Ward Valley An Examination of Seven Issues in Earth Sciences and Ecology (1995) / Chapter Skim
Currently Skimming:
2 SETTING OF THE WARD VALLEY SITE
2 SETTING OF THE WARD VALLEY SITE
Pages 27-62
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 27... ...
The proposed facility is located about 20 km from the northern end of Ward Valley, approximately I.5 km south of Interstate 40 in the northeastern quarter of Section 34, Township 9 North, Range 19 East, San Bernardino Baseline and Mendian. The site is about 760 m west of Homer Wash (Figure 2.3)
|
From page 29... ...
l _ Fault, dotted where concealed ,, . ,, ~ - ~ Detachment fault, dotted where concealed.
|
From page 31... ...
WV-MOO-03 34 35 State Ownership Site Boundary O Proposed Wells · WV-MW- Existing Wells Disposal Site Boundary State Ownership Site Boundary + Section Corner Location 31 N o 150 300 ~ ~ ~ Meters 0 500 1 000 , ~ Feet Figure 2.4 Relationship of various proposed Ward Valley site boundaries, and location of proposed and existing monitoring wells (after LA Figure 2420-4~.
|
From page 32... ...
REGIONAL GEOLOGIC SETTING The geologic history of the eastern Mojave Desert spans more than I.7 billion years (Howard et al., 1987; Wooden et al., 1988; Wilshire et al., 1994) and is very complex, reflecting multiple episodes of tecton~sm2, or large-scale movements, disruptions and heating of the earth's crust, such as faulting, folding, mountain building, metamorphism, and magmatism.
|
From page 33... ...
33 = ._ _ , ~ E a, _ 0 · ~ Lit ~ ,; Dk MAZY \~ ~ ~Q · · id Ed ,, _L ~ .
|
From page 34... ...
34 WARD VALlEY - SEVEN ISSUES Table 2.! Geologic Time Scale Beginning of epoch or period (millions of years Era Penod Epoch ago)
|
From page 35... ...
costar extension and broadly synchronous sedimentation and magmatism; and · Late Cenozoic post-extension erosion of the mountain ranges, filling of the intervening basins with the resulting sediments, and partial integration of drainage systems during a time of relative tectonic stability. The three pre-Cenozoic phases, i.e.
|
From page 36... ...
Cenozoic Era Miocene Extension anciMagmatism The present-day basins and ranges in the Ward Valley area formed when the earth's crest in the region was pulled apart, or extended, in Miocene time (Howard et al., 1982; Spencer, 1985; Howard and John, 1987~. Ward Valley lies along the western side of a 50- to lOO-km wide belt of extreme crustal extension that trends northward along the Colorado River Figure 2.3 and 2.6~.
|
From page 37... ...
37 ~ ~ JO Red , .~ ~ .
|
From page 38... ...
Warping of the detachment faults during crustal extension gave them a dome-like shape Over the core complexes (Figure 2.~. The faults are exposed on the flanks of the corecomplex ranges, where they juxtapose the tilted fault blocks and associated Miocene volcanic and sedimentary rocks against the underlying deep-level rocks within the ranges (Figure 2.~.
|
From page 39... ...
. Breakaway Fractured and i/ Tilted Fault Blocks 10 20 onus a~nd:Alterat~on : ~ ~ ~~ Ache ~Brittle:: :~:~ ~ ~~Brecciafion and Alteration A/ ~ ~ Overprinting Mylonitic Rocks ~~Mylonitization Mylonitic Rocks Exposed At Surface ::~lr~active I: ~ I: ~ ~ ~ ~ ~ ~ ~ :~ ~~ ~~ ~ : I; VIA i: ~ ~~.~.~ ~3~ ~ ~ A: : :: ~ ~ if: ~~ ~~ ~ Brecciabon~ar~d Alteration /_ i_ : ~ _-~Brible :verprinti-ng Mylonitic Rocks:: ~~ ~~ ~;= ::~ ~~ ~~:-~::~: ~~:::~:: ~ : :~:Mylonitizat~on~ OF : ~ : ~ ~ ~ ~ ~ , ~ ~~.~ ~~ ~~: ~ ~ ~ ~~ 2 0 ~ : 39 Figure 2.8 Interpretive model for the evolution of detaclunent faults and metamorphic core complexes.
|
From page 40... ...
