DEPARTMENT OF GEOLOGICAL SCIENCES

MASTER'S THESES: 1969 - Present

(Abstracts; 1996-present)

2002

2002
Holland, Austin, 2002, Microearthquake study of the Salton Sea geothermal field, California: Evidence of stress triggering (D.I. Doser).

2001
Couroux, Emile Gabriel, 2001, An integrated study of landform development using near-surface geophysics, remote sensing, and geomorphology, at the Great Sand Dunes National Monument; 175 p. (Outstanding Geology Thesis; Dept.Geol. Sci.) (R.P. Langford and D.I. Doser).

Depret, Pierre-Andre, 2001, Influence of diagenesis on the reservoir quality of the Cedar Mesa Sandstone, southeastern Utah, and comparison with the Rotliegende Sandstone, North Sea (R.P. Langford) (Outstanding Geology Thesis; Dept. Geol. Sci.)

Hicks, Nigel Oakley, 2001, Lithospheric structure of the Basin and Range-Southwestern Colorado Plateau: Southeastern California, southern Nevada, and western Arizona (G.R. Keller)

Hincapie, Jaime O., 2001, The regional tectonic stress field in the Buller Region, New Zealand: Evolution through time and relation to large historical earthquakes (D.I. Doser).

Guan, Huade, 2001, Virus transport in a saturated porous medium with special emphasis on the effect of permeable barriers; 86 p. (D. Schulze-Makuch).

Rohrbaugh, Rob,, 2001, Contractional and extensional deformation kinematics of the southern Indio Mountains, Trans-Pecos; 83 p. (C.L. Andronicos) .

Rodriguez, Christina M., 2001, A study of microseismicity in southwest Puerto Rico using joint hypocenter determination (Outstanding Geophysics Thesis; Dept. Geol Sci) (D.I. Doser).

Wilson, Paul, 2001, Geology and gold placers of the El Boludo mineral district, Sonora, Mexico; 186 p. (K.F. Clark).

2000
Barud-Zubillaga, Alberto, 2000 , A conceptual model of the hydrogeology of White Sands National Monument, south-central New Mexico; 138 p. (Outstanding Geology Thesis; Dept. Geol Sci) (D. Schulze-Makuch)

Brown, Wesley, 2000, A seismotectonic study of the south-central Alaskan Margin between the 1938 and 1964 Great Alaskan Earthquake Rupture Zones (D.I. Doser).

Cline, Veronica, 2000 , An integrated geophysical analysis of the Great Divide Basin and adjacent uplifts, southwestern Wyoming; 86 p. (G.R. Keller)

Hiett, Brett Joseph, 2000, 3-D Geometry and velocity structure of the Tacoma Basin, western Washington; 119 p. (Outstanding Geophysics Thesis; Dept. Geol. Sci.) (K.C. Miller)

Pérez, Adriana E., 2000 , Satellite Detection of Land Use Changes in the Rio Grande Valley from Elephant Butte Dam, New Mexico, to Fort Quitman, Texas (N.E. Pingitore) .

Quezada Rodas, Oscar Andres, 2000 , A seismic reflection, gravity, and remote sensing study of the southeastern Sangre de Cristo Mountains, New Mexico; 105 p. (G.R. Keller)

Rothemund, Kirk, 2000, The structural framework and mineralization of the Lluvia de Oro Mine, Sonora, Mexico; 147 p. (K.F. Clark).

1999
Belzer, Wayne L., 1999, Gravity and seismic studies of the Tularosa graben for groundwater studies; 124 p. (K.C. Miller)

Dober, Mark, 1999, Earthquake studies of the Anninghe and Xiaojiang faults of southwestern China; 94 p. (D.I. Doser).

Kaip, Galen M., 1999, Uses of seismic methods in geotechnical studies, southern New Mexico and west Texas; 70 p. (D.I. Doser).

Jimenez, Alberto Jose, 1999, An integrated analyses of basins in the Rio Grande Rift in northern Chihuahua, Mexico (G.R. Keller)

Veilleux, Annette M., 1999, Shallow surface geophysics of the Pajarito Plateau, New Mexico; 90 p. (D.I. Doser).

Velasquez, Monique, 1999, Seismotectonic study of Kennedy Entrance, South-Central Alaska; 109 p. (D.I. Doser).

Wilrich, Kerry, 1999, The biostratigraphy of the Middle Pennsylvanian (Desmoinesian) Fusulinidae of Bug Scuffle Canyon, Otero County, New Mexico; 75 p. (Outstanding Geology Thesis; Dept. Geol. Sci.) (W.C. Cornell).

1998
Borrego, Patricia, 1998, Heavy metals in soil from the Mesa Quadrangle, Arizona, using NURE data; 63 p. (D.V. LeMone)

Latter, Kelly, 1998, Sand provenance within the Alboran Sea, western Mediterranean 79 p. (D.V. LeMone)

O'Donnell, Jr., Terry M., 1998, Integrated gravity and seismic reflection/refraction study of a potential geothermal source, McGregor Range, New Mexico; 142 p. ( Outstanding Geophysics Thesis; Dept. Geol. Sci.) (K.C. Miller)

Snelson, Catherine, 1998, An integrated lithospheric study of the Rocky Mountain region along the Deep Probe Seismic Profile; 151 p. (K.C. Miller and G.R. Keller)

1997
Ballard, Jenny, 1997, The depositional history of the Mundy Breccia and the lowermost Lanoria Formation; 180 p. (E.Y. Anthony)

Duran, Alejandro, 1997, A crustal structure study of the Owens Valley-Death Valley Region, eastern California; 126 p. (G.R. Keller)

Guerrero-S., Martin, 1997, Depositional history and sedimentary petrology of the Huetamo sequence, southwestern Mexico; 120 p. (W.C. Cornell).

