Wisconsin Environment of Interior Alaska: Pollen and Macrofossil Analysis of a 27 Meter Core from the Isabella Basin (Fairbanks, Alaska)

Abstract

Information on the Wisconsin environment of interior Alaska has been obtained from study of pollen as well as the plant and animal macrofossils contained in sediments of a 27 m core at Isabella Creek, near Fairbanks, Alaska. The pollen assemblages indicate three major zones.Zone A (35 000 to 32 000 BP) represents a mid-Wisconsin interstadial during which spruce treeline was lower in elevation than at present though not nearly as low as during early and late Wisconsin time. Zone B represents a late Wisconsin interval of severe arctic climate. Forests disappeared from interior Alaska or were greatly diminished and much of the region was characterized by steppe-tundra vegetation. Steppe conditions may have been favored by rapid deposition of primary and reworked loess. Zone C shows that spruce forests and some of the associated boreal biota had returned to interior Alaska by 8500 years BP. A fluctuation of alder percentages within Zone C may result from mid-Holocene warming.Plant macrofossils from the Isabella sequence show that some species now having a boreal or taiga distribution survived the late Wisconsin of interior Alaska in a steppe-tundra environment. Other plants that were growing at Isabella during mid-Wisconsin time apparently became extinct in Alaska during the late Wisconsin.