Late Pliocene-Pleistocene high resolution pollen sequence of Colombia: An overview of climatic change

Abstract

Two long continental pollen records, Funza I (357 m) and Funza II (586 m) from the high plain of Bogotá (Colombia) at 2550 m elevation, have been studied palynologically. Fission track dates on zircon from intercalated volcanic ashes provided a chronological framework and showed the pollen records, which correlate with high precision, to be continuous over the interval from ca. 3.2 Ma to ca. 27 ka. The Late Pliocene-Pleistocene history of the montane forests and open alpine paramo vegetation is documented with a temporal resolution of ca. 6-5 ka, and for the upper 1.1 Ma with a resolution of ca. 1.2 ka. The immigration of the northern hemisphere elements Alnus (at ca. 1 Ma) and Quercus (at ca. 0.33 Ma), which travelled along the Panamanian landbridge, caused significant changes in the composition of the Andean montane forests. The successive Pleistocene glaciations forced the Andean vegetation belts to an almost continuous altitudinal movement; the upper forest line (at present at ca. 3200 m) shifted between 1800 m (glacials) and ca. 3500 m (interglacials), corresponding to a variation in temperature between ca. 5 and 15°C at 2550 m altitude. A provisional land-sea correlation (Funza pollen-ODP Site 677δ 18O) is shown for the upper 1.2 Ma (Stages 3–35). Frequency analysis of several time series showed significant periods of the eccentricity (100 ka) and precession (23 and 19 ka) bands, showing orbital forcing and a strong change in climatic variability around 800 ka. At ca. 2.7 Ma, a significant cooling of ca. 5°C is documented, reflecting the classical terrestrial Pliocene-Pleistocene boundary, which correlates to the Reuverian-Praetiglian boundary of the NW European stratigraphical climatic subdivision.