The Plio-Pleistocene climatic record of the tropical Andes

Abstract

Sequences of lake sediments on the high plains of the Colombian Cordillera Oriental (at an altitude of c. 2500 m) represent some 5 or 6 Ma. The last glacial–interglacial cycle is well documented in the sediments of Lake Fuquene; very long sequences (up to 350-m long cores) were collected in the high plain of Bogota, representing more than 3.5 Ma. Pollen diagrams are now available, covering that time and representing the longest known continuous terrestrial record available. They were dated using potassium-argon and fission track methods on material from intercalated volcanic ash layers. The pollen diagrams can be interpreted in terms of shifting vegetation zones, and these in turn enable us to draw approximate temperature and humidity curves. The temperature curve for the last 3.5 Ma can be correlated with deep-sea curves (oxygen isotopes, temperature). An important change in rhythm and intensity seems to take place at approximately 3.1 Ma and a cold period that should correspond in time with the Pre-Tiglian of Western Europe is conspicuous.