Precise radiocarbon dating of late-glacial cooling in mid-latitude South America

Variability of atmospheric C-14 content often complicates radiocarbon-based chronologies; however, specific features such as periods of constant C-14 age or steep changes in radiocarbon ages can be useful stratigraphic markers. The Younger Dryas event in the Northern Hemisphere is one of those periods, showing conspicuous C-14 wiggles. Although the origin of those variations is not fully understood, we can make practical use of them and determine: (i) whether the Younger Dryas was global in extent; if so, (ii) were the initial cooling and the final warming synchronous worldwide; and (iii) what are the implications of these similarities/differences? Here we report high-resolution AMS C-14 chronologies from the mid-latitudes of South America that pinpoint a cool episode between 11,400 and 10,200 C-14 yr B.P. The onset of the final cool episode of the Late Glacial in the southern mid-latitudes, i.e., the Huelmo/Mascardi Cold Reversal, preceded the onset of the Younger Dryas cold event by similar to550 calendar years. Both events ended during a radiocarbon-age plateau at similar to10,200 C-14 yr B.P. Thus, the Huelmo/Mascardi Cold Reversal encompasses the Younger Dryas, as well as a couple of short-term cool/warm oscillations that immediately preceded its onset in the North Atlantic region. (C) 2003 Elsevier Science (USA). All rights reserved.