Subsection M261Au
Rattlesnake Creek

Lithology and Stratigraphy.  This subsection is dominated by Paleozoic to Jurassic metavolcanic and metasedimentary rocks and serpentinized peridotite of Rattlesnake Creek terrane.  These rocks are intensely faulted.  There are small areas of Mesozoic granitic rocks in the subsection.  There is a small area of Oligocene nonmarine sedimentary rocks of the Weaverville Formation in Hyampom Valley and Quaternary alluvium occurs there and elsewhere along the South Fork Trinity River.

Geomorphology.  This is a subsection of mountains with rounded ridges, steep sides,  and narrow canyons.  Narrow floodplains occur along the South Fork Trinity and Trinity  Rivers and are broader in Hyampom Valley.  The elevation range is from about 400 feet up to 5881 feet on Dubakella Mountain.  Mass wasting and fluvial erosion are the main geomorphic processes.

Soils.  The soils are mostly Dystric, Dystric Lithic, Lithic, and Typic Xerochrepts and Ultic and Mollic Haploxeralfs.  Soils on Lithic and Typic Xerochrepts and Mollic Haploxeralfs are on serpentinized peridotite.  Shallow Dystric Xerochrepts on granitic rocks generally have paralithic contacts, rather than lithic contacts.  Soils on the Weaverville formation are mostly Argixerolls and those on floodplains are mostly Xerofluvents.  The soils well drained.  Soil temperature regimes are mesic.  Soil moisture regimes are xeric.

Vegetation.   The predominant natural plant communities are Douglas-fir series, Mixed conifer series, Douglas-fir - ponderosa pine series, and Ponderosa pine series.  Jeffrey pine series occurs on serpentinized peridotite.  Canyon live oak series is common on very steep rocky slopes with stony soils.

Characteristic series by lifeform include:
Grasslands: California annual grassland series, Montane meadow habitat.
Shrublands: Brewer oak series, Greenleaf manzanita series, Holodiscus series, Tobacco brush series, Wedgeleaf ceanothus series.
Forests and woodlands: Black oak series, Birchleaf mountain-mahogany series, Canyon live oak series, Douglas-fir series, Douglas-fir - ponderosa pine series, Foothill pine series, Jeffrey pine series, Knobcone pine series, Mixed conifer series, Oregon white oak series, Ponderosa pine series, White alder series, White fir series.

Surface Water.  Runoff is rapid.  It drains to the South Fork Trinity River, except at the southeast end of the subsection where runoff drains to tributaries of the Sacramento River.  All but the larger streams are dry through most of summer.  There are no natural lakes in the subsection.