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separated the Green River Basin into two parts. Its upward movement was reactivated during
<br />the Tertiary and since then most of the Tertiary -age rocks have been eroded away (Young and
<br />Young 1977: 57). Within the study area, Cretaceous -age sedimentary rocks form the bedrock
<br />and include sandstones, shales, and coal beds of the Williams Fork Formation.
<br />Soils in the project area are numerous (Bulkley silty clay, Clayburn loam, Foidel
<br />loam, Hesperus loam, Hesperus fine sandy loam, Lamphier-Jerry complex, Maudlin-
<br />Duffymount complex, Morapos loam, Torriorthents-Rock outcrop, Ustorthents frigid-Borolls
<br />complex, and Winevada-Spiltro complex), and are found on hills, alluvial fans, plateaus,
<br />and/or mountainsides. These soils are well -drained and generally formed from colluvium
<br />and/or residuum derived from sandstone, shale, loess, and/or sedimentary rocks. Depth
<br />ranges from 2 to 60 inches (USDA NRCS 2004).
<br />The study area lies within the Williams Fork Mountains. These divide a region
<br />heavily dissected by tributary drainages, some of which flow north to the Yampa River
<br />Valley and others that flow southwest to the Williams Fork Valley. Permanent and
<br />intermittent drainages occurring near or within the project area include Jeffway Gulch, Deal
<br />Gulch and Spring Gulch, which drain into the Williams Fork River to the south, and Deacon
<br />Gulch, which drains into the Yampa River to the north. The headwaters of many of these are
<br />fed by unnamed springs located in the study area.
<br />Elevations within the project area range from approximately 6680 to 7930 feet. The
<br />dominant vegetation within the project area is comprised of Transitional Zone brush
<br />including oakbrush, serviceberry, Gamble oak, and chokecherry. Aspen, dogwood, prickly
<br />pear, sagebrush, yarrow, mules ears, manzanita, aster, globe mallow, snap dragons, sego lily,
<br />wild pea, saw grass, thistle, Indian paintbrush, snakeweed, lupine, mint, wild rose, wetland
<br />grasses, and wild sunflower are also present in some parts of the study area. Overall, ground
<br />visibility was poor to moderate. This biome supports a variety of wildlife species. Mule deer,
<br />elk, coyote, and black bear are locally common as are jack rabbits, cottontail rabbits, and
<br />various other rodents. Mountain lion, bobcat, fox, beaver, skunk, badger, and weasel are also
<br />area inhabitants. Observed bird species include the pinyon jay, raven, red -shafted flicker,
<br />red-tailed hawk, golden eagle, bald eagle, and various other raptors.
<br />Climatically, the yearly average temperature is 32 to 45 degrees F., and there is a
<br />maximum of 100 frost -free days in a year. Annual precipitation is about 18 to 20 inches
<br />(USDA SCS 1976).
<br />PALEOCLIMATE
<br />Based on an analysis of the area's late Quaternary stratigraphy, the geologic history of
<br />the last 18,000 calendar years in the region follows something like the following scenario
<br />(Miller 2010: Chapter 2; Conner et al. 2011:2.35-2.36). [Dates (*) are calibrated. ]
<br />2
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