The Bucks , Elk , Unadilla and Wellston series are in other related families. Bucks, Elk and Wellston soils have more than 18 percent clay in the particle-size control section. Unadilla soils lack an argillic horizon. These soils are on nearly level to moderately steep uplands and terraces. The soils formed in silty to very fine sandy loam material, presumed to be eolian, overlying a variety of materials of shale, sandstone, limestone, schist, stream deposits and glacial deposits.
Climate is continental with warm summers and cold winters.
Rainfall averages 35 to 48 inches and is evenly distributed throughout the year. Average annual air temperature is 50 degrees to 60 degrees F. and the frost free season is 150 to 180 days. Duncannon is the well drained member of a drainage sequence that includes the moderately well drained Lawrenceville , the somewhat poorly drained Chalfont and the poorly drained Doylestown soils. The competing Bucks and the Abbottstown , Chester , Croton , Gilpin , Lansdale , Penn , Readington , Raritan , Wellston and Zanesville soils are nearby. Abbottstown, Croton, Readington, Raritan and Zanesville soils have fragipans.