Lithology and Stratigraphy
This subsection contains late Quaternary alluvium. The alluvium is predominantly from sedimentary rocks sources in the Temblor Range of the Coast Ranges.
This subsection is on nearly level to gently sloping alluvial fans. The subsection elevation range is from 250 to about 1200 feet. Fluvial erosion and deposition are the main geomorphic processes.
The soils are mostly Typic Torriorthents, and lesser amounts of Typic Natrargids. The soils are well drained. Leaching and accumulation of clay and calcium carbonates in subsoils are the main pedogenic processes, but most of the soils are too young to have argillic and calcic horizons. The soil temperature regimes are thermic. Soil moisture regimes are aridic.
The predominant natural plant communities are Allscale series, and, on floodplains and toe slopes, Greasewood series.
Characteristic series by lifeform include:
- Grasslands: Alkali sacaton series, California annual grassland series, Creeping ryegrass series, Saltgrass series.
Shrublands: Allscale series, Arrow weed series, Bladderpod - California ephedra - narrowleaf goldenbush series, Pickleweed series, Shadescale series, Spinescale series.
The mean annual precipitation is about 5 to 6 inches. It is practically all rain. Mean annual temperature is about 59° to 62° F. The mean freeze-free period is about 250 to 275 days.
The streams drain from the Coast Ranges toward the basin at the toes of the fans. All streams are small and dry during the summer. There are no lakes.