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Late Pliocene to late Pleistocene environments preserved at the Palisades Site, central Yukon River, Alaska |
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| Authors: | Paul Matheus James BegétOwen Mason Carol Gelvin-Reymiller |
| Institution: | a Alaska Quaternary Center and the Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-5540, USA b Department of Geology & Geophysics and the Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-5780, USA c Department of Anthropology, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA d 1191 Dolphin Way, Fairbanks, AK 99709, USA |
| Abstract: | The Palisades Site is an extensive silt-loam bluff complex on the central Yukon River preserving a nearly continuous record of the last 2 myr. Volcanic ash deposits present include the Old Crow (OCt; 140,000 yr), Sheep Creek (SCt; 190,000 yr), PA (2.02 myr), EC (ca. 2 myr), and Mining Camp (ca. 2 myr) tephras. Two new tephras, PAL and PAU, are geochemically similar to the PA and EC tephras and appear to be comagmatic. The PA tephra occurs in ice-wedge casts and solifluction deposits, marking the oldest occurrence of permafrost in central Alaska. Three buried forest horizons are present in association with dated tephras. The uppermost forest bed occurs immediately above the OCt; the middle forest horizon occurs below the SCt. The lowest forest bed occurs between the EC and the PA tephras, and correlates with the Dawson Cut Forest Bed. Plant taxa in all three peats are common elements of moist taiga forest found in lowlands of central Alaska today. Large mammal fossils are all from common late Pleistocene taxa. Those recovered in situ came from a single horizon radiocarbon dated to ca. 27,000 14C yr B.P. The incongruous small mammal assemblage in that horizon reflects a diverse landscape with both wet and mesic environments. |
| Keywords: | Alaska Yukon River Beringia Interglacial Peat Dawson Cut Forest Bed Tephra Permafrost Mammals |
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