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Jama 65 - Križna jama
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Naslov Križna jama (SW Slovenia): Numerical- and correlated-ages from cave bear-bearing sediments
Povzetek Križna jama is a large river cave located between Loško and Cerkniško poljes under Križna gora Mountain in southern Slovenia. It has been known since the mid-19th century due to numerous cave bear finds.
Vsebina Križna jama is a large river cave located between Loško and Cerkniško poljes under Križna gora Mountain in southern Slovenia. It has been known since the mid-19th century due to numerous cave bear finds. The cave is filled by complicated sequences of cave fluvial and lacustrine sediments, which are recently partly eroded. We studied two paleontological excavations and profiles in the Medvedji rov to contribute to dating the bone-bearing lithological horizons. The Križna jama I profile consists of an alternation of speleothem layers (flowstone sheets with small stalagmites, sometimes with in situ cemented Ursus gr. spelaeus bones) and fine-grained siliciclastics often with bones of cave bear. It can be correlated with the upper part of the Križna jama II profile, but with a slightly less well preserved stratigraphic record. Radiocarbon and U-series dates clearly indicate two different ages of cave bear thanatocenoses in the Križna jama I profile: those above flowstone crusts were dated to ca. 47–45 ka by radiocarbon dating; those included in speleothem layers and clay interbeds are older than 94 ka (U-series date). Details of internal lithology, thinness of layers and the state of bone preservation exclude insertion of younger layers into eroded/washed out spaces among the flowstones. Numerical dating excludes re-deposition of bear bones from older assemblages to sediments above flowstones. According to the paleomagnetic findings (prevailing normal polarization), deposition occured within the Brunhes Chron (< 780 ka). A total of four short-lived magnetic reverse excursions were discovered. According to U-series data, the upper one (profile I) might be correlated with the Blake excursion. The lower ones are older than ca 190 ka and can be correlated with some of the Jamaica-Pringle Falls, Namaku, Calabrian Ridge, Portuguese margin or Calabrian Ridge 1 excursions. Sediments in the studied profiles were deposited during the Last Glacial (Weichselian), Eemian interglacial, Saalian glacial and Holsteinian interglacial.
Url http://carsologica.zrc-sazu.si/?stran=article&id=475

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