Abstract

Radiocarbon-dated pollen records of two adjacent sediment cores from Canal de la Puntilla (40 degrees 57'09 " S, 72 degrees 54'18 " W) in the Chilean Lake District reveal that a sparsely vegetated landscape prevailed during the portion of the Last Glacial Maximum between 20 200 and about 14800 C-14 yr BP. Dominating the vegetation was Nothofagus, Gramineae and Compositae, along with taxa commonly found today above the Andean treeline (Perezia-type, Valeriana) and in Magellanic Moorlands (Donatia, Astelia). Nothofagus expanded between 20200 and 15800 C-14 yr BP, interrupted by a reversal at 19200 C-14 yr YP and followed by a prominent increase in Gramineae pollen between 15800 and about 14800 C-14 yr BP. A major increase in Nothofagus started at about 14800 C-14 yr BP, followed by an abrupt expansion of thermophilous Valdivian/North Patagonian Rain Forest taxa (Myrtaceae, Lomatia/Gevuina, Hydrangea, etc.) at about 14000 C-14 yr BP. An opening of the rain forest and an expansion of Podocarpus nubigena, Misodendrum, and Maytenus disticha-type subsequently occurred between 11000 and 10000 C-14 yr BP. These results suggest that mean annual temperature was 6-7 degrees C colder than at present, with twice the modern annual precipitation between 20200 and 14000 C-14 yr BP, implying a northward shift and intensification of the westerlies storm-tracks. Slight climate warming occurred between 20200 and 15800 C-14 yr BP, featuring cooling reversals at 19200 C-14 yr BP, and later at 15800 C-14 yr BP. The warming of the last termination started at about 14800 C-14 yr BP, and reached a total temperature rise of greater than or equal to 5 degrees C by 12400 C-14 yr BP, followed by cooling between 11000 and 10000 C-14 yr BP. (C) 1997 by John Wiley Sons, Ltd.