A Great Basin lake-level response to 38–34 ka Dansgaard–Oeschger oscillations

Abstract

Paleontological, geochemical, and geophysical data from pluvial Lake Chewaucan, Oregon, northwestern Great Basin provide a high-resolution paleoclimate record spanning the interval (38–34 ka) that includes the Mono Lake paleomagnetic excursion, Dansgaard–Oeschger Interstadials #8–#6, and the end of Heinrich Event 4. New climate proxies presented here from the BB3-I core, whose chronology was established in a recent publication focusing on its paleomagnetic record, consist of sediment grain-size, C org /N, ostracode faunal counts, lipid molecular stratigraphy, and palynology. They build on previously publised proxies from this basin based on environmental magnetism and supporting lithological features found in outcrop and core. Results from granulometry, geochemical analysis and the presence of the ostracode Cytherissa lacustris consistently demonstrate the correspondence of low lake conditions and colder water temperatures during Dansgaard–Oeschger stadials during a time interval including the low magnetic intensity feature of the Mono Lake Excursion, a paleomagnetic event found both in the lake core of this study and the composite Greenland ice core record between Interstadials #7 and #6. Pollen data also support this finding, suggesting colder and drier continental montane woodland conditions during stadials versus warmer and wetter semi-arid woodland conditions during interstadials. This is further supported with lipid molecular stratigraphy, indicating a consistent tendency toward terrestrial-sourced vegetation, reflecting increased stream discharge into deeper lakes during interstadials versus dominance of aquatic vegetation during low-discharge, low lake stadials. These results suggesting wet interstadials confirm those of earlier studies at Summer Lake and for other lake records in the Great Basin for millennial-scale climate change during MIS 3 age.