Although fewer studies of the late Quaternary eolian record have been conducted in northern South America, one spectacular example of a large, stabilized dune field is discussed here. In the Llanos del Orinoco of Venezuela and extending into Colombia, Roa (1980) mapped a large dune field of geomorphically well-expressed linear and parabolic dunes (Fig. 5). Aminimum limiting radiocarbon age of —11,000 years B.P. was obtained by Roa (1979) from a paleosol capping one of these dunes, which in turn is overlain by younger eo-lian sand. Iriondo (1997) also described a finer grained loess that occurs downwind of the dune field. Roa (1979), Iriondo (1997), and Clapperton (1993) interpreted this sand to represent deposition during a time when there was a migration of the Intertropical Convergence Zone (ITCZ) to the south during the last (?) glacial period, with the result that the Llanos del Orinoco region became drier and favored dune formation. If this interpretation is correct, it is consistent with the paleontological, geochemical, and mineralogical record of relatively dry conditions in this part of Venezuela during the late glacial period (—13,000-
Was this article helpful?