Palaeomagnetic and U-series Dating of Cave Sediments in Baradla Cave, Hungary

Povzetek

Drobnozrnati siliklastični sedimenti glavne galerije in gornjega nivoja jame Baradla, izkazujejo veliko homogenost v zgradbi in sedimentnih teksturah. Paleomagnetne analize kažejo normalno polarizacijo vseh vzorcev, kar pomeni starost, ki je mlajša od meje Brunhes/Matuyama pri 780 ka. Siga oz. stalagmiti, ki pokrivajo siliklaste v gornjem jamskem nivoju, vsebujejo tudi reverzno polarizirane vzorce, katerih datacije z uran torijevo metodo kažejo na starost 114-115 ka, kar nakazuje na dogodek Blake. Homogenost sedimentov lahko razložimo z enkratnim dogodkom, kjer je zapolnitev s sedimentom povzročil zastoj pretoka. Temu so lahko botrovali geološki (npr. podor) ali paleoklimatski vzroki pred približno 130-150 ka, kolikor je tudi najvišja starost sedientov v sistemu Domica-Baradla izmerjena z metodo uran-torij.

Fine-grained siliciclastic sediments from the main gallery and upper cave level show nearly uniform composition and sedimentary textures. Palaeomagnetic analysis indicates normal magnetic polarisation of all samples, i.e. the age younger than Brunhes/Matuyama boundary at 780 ka. Flowstone/stalagmite covering siliciclastics in the upper cave level contains reverse polarised samples dated by U-series method to about 114–115 ka, which can be identified as the Blake Event. The uniform composition of sediments can indicate the infill of the cave during a single event caused by the blockage of drainage routes due to geological (collapse) or palaeoclimatic (ice) changes, which took part before ca 130 to 150 ka as indicating by the oldest U-series data from the whole Domica–Baradla Cave System.