LATE QUATERNARY VEGETATIONAL HISTORY OF GRAYS LAKE, IDAHO AND THE ICE SLOUGH, WYOMING

• Main Author: BEISWENGER, JANE MILLER
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1987
• Subjects: Paleobotany; Paleontology
• ISBN: 9798206836257

Pollen contained in sediment cores from Grays Lake, Idaho and the Ice Slough, Wyoming have provided a description of late Quaternary vegetational history for these low elevation sites in the Central Rocky Mountain region. The Grays Lake record encompasses about 80,000 years and indicates a cold, dry full-glacial lasting to 13,000 years ago. Until 35,000 years ago, the vegetation around Grays Lake was a dense Artemisia steppe. From 35,000 to 13,000 years ago, growing conditions were restricted; Pinus and other conifers were mainly confined to protected locations in mountain valleys and ravines while Artemisia continued to dominate the open plains. A cool, moist late-glacial climate existed from 13,000 to 10,000 years ago. The most favorable conditions for Picea occurred 12,000 years ago. Contemporaneous increases in pollen from Pinus, Artemisia, and Chenopodiaceae between 12,500 and 10,200 years ago suggest a rapid vegetational response to increased moisture availability accompanying climatic warming. Subsequent decreases in Picea and Pinus and increases in Juniperus, Artemisia, Gramineae, and Chenopodiaceae between 10,200 and 10,000 years ago reflect increasing temperature and aridity. Warm, xeric Holocene conditions reached a maximum 7300 years ago and persisted until 5800 years ago when a cooling trend began. The Ice Slough pollen record spans the Holocene. A moist early Holocene climate supported a dense Atremisia steppe until 8200 years ago. A long, xeric period occurred from 8200 until 3500 years ago in the vicinity of the Slough when a mixture of Artemisia and Chenopodiaceae species dominated the vegetation. A change to moister conditions after 3500 years ago resulted in increases in Artemisia near the Slough and in the conifers in the nearby mountains. The Grays Lake and Ice Slough records show two major differences. Mesic late-glacial conditions ended 10,000 years ago near Grays Lake, but persisted until 8200 years ago near the Ice Slough. A middle Holocene xeric period, from 10,000 until 5800 years ago, reached a maximum 7300 years ago in the Grays Lake Basin. In contrast, the data show no xeric maximum for the Ice Slough where warm, dry conditions prevailed until 3500 years ago.