Luminescence geochronology of Pleistocene slack-water deposits in the Frasassi hypogenic cave system, Italy

The earliest Pleistocene fossil forest of Dunarobba (Umbria, Italy) consists of a set of more than 70 tree trunks of an extinct species of sequoia or cypress with original cellulose still preserved. Spectral analyses of tree-ring series (325 and 448 yr in duration) combined with oxygen isotope analyses of the cellulose provide a glimpse into the mean annual temperature and the interannual climate variability that characterized this region at the beginning of the Pleistocene, when the concentration of atmospheric CO (sub 2) was approximately 400 ppm. The high-frequency variability of the ring width time series shows significant spectral components that are consistent with the influence from the North Atlantic Oscillation, and to a lesser extent, solar cycles and El Nino-Southern Oscillation. The mean annual temperature estimate of approximately 19 degrees C, based on a model that combines ring widths and oxygen isotope values, is a full 6 degrees C warmer than the present-day value for this region. These elevated temperatures are consistent with estimates from pollen analyses and with estimates from higher latitudes.