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

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 26.21-1.64 m interval of a new sediment core from Lake Riquene (2540 m elevation; 5 degrees 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 27 ka and the 1-cm sample increments yield an average resolution of 60 years. We analyzed in 2032 samples 66 pollen and spore taxa with optimal ecological constraints. We reconstructed upper forest line (UFL) positions between similar to 2200 and similar to 3400 m elevation. We found frequent temperature changes up to 2-3 degrees C/100 yr. Regional vegetation change is mainly driven by obliquity (41 kyr), and eccentricity (100 kyr). 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 similar to 1.5 to 3 kyr with an average of 2.7 kyr. 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. (C) 2013 Elsevier B.V. All rights reserved.