The Armster series consists of very deep, moderately well drained soils that formed in a thin layer of loess or loess and pedisediment and the underlying paleosol in glacial till.
Permeability is moderately slow.
These soils are on uplands and have convex slopes ranging from 2 to 25 percent. Mean annual temperature is 53 degrees F, and mean annual precipitation is 37 inches. Solum thickness ranges from 40 to about 80 inches. There commonly is a weak pebble line at the top of the 2Bt horizon. Some pedons have a cobbly surface.