy exponents are shown as red lines in Figure 7. Figure 7a shows that the prominent period in the magnetic susceptibility data series of the Pontian deposits is 3.6 m. The minimum of the constancy exponent at 15.2 m can be considered a 'weak' period. The  
Figure 5: The results of applying spectral methods to the magnetic susceptibility data from the Lower-Upper Pontian deposits of the Zhelezny Rog Cape section (Figure 2a): (**a**) Fourier and Lomb periodograms (the black bold solid line indicates the 95% confidence interval for the Lomb periodogram); (**b**) the spectrum constructed by the REDFIT algorithm (the black bold solid line indicates the 95% confidence interval). Figure 6: The results of applying spectral methods to the magnetic susceptibility data of the Lower Maeetian deposits of the Zhelezny Rog Cape section (Figure 2b): (**a**) Fourier and Lomb periodograms (the black bold solid line indicates the 95% confidence interval for the Lomb periodogram); (**b**) the spectrum constructed by the REDFIT algorithm (the black bold dotted line indicates the 95% confidence interval). absence of the \(\sim\)23 m period in Figure 7a is due to the algorithm considering values in half of the studied segment to be contenders for the period, which in this case is 41.2 m. For the Lower Meotian deposits, only one period of 7 m can be distinguished (Figure 7b). Strong periods in Figure 7 emerge as very close to the periods obtained using spectral methods of analyzing data series.