A PRIBILOF ISLAND CAVE: LATE QUATERNARY MAMMAL BONE ASSEMBLAGES FROM ST. PAUL ISLAND, BERING SEA, ALASKA

A newly-discovered cave in a collapsed lava tube on St. Paul Island contains a Late Quaternary mammal bone assemblage deposited when it was a high-altitude site near the mouth of the paleo-Yukon River along the south shore of the Bering Land Bridge. Bones of four taxa have been recovered: woolly mammoth (Mammuthus primigenius), caribou/reindeer (Rangifer tarandus), large bear (Ursus sp.), and fox (probably Arctic fox, Alopex lagopus). In July 2003 the cave was mapped and ca. 2000 faunal elements and associated sediments were collected from the floor. Mammoth materials (molar teeth/tooth plates, with some postcranial elements) are apparently derived from sandy sediments that may be Pleistocene or early Holocene in age, which were in turn covered by substantial roof fall. In the center of the cave is a large debris cone that appears to be Holocene in age, comprised of highly plastic clay-to-silt sized sediments containing little fauna. The debris cone contains numerous large blocks suggesting that roof fall events continued throughout the Holocene.

Analyses of the faunal materials from the cave will focus on chronology, taphonomy, and paleoecology. Dating of mammoth elements will help determine if they represent Beringian populations or insular, late-surviving populations. Identification and dating of bear remains will amplify earlier work on insular bear populations from southeastern Alaska. Dating and morphological analysis of fossils, as well as comparisons with DNA of contemporary brown/polar bears, will help explain evolution of Ursus populations. Paleoecological significance of these faunas and their sedimentary matrices will be assessed, to elicit roof fall episodes, shifting wind and moisture regimes, and vegetational changes in late Pleistocene/Holocene Beringia. These analyses will be enhanced by the availability of the nearby Lake Hill pollen core studied by Colinvaux, which revealed climate and vegetation from the LGM to the Holocene. Taphonomic studies on the bones will focus on animal tooth pits and gnawing marks, as well as percussions and scrapes caused by rock fall and abrasion. These studies will add substantively to curent knowledge of the late Pleistocene/early Holocene paleoecology of central Beringia, where continental climates were more rapidly replaced by cool, maritime climates than elsewhere on the Land Bridge.