LATE QUATERNARY VEGETATION AND CLIMATE OF THE WIND-RIVER RANGE, WYOMING

Sediments from Rapid Lake document glacial and vegetation history in t he Temple Lake valley of the Wind River Range, Wyoming over the past 1 1,000 to 12,000 yr. Radiocarbon age determinations on basal detrital o rganic matter from Rapid Lake (11,770 +/- 710 yr B.P.) and Temple Lake (11,400 +/- 630 yr B.P.) bracket the age of the Temple Lake moraine, suggesting that the moraine formed in the late Pleistocene. This termi nal Pleistocene readvance may be represented at lower elevations by th e expansion of forest into intermontane basins 12,000 to 10,000 yr B.P . Vegetation in the Wind River Range responded to changing environment al conditions at the end of the Pleistocene. Following deglaciation, a lpine tundra in the Temple Lake valley was replaced by a Pinus albicau lis parkland by about 11,300 C-14 yr B.P. Picea and Abies, established by 10,600 C-14 yr B.P., grew with Pinus albicaulis in a mixed conifer forest at and up to 100 m above Rapid Lake for most of the Holocene. Middle Holocene summer temperatures were about 1.5 degrees C warmer th an today. By about 5400 C-14 Yr B.P. Pinus albicaulis and Abies became less prominent at upper treeline because of decreased winter snowpack and higher maximum summer temperatures. The position of the modern tr eeline was established by 3000 C-14 yr B.P. when Picea retreated downs lope in response to Neoglacial cooling. (C) 1995 University of Washing ton.