Paleoenvironmental data, including pollen and sediment analyses, radiocarbon ages, and tephra identifications of a core recovered from a fen, provide a ca. 16,500 14C yr B.P. record of late Quaternary vegetation and climate change in the Long Valley area of west-central Idaho. The fen was deglaciated prior to ca. 16,500 14C yr B.P., after which the pollen rain was dominated by Artemisia, suggesting that a cold, dry climate prevailed until ca. 12,200 14C yr B.P. From ca. 12,200 to 9750 14C yr B.P. temperatures gradually increased and a cool, moist climate similar to the present prevailed. During this period a closed spruce–pine forest surrounded the fen. This cool, moist climate was briefly interrupted by a dry and/or cold interval between ca. 10,800 and 10,400 14C yr B.P. that may be related to the Younger Dryas climatic oscillation. From ca. 9750 to 3200 14C yr B.P. the regional climate was significantly warmer and drier than at present and an open pine forest dominated the area around the fen. Maximum aridity occurred after the deposition of the Mazama tephra (ca. 6730 14C yr B.P.). After 3200 14C yr B.P. regional cooling brought cool, moist conditions to the area; the establishment of the modern montane forest around the fen and present-day cool and moist climate began at ca. 2000 14C yr B.P.

Burial Lake in northwest Alaska records changes in water level and regional vegetation since ∼ 39,000 cal yr BP based on terrestrial macrofossil AMS radiocarbon dates. A sedimentary unconformity is dated between 34,800 and 23,200 cal yr BP. During all or some of this period there was a hiatus in deposition indicating a major drop in lake level and deflation of lacustrine sediments. MIS 3 vegetation was herb-shrub tundra; more xeric graminoid-herb tundra developed after 23,200 cal yr BP. The tundra gradually became more mesic after 17,000 cal yr BP. Expansions of Salix then Betula, at 15,000 and 14,000 cal yr BP, respectively, are coincident with a major rise in lake level marked by increasing fine-grained sediment and higher organic matter content. Several sites in the region display disrupted sedimentation and probable hiatuses during the last glacial maximum (LGM); together regional data indicate an arid interval prior to and during the LGM and continued low moisture levels until ∼ 15,000 cal yr BP. AMS 14C dates from Burial Lake are approximately synchronous with AMS 14C dates reported for the Betula expansion at nearby sites and sites across northern Alaska, but 1000–2000 yr younger than bulk-sediment dates.