Conclusions - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 306

subsurface horizon in soils of the USA and occurs in Alfisols from residual clays
and alluvium in CA and CO, coastal plain sediments in TX, and loess and glacial
drift the Midwest (MN, WI, MI, MO, IL, IN, OH, KY, TN) and in Mollisols from
loess and glacial drift in the northern Great Plains (MT, ND, SD, NE, KS) and the
Midwest (IA, IL). Natric horizons are common in soils developed from alluvium
and residuum in western USA (AZ, NM, NV, and WY). Kandic horizons are
common in coastal plain deposits and residuum in the piedmont of southeastern
USA (AR, MS, AL, GA, SC, NC, VA), eastern USA (DE, NJ), and in the
Appalachian Mountains (TN, KY, WV, PA).
Calcic horizons are common in residuum and alluvium of western USA (CA,
NV, AZ, UT, CO, NM, TX, ID, and MT) and in soils derived from glaciolacustrine
deposits in MN. Petrocalcic horizons occur almost exclusively in western USA
(CA, NV, AZ, NM, TX, and ID). Cambic horizons occur in soils of every state but
are least common in southwestern USA. Duripans are derived from alluvium and
basalt residuum in western USA, especially NV, southern ID, southeastern CA, and
central WA and OR. Fragipans occur in silt-rich materials (loess, alluvium, resid-
uum) under forest (or former forest) in the southern Midwest (MO, IL, IN, OH),
south-central USA (AR, MS, AL, KY, TN), southeastern USA (GA, SC, NC), and
the Northeast (WV, PA, NY, MD).
Glossic horizons occur in soils that have been influenced by recent loess
deposition or vegetation change, including tension zones of the eastern Rocky
Mountains (MT, WY, CO), the Midwest (MN, WI, MI), the coastal plain of TX
and LA, and the Northeast (NY, VT, NH). Gypsic horizons occur in western USA,
especially TX, NM, and UT, and petrogypsic horizons are limited to NV. Ortstein is
present in soils of southeastern AK, western OR and WA, the upper Great Lakes
region (WI, MI), FL, and the Northeast (NY, VT, NH, ME). Placic horizons are
limited to high precipitation areas, HI, WA, and southeast AK.
Due to the limited extent of tropical forest and savanna in the USA, soils with
oxic horizons occur only in HI and Puerto Rico. Soils with salic horizons occur in
pluvial lake basins, including the Great Salt Lake, the Salton Sea, and smaller lakes
in the Basin and Range province of NV. The sombric horizon is limited to tropical
mountains and has not been reported in the USA.
Reference
Soil Survey Staff (2010) Keys to soil taxonomy, 11th edn. USDA, National Resources Conserva-
tion Service, National Soil Survey Center, Lincoln