The soils formed in calcareous reddish brown sediments of low aggregate stability derived principally from redbed shale and sandstone. At the type location average annual precipitation is 12 to 16 inches with peak periods of precipitation occurring during the spring and summer. The frost-free season is 95 to 125 days. These are the La Fonda and Harlan soils. La Fonda soils lack argillic horizons and Harlan soils have mollic epipedons.
Native vegetation is western wheatgrass, snakeweed, cactus, and some blue grama.
The series is of moderate extent.