This subsection includes Mason and Smith Valleys between the Pine Nut Mountains on the west and the Wassuck Range on the east, the valley of the Carson River north of the Pine Nut Mountains, Antelope Valley south of the Pine Nut Mountains, and the Singatse Range between Mason and Smith Valleys.    The climate is temperate and arid to semi-arid.  MLRA 26f.

Lithology and Stratigraphy.  Quaternary alluvium predominates in this subsection.  Bedrock in the Singatse Range and hills between the Wassuck Range and the Pine Nut Mountains is Triassic and Jurassic volcanic and sedimentary rocks and Tertiary andesite and tuffaceous sediments, plus some Jurassic and Cretaceous granitic rocks.  Hills at the north end of the Pine Nut Range are mostly Tertiary andesite, basalt, and tuffaceous sediments.

Geomorphology.   This subsection contains steep mountains, moderately steep hills, gently to moderately sloping alluvial fans and pediments, and nearly level floodplains, terraces, and basin floor.  The Singatse Range and valleys on both sides of it are aligned north-south.  The Carson River runs across this trend.  The elevation range is from about 4200 feet up to 6778 feet on Mt. Wilson in the Singatse Range and on alluvial fans adjacent to the Wassuck Range.  Mass wasting, fluvial erosion and deposition, and freeze-thaw are the main geomorphic processes.

Soils.  The soils on mountains and hills are mostly Lithic Camborthids; Lithic and Aridic Argixerolls; Lithic Xerollic and Xerollic Haplargids; and Typic, Xerollic, and Mollic Durorthids and Durargids.  Those on alluvial fans are mostly Duric Mollic Camborthids, Mollic and Duric Haplargids, and Typic and Mollic Durargids.   Those on floodplains and basin floors are mostly Aquic Xerorthents and Typic subgroups of Haplaquents, Haplaquepts, and Haplaquolls;  also, there are Aquic Natrixerolls and Aquic Natrargids. There are Typic Torripsamments on eolian sand.  The soils are well to poorly drained.  Soil temperature regimes are mesic.  Soil moisture regimes are aridic, except for wet soils on floodplains and basin floors that have xeric or aquic moisture regimes.

Vegetation.   The predominant natural plant communities are Shadscale series and, on floodplains and basin floors, Greasewood series, Saltgrass series, and Sedge meadow alliances.  Low sagebrush series is common on shallow soils.  Some Big sagebrush series and Singleleaf pinyon series occur at higher elevations.  Indian ricegrass series predominates on eolian sand.

Characteristic series by lifeform include:

Grasslands: Alkali sacaton series, Ashy ryegrass series, Cordgrass series, Creeping ryegrass series, Indian ricegrass series, Needle-and-thread series, Saltgrass series.

Shrublands: Allscale series, Bush seepweed series, Greasewood series, Low sagebrush series, Mixed saltbrush series, Scadscale series, Winter fat series.

Forests and woodlands: Bittlebrush series, Curlleaf mountain-mahogany series, Singleleaf pinyon series.

Surface Water.  Runoff is rapid from alluvial fans and slow from basin-fill.  All runoff drains to the Walker River, except on the north side of the Pine Nut Mountains where runoff drains to the Carson River.  Topaz Lake in Antelope Valley and Artesia Lake in Smith Valley are natural lakes, and there are some smaller ones on floodplain or basin floor along the Walker River in Mason Valley.