"barcan wilderness"

This question's been bugging me all day, so I did a little research. The phrase "barcan wilderness" in Thanatopsis refers to the north African desert. A barcan, I have learned, is this:

"sand dunes come in two basic varieties, barcans and transverse dunes. Within these two basic types, subsets include dunes that are modified by transitory or multidirectional wind regimes. Barcan dunes develop under unidirectional wind regimes and transverse dunes develop under bi- or multi-directional wind regimes.

A classic barcan is shaped like a smoothly rising hill that drops off suddenly at its highest point into a scalloped cliff-face called the slipface..."

That's according to one Melody Higdon (probably a class assignment, but it sounds very authoritative to me).