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The article presents a new sedimentary-climatic model for explaining autochthonous clastic sediment in the Upper Pleistocene site, Divje babe I, Slovenia. The sediment analysed here was deposited during Oxygen Isotope Stages 1, 3 and 5 (OIS, OIS 3, OIS 5). The stress is on precipitation, which we explained on the basis of the quantity of authigenic structural aggregates in the sediment. We supported the results with quantitative analysis of clasts with etched surface, which represent corrosion of the cave ceiling, and etched bones, which represent corrosion on the cave ground. We also analysed the relation between climate and cave bears, and Neanderthals and climate, on the basis of mass fossil remains and finds of artefacts. All analyses were made on the basis of three-dimensional sampling, i.e., in horizontal and vertical directions. We sampled 65 profiles over an area of 65 m2. Each profile had 35 arbitrary stratigraphic units (splits) with data on aggregates, etched bones, fossil remains and artefacts. In explaining the sediment characteristics that point to climatic parameters, we consistently took into account the Holocene standards for the site. We found that the climate in OIS 3 was colder and damper than in OIS 1 and OIS 5. People and animals responded to the climatic changes in OIS 3 with more visits to the cave, but not at the same time. The climatic change was presumably reflected in the microlocation of the cave mainly by the longer duration of snow cover.
The fossil population structure of the cave bear from the Mokrica cave was evaluated to provide new data concerning the behaviour and mortality of this extinct species. Age at death was estimated for 128 different individuals by analysing cementum increments, root formation and crown wear of left M1 teeth. After the frequency distribution of specimens through one- year intervals, the mortality trends can be estimated for various lifetime periods, and interpreted in accordance with data for present-day bears. The original death assemblage was presumably juvenile-dominated. Extremely fragile molars of less than 6 month old cubs did not get preserved. Yearlings are the most numerous age class in the fossil population from the Mokrica cave. Mortality drastically dropped after cave bears survived their first hibernation in the second winter. The lowest mortality rate was observed in the 9-15 years age group, when cave bears would be expected to be in their prime. The oldest age recorded by cementum analysis is approximately 30 years, which indicates that the maximum life span was similar to present-day bears. Study of dental tissues shows that the mortality in the cave was seasonally restricted – the majority of deaths in the cave occured during winter and in early spring. Sex structure of the fossil population has been studied on the sample of 750 canines. The significantly higher proportion of males in the group of older juveniles and subadults could be explained by the fact that the weaning period is more critical for males also in present- day bears. In young adults and prime adults the mortality was presumably higher in females. The sex structure of adult bears, especially in the sample of older individuals, indicates that the Mokrica cave was used as winter den mostly by solitary males.
The Inner Range of the Crimea Mountains has recently been identified as an area of previously unrecognized hypogene speleogenesis (Klimchouk et al. 2009). The entrance of the Tavrskaya cave is located in the middle of the 25 m-high scarp of the cuesta built up of Paleocene limestone. The cave comprises two parallel major passages (ca. 180 m long, up to 7-8 m high and up to 5-6 m wide) connected by a smaller passage. The major passages are slightly inclined toward the north-west following the dip of bedding. The morphology of the cave bears strong indications of dissolution at conditions of ascending flow in a confined aquifer setting.
A massive calcite crust, studied in this paper, was first found in a small cave located ca. 200 m from Tavrskaya cave along the cuesta scarp. According to its position and morphology, the cave corresponds to the rift-like “feeder” zone of Tavrskaya cave. Recently, similar calcite crust was found in Tavrskaya cave, in a rift-like passage of the near-scarp zone. The crust is built up of a brownish translucent calcite whose columnar crystals (bounded by competitive growth surfaces) are arranged in a characteristic radiating pattern. Calcite contains only all-liquid inclusions indicating deposition at less than ca. 50ºC. It also contains filamentous biological material (possibly fungi or cyanobacteria), which sometimes facilitated entrapment of fluid inclusions. This calcite body is tentatively
interpreted as a paleo-spring deposit (ascending flow). In order to characterize the isotopic properties of this calcite and the bedrock limestone we drilled small-diameter cores through the calcite formation, as well as through the wall of a cavity devoid of calcite. Stable isotope analyses were performed along these cores. To provide a basis for comparison several samples from the same lithostratigraphic units were collected far from the cave. Along a 15 cm-long profile, both oxygen and carbon isotopes of the limestone remain stable at 18O = -4.3 0.2
h and 13C = -1.7 0.3 h (1). Only within the 1.5 cm-thick zone immediately underlying the calcite 18O and 13C values plunge to ca. -8 h and -9 h respectively,. It appears from this data that water rock-interaction associated with the deposition of this calcite produced only a thin alteration halo in the limestone. However, when data from the cave-wall cores are compared with those collected far from the cave, it appears that the “constant” values from cave walls are shifted relative to the presumably unaltered limestone values toward lower values by
ca. 1.5-3.0 h (oxygen) and 3-4 h (carbon). On the 18O-13C cross-plot the data for unaltered limestone, cave wall limestone, alteration halo, and secondary calcite plot along a well-defined line (R2=0.99).
We propose that the Paleocene limestone in the vicinity of the Tavrskaya cave has experienced a two-stage alteration. During the first stage, presumably associated with the process of cave excavation, the bedrock has been altered (18O depleted by 1.5 to 3.0 h and 13C by 3 to 4 %). The thickness of this zone of early alteration is unknown but must be larger than 15 cm (length of our cores). The second stage of alteration was associated with the deposition of calcite; during this stage the isotopic composition was further depleted (by 4-5 h in 18O and 8-10 h in 13C). The extent of alteration was much smaller, though, and restricted to zones where calcite was deposited (ca. 15 mm beneath the calcite).