Molina-S., Castulo, 1997, Stratigraphy and structure of the Sierra Samalayuca, northern Chihuahua, Mexico; 135 p. (D.V. LeMone).

Pérez-Santiago, Vilma, 1997, Heterogeneity and water quality in the Rio Grande Alluvium, downtown El Paso, Texas; 137 p. (P.C. Goodell).

Sellepack, Steven, 1997 The geology and geochemistry of the El Sauzal Gold prospect, southwest Chihuahua, Mexico; 89 p. (P.C. Goodell).

van Dusen, Shelley, 1997, Seismotectonics of the Xianshuihe fault system, southwestern China; 65 p. (D.I. Doser)

1996
Maciejewski, Tim, 1996, Evaluation of seismic data for NASA Johnson Space Center, White Sands Test Facility (NASA-WSTF); 123 p. (K.C. Miller)

Martinez, Ruben, 1996, A study of the effects of the addition of tellurium into the acanthite-Naummanite (Ag₂S-Ag₂Se) system (N.E. Pingitore)

Palsole, Sunay, 1996, A geophysical study of the Salt and Valentine basins, West Texas; 51 p. (G.R. Keller and (D.I. Doser)

Virtue, Terence, 1996, Geology, mineralogy, and genesis of supergene enrichment at the Cananea porphyry copper deposit, Sonora, Mexico; 251 p. (K.F. Clark).

1995
Afseth, Daniel, 1995, The development of a multi-element toxic chemical environmental factor for A southwestern New Mexico target region; 120 p.

Gillespie, Cindy L., 1995, Imaging geological materials using the acoustic microscope; 349 p.

Johnson, Ada Suzanne, 1995, Spatial distribution of trace elements in irrigated fields: Examples from the Texas-Mexico border system; 135 p.

Lanka, Kalidas, 1995, Integrated study of structure and water resources of the Tularosa Basin, south-central New Mexico; 64 p.

Sandoval, Juan, 1995, The evaluation of saline lakes in eastern New Mexico and western Texas for their potential utilization as salinity-gradient solar ponds region; 250 p.

Tesha, Aloyce, 1995, Lithospheric structure of northeastern and central Tanzania from gravity interpretation; 92 p.

1994
Gerstenberger, Matthew C., 1994, Development of new techniques in Crosswell seismic travel time tomography

Long, Christopher, 1994, Geochemical Investigations of the ultramafic mantle xenoliths from Kilbourne Hole, Potrillo volcanic field, southern New Mexico.

Wong, Virgina, 1994, The Nopal I uranium deposit, Pena Blanca District, Chihuahua, Mexico: A study of radionuclide migration in a natural analogue to Yucca Mountain, Nevada. Formation.

Williams, Jeffrey L., 1994, Seismic tomography of freezing and thawing soil tomography

1993
Barnes, Brenda E., 1993, An evaluation of metals concentrations in surficial soils, El Paso County, Texas

Braile, William J., 1993, Crustal structure of the northern Mississippi embayment and Reelfoot Rift from seismic refraction and reflection profiling

Burgos, Arturo, 1993, A gravimetric study of the thickness of the unconsolidated materials in the Hueco Bolson aquifer, Juarez area, Chihuahua Mexico

Chang, Jer-Yuan, 1993, Interpretation of geophysical data in southwesternmost New Mexico and adjacent areas

Farzat, Isber, 1993, A geophysical study of the San Luis Basin profiling

Guillen, Rosalio, 1993, Albite dissolution at two temperatures in the presence of barite under saturated and unsaturated flow conditions in soil columns

Machorro-S, Rudy A., 1993, Geology of the northwestern corner of the Granados quadrangle, central Guatemala

Moreno, Frederico A., 1993, The extent of the Ouachita orogenic belt in northern Mexico

Ndame, Emmanuel C., 1993, Heavy metals in soils in the vicinity of the University of Texas at El Paso (El Paso County, Texas)

Roberts, Donald G., 1993, A long offset seismic profile across the Rio Grande Rift and its transition zones in central New Mexico

Sandidge, Michael H., 1993, Depositional history of the Finlay Formation (Middle Albian), Rimrock escarpment, Hudspeth County, Texas

1992
Barrow, Ronald K., 1992, An integrated geophysical study of the Estancia Basin, central New Mexico

Crain, Kevin D., 1992, A 3-D gravity inversion with a priori and statistical constraints

Fetzner, Keith, 1992, The interpretation of principal strains from calcite twins in the Franklin Mountains, Texas

Fitzpatrick, Scott W., 1992, The trace fossil faunas of the Rara Formation, Sierra del Cuervo, Chihuahua, Mexico

Garibay, Gerardo, 1992, Electrophoretic and sorptive behavior of lithium in clay suspensions

Montana, Carlos, 1992, Inversion of vertical component gravity and gravity gradient tensor for 2.5 dimensional bodies

Pattison, Ann D., 1992, The structural geology of the San Francisco del Oro Region, Chihuahua, Mexico

1991
Chen, Weiping, 1991, Evolution of the Potrillo Volcanic Field, southern New Mexico.

Giles, Geoffrey, 1991, Progressive megascopic, microscopic and geochemical changes related to alteration within host rocks to the south of Round Mountain, Nevada.

