This is a renewal of research to establish a climatic reference section for examining the synchroneity of the exceptionally large and rapid changes in climate that occurred before, during, and after the last glacial maximum (~35Ka to 12.5ka). The hydrologically closed Estancia basin in central New Mexico is especially well suited as a reference section because of its previous location under the Polar Front Jet Stream, because of its uninterrupted high-resolution stratigraphic and paleontologic record, and because it recorded a strong, clear, and measurable response to climate forcing. Abundant ostracodes and pollen are available for AMS dating. The sampling interval, owing to a high accumulation rate and weak bioturbation, has a practical resolution for changes in climate of less than a decade. Closely spaced (~50- yr) analyses of sediment composition, oxygen 18 and carbon 13, and hydrochemistry (ostracode species abundance), along with mass- balance calculations and a hydrologic model will be used to quantify P-E on the time scale of centuries to millennia. Gray- scale images linked to compositional and other changes analyzed at more closely spaced intervals will characterize interannual to century-scale climatic variability. Patterns of recorded climatic variability include ~2000-yr highstand and lowstands, very strong ~200-to 250-yr, Maunder-scale oscillations, and ~20-years cycles. A more accurate age model and chronostratigraphy based on AMS dating of abundant ostracodes will determine the timing of the unusually large and rapid climatic fluctuations recorded at the Estancia site during the glacial maximum and during the later part of isotope stage 3. The Estancia reference section will be the first complete, land-based high-resolution chronology for changes in climate during this important time interval. It will serve as the basis for correlating and interpreting regional shifts in climate as well as hemispheric and global climatic events.
