The primary objective of this study is to further substantiate multistep climatic forcing of late-glacial vegetation in southern South America. A secondary objective is to establish the age of deglaciation in Estrecho de Magallanes-Bahia Inutil. Pollen assemblages at 2-cm intervals in a core of the mire at Puerto del Hambre (53 degrees 36'21 " S, 70 degrees 55'53 " W) provide the basis for reconstructing the vegetation and a detailed account of palaeoclimate in subantarctic Patagonia. Chronology over the 262-cm length of core is regulated by 20 AMS radiocarbon dates between 14 455 and 10 089 C-14 yr BP. Of 13 pollen assemblage zones, the earliest journal of Quaternary Science representing the Oldest Dryas chronozone (14 455-13 000 C-14 yr BP) records impoverished steppe with decreasing frequencies and loss of southern beach (Nothofagus). Successive 100-yr-long episodes of grass/herbs and of heath (Empetrum/Ericaceae) before 14 000 C-14 yr BP infer deglacial successional communities under a climate of increased continentality prior to the establishment of grass-dominated steppe. The Bolling-Allerod (13 000-11 000 C-14 yr BP) is characterised by mesic grassland under moderating climate that with abrupt change to heath dominance after 12 000 C-14 yr BP was warmer and not as humid. At the time of the Younger Dryas (11 000-10 000 C-14 yr BP), grass steppe expanded with a return of colder, more humid climate. Later, with gradual warming, communities were invaded by southern beach. The Puerto del Hambre record parallels multistep, deglacial palaeoclimatic sequences reported elsewhere in the Southern Andes and at Taylor Dome in Antarctica. Deglaciation of Estrecho de Magallanes-Bahia Inutil is dated close to 14 455 C-14 yr BP, invalidating earlier dates of between 15 800 and 16 590 C-14 yr BP. Copyright (C) 2000 John Wiley & Sons, Ltd.
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