Hsueh, Fu-Jen, 1991, Application of ray trace modeling to a large scale seismic experiment in Oklahoma

Jamal, Muhammad, 1991, A regional crustal structure study of the Appalachian Basin region of the eastern United States

Kingwell, Julia, 1991, Three-dimensional velocity structure of a portion of the Permian Basin

Murphy, Brian P., 1991, Determination of shear wave velocity structure in the Rio Grande Rift through receiver function and surface wave analysis

Pittenger, Michelle, 1991, Sedimentation and tectonics of Proterozoic metasedimentary rocks exposed in the Franklin Mountains, El Paso, Texas

Stacy, John K., 1991, Structural and tectonic history of McKelligon Canyon, El Paso County, Texas

1990
Gainer, Gabriela M., 1990, Boron adsorption on hematite and clinoptiloite

Ntsimanyana, Mokwaledi, 1990, Mineralogy and exploration of the Anapra and Mesilla Valley shales for the production of brick and tile, Anapra, Dona Ana County, New Mexico

1989
Gilder, Stuart A., 1989, Geochemistry of fluorite in the caldera environment

Hamilton, Lindsay S., 1989, Structure of the Wichita Uplift, southern Oklahoma, from a wide-angle seismic experiment

Hill, Kerry W., 1989, Geochemistry, mineralogical associations, and origin of near-surface dolomite from Salt Basin, west Texas

Jenkins, Richard D., 1989, An interpretation of basement structures from gravity anomalies in the central portion of the Colorado Plateau

Jurick, Dana M., 1989, Basement structure of the north-central Gulf coastal plain, Mississippi and Alabama

Roberts, David C., 1989, Sedimentation and tectonics of the Cerro los Panales area, east-central Chihuahua, Mexico

Robinson, John Q., 1989, A clastic evaporite deposit in the Lower Castile Formation (Permian), Delaware Basin

Summerour, Jr., Joseph H., 1989, The geology of five unusual craters, Aden basalts, Dona Ana County, New Mexico

1988
de Angelo, Michael V., 1988, Geophysical anomalies in southwestern New Mexico and adjacent areas.

Dicke, Craig A., 1988, Modeling the feasibility of strontium remobilization from geothite surfaces in a saturated tuff at Yucca Mountain, Nye County, Nevada Salt Basin

Filsinger, Bradford, 1988, Geology and genesis of the Palm Park and Horseshoe barite deposits, southern Caballo Mountains, Dona Ana County, New Mexico

Fisher, Marci A., 1988, Transport and fate of organic chemicals in Bandelier Tuff at Los Alamos National Laboratory Chemical Waste Site, New Mexico.

Holt, Robert M., 1988, The depositional environments of the late Permian Rustler Formation, in the vicinity of the Waste Isolation Pilot Plant (WIPP), site, southeastern New Mexico

Miller, Rebecca A., 1988, Geology of the Llanitos Mining District, Chihuahua, Mexico

Newman, Brent D., 1988, Experimental determination of reactive tracer suitability for groundwater tracer tests

Pearson, John W., 1988, Genesis of the vein deposits along the Great Master Lode, Phillipsburgh area, northern Black Range, Sierra and Catron Counties, New Mexico

Schiel, Kathryn A., 1988, The Dewey Lake formation: End stage deposit of a peripheral foreland basin

Sivils, David J., 1988, Geology of northern Sierra de Palomas, Chihuahua, Mexico

Yarwood, Dennis R., 1988, The seismicity of northern Tanzania and southern Kenya, and its tectonic implications

1987
Belle, Eddie R., 1987, A geochemical study of the organic matter within the lower Cretaceous Mesilla Valley Shale, Cerro de Cristo Rey Uplift, Dona Ana, County, New Mexico

Davis, Lisa M., 1987, A geochemical survey of the Loma Plata area, Presidio County, Texas

Flint, Frederick F., 1987, Diagenesis of Tertiary (Miocene) sedimentary rocks of the Old Woman Mountains area, southeastern California

Gilmer, Allen L., 1987, The geology and genesis of the Sierra de Santa Maria metalliferous deposits, Velardena, Durango, Mexico.

Gurrola, Harold, 1987, A crustal structure study of the northern margin of the Gulf of Mexico.

Guthrie, Robert S., 1987, Geology of the northern Sierra Boca Grande area, Chihuahua, Mexico.

Holtzclaw, Stuart R., 1987, Stratigraphy and sedimentology of the lower Frontier Formation (Cretaceous, southwestern Bighorn Basin, Wyoming

Kahn, Peter A., 1987, Geology of Aden Crater, Dona Ana County, New Mexico

Kiley, James M., 1987, Diagenesis and depositional setting of the fanglomerate of Little Florida Mountains (Miocene), southwestern New Mexico

Lehtonen, Lee R., 1987, Late Paleozoic evolution of the Val Verde Basin, west Texas

McCabe, Marcella R., 1987, The coal deposits of the Lee Ranch coal mine, McKinley County, New Mexico

Peters, Lisa, 1987, Origin of vertical rhythmic layering in the marginal border group of the skaergaard intrusion, east Greenland

Rimando, Philip M., 1987, Design and implementation of filters for potential field data.

