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Geology topics

R.W. Spengler

Publications and source records attributed to R.W. Spengler.

At least 19 recordsLinked to original sources
USGS2006

A revised lithostratigraphic framework for the southern Yucca Mountain area, Nye County, Nevada

An informal, revised lithostratigraphic framework for the southern Yucca Mountain area, Nevada has been developed to accommodate new information derived from subsurface investigations of the Nye County Early Warning Drilling Program. Lithologies penetrated by recently drilled boreholes at locations between Stagecoach Road and Highway 95 in southern Nye County include Quaternary and Pliocene alluvium and alluvial breccia, Miocene pyroclastic flow deposits, Miocene intercalated lacustrine siltstone and claystone sequences, early Miocene to Oligocene pre-volcanic sedimentary rocks, and Paleozoic strata. Of the 37 boreholes currently drilled, 21 boreholes have sufficient depth, spatial distribution, or traceable pyroclastic flow, pyroclastic fall, and reworked tuff deposits to aid in the lateral correlation of lithostrata. Medial and distal parts of regional pyroclastic flow deposits of Miocene age can be correlated with the Timber Mountain, Paintbrush, Crater Flat, and Tram Ridge Groups. Rocks intercalated between these regional pyroclastic flow deposits are substantially thicker than in the central part of Yucca Mountain, particularly near the downthrown side of major faults and along the southern extent of exposures at Yucca Mountain.

Conference Paper↗
USGS1998

Development of a technically consistent, qualified lithostratigraphic data base for the Yucca Mountain Project

Studies of Yucca Mountain, Nevada, as a potential geologic nuclear-waste repository began in the late 1970s and continued to 1988 when the U. S. Nuclear Regulatory Commission determined that the quality assurance (QA) programs in place were not adequate and demanded restructuring to a new QA program. The new QA program was accepted in 1989, but many activities did not resume until new procedures were in place, until the early 1990s. These two generations of QA programs have resulted in a highly convoluted assignment of qualified (Q)-status for much of the data related to boreholes. In the simplest case, any data that came from boreholes drilled before 1989 had been assigned non-qualified (non-Q) status, and all post1989 boreholes (none of which were drilled until 1991) have been assigned Q status. This pre- and post1989 distinction in Q status of borehole data has meant that lithostratigraphic descriptions and contacts from the pre-1989 boreholes have been classed as non-Q, and any models' that used these data also carried the non-Q status (R.W. Clayton, W.P. Zelinski, and C.A. Rautman, TRW Environmental Safety Systems, Inc., written commun., 1997). This Q-status barrier has also limited the amount of lithostratigraphic work done on the pre-1989 boreholes because of the drive to produce Q-status descriptive reports that contain only Q-status data. A parallel and critical concern that arises from such a long history of data collection is the consistent identification of lithostratigraphic units. In the spring of 1996, an intensive effort began to reexamine 11 lithostratigraphic contacts in boreholes. This work was expanded in 1997 to include as many as 50 lithostratigraphic contacts in 80 boreholes. All this work has been done under the post-1989 QA program and emphasizes technically consistent contacts and the Q-status of each contact rather than carteblanche assignment by borehole.

Conference Paper↗
USGS1996

Localized alteration of the paintbrush nonwelded hydrologic unit within the exploratory studies facility

The mound-like feature in the lower part of the PTn, composed of highly disrupted strata and open-system alteration were the result of intense water-rock interaction. This feature was formed by fumarolic activity during cooling of the 12.8 Ma Topopah Spring Tuff and prior to deposition of the pre-Pah Canyon bedded tuff. Evidence of vapor phase crystallization, commonly observed in fumaroles, is not pervasive but may have been destroyed by subsequent low-temperature water-rock interaction. The ESF has provided a unique opportunity to view the internal morphology and to sample the compositional variability of this feature, however, outcrop and borehole studies suggest that such localized occurrences of alterative are not uncommon phenomenon within the PTn Hydrology Unit.

Conference Paper↗
USGS1994

Integrated geology and preliminary cross section along the north ramp of the Exploratory Studies Facility, Yucca Mountain

The Exploratory Studies Facility is a major part of the site characterization activities at Yucca Mountain, Nevada, and the north ramp is the first phase of construction. The N61W trending north ramp will transect the Bow Ridge and Drill Hole Wash faults and numerous minor faults, and traverses two thick welded tuffs and several nonwelded tuff units. A preliminary cross section along the north ramp was created by integration of geologic map relations, lithostratigraphic data from core collected from boreholes, and surface and borehole geophysical data. The Bow Ridge fault is a west-dipping normal fault with about 410 feet of dip-slip separation. East-dipping strata in the hanging wall adjacent to the fault is contrary to early structural interpretations. West of the Bow Ridge fault the ramp might traverse about 220??65 feet of nonlithified tuffaceous material. Geometry of the Drill Hole Wash fault is not known, but is modeled in part as two strands that juxtapose different thicknesses and facies of formations with a complex sense of movement.