During the faulting, hot, chemically rich, ground water passed through and altered the rocks, depositing minerals in the fractured zones as it cooled (Reynolds and Lister, 1987; Roddy et al., 198X; Spencer and Welty, 1989~. A model for the evolution of detachment faults and metamorphic core complexes is shown in Figure 2.8 (Wernicke, lL981; Davis et al., 1986; Howard and John, 1987; Reynolds et al., 1988~.
|
From page 42... ...
In addition, locally derived basin fill in the Colorado River valley interfingers with the late Miocene to Pliocene Bouse Formation, which accumulated in a brackish water estuary (salty, but less than sea water) , probably linked to a proto-Gulf of Califorrua (Metzger and Loeltz, 1973; Lucchitta, 1979~.
|
From page 45... ...
The Piute Mountains west of the site, where drainage across the alluvial fan originates, are the source of the sediments at the site surface. The Sacramento Mountains to the east of Homer Wash, across the valley Tom the Ward Valley site, shed sediments forming alluvial fan deposits east of Homer Wash.
|
From page 46... ...
Because the Colorado River is topographically lower, and the drop to the lower base level along the river is relatively rapid, it resulted in more erosional downcutting by rivers, removal of basin fill, and a lower overall elevation of the basin floor, for those basins that are connected with the regional drainage network leading to the Colorado. Drainages within the Colorado River trough carved deeply into the adjacent mountain ranges, commonly causing the ranges to be steepest axle have their greatest local relief on the side facing the Colorado.
|
From page 48... ...
The bedrock surface configuration is portrayed as a narrow-floored, V-shaped canyon located west of the present-day Homer Wash drainage in a diagram by Harding Lawson Associates (Figure 2.12a)
|
From page 49... ...
49 so: ~ ~ E m us 'e cd cd · v)
|
From page 51... ...
(Law/Crandall, character of the Mniave Desert region for Ward Valley. Several sections of the administrative record provide general and specific data for the region and the Ward Valley site.
|
From page 52... ...
Hydrologic Soil Group Classification 2410~: Ward Valley has been characterized in terms of four hydrologic zones: MA Section Zone ~ is the outcropping rock and shallow soil areas formed by the Piute, Sacramento, Old Woman, Stepladder, and Turtle Mountains on the eastern and western boundaries of the basin. The San Bernardino County hydrologic soil group classification map for Ward Valley assigns soils in Zone ~ to the "D" or high runoff, low infiltration potential soils group.
|
From page 53... ...
The extensive unsaturated zone above the water table and beneath the site of the proposed disposal facility is a consequence of this depth. At Danby Dry Lake, the local base level, or regional sink, for surface-water flow, the water table is located a few meters below the ground surface.
|
From page 54... ...
are commonly found within this desert but at low densities. Joshua tree may be an aspect dominant in some locations of the Mojave Desert but is not found on the Ward Valley site.
|
From page 55... ...
The density of the tortoise in the Chemehuevi DWMA is listed as 10-275 adults per square mile (USFWS, 1994b) , which is among the higher concentrations of Mojave Desert tortoise in the 14 DWMAs.
|
From page 56... ...
1980. Mylon~tization and detachment faulting in the Whipple-Buckskin-Rawhide Mountains terrain, southeastern California and western Arizona, in Cordilleran Metamorphic Core Complexes, Crittenden, M
|
From page 57... ...
1990. The 40Ar/39AT thermochronology of the eastern Mojave Desert, California, and adjacent Arizona with implications for the evolution of metamorphic core complexes.
|
From page 58... ...
Ross, eds. Geological Society of America Cordilleran Section Guidebook, 27th Annual Meeting, San Bernardino, Californian March 21-23, 1994.
|
From page 59... ...
1982. Structural geology of the central Sacramento Mountains, San Bernardino County, California, in Mesozoic-Cenozoic Tectonic Evolution of the Colorado River Region, California, Arizona, and Nevada (Anderson-Ham~lton Volume)
|
From page 60... ...
1980. Mid-Tertiary plutonism and mylonitization, South Mountains, central Arizona, in Cordilleran metamorphic core complexes, Crittenden, M
|
From page 61... ...
Stone, eds. Arizona Geological Society Digest 12.
|
From page 62... ...
1960. Geology and mineral resources of Township 10 North, Ranges 19 and 20 East, San Bernardino base and meridian, San Bernardino County, California.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.