Russo, Joseph F., 1987, Influence of framework grain composition on sandstone diagenesis, Lobo Formation Tertiary), southern New Mexico

Ryan, Elizabeth, B., 1987, Liquidus phase relations in part of the system Mg₂SiO₄-FeSiO₄-CaMgSi₂0 ₆-CaFeSi₂0₆-KAlSi₃0₈ along the nickel-nickel oxide buffer curve

Saenz, Guadalupe., 1987, Geochemical exploration for petroleum in a marsh area: Examination and statistical analysis of C₁-C₇ hydrocarbons in near surface samples taken over producing and barren structures

Seigler, William C., 1987, A study of the cooling history of a pluton in the Finlay Mountains, Hudspeth County, Texas

1986
Abrams, Gary S., 1986, The relationship between electric logs and sidewall core analyses, Wilcox Group (Eocene) in southwest Mississippi.

Chavez-Quirarte, Ramon, 1986, Stratigraphy and structural geology of Sierra de Sapello northern Chihuahua, Mexico.

Handschy, James W., 1986, The geology and tectonic history of south-central Sierra del Cuervo, Chihuahua, Mexico.

Miranda-G., Miguel A., 1986, Geology of the Sierra los Arados Cenozoic volcanic field, Chihuahua, Mexico

Norland, William D., 1986, Thermal maturation of the Mesilla Valley shale (Late Albian) on the north and east flanks of the Cerro de Cristo Rey pluton, Dona Ana County, New Mexico

Phillips, Joseph D., 1986, Geology of the southern portion of Sierra de Palomas, northwestern Chihuahua, Mexico

Pickens, Craig A., 1986, Facies analysis of an early Cretaceous rudist biostrome, East Potrillo Mountains, Dona Ana County, New Mexico

Roark, Robert C., 1986, Stratigraphy and microfacies of the Pennsylvanian, system, north Franklin Mountains, Dona Ana County, New Mexico

Shannon, William M., 1986, Lithogeochemical characterization of intrusive rocks comprising the Quitman-Sierra Blanca igneous complex, Hudspeth County, Texas.

Smith, Karl J., 1986, A gravity and tectonic study of the southwestern portion of the Ouachita system.

Wilmar, Glenn C., 1986, Relation of diagenesis to lithofacies distribution, Nugget Sandstone Washakie Basin, Wyoming.

Wood, II, Douglas R., 1986, Geology at Timber Mountain Pass, northern Seaman Range, Nye County, Nevada.

1985
Basden, Wayne A., 1985, Inversion of dispersed love wave phase velocity for data multiple continuous parameters.

Brown, Michael L., 1985, Geology of Sierra de Los Chinos-Cerro La Cueva area, northwest Chihuahua, Mexico.

Bullock, James S., 1985, Biostratigraphy study of foraminifera from the Smeltertown Formation (Lower Cretaceous, Albian) of southeastern New Mexico

Deshler, Richard M., 1985, The geology of El Borracho Caldera, Chihuahua, Mexico.

Gates, Edward E., 1985, The geology of the Carrizalillo Hills, Luna County, New Mexico.

Harkey, Donald A., 1985, Structural geology and sedimentologic analysis (Las Vigas Formation, Sierra San Ignacio, Chihuahua, Mexico.

Harvey, David B., 1985, Cassiterite mineralization in the Black Range tin district, Sierra and Catron Counties, New Mexico

Mauldin, Randall A., 1985, Foraminiferal biostratigraphy, paleoecology, and correlation of the Del Rio Clay (Cenomanian) from Big Bend National Park, Brewster County, Texas and to the Cerro de Muleros Area, Dona Ana County, New Mexico

Muela, Jr., Pedro, 1985, The geology of the northern portion of Sierra Santa Rita, Chihuahua, Mexico.

Pau, Joseph H.K., 1985 Stratigraphy, microfacies analysis, and thermal maturation of the Mississippian Rancheria and Helms formations Spike "S" Ranch, southern Hueco Mountains, Hudspeth County, Texas.

Pearson, Mark F., 1985, Geology, mineralogy, and sulfur isotope studies of the Real de Angeles silver deposit, Zacatecas, Mexico.

Ponce, Benjamin F., 1985, Caldera development and economic mineralization in the Zacatecas mining district, Zacatecas, Mexico.

Raksaskulwong, Manop, 1985, Combined electrical studies in the southern Hueco Bolson, El Paso County, Texas.

Reyes-C., Ignacio A., 1985, Geology and uraniferous mineralization in the Sierra de Coneto, Durango, Mexico.

Schneider, Robert V., 1985, The vertical distribution of uranium, thorium, and potassium in the Canadian shield, Sudbury, Ontario, Canada.

Wuellner, Dirck E., 1985, Tectonic evolution of the Marathon region with emphasis on mid-carboniferous tectonism and sedimentation.

1984
Abuzekri, Sadegh K, 1984, Microfacies analysis of the upper Beda Formation in the Balat field, Sirte Basin, Libya.

Adame, Javier, 1984, The effects of a vertical pipe on induced polarization readings.

Broderick, John C., 1984, The Geology of Granite Hill, Luna County, New Mexico.

Burrows, Lloyd A., III, 1984, A gravity and magnetic survey in the Hueco Mountains, western Diablo Plateau, Texas.

Campbell, Michael P., 1984, The geology of the southern Sierra Santa Rita, Chihuahua, Mexico.

