North Andean environmental and climatic change at orbital to submillennial time-scales: Vegetation, water levels and sedimentary regimes from Lake Fúquene 130–27 ka

Abstract

We present a record of environmental and climatic change in the northern Andes during the last interglacial–glacial cycle based on integrated information from pollen and grain size distributions (GSD). The record reflects the 26.21–1.64m interval of a new sediment core from Lake Fúquene (2540m elevation; 5°N) in the Colombian Andes. The age model was developed by Groot et al. (2011) and shows this core interval reflects the period from 130 to 27ka and the 1-cm sample increments yield an average resolution of 60years. We analyzed in 2032 samples 66 pollen and spore taxa with optimal ecological constraints. We reconstructed upper forest line (UFL) positions between ~2200 and ~3400m elevation. We found frequent temperature changes up to 2–3°C/100yr. Regional vegetation change is mainly driven by obliquity (41kyr), and eccentricity (100kyr). Important short-lived upslope excursions of the UFL reflect millennial-scale climate variability superimposed on orbital-scale variability. These cycles reflect Dansgaard–Oeschger (DO) climate cycles in time and signature. DO cycles 8, 12, 14, 19, 20, 26, 27 and 28 are most prominently documented. Cycles vary from ~1.5 to 3kyr with an average of 2.7kyr.Changes in species composition of montane forest are evident and trees with mostly pioneer qualities (Alnus, Myrica, Quercus and Weinmannia) migrate in the forefront. Other trees like Podocarpus, Miconia, and Hedyosmum mostly follow later. Changes in regional vegetation distribution and forest composition, changes in local aquatic vegetation, and changes in GSD of sediments supplied to the lake allow to develop an integrated reconstruction of the biotic and abiotic environments in the drainage basin.