HOLOCENE GLACIAL CHRONOLOGY IN PATAGONIA - TYNDALL AND UPSALA GLACIERS

From glacial landforms and new radiocarbon datings at Tyndall and Upsa la Glacier areas of the Southern Patagonia Icefield, four Neoglacial a dvances are recognized. At Tyndall Glacier, a First Neoglacial advance , marked by obscure terminal moraines and distinctive lateral moraines occurred at ca. 3600 yr BP. A Second Neoglacial advance, indicated by conspicuous trimlines on the side-valley wall and on the flank of the lateral moraines of the First Neoglacial advance, presumably occurred at ca. 2300 yr BP. A Third Neoglacial advance, distinguished by the d ifferent color and surficial materials of the terrain, occurred at ca. 1400 yr BP. A Fourth Neoglacial advance occurred at ca. A.D. 1700. At Upsala Glacier, a new scheme was presented, modifying the classical s cheme of Mercer. He identified two Neoglaciations from radiocarbon dat ings at ca. 3600 yr BP, and ca. 2300 yr BP (Pearson I), and the Little Ice Age glaciation, Pearson II, at A.D. 1600-1760 from dendrochronolo gical analyses. In this study, Herminita moraines that were first reco gnized in 1990 were dated to be ca. 2400-2200 yr BP, corresponding to a Second Neoglaciation. Pearson I moraines which were long believed to be ca. 2300 yr BP were dated to be ca. 1600, 1400, and 900 yr BP. The se dates are close to a Third Neoglaciation. The existence of the earl iest Neoglaciation, ca. 3600 yr BP, was not directly supported by new data; however, the data from Tyndall and other glaciers suggest that i t probably occurred at Upsala Glacier.