Davison, Jr., Charles H., 1984, Simulation by finite difference methods of water levels in the Horizon City area, Texas, 1983-2030.

Dupuy, John R., 1984, The hydrologic significance of geologic structure within the southeastern Hueco Bolson, El Paso County, Texas.

Durfee, Barbara A., 1984, Geology and structure of the Carrizozo Mountain metarhyolites, Hudspeth and Culberson Counties, Texas.

Kondelin, Robert J., 1984, Stratigraphy and microfacies analysis of the Ordovician system, north Franklin Mountains, Dona Ana County, New Mexico.

Lueth, Virgil W., 1984, Comparison of copper skarn deposits in the Silver City mining region, southwestern New Mexico.

Madden, H. Douglas, 1984, Stratigraphy and microfacies analysis on the Mississippian system, north Franklin Mountains, Dona Ana County, south-central New Mexico.

McEvers, Lloyd K., 1984, Stratigraphic and petrographic analysis of the Fusselman dolomite (Lower to Middle Silurian), north Franklin Mountains, Dona Ana County, New Mexico.

Renbarger, K. Scott, 1984, A crustal structure study of South America.

Riess, C. Maurine, 1984, A thermal maturation study of Cretaceous petroleum source rocks in Presidio County, Texas.

Riley, Robert, 1984, Stratigraphic facies analysis of the Upper Santa Fe Group, Fort Hancock and Camp Rice Formations, far west Texas and south-central New Mexico

Roepke, Timothy J., 1984, Stratigraphy and microfacies analysis of the Pennsylvanian System, Robledo Mountains, Dona Ana County, New Mexico.

Shepard, Mark D., 1984, Geology and ore deposits of the Hermosa mining district, Sierra County, New Mexico.

Suleiman, Abdunnur S., 1984, Integrated geophysical and subsurface studies of tectonic features in northeastern New Mexico and adjacent regions.

1983
Abugares, Youssef I, 1983, Pecos slope Abo gas field, Chaves and DeBaca Counties, New Mexico.

Abushagur, S.ulaiman A, 1983, Microfacies analysis of the Farrud lithofacies in the Ghani field, Sirte Basin, Libya.

Beard, Thomas C., 1983, Photogeology of the Spike "S" Ranch, southern Hueco Mountains, Hudspeth County, Texas.

Coughlon, John P., 1983, Stratigraphy and microfacies analysis of the Pennsylvanian System, Spike-S Ranch, El Paso and Hudspeth Counties, Texas.

Girten, Nancy A., 1983, An assessment of chromium in the unsaturated zone at an aerospace plating facility in Los Angeles County, California.

Gomez, Filiberto, 1983, The geology of the Sierra del Aquila, Chihuahua, Mexico.

Kornas, Barbara E., 1983, Chemical composition, mineralogy, and texture of tephra, El Chichon, Mexico, March 28-April 7, 1982 eruption.

Kruger, Joseph M., 1983, Regional gravity anomalies in the Ouachita system and adjacent areas.

LaFreniere, Jon E., 1983, A gravity and geothermal study of the Presidio Bolson, Presidio County, Texas.

Papesh, Henry, 1983, A regional geophysical study of the southern Oklahoma aulacogen.

Powell, Darron L., 1983, The structure and stratigraphy of the early Cretaceous of the southernmost east Potrillo Mountains, Dona Ana County, New Mexico.

Rahman, John L., 1983, Geothermal studies of drill holes in northern Illinois and the Hueco Tanks region, Otero County, New Mexico.

Scheubel, Frank R., 1983, The geology and mineralization of the San Martin de Bolanos mining district, Jalisco, Mexico.

Trujillo, Mario R., 1983, Petrology and facies analysis of the Drinkard Sandy Member (Lower Leonard), in the central Drinkard Unit No. 431 well, Lea County, New Mexico.

Wen, Cheng-Lee, 1983, A study of bolson fill thickness in the southern Rio Grande rift, southern New Mexico, west Texas and northern Chihuahua.

1982
Aiken, Olaf W., 1982, Geological significance of surface gravity measurements in the vicinity of the Illinois deep drill hole.

Bodnar, Christopher A., 1982, Crustal structure of the Great Plains of North America from Rayleigh wave analysis.

Coultrip, Robert, 1982, Regional gravity anomalies of the Four Corners states.

Harden, Stephen N., 1982, A seismic refraction study of west-central New Mexico.

Harder, Vicki M., 1982, Oil and gas potential of the Tularosa Basin-Otero platform area, Otero County, New Mexico.

Leonard, Mary L., 1982, The geology of the Tres Hermanas Mountains, Luna County, New Mexico.

Matek, Joel E., 1982, Sedimentology of the Bliss Sandstone, Franklin Mountains, Texas.

McCutcheon, Tim, 1982,  The petrology and geochemistry of the Precambrian Red Bluff Granite Complex, Northern Franklin Mountains, El Paso County, Texas.

McCutcheon, Janice A., 1982, A geophysical investigation of the Precambrian rocks in the Llano Uplift region, Texas.

Phillips, Stephen E., 1982, Geology and economic mineral potential of the Klondike Mine area, Saguache County, Colorado

Ray, David R., 1982, Geology of the Precambrian Red Bluff granite complex, Fusselman Canyon area, Franklin Mountains, El Paso County, Texas.

Robinson, Rosalie M., 1982, Tertiary volcanic rocks of the central David Mountains, Jeff Davis County, Texas.

