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David C. Buesch

Publications and source records attributed to David C. Buesch.

32 records · Page 2Linked to original sources
USGS2016

Accretionary lapilli: what’s holding them together?

Accretionary lapilli from Tagus cone, Isla Isabela, Galápagos were analyzed using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. Our main findings are (1) the lapilli formed and hardened in a few minutes while still aloft in the dispersing eruption column. (2) Palagonite rinds developed first on the basaltic glass clasts, and subsequently crystallized (3) The crystallization products contain submicron lamellar crystals of a clay (probably smectite) on the surfaces of basaltic glass clasts and (4) The interlocking of these lamellar clays from adjacent clasts binds and cements them together to form the accretionary lapillus. We argue that palagonite and possibly clay formation occur primarily in the presence of hot water vapor.

Conference Paper↗
USGS2016

Regional and local correlations of feldspar geochemistry of the Peach Spring Tuff, Alvord Mountain, California

The chemical composition of feldspar grains in an ignimbrite from the Spanish Canyon Formation in the Alvord Mountain area, California, have been used to confirm similarities in three measured sections locally, and they are similar to exposures of the Peach Spring Tuff (PST) regionally. Feldspar grains were identified on the basis of texture (zoning, as mantled feldspars, or in crystal clusters), whether the grains were attached to glass or were in pumice clasts, or were simply crystal fragments with no textural context. Chemistry was determined by electron microprobe analysis, and each analysis is calculated in terms of the percent endmember and plotted on orthoclase (Or) versus anorthite (An) plots. In general, the PST has sanidine and plagioclase compositions that are consistent with having formed in high-silica rhyolite and trachyte within a zoned magma chamber. Feldspars from the PST in Spanish Canyon area cluster along the rhyolitic trend with no grains along the trachytic trend. Similar clustering of feldspars along the rhyolitic trend with no grains along the trachytic trend also occur in the PST from Granite Spring and Providence Mountains to the east of the Alvord Mountain area, and the ranges in compositions are also similar in these locations. In contrast, the PST in the Kane Wash area of the Newberry Mountains has feldspars only from the rhyolitic trend in the basal deposits, but some grains from the trachytic trend are in the upper part of the deposit, and the range in compositions are greater than in the Spanish Canyon area. The variations in vertical compositional zoning and compositional range in these different deposits suggests there were probably different flow paths (or timing of the delivery) during the eruption and runout of the pyroclastic flow(s) generated from the climactic eruption of the PST magma chamber.

Arizon, California, Nevada↗
USGS2014

Introduction to the geologic and geophysical studies of Fort Irwin, California

Geologic and geophysical investigations in the vicinity of Fort Irwin National Training Center, California, have been completed in support of groundwater investigations, and are presented in eight chapters of this report. A generalized surficial geologic map along with field and borehole investigations conducted during 2010–11 provide a lithostratigraphic and structural framework for the area during the Cenozoic. Electromagnetic properties of resistivity were measured in the laboratory on hand and core samples, and compared to borehole geophysical resistivity data. These data were used in conjunction with ground-based time-domain and airborne data and interpretations to provide a framework for the shallow lithologic units and structure. Gravity and aeromagnetic maps cover areas ~4 to 5 times that of Fort Irwin. Each chapter includes hydrogeologic applications of the data or model results.

California↗
USGS2014

Interstratified arkosic and volcanic rocks of the Miocene Spanish Canyon Formation, Alvord Mountain area, California: Descriptions and interpretations

The Spanish Canyon Foundation in the Alvord Mountain area, California, varies from about 50 to 120 m thick and records the interstratification of arkosic sandstone and conglomerate with tuffaceous deposits and lava flows. In the lower third of the formation, arkosic sandstone and conglomerate are interstratified with tuffaceous deposits. Some tuffs might have been deposited as primary, nonwelded to partially welded ignimbrites or fallout tephra. Many of the tuffaceous deposits represent redeposited material that formed tuffaceous sandstone, and many of these deposits contain arkosic grains that represent mixing of different source matieral. Arkosic sandstone, and especially conglomerate (some with maximum clast lengths up to 1 m), represent intermittent incursions of coarser plutoniclastic fan deposits into other finer grained and mostly volcaniclastic basin deposits. After deposition of the 18.78 Ma Peach Spring Tuff, the amount of tuffaceous material decreased. The upper two-thirds of the formation has arkosic sandstone and conglomerate interstratified with two olivine basalt lave flows. locally, conglomerate clasts in this part of the section have maximum lengths up to 1 m. Many tuffaceous and arkosic sandstone beds of the Spanish Canyon Formation have tabular to broad (low-relief) lenticular geometry, and locally, some arkosic conglomerate fills channels as much as 1.5 m deep. These bedforms are consistent with deposition in medial to distal alluvial-fan or fluvial environments; some finer-grained deposits might have formed in lacustrine environments.

California↗
USGS2006

Characterization of unsaturated zone hydrogeologic units using matrix properties and depositional history in a complex volcanic environment

Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture-retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (<100 m) and 10 deep (500–1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture-retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and accurate representations of the core-scale hydrologic processes ongoing at Yucca Mountain.

Vadose Zone Journal↗
USGS2005

Geology of the proposed Yucca Mountain repository site, Nevada

Yucca Mountain, located about 100 miles northwest of Las Vegas, Nevada, has been recommended by the President for a mined geologic repository for high-level radioactive waste. This field trip will examine the geologic and hydrologic setting for Yucca Mountain, as well as specific results of the site characterization program. The field trip will visit the locations for underground in situ testing in the “Exploratory Studies Facility” plus several locales for surface-based tests. Discussions will comprise selected topics of Yucca Mountain geology, unsaturated zone hydrology, saturated zone hydrology and geochemistry and will include the probabilistic volcanic hazard analysis and the seismicity and seismic hazard analyses in the Yucca Mountain area. Emphasis of the field trip is the relationship of the geology and hydrology of Yucca Mountain to the performance of a repository that will safely isolate nuclear waste.

Nevada↗
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↗
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↗