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

Sediments from Rapid Lake document glacial and vegetation history in the Temple Lake valley of the Wind River Range, Wyoming over the past 11,000 to 12,000 yr. Radiocarbon age determinations on basal detrital organic 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 terminal Pleistocene readvance may be represented at lower elevations by the expansion of forest into intermontane basins 12,000 to 10,000 yr B.P. Vegetation in the Wind River Range responded to changing environmental conditions at the end of the Pleistocene. Following deglaciation, alpine tundra in the Temple Lake valley was replaced by a Pinus albicaulis 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 than 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 treeline was established by 3000 C-14 yr B.P. when Picea retreated downslope in response to Neoglacial cooling. (C) 1995 University of Washington.