1981
Bell, Richard C., 1981, Geology of central Sierra Pena Blanca.

Danko, Jeffrey H., 1981, Stratigraphy and microfacies analysis of the Canutillo Formation (Late Middle Devonian), Franklin Mountains, Texas and New Mexico, and Bishop Cap Hills, New Mexico

Decker, Guy M., 1981, A surface and subsurface study along the northwest margin of the Val Verde Basin, Pecos, Terrell, and Brewster Counties, Texas.

El-Dadah, Ghazi, 1981, Permian subsurface carbonate facies of the shelf edge Midland Basin, north Terry and south Hockley Counties, Texas

Frantes, Thomas J., 1981, The geology of the Palomas volcanic field Luna County, New Mexico and Chihuahua, Mexico

Jacobs, Michael A., 1981, Tertiary rhyolite intrusives of the northeastern Eagle Mountains, Hudspeth County, Texas

Osleger, David A., 1981, Stratigraphy and microfacies analysis of the La Tuna Formation (Morrowan-Atokan) Franklin Mountains, Texas and New Mexico and Bishop Cap Hills, New Mexico

Reuter, Stephen G., 1981, A gravity study of the Escalante Desert region, southwestern Utah.

Rinowski, Robert D., 1981, Stratigraphy and microfacies analysis of the Helms Formation, Franklin Mountains and Bishop Cap Hills, Texas and New Mexico

Sheffield, Tatum M., 1981, Petrography and geochemistry of the west Potrillo basalt field, Dona Ana County, New Mexico.

Aiken, Mary J., 1981, Mineralogy and geochemistry of a lacustrine uranium occurrence, Andersen Ranch, Brewster, County, Texas.

1980
Mitchell, Stephen M., 1980, Geology of Sierra Gomez, Chihuahua, Mexico.

Cofer, Richard S., III, 1980, Geology of the Shelly Cauldron Complex, Pinto Canyon area, Presidio County, Texas.

Cornelius, Howard E., 1980, Synthetic seismograph modeling and its application to data from the Rio Grande Rift.

House, Larry A., 1980, A geophysical and subsurface investigation of the Illinois Basin.

Kourse, Lauralee D., 1980, Silicoflagellate biostratigraphy of the Upper Monterrey Formation and Lower Sisquoc Formation, Johmansville Quarry, Lompoc, California

Lewis, Laurel M., 1980, A gravity study of north-central New Mexico.

Pyron, Arthur J., 1980, Geology and geochemistry of the El Paso Tin Deposit, Franklin Mountains, El Paso County, Texas

Stege, Bruce, 1980, Stratigraphy and significance of the carbonates of the Sierra Pena Blanca, Chihuahua, Mexico

Strickland, Frank G., 1980, Structure, stratigraphy and economic geology of Goat Ridge, Lune County, New Mexico.

Veldhuis, Jerry H., 1980, A geophysical and geological analysis of the Salt Flat Basin of Trans-Pecos Texas and southern New Mexico

Willingham, Daniel L., 1980, Stratigraphy and sedimentology of the Upper Santa Fe Group in the El Paso region west Texas and south-central New Mexico

Woodrome, Larry S., 1980, Uranium: Trans-Pecos, Texas Tertiary intrusive and groundwater anomalies.

1979
Davis, Gene H., 1979, A gravity study of the San Luis Basin, Colorado.

Djeddi, Raba, 1979, An integrated geophysical and geological study of the deep structure and tectonics of the Permian Basin of west Texas and southeastern New Mexico.

Dowdney, Jack R., 1979, Geology of the central Delaware Mountains of west Texas

Hobbs, Thomas M.C., 1979, Geology of the Square Peak Volcanic series, northern Quitman Mountains, Hudspeth County, Texas.

Legett, Bob D., 1979, Tertiary volcanics of the northwest Eagle Mountains, Hudspeth County, Texas.

Messenger, Harold M., III, 1979, Geology and fluorspar deposits of the southern Zuni Mountains fluorspar district, Valencia County, New Mexico.

Murry, David H., 1979, Economic mineral potential of the northern Quitman Mountains, Hudspeth County, Texas.

Ortiz, Terry S., 1979, Megacrysts and mafic and ultramafic inclusions of the southern west Potrillo Basalt Field, Dona Ana County, New Mexico.

Teal, Lewis W., 1979, Geology and petrology of the Chispa Mountain quadrangle and vicinity, Culberson and Jeff Davis Counties, Texas.

Verrillo, Dan E., 1979, Geology and petrography of the Tertiary volcanic rocks in the southwest Eagle Mountains, Hudspeth County, Texas.

1978
Austin, C. Bradford, 1978, A crustal structure study of the Mississippi Embayment.

Curtis, Jr., Robert E., 1978, A hydrogeochemical reconnaissance for uranium in Trans-Pecos, Texas.

Deen, Roy D., 1978, Geology and mineralization of the Precambrian rocks of the northern Franklin Mountains, El Paso County, Texas

Macer, Robert J., 1978, Fluid inclusion studies of the fluorite around the Organ Cauldron, Dona Ana County, New Mexico.

Martin, William R., IV, 1978, A seismic refraction study of the northeastern Basin and Range and its transition with the Eastern Snake River Plain.

Murray, Danny L., 1978, Barite deposits in the Seven Heart gap area, Culberson County, Texas.

