Abstract: Coastal-Dune Geomorphology and Classification
V. Goldsmith, A. Gutman, H. Hennigar
Numerous descriptive names are applied indiscriminately to eolian-formed topographic features in the coastal zone. A coastal dune classification scheme, which encompasses both prevalent dune geomorphology and genetic eolian processes, is proposed: (1) vegetated dunes; (2) artificially induced dunes (AID); (3) Medanos; (4) parabolic dunes; and (5) others.
Vegetated dunes accumulate around vegetation which act as sediment baffles (vertical growth of 0.3 to 1.0 m/year) and also as an internal skeleton fixing the dunes in place, and result in a characteristic internal geometry containing low-angle dipping beds (m = 12°) and polymodal dip directions. AIDs are man-made, but the concomitant and subsequent sand accumulation processes are natural, and AIDs commonly are transitional into vegetated dunes. Examples of the "seed" are dune fencing, vegetation plantings, bulldozing, and man-made sedimentation.
Medanos are large, isolated hills of sand 20 to 100 m in elevation, asymmetric in profile, lacking vegetation; they migrate downwind up to tens of m/year. Resulting characteristic slipfaces of unconsolidated sand at the angle of repose are oriented transverse to the wind.
Parabolic dunes (defined by their characteristic plan view) are similar to Medanos in that they have a slipface formed in direct response to the dominant wind, and a deflation zone within their upwind concave side, but are different in that they have an internal geometry more characteristic of vegetated dunes and may be fixed in place depending on their recent vegetation history. Thus, their areal distribution typically grades from vegetated to transverse dunes upwind. Parabolics also show in-situ temporal changes to other dune types.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC