Combining ground penetrating radar surveys and optical dating to determine dune migration in Namibia

Ground penetrating radar (GPR) profiles across a complex linear dune in the Namib Sand Sea have been used to image sets of cross-stratification and their bounding surfaces. A combination of radar facies analysis and radar stratigraphy has been used to interpret the radar profiles and define a relative chronology. Thick sets of cross-stratification indicate when the dune was most active, whereas thin sets of cross-stratification are interpreted to indicate the increased prevalence of wind reversals and lower rates of dune migration, with bounding surfaces formed during periods of stabilization, non-deposition or erosion. A drilling and dating campaign was designed on the basis of the dune stratigraphy as defined by the GPR survey Sampling was targeted at large sets of cross-stratification formed when the dunes were most active, and avoiding bounding surfaces formed when the dune was stable or even eroded. The results from optical dating give ages between 0.34 +/- 0.02 ka and 1.57 +/- 0.07 ka, indicating a time-averaged dune migration rate of 0.12 m a(-1) over the past 1600 years.