Geomorphological and Stratigraphic Identification of Lunettes at the Great Sand Dunes National Park and Preserve, Colorado

The Great Sand Dunes National Park and Preserve (GRSA), located in the San Luis Valley of southern Colorado, contains Quaternary-aged deposits of dune sands, alluvial fans, stream channels, floodplain alluvium and lake sediments. The most well-known deposits within the GRSA are the dune features, which include star, parabolic, barchan, transverse, and nebkha dunes that are present in the active dune field. In addition to the dune deposits, are lesser known fluvial deposits associated with ephemeral streams. The fluvial deposits are part of a complex cycle of erosion and deposition between aeolian and fluvial processes.

An added complexity to this system are the playa and sabkha environments surrounding the Dry Lakes and San Luis Recreational areas, that lie to the west and south of the active dune fields. In the Dry Lakes area, well formed lunettes have been identified that lie along the rim of playas. In the San Luis Recreational area, large dune-shaped features that have been mapped, but the origin of these features has not been identified. It has been suggested that these large features are parabolic dunes, a series of blowouts, or lunettes. Identification of these features is key to determining their role and importance in understanding the geomorphological evolution of the GRSA and surrounding areas.

This study presents the results of a geomorphological and stratigraphic study that were used to identify the lunette features within the San Luis Recreational area. The results show key findings in developing an understanding of the geomorphological evolution of lunettes in this area and the relationship with the GRSA.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California