Subsection M261Ba
Eastern Franciscan

Lithology and Stratigraphy.  This subsection is dominated by Jurassic and Cretaceous Franciscan metaclastic  rocks of the Eastern Belt.  They are intensely folded and faulted.  Ultramafic rocks are minor components in this subsection.

Geomorphology.  This is a subsection of mountains with rounded ridges, steep sides,  and narrow canyons.    Most of the mountains are elongated in north-northwest to northwest directions and have subequal summits with increasing elevation toward the interior.   The elevation range is from about 1200 feet up to 8092 feet on Mt. Linn in the South Yolla Bolly Mountains.  Mass wasting and fluvial erosion are the main geomorphic processes.

Soils.  The soils are mostly Dystric Xerochrepts, Dystric Lithic Xerochrepts, and Lithic Xerorthents.  At higher elevations, Typic and Lithic Xerumbrepts are most common.  The soils are leached free of carbonates.  Few surfaces are old enough, because of active erosion, to have Alfisols or Ultisols.  Soil temperature regimes are predominantly mesic, some frigid, and minor cryic.  Soil moisture regimes are almost exclusively xeric.

Vegetation.   The predominant natural plant community is Mixed conifer series, except in the northern part of the subsection where Douglas-fir - tanoak series is the predominant plant community.  Red fir series and White fir series are common in areas of frigid soil temperature regimes.

Characteristic series by lifeform include:

Grasslands: California annual grassland series, Introduced perennial grassland series, Montane meadow habitat, Rocky Mountains sedge series.
Shrublands: Brewer oak series, Bush chinquapin series, Chamise series, Chamise - wedgeleaf ceanothus series, Greenleaf manzanita series, Holodiscus series, Leather oak series, Huckleberry oak series, Interior live oak shrub series, Low sagebrush series, Montane wetland shrub habitat, Mountain alder series, Mountain whitethorn series, Rubber rabbitbrush series, Sitka alder series, Tobacco brush series, Whiteleaf manzanita series.
Forests and woodlands: Birchleaf mountain-mahogany series, California buckeye series, Canyon live oak series, Douglas-fir series, Douglas-fir - ponderosa pine series, Douglas-fir - tanoak series, Foothill pine series, Foxtail pine series, Incense-cedar series, Knobcone pine series, Jeffrey pine series, Mixed conifer series, Red fir series, White fir series.

Surface Water.  Runoff is rapid and all but the larger streams are dry through much of the summer.  There are a few small lakes and wet meadows in glacial basins at higher elevations.