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The
distinctive feature of this subsection is a complex pattern of Mesozoic
sedimentary, metasedimentary, metavolcanic, and ultramafic rocks.
It has a hot, subhumid to humid climate. MLRA 15d.
Lithology and Stratigraphy. This subsection contains Jurassic and Cretaceous Franciscan rocks of the Central and Eastern Belts, including much ultramafic rock, and Cretaceous sedimentary rocks of the Great Valley Sequence. There are large areas of late Quaternary alluvium in Coyote, Long, and Pope Valleys, but they are only minor parts of the subsection.
Geomorphology. This is a subsection of north-northwest to northwest trending mountains that generally have rounded summits and steep sides. Most of the canyons are narrow, but some have broad alluvial plains. The elevation range is from about 300 feet up to 3196 feet on Brushy Skyhigh. Mass wasting by flow and sliding, and fluvial erosion are the main geomorphic processes.
Soils. The soils are mostly serpentinitic Lithic Argixerolls and Haploxerolls and nonserpentinitc Dystric Lithic Xerochrepts and Typic and Mollic Haploxeralfs. The soils are generally leached free of carbonates. Soil temperature regimes are mostly thermic, but are mesic on some north-facing slopes and at higher elevation. Soil moisture regimes are xeric. There are no extensive surfaces old enough to have Palexeralfs.
Vegetation. The predominant natural plant communities are Leather oak series on serpentinitic soils, Chamise series on shallow nonserpentinitic soils, Mixed conifer series on deep soils with mesic temperature regimes, and Blue oak series on other soils. There is Coast live oak series on many north-facing slopes.
Surface Water. Runoff is rapid and all but the larger streams
are dry through most of the summer. Natural lakes are absent.
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