Tropical rain-forest history from the Colombian Pacific area: a 4200-year pollen record from Laguna Jotaordó

Abstract

Pollen analysis of a 5 m long core from Lake Jotaordó, located in northern ‘Chocó biogeographic area’ (5°48[.minute] N, 76°42[.minute] W) along the Pacific coast of Colombia, shows the environmental history of the rain forest during the last 4200 years. Time control has been based on 6 AMS 14C dates ranging from 4230 to 365 14C yr BP. The period of 4230 to 4053 14C yr BP shows sandy deposits and river influence and represents at that time the initial phase of the lake. The composition of the rain forest was different compared to the last 1400 years. Pioneer taxa belonging to Cecropia, Melastomataceae/Combretaceae and Moraceae/Urticaceae dominated the forest. A 30 cm thick organic rich clay from 440 to 410 cm core depth spans a period of 2600 years (from 4050 to 1450 14C yr BP), pointing to a hiatus in the sediment record, possibly caused by riverine erosion of previously deposited sediments. During the last 1400 years rain forest is characterized by Mauritiella, Euterpe/Geonoma, Iriartea, Pachira aquatica and Malpighiaceae. Floral composition of the rain forest is not constant. Abiotic dynamics caused changes in the drainage system. The presence of human settlements during the last 1000 yrs is evidenced by Zea mays and possibly also by the increase of palms.