Conference Paper↗
USGS1993

Development of 3-D lithostratigraphic and confidence models at Yucca Mountain, Nevada

Computerized three-dimensional geologic models of potential high-level nuclear waste repositories such as Yucca Moutain, Nevada, are important for visualizing the complex interplay of (1) thickness and facies variations in lithostratigraphic units and (2) the disruption of these units by faults. The concept of a 'model of confidence' in the lithostratigraphic model is introduced to show where data are located versus regions where interpolations are included. Models of confidence can be based on (1) expert judgment, (2) geostatistical analysis, or (3) a simplified combination of these two methods. Linking of lithostratigraphic models and models of confidence provide guidelines for future characterization and modeling activities, as well as for design and construction of the Exploratory Studies Facility.

Conference Paper↗
USGS1993

Structural character of the Ghost Dance fault, Yucca Mountain, Nevada

Detailed structural mapping of an area that straddles the southern part of the Ghost Dance Fault has revealed the presence of several additional subparallel to anastomosing faults. These faults, mapped at a scale of 1:240, are: 1) dominantly north trending, 2) present on both the upthrown and downthrown sides of the surface trace of the Ghost Dance fault, 3) near-vertical features that commonly offset strata down to the west by 3 to 6 m (10 to 20 ft), and 4) commonly spaced 15 to 46 m (50 to 150 ft) apart. The zone also exhibits a structural fabric, containing an abundance of northwest-trending fractures. The width of the zone appears to be at least 213 m (700 ft) near the southernmost boundary of the study area but remains unknown near the northern extent of the study area, where the width of the study area is only 183 m (600 ft).

Conference Paper↗
USGS1993

Seismic reflection profiling: essential geophysical data for Yucca mountain, Nevada

Yucca Mountain, Nevada, consists of a thick sequence of ashflow tuffs and lavas fractured into intact blocks with east-dipping strata, marginal broken zones characterized by dense faulting and brecciation, and intervening down-to-the-west fault zones with locally atypical west-dipping strata. Uncertainty in the structural setting of Yucca Mountain has resulted in multiple interpretations of the role and style of faulting. One interpretation describes steep normal faulting extending to seismogenic depth (10 to 15 km), and an alternate explanation suggests listric faults and a major low-angle detachment between the Tertiary volcanic sequence and the underlying Paleozoic rocks. Resolution of the deep geology is critical to evaluations of the potential tectonic and hydrologic hazards of the site. Seismic reflection profiling will provide essential data for defining the subsurface geometry of Yucca Mountain and for distinguishing between alternate interpretations of the structure of the mountain.

Conference Paper↗
USGS1993

Isotopic and trace element variability in altered and unaltered tuffs at Yucca Mountain, Nevada

Reference stratigraphic sections near Yucca Mountain, Nevada were established and sampled in outcrop areas where the volcanic rocks have been minimally altered. Isotopic and trace element analyses obtained for these reference sections are baseline data for assessing the degree and extent of element mobility attendant with past zonal alteration of the rock mass. In agreement with earlier studies, zeolitization is shown to have occurred under wholesale open-system conditions. Calcium was increased by two three times the baseline values and strontium up to twenty times. In contrast, barium displays less variability, and the high-field strength elements zirconium and titanium were the least mobile during zeolitization. The data reported here establish the usefulness of reference sections of assessing past elements mobility. The information gained will be helpful in predicting possible future element mobility induced by thermally activated fluids in the near field of a potential repository.

Conference Paper↗
USGS1993

Three-dimensional lithostratigraphic model at Yucca Mountain, Nevada: A framework for fluid transport modeling and engineering design

A three-dimensional lithostratigraphic model of the central block of Yucca Mountain, Nevada, illustrates how some activities can serve both site characterization and design and construction of the Exploratory Studies Facility (ESF). Site-characterization activities supported by this model include characterizing the three-dimensional geometry of lithologic units and faults, and providing boundary conditions for geostatistical models and site-scale fluid flow modeling. This model supports the conceptual design as well as construction efforts for the proposed ramps of the ESF and potential high-level nuclear waste repository.

Nevada↗
USGS1986

Rock-water interaction in ash-flow tuffs (Yucca Mountain, Nevada, USA)- The record from uranium studies

Forty-eight core samples of ash-flow tuffs from Yucca Mountain, NV, were selected for comparative analysis by uranium-based methods to estimate past interaction with oxidizing water. Results aid in the selection of hydrologically isolated host rocks for radioactive waste disposal. U abundances were consistently more variable than thorium in whole rocks, suggesting some selective redistribution of U. Dissolved U correlates most strongly with dissolved manganese, indicating a predominant association of U with manganese oxides.

Nevada↗
USGS1984

Geohydrologic and drill-hole data for test well USW H-3, Yucca Mountain, Nye County, Nevada

Test well USW H-3 is one of a series of test wells drilled in and near the southwestern part of the Nevada Test Site for hydraulic testing, hydrologic monitoring, and geophysical logging. The work was performed in cooperation with the U.S. Department of Energy as part of the Nevada Nuclear Waste Storage investigations. The well penetrated volcanic tuffs of Tertiary age to a depth of 1,219 meters. This report presents data collected to determine the hydraulic characteristics of rocks penetrated. Data on drilling operations, lithology, borehole geophysics, hydrologic monitoring, pumping, swabbing, and injection tests for the well are contained in this report. (USGS)

Open-File Report↗