Abstract

Multiple overlapping and replicate pollen stratigraphies from Canal de la Puntilla (40 degrees 57'09"S, 72 degrees 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 C-14 yr sp. 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 C-14 yr sp, interrupted by a brief reversal between 19,200 and 18,800 C-14 yr sp and followed by a prominent increase in Gramineae pollen between 15,800 and about 14,600 C-14 yr sp. A major rise of Nothofagus dombeyi-type began at about 14,600 C-14 yr sp, 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 C-14 yr sp. Podocarpus nubigena expanded between 12,200 and 9800 C-14 yr BP, along with increases in Misodendrum and Maytenus disticha-type between 11,000 and 9800 C-14 yr sp. Paleovegetation records suggest that mean annual temperature was 6-7 degrees C colder than at present during the coldest episodes between 20,200 and about 14,600 C-14 yr sp, with twice the modern annual precipitation between 20,200 and 13,000 14C yr sp, suggesting a northward shift and intensification of westerly storm-tracks. Slight climate warming occurred between 20,200 and 15,800 14C yr sp, interrupted by cooling events at 19,200 and 15,800 C-14 yr sp. The initial warming of the last termination started at 14,600 C-14 yr sp, followed by warming pulses at 14,200 and 13,000 C-14 yr sp. These events brought glacial conditions to a cool-temperate climate, slightly cooler and wetter than modem climate, accounting for a total temperature recovery of greater than or equal to 5 degrees C by about 13,000 C-14 yr sp. A general reversal in trend is inferred with cooling events at 12,200 and 11,000 C-14 yr BP.