by Tad Bennicoff, Assistant Archivist, Smithsonian Institution Archives Loess bluffs above Aftonian gravel and Nebraska drift. S. of Turin, IA. Smithsonian Institution Archives. RU 7082 Box 5 Folder 3 Aftonian Gravel 379. Chances are, few of you reading this piece can define or describe a loess. I certainly could not,... More...