Chronology and climatic controls of late Quaternary lake-level fluctuations in Chewaucan, Fort Rock and Alkali basins, south-central Oregon
Thesis/Dissertation
·
OSTI ID:7081577
In this study, lake-level chronologies of three closed-basin lakes in south-central Oregon were developed and compared with the chronologies of Lakes Bonneville and Lahontan in Utah and Nevada. Geomorphic and stratigraphic study of shoreline features, and radiocarbon dating of rock varnish and gastroped shells associated with high shorelines indicate that the three Oregon paleolakes reached their most recent high stands synchronously before 18,000 to 17,000 radiocarbon yrs B.P., three thousand to forty-five hundred years earlier than the high stands of Lakes Lahontan and Bonneville. Levels of the Oregon paleolakes began to drop at a time when Lakes Lahontan and Bonneville were still rising. This study employed water balance modelling to evaluate several climatic scenarios that would generate high stands in the three Oregon lakes. Latitudinal shifts in the polar jet stream and associated westerlies, that occurred in response to the growth and decay of the continental ice sheets, have been proposed as a mechanism for the timing and magnitude of the Northern Great Basin paleolake high stands. General circulation model simulations and paleoenvironmental evidence indicate that at 18,000 radiocarbon yrs B.P. colder and moister than present conditions prevailed in the Northern Great Basin, while very cold, arid climatic conditions prevailed in the Northwest due to strong, glacial anticyclonic circulation generated by the continental ice sheet. Water balance modelling in this study indicates that colder and moister than present climatic conditions caused the Oregon lakes to rise to their highest level. Climatic conditions of south-central Oregon at 18,000 radiocarbon yrs B.P. were probably influenced more by the westerlies associated with the jet stream to the south than by the glacial anticylonic circulation to the north.
- Research Organization:
- Oregon Univ., Eugene, OR (United States)
- OSTI ID:
- 7081577
- Country of Publication:
- United States
- Language:
- English
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