FRAGMENTS OF ICE AGE ENVIRONMENTS

Climatostratigraphic classification of sediments in the western sector of Potočka zijalka, based on reconstruction of snow conditions at the time of their deposition

Janez TURK

Longitudinal profile in the western sector of the anterior part of the Potočka zijalka. The reconstruction of the snow talus in cool climatic periods of the Pleistocene is depicted (for winter and early summer). The author of the sketch is Ivan Turk (1996).

Abstract

Cave sediments in Potočka zijalka are of Pleistocene and Holocene age. The longitudinal profile through sediments at the anterior part of the cave exhibits some peculiarities. Holocene sediments are relatively thick at the talus (sedimentary cone directly at the cave mouth), while they are relatively thin at the protalus section. The protalus appears at the base of the talus, in the cave. The spatial distribution of Pleistocene sediments is just the reverse. We tried to interpret this characteristic of sediments by considering the snow conditions. These conditions were totally different in the Pleistocene than in the Holocene. During cool and humid climatic periods, snow was accumulating directly at the entrance to the cave. Consequently, a snow cone was formed. It could extend ten or more metres far into the cave. The snow cone could persist for the major part of the year due to the severe and long winters. It presumably didn't melt and disappear totally before the summer; occasionally it might even not disappear at all. Clastic material (debris), which spalled from the cave ceiling and walls around the cave mouth, did not accumulate on the snow cone. It rather slid down the slope of the snow cone and accumulated at the base of the snow slope (cone). Hence protalus sediments accumulated. In warm periods, such as the Holocene, the accumulation is different, with the sediments accumulating directly at the cave mouth. Hence the sediment cone (talus) formed there. In these times the snow persists for only a few months per year in front of the cave (in winters). For this reason it does not have any significant influence on the distribution of debris deposition.

Keywords: Pleistocene, Holocene, talus, aurignacien, Karavanke, Slovenia

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2011, (Opera Instituti Archaeologici Sloveniae, 21), 280 pages, 44 b-w photographs, 10 drawings, 52 tables, 71 graphs and 9 maps, 20 x 29 cm hardcover, ISBN 978-961-254-257-3.

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