Nielson, Thomas W., 1978, Stratigraphy and microfacies analysis of the Colina Limestone (Lower Permian, Hidalgo County, New Mexico

Tschirhart, Sid C., 1978, Velocity and logarithmic decrement in multiphase media.

Uphoff, Thomas L., 1978, Subsurface stratigraphy and structure of the Mesilla and Hueco bolsons, El Paso region, Texas and New Mexico

1977
Bersch, Michael G., 1977, Petrography and geology of the southern West Potrillo Basalt Field, Dona Ana County, New Mexico.

Hair, Gregory L., 1977, Stratigraphy and microfacies analysis of Panther Seep Formation (Virgilian, Franklin Mountains, Texas and New Mexico

Kasdarli, Mustapha E., 1977, Stratigraphy and microfacies analysis of the Rancheria Formation (Meramec) Vinton Canyon, Franklin Mountains, El Paso County, Texas.

Kopp, Richard A., 1977, Geothermal exploration of Presidio County, Texas.

Mraz, Joseph R., 1977, A gravity and subsurface investigation of the Presidio Bolson area, Texas.

Nodeland, Steven K., 1977, Cenozoic tectonics of Cretaceous rocks in the northeast Sierra de Juarez, Chihuahua, Mexico

Shaheen, Elias J., 1977, Crustal structure and tectonics of the Middle East.

Wise, Henry M., 1977, Geology and petrography of igneous intrusions of northern Hueco Mountains, El Paso and Hudspeth Counties, Texas.

1976
Allouani, Rabah Noday, 1976, Stratigraphy and microfacies analysis of the Berino Formation (Atokan-Des Moines), Vinton Canyon, El Paso County, Texas.

El Foul, Djamal, 1976, Stratigraphy and microfacies analysis of the Bishop Cap Formation (Des Moines) Vinton Canyon, Franklin Mountains, El Paso County.

Flih, Baghdad, 1976, The Osagian bioherms at the Bishop Cap Hills, Dona Ana County, New Mexico.

Gunn, Robert C., 1976, Economic geology of the tenth potash ore zone: Permian Salado Formation, Carlsbad District, New Mexico.

Hoenig, Margaret 1976, Stratigraphy of Upper Silurian and Lower Devonian, Permian Basin, west Texas (J.M. Hills)

Hoffer, Roberta L., 1976, Contact metamorphism of the Precambrian Castner Marble, Franklin Mountains, El Paso County, Texas.

Lattu, Andrew C., 1976, Missourian facies and lithofacies and depositional environments, Hockley County, Texas.

Oden, James R., 1976, Microfacies and correlation of the San Andres Formation in El Paso Products Company's Mine No. 1 Well, Ector County, Texas.

Setra, Abdelghani, 1976, Stratigraphy and microfacies analysis of the Mississippian Las Cruces Formation (Osage-Meramec) Vinton Canyon, El Paso County, Texas

Simpson, Ronald D., 1976, Systematic paleontology and paleoenvironmental analysis of the Upper Hueco Formation, Robledo and Dona Ana Mountains, Dona Ana County, New Mexico

Varnell, Ronnie J., 1976, Geology of the Hat Top Mountain quadrangle, Grant and Luna Counties, New Mexico.

Wagner III, Harry A., 1976, Stratigraphy and environmental interpretation of the Cuchillo, Benigno, Lagrima, and Finlay Formations, lower Cretaceous, Juarez, Mountains, Chihuahua, Mexico.

1975
Barrie, F.J., 1975, A gravimetric survey of south-central New Mexico and west Texas.

Glover, Thomas J., 1975, Geology and ore deposits of the northwestern Organ Mountains, Dona Ana County, New Mexico.

Huskinson, Jr., Edward J., 1975, Geology and fluorspar deposits of the Chise fluorspar district, Sierra County, New Mexico.

Larson, Marvin E., 1975, Geology and ore deposits of the Silver Monument and New Era Mines, Sierra County, New Mexico.

Petty, Jr., Andrew J., 1975, Biostratigraphy of the Grafford Formation, Missourian, Wise County, Texas

Wallace, Andy B., 1975, Mineral deposits of the Indio Mountains, Hudspeth County, Texas.

Willcox, Jr., Ralph, 1975, The geology of the Giardarray Region in the Sierra San de Lorenzo, Durango, Mexico.

Winston, Michael R., 1975, Geology of the Silver Monument area, Sierra County, New Mexico.

Wollschlager, Larry R., 1975, Hypostratotype (reference section) of Lower Permian (Wolfcamp) shallow shelf carbonates in Hueco Mountains, El Paso and Hudspeth Counties, Texas.

1974
Arnold, Randall I., 1974, Geology and Mineral Deposits of Little Whitewater Canyon, Holt Gulch, and Goddard Canyon Catron County, New Mexico.

Biggerstaff, Bradley P., 1974, Geology and ore deposits of Steeple Rock-Twin Peaks, area, Grant County, New Mexico.

Morris, Richard W., 1974, Geology and mineral deposit of the northern Cook's Range, Grant County, New Mexico.

Nelson, Martin A., 1974, Geology and fluorspar deposits of the southern Caballo Mountains, Sierra and Dona Ana Counties, New Mexico.

Thomson, Kenneth, 1974, Geology of Sugarloaf fault block south Franklin Mountains, El Paso County, Texas.

1973
Callahan, Chester, 1973, Aden Basalt depressions, Dona Ana County, New Mexico.

Campuzano, Jorge, 1973, The structure of the Cretaceous rocks in the southeastern part of the Sierra de Juarez, Chihuahua, Mexico

Page, Richard O., 1973, Stratigraphy and structure of the Quaternary Malpais maar volcano, Dona Ana County, New Mexico.

Swift, Douglas B., 1973) Lithofacies of the Cuchillo Formation southern Sierra de Juarez, Chihuahua, Mexico.

1972
Chacon, Roberto, 1972, Geology of the San Carlos Dome, Manuel Benavides, Chihuahua, Mexico.

Reid, Steven G., 1972, Geology and ore deposits of the Mina Palmosas district, Chihuahua, Mexico.

Wacker, Herbert J., 1972, The stratigraphy and structure of Cretaceous rocks in north-central Sierra de Juarez, Chihuahua, Mexico.

1971
Al-Shamlan, Ali Abdulla, 1971, Microfacies analysis of Lower Wolfcamp carbonates (Hueco Limestone), Tom Mays Park, El Paso, Texas.

Ellis, Roger D., 1971, Geology and ore deposits of the Winkler anticline, Hidalgo County, New Mexico.

Millican, Richard S., 1971, Geology and petrology of the Tertiary Riley-Cox Pluton, Dona Ana County, New Mexico.

Mims, Jr., Robert L., 1971, Microfacies analysis of the La Tuna Formation (Morrowan), Vinton Canyon, El Paso County, Texas
 

1970
Dye, James L., 1970, Geology of the Precambrian rocks in the Southern Franklin Mountains.

Garcia, Rafael A., 1970, Geology and petrography of andesitic intrusions in and near El Paso, Texas.

Kadhi, Abdullah, 1970, Structure of the Tom Mays Park area, Franklin Mountains, El Paso County, Texas

Kramer, Walter V., 1970, Geology of the Bishop Cap Hills, Dona Ana County, New Mexico.

Rosado, Roberto V., 1970, Devonian stratigraphy of south-central New Mexico and far west Texas

1969
Bolich, Leonard A., 1969, Petrography of the western portion of the Juriquipa Stock, Nacozari, Sonora.

Myers, John B., 1969, Permian patch reefs in the Finlay Mountains, west Texas.

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Shallow Subsurface Geophysics of the Pajarito Plateau, New Mexico

Veilleux, Annette M.
Department of Geological Sciences

The Pjarito Plateau is situated at the edge of the Rio Grande Rift and adjacent to the Colorado Plate northern New Mexico. It is a dissected terrain with thick sequences of volcanic deposits and severe topography that has hampered detailed geophysical studies of the hydrogeologic framework. Deposits of the Bandelier Tuff, lavas of the Tschicoma Formation, volcanogenic alluvial fan deposits of the Puye Formation, Cerros del Rio basalts and ancestral deposits of the Santa Fe Group are found on the Pajarito Plateau. The north-south trending active Pajarito fault zone transitionally divides the Valles Caldera of the Jemez Mountains Range and the Pajarito Plateau.

Objectives of this study were to: 1) test an innovative gravity modeling approach that directly incorporates digital terrain data for an area of rugged topography, 2) develop three-dimensional model of the subsurface based on forward gravity modeling, 3) determine the subsurface structure/pre-Bandelier topography and influence on hydrogeologic framework, 4) delineate the plateau to caldera transition, and 5) understand the influence of subsurface structure on earthquake hazards.

Previous studies have focused on forward modeling of the gravity field and only considered two-dimensional models of the subsurface which incorporated average layer densities that did not account for the distribution of densities and thickness found in the Bandelier Tuff. By contrast, this study applied an innovative, geologically constrained method to develop a 3-D model of the subsurface. The geologic constraints were based on digitization of geologic maps and integrated with digital elevation data, borehole data and limited seismic reflection data. The resulting residual anomaly map resolves both boundaries of the Velarde Graben in considerable detail and suggest the presence of an accommodation zone at its southern end.

The Biostratigraphy of the Middle Pennsylvanian (Desmoinesian) Fusulinidae of Bug Scuffle Canyon, Otero County, New Mexico

Wilrich, Kerry
Department of Geological Sciences

The Sacramento Mountains are a tilted fault block that borders the Basin and Range's eastern margin. Studies in and of the Sacramentos began at about the turn of the century with G. H. Girty in 1908 and continue to present day. Cursory studies by Darton in 1922 and 1928 led to extensive studies conducted by Thompson in 1942, Kottlowski in 1960, Pray in 1961, and others. Studies of the escarpment and the northernmost canyons have been the focus of most Sacramento Mountains investigations. This study focuses primarily on Bug Scuffle Canyon but is extended into Negro Ed Canyon for correlation purposes. Both canyons are located in the southern portion of the Sacramento Mountains in southeastern New Mexico.

The purpose of this investigation is to establish the middle Pennsylvanian (Desmoinesian) boundaries within the Gobbler formation. Establishing these boundaries is of economic importance to petroleum companies, because understanding these boundaries can aid in locating areas of petroleum generation within southern New Mexico. Information derived from this study can also be used to tie existing information on the northern Sacramento Mountains to Otero Mesa and the Hueco Mountains.

This investigation was conducted using fusulinids as biostratigraphic markers to indicate the upper and lower Desmoinesian boundaries. These boundaries were based on the expected location of the Beedeina and Eowaeringella biozones. Beedeinas were located from parasequence one through parasequence three. Wedