CORRELATION OF LATE QUATERNARY PALEOCLIMATE RECORDS FROM THE CONTINENTAL MARGINS OF THE CALIFORNIAS WITH THOSE FROM UPPER KLAMATH LAKE, OREGON

The production and accumulation of organic matter on the upper continental slope off central Alta California and southern Baja California was markedly lower during the last glacial interval (LGI; ca. 24-10 ka) than during either the Holocene or the last interstadial, oxygen-isotope stage 3 (OIS3; ca. 60-24 ka). Highest productivity over the past 55 ky occurred during certain intervals within OIS3 when organic-rich, laminated sediments accumulated within the present oxygen-minimum zone (OMZ) on the upper continental slope. These high-productivity intervals in a well-dated Baja California core generally correspond to warm stadial intervals as recorded in the oxygen-isotopic composition of Greenland ice. Today, high productivity upwelling conditions along the California Current occur during the summer when the Aleutian low pressure system is north of the Aleutian Islands and the subtropical high pressure system dominates the eastern North Pacific. Sixteen radiocarbon and four tephra dates on a 12.8-m piston core from Upper Klamath Lake, Oregon, provide a high-resolution paleoclimate record of the past 45 kyr based on interpretations of diatoms, geochemistry, pollen, and sediment magnetic properties. Cyclic fluctuations in the abundances of two planktic diatoms with different seasonal adaptations in sediments deposited during OIS3 suggest alternating warm and cold climate regimes. Aulacoseira subarctica blooms in northern temperate and boreal lakes, and suggests colder climates. Aulacoseira ambigua blooms during the summer months and is found in warmer and more eutrophic lakes than A. subarctica. The age models of the California margin cores and the Upper Klamath Lake core are not sufficiently precise to provide exact temporal correlations between these marine and continental records of climate change. Nevertheless, it is probable that both relate to major changes in the strength, position, and duration of the Aleutian low and the subtropical high. The warm-climate diatom A. ambigua occurs in Upper Klamath Lake when the subtropical high dominates the eastern North Pacific bringing strong upwelling and high organic productivity.