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A megaslump at Batagaika, in northern Yakutia, exposes a remarkable stratigraphic sequence of permafrost deposits ~50–80 m thick. To determine their potential for answering key questions about Quaternary environmental and climatic change in northeast Siberia, we carried out a reconnaissance study of their cryostratigraphy and paleoecology, supported by four rangefinder 14C ages. The sequence includes two ice complexes separated by a unit of fine sand containing narrow syngenetic ice wedges and multiple paleosols. Overall, the sequence developed as permafrost grew syngenetically through an eolian sand sheet aggrading on a hillslope. Wood remains occur in two forest beds, each associated with a reddened weathering horizon. The lower bed contains high amounts of Larix pollen (>20%), plus small amounts of Picea and Pinus pumila, and is attributed to interglacial conditions. Pollen from the overlying sequence is dominated by herbaceous taxa (~70%–80%) attributed to an open tundra landscape during interstadial climatic conditions. Of three hypothetical age schemes considered, we tentatively attribute much of the Batagaika sequence to Marine Oxygen Isotope Stage (MIS) 3. The upper and lower forest beds may represent a mid–MIS 3 optimum and MIS 5, respectively, although we cannot discount alternative attributions to MIS 5 and 7.
Two female woolly mammoth neonates from permafrost in the Siberian Arctic are the most complete mammoth specimens known. Lyuba, found on the Yamal Peninsula, and Khroma, from northernmost Yakutia, died at ages of approximately one and two months, respectively. Both specimens were CT-scanned, yielding detailed information on the stage of development of their dentition and skeleton and insight into conditions associated with death. Both mammoths died after aspirating mud. Khroma's body was frozen soon after death, leaving her tissues in excellent condition, whereas Lyuba's body underwent postmortem changes that resulted in authigenic formation of nodules of the mineral vivianite associated with her cranium and within diaphyses of long bones. CT data provide the only comprehensive approach to mapping vivianite distribution. Three-dimensional modeling and measurement of segmented long bones permits comparison between these individuals and with previously recovered specimens. CT scans of long bones and foot bones show developmental features such as density gradients that reveal ossification centers. The braincase of Khroma was segmented to show the approximate morphology of the brain; its volume is slightly less (∼2,300 cm3) than that of neonate elephants (∼2,500 cm3). Lyuba's premaxillae are more gracile than those of Khroma, possibly a result of temporal and/or geographic variation but probably also reflective of their age difference. Segmentation of CT data and 3-D modeling software were used to produce models of teeth that were too complex for traditional molding and casting techniques.
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