MORPHOLOGIC DIFFERENCES BETWEEN CLASSES OF PARABOLIC DUNES, WHITE SANDS NATIONAL MONUMENT, NEW MEXICO

Parabolic dunes are one of the major types of eolian dunes, but little is known of their origin or the controls on their movement. White Sands National Monument has one of the largest clusters of parabolic dunes in the world. This study describes six different classes of parabolic dunes at White Sands. Classes are distinguished by differences in the interdune morphology, and length-to-width ratios. Group A consists of widely spaced, very long dunes (857 meters long and 123 meters wide). These dunes are associated with well-vegetated interdunes and extend far from sand sources. Group B are an older generation of parabolic dunes that have been overridden by younger transverse and parabolic dunes. Group C(344.33 meters long by 168.29 meters wide) consist of closely spaced wide and short dunes with straight fronts that are transitional to transverse dunes. Group D are intermediate between groups E and A in their size and shape. Group E(172.6 meters long by 120.5 meters wide) are dunes emerging from transverse ridges of the interior White Sands dunes. Group F are small (80.1 meters long by 38.7 meters wide) that are forming on the arms of the dunes of Group A.

Different methods are applied to distinguish between the six classes. The distribution of vegetation on the dunes does not seem to correlate with differences in dune shape and movement. Interdune vegetation correlates with increased dune spacing and dune length. The parabolic dunes have formed through several different processes. Group C and D start as blowouts of transverse dune ridges and may be observed forming today. Group B seems to have formed from excavation of the interdunes upwind of them. Group A has a more problematic origin and may represent reactivation of older generations of parabolic dunes.