Pollen evidence from a 350-cm section of a fen in a moraine belt at Rucañancu (39°33′S, 72°18′W) bears on the controversy regarding interpretation of late-glacial and Holocene climate in midlatitude Chile. Earlier pollen studies, indicating a cooling trend between approximately 11,000 and 10,000 yr B.P., disagreed with observations of glacier fluctuations which show continuous glacier wastage and, by inference, warming after 12,500 yr B.P. and possibly earlier, up until Neoglaciation, beginning after 6850 yr B.P. Fossil beetle assemblage data in this time range support the interpretation of climate made from the observed glacier behavior. At Rucañancu, a pollen assemblage containing upper montane podocarp (Podocarpus andinus) in quantities reaching 34% and dating between 10,440 and 10,000 yr B.P. implies a cold climate with summer temperatures possibly 5–8°C lower than today's. Holocene warming began afterward, later than the glacier and beetle records indicate, and continued until at least 8350 yr B.P., as suggested by the sequence of assemblages dominated by Myrtaceae, by Aextoxicon punctatum, and by Gramineae. A subsequent assemblage of Nothofagus obliqua type implies an increase of moisture until 6960 yr B.P., following which N. dombeyi type, under a cool and humid Neoglacial climate, became dominant.
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