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)

Abstract

ABSTRACT. 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 14C 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 14C 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 14C yr BP. A major rise of Nothofagus dombeyi‐type began at about 14,600 14C 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 14C yr BP. Podocarpus nubigena expanded between 12,200 and 9800 14C yr BP, along with increases in Misodendrum and Maytenus disticha‐type between 11,000 and 9800 14C 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 14C yr BP, with twice the modern annual precipitation between 20,200 and 13,000 14C yr BP, suggesting a northward shift and intensification of westerly stormtracks. Slight climate warming occurred between 20,200 and 15,800 14C yr BP, interrupted by cooling events at 19,200 and 15,800 14C yr BP. The initial warming of the last termination started at 14,600 14C yr BP, followed by warming pulses at 14,200 and 13,000 14C 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 14C yr BP. A general reversal in trend is inferred with cooling events at 12,200 and 11,000 14C yr BP.