4.2. Sediment Deposition and Sedimentation Rate
According to Lundberg et al. (2014) the cave was filled with water during the sedimentation which was continuously active without any climatic change or hiatus. This provides the continuous magnetic record of the reversal in the cave sediment and allows the sediment to acquire and keep the primary magnetization without the possibility of secondary mineralization. Also, there are no obvious marks in the studied sediment section that one would expect if breaks in deposition (e.g. lithological boundaries, desiccation cracks).
Our estimate of the Za Hajovnou cave’s sedimentation rate (0.2 cm/kyr – 1.0 cm/kyr) seems to be significantly lower than the sediments from other studies (Sagnotti et al., 2010; Jin and Liu, 2011; Giaccio et al., 2013; Liu et al., 2016; Okada et al., 2017). This is likely due to contrasting sediment types. While the duration of the M/B transition was reported to last between 4-13 kyr (Yamazaki and Oda, 2001; Suganuma et al., 2010; Valet et al., 2014; Okada et al., 2017), the averaged sedimentation rate of 0.6 cm/kyr in this study suggests transition duration of 9.66 kyr (7.1-12.8 cm sediment transition depth section) and thus strengthen our confidence to the reliability of our sedimentation rate and paleomagnetic record estimates. Additionally, low sedimentation rates (<1 cm/kyr) were reported in previous Matuyama-Brunhes magnetic reversal studies (Clark, 1970; Love and Mazaud, 1997; Nowaczyk et al., 2001).
Analyzes of cave sediments by paleomagnetism carried out in different locations around the earth such as in Western Europe (Parés et al., 2018), South Africa (Nami et al., 2016), South America (Jaqueto et al., 2016), North America (Stock et al., 2005), Southern Europe (Pruner et al., 2010), Eastern Asia (Morinaga et al., 1992) showed that cave sediments recorded magnetic reversals. Morinaga et al. (1992) suggested a low sedimentation rate for the Western Japan cave sediments 1.6 cm/kyr which shows a similar rate with our Central European cave sediment estimation. King and Channell (1991) suggested that large ”lock-in” depths are associated with interparticle rigidity and strength, characteristic of clayey low accumulation rate sediments (<1 cm/kyr) which results in delays of magnetic acquisition. This shows that magnetic polarity reversal could have a large (25 kyr) apparent age offset between sediments with high and very low accumulation rates (King and Channell, 1991).