The Dunes at Oceano
Another article for On Landscape was published recently in Issue 186 (at On Landscape Dunes at Oceano).
The Introduction includes my error (see Comments). White Sands is in New Mexico and Great Sand Dunes National Park in Colorado.
These photos were taken on film back in 1997 using a Mamiya 6. More can be found in the Still Dynamic Monochrome Gallery.