Paleoenvironmental history of the Popayán area since 27 000 yr BP at Timbio, Southern Colombia

Abstract

A pollen record from Timbio, located at an elevation of 1750 m on the high plain of Popayán (2°24′N, 76°36′W) is presented. This forms the basis for reconstructing the vegetation and climate history for the periods from 27 000 to 9200 radiocarbon years before the present ( 14C yr BP) and 2100 14C yr BP to sub-recent. The 5 m sediment core has time control based on seven AMS radiocarbon dates. Four pollen assemblage zones (TIM-1 to TIM-4) are recognized. During the period of 27 200 to 26 000 14C yr BP, an Andean forest was near the site. The vegetation consisted of forest and open herb-rich vegetation, climatic conditions were moist and temperatures some 6°C lower than compared to those of today. During the period of 26 000 to 16 000 14C yr BP forest was less open. The observed succession from a Podocarpus-Weinmannia dominated forest to a Hedyosmum dominated forest, and finally to a forest with Ilex, Myrica and ferns indicates a progressive decrease of temperature during this period, with a maximum temperature depression of ca. 5–7.5°C compared to present-day conditions. During the period of 16 000 to 9200 14C yr BP, temperature decrease is estimated at ca. 7.5°C and the climate was the driest. During the period of 2100 to 600 14C yr BP, deforestation and crop cultivation point to significant human influence, subsequently followed by a period of forest recovery that started before the arrival of the Spanish conquistadors. The estimated temperature depression at the Last Glacial Maximum (LGM, ca. 6.5°C) is between the estimated values at >2600 m altitude (ca. 8°C) and those at sea-level (2.5–6°C) and supports the observation that glacial lapse rates were higher than in modern times.