Interglacial deposits at Birch Creek, northeast interior Alaska

Abstract A 12-m sequence of lake sediment and peat in a 45-m high exposure on Birch Creek, northeast Alaska, contains pollen of Picea, Betula, Alnus and Populus , and wood of Picea and Populus . This sequence, which may represent 10,000 yr of more of accumulation, is beyond the limit of radiocarbon dating. It lies between two units of loess; the underlying loess lies above the Old Crow Tephra, recently dated at 149,000 ± 13,000 yr B.P. The lake sediments probably were deposited during the last interglaciation (isotope substage 5e) and subsequently buried by Wisconsinan loess. Analogs for the ancient lake may be deep, long-lived thaw lakes that are present in the modern landscape. When Birch Creek is correlated with other sites across nonglaciated Alaska and northwest Canada, there appears to be a common interglacial signal in sediments overlying the Old Crow Tephra.