Sedimentary rocks from the Miocene-Pliocene epoch, along with rocks from the Pennsylvanian period, are found, and limestone and dolomite from the Cambrian period occur. Intrusive igneous rocks form many of the mountain ranges. Playas are also evident in the internally drained valleys of this Section. Alluvial deposits occur in most of the valleys, and these include sand dunes. Entisols and Aridisols occur in combination with mesic, frigid, and cryic soil temperature regimes, along with xeric and aridic soil moisture regimes.
Large areas have saline-sodic affected soils.
Potential Natural Vegetation. Bighorn sheep and pronghorn antelope were once common. Presently the common ungulates are mule deer and introduced elk. Coyote and mountain lion are the typical large predators. Characteristic herpetofauna include western whiptail, rubber boa, common garter snake, leopard lizard, side-blotched lizard, and western toad.