One site
This isn't the one I remember, but it's pretty close. Plug "aeolian" and "erosion" into Google, and you get a lot of this.
"Deflation" was the word I was racking my brain for, the process where wind removes layer after layer of light particles and just leaves loose rocks.
That the surface around Opportunity has few rocks compared to the area around Spirit is interesting. Only one invulnerable steel chunk. Implies that there aren't a lot of loose chunks buried in the sand to be revealed by the wind.