Holocene Glacial Chronology in Patagonia: Tyndall and Upsala Glaciers

Abstract

From glacial landforms and new radiocarbon datings at Tyndall and Upsala Glacier areas of the Southern Patagonia Icefield, four Neoglacial advances are recognized. At Tyndall Glacier, a First Neoglacial advance, marked by obscure terminal moraines and distinctive lateral moraines occurred at ca. 3600 yr BR 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 different color and surficial materials of the terrain, occurred at ca. 1400 yr BR A Fourth Neoglacial advance occurred at ca. A.D. 1700. At Upsala Glacier, a new scheme was presented, modifying the classical scheme of Mercer. He identified two Neoglaciations from radiocarbon datings 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 dendrochronological analyses. In this study, Herminita moraines that were first recognized in 1990 were dated to be ca. 24002200 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 These dates are close to a Third Neoglaciation. The existence of the earliest Neoglaciation, ca. 3600 yr BP, was not directly supported by new data; however, the data from Tyndall and other glaciers suggest that it probably occurred at Upsala Glacier.