Abrupt vegetation and climate changes during the last glacial maximumand last termination in the chilean lake district: a case study from canal de la puntilla (41°s)

Multiple overlapping and replicate pollen stratigraphies from Canal de la Puntilla (40°57'09"S, 72°54'18"W, 120 m elevation) reveal that a Nothofagus dombeyi-type parkland occupied the Valle Central of the Chilean Lake District during the portion of the Last Glacial Maximum betwe...

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Bibliographic Details
Published in:Geografiska annaler. Series A, Physical geography Physical geography, 1999-08, Vol.81 (2), p.285-311
Main Authors: Moreno, P.I., Lowell, T.V., Jacobson jr, G.L., Denton, G.H.
Format: Article
Language:English
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Summary:Multiple overlapping and replicate pollen stratigraphies from Canal de la Puntilla (40°57'09"S, 72°54'18"W, 120 m elevation) reveal that a Nothofagus dombeyi-type parkland occupied the Valle Central of the Chilean Lake District during the portion of the Last Glacial Maximum between 20,200 and about 14,600 14 C yr BP. Dominating this landscape was Nothofagus dombeyi-type and Gramineae, accompanied by taxa commonly found today in Subantarctic environments and above the Andean tree-line in the Lake District (Perezia-type, Valeriana, and Huperzia selago), along with cushion bog taxa characteristic of Magellanic Moorlands (Donatia fascicularis and Astelia pumila). Within this open landscape Nothofagus dombeyi-type expanded between 20,200 and 15,800 14 C yr BP, interrupted by a brief reversal between 19,200 and 18,800 14 C yr BP and followed by a prominent increase in Gramineae pollen between 15,800 and about 14,600 14 C yr BP. A major rise of Nothofagus dombeyi-type began at about 14,600 14 C yr BP, followed by decline in non-arboreal taxa and a remarkable expansion of North Patagonian Rain Forest taxa in pulses centered at 14,200 and 13,000 14 C yr BP. Podocarpus nubigena expanded between 12,200 and 9800 14 C yr BP, along with increases in Misodendrum and Maytenus disticha-type between 11,000 and 9800 14 C yr BP. Paleovegetation records suggest that mean annual temperature was 6-7°C colder than at present during the coldest episodes between 20,200 and about 14,600 14 C yr BP, with twice the modern annual precipitation between 20,200 and 13,000 14 C yr BP, suggesting a northward shift and intensification of westerly stormtracks. Slight climate warming occurred between 20,200 and 15,800 14 C yr BP, interrupted by cooling events at 19,200 and 15,800 14 C yr BP. The initial warming of the last termination started at 14,600 14 C yr BP, followed by warming pulses at 14,200 and 13,000 14 C yr BP. These events brought glacial conditions to a cool-temperate climate, slightly cooler and wetter than modern climate, accounting for a total temperature recovery of ≥5°C by about 13,000 14 C yr BP. A general reversal in trend is inferred with cooling events at 12,200 and 11,000 14 C yr BP.
ISSN:0435-3676
1468-0459
DOI:10.1111/1468-0459.00059