QUATERNARY GLACIATIONS IN THE NORTHERN ANDES (VENEZUELA, COLOMBIA AND ECUADOR)

The nature and distribution of glacial drift in the high Andes of Venezuela, Colombia and Ecuador suggest that deposits of only the last two Quaternary glaciations (Isotope Stages 6 and 4 + 2) are present. The Penultimate Glaciation in Ecuador may be represented by deeply weathered drift that is beyond the range of radiocarbon dating; in Colombia and Venezuela subdued moraines covered with loess may be of equivalent age. In places, this drift extends 1000 m lower in altitude than the limits of the Last Glaciation, which comonly reach 3400-3600 m. Radiocarbon dated organic deposits (33->43 ka BP) lying between tills composing superposed terminal moraines suggest that Andean glaciers may have been as extensive during Isotope Stage 4 as during Isotope Stage 2. A relatively long interstadial, from >43->33 ka BP preceded the glacier advance that culminated during the interval ca. 28-15 ka BP. Two late-glacial stadials are marked by moraine complexes at 3900-4200 m altitude; they are partly constrained by radiocarbon ages of >12.9 ka BP and 12-10 ka BP. Moraines apparently deposited during Neoglacial advances of the last ca. 5 ka lie in front of most of the glaciers remaining in the northern Andes. © 1990.