New Mexico Geological Society Annual Spring Meeting
April 7, 2017
[view as PDF]
What Lies Beneath the Dunes? Gravity Measurements to Characterize Sub-Surface Density Structure and Understand Controls on Dune Migration in White Sands National Monument, New Mexico
Ryan Dunagin1, M. Roy1, Shari Kelley2, L. Worthington1 and J. Butts1
White Sands National Monument is home to the largest gypsum sand dune field in the world. This unique landscape is both a popular tourist destination and a valuable natural resource shaped by complex interactions between erosion, climate, and groundwater extraction. The underlying basin structure and geology of the region must influence the evolution of the dunefield by controlling the supply and transport of the gypsum sands. This study we focus on how sub-surface structure, as illuminated by gravity measurements and forward models, may influence the transport and migration of the dunes. Specifically, we target two locations within White Sands National Monument where the dunefield has not moved significantly in the past 50 years, to see if subsurface structures in these areas may play a role in causing this stagnation. In each survey area, we analyze observed gravity variations (after drift, tide, elevation, and latitude corrections) using simple forward models of the effect of the terrain. In some cases, we remove a regional (long-wavelength) linear fit to the data. The resulting complete Bouguer anomalies are calculated by discretizing the terrain into right-rectangular prisms based on a LIDAR point-cloud for the study area. We interpret the complete Bouguer anomalies for our study areas in terms of shallow subsurface density variations (possibly caused by faulting). In each study area, we then assess the role of subsurface structure in controlling the migration of the dunes.
2017 New Mexico Geological Society Annual Spring Meeting
April 7, 2017, Macey Center, New Mexico Tech campus, Socorro, NM