Skip to main content
U.S. flag

An official website of the United States government

Geology, palynology, and climatic significance of two pre-Pinedale Lake sediment sequences in and near Yellowstone National Park

January 1, 1978

Pollen analysis of a section of lake sediments at Grassy Lake Reservoir indicates a vegetational sequence changing from tundra, to spruce-fir-pine forest, to pine forest, to tundra at the top. Pollen analysis of a section of lake sediments on Beaverdam Creek indicates a tundra vegetation at the base, followed by a brief episode of spruce-fir forest and a return to a tundra vegetation at the top. The analyses of both sections suggest a cold to cool to cold climatic sequence, interpreted as interstadial in character. However, differences suggest that they represent separate interstadials. Pinedale Till disconformably overlies the lake deposits at Grassy Lake Reservoir. The upper sediments contain wood 14C dated at >42,000 yr; the lowermost interfinger with till shown to be more than about 70,000 yr old. The deposits at Beaverdam Creek grade upward into proglacial Pinedale deposits, contain an ash that is probably about 70,000 yr old near their base, and rest comformably on gravel that grades down into lake sediments containing wood debris suggestive of an older climatic amelioration. We conclude that the warmest part of the interstadial at Grassy Lake Reservoir is probably more than 70,000 yr old, and that the warmest part of the interstadial analyzed at Beaverdam Creek is slightly younger than 70,000 yr old. ?? 1978.

Citation Information

Publication Year 1978
Title Geology, palynology, and climatic significance of two pre-Pinedale Lake sediment sequences in and near Yellowstone National Park
DOI
Authors R.G. Baker, G.M. Richmond
Publication Type Article
Publication Subtype Journal Article
Series Title Quaternary Research
Series Number
Index ID 70012507
Record Source USGS Publications Warehouse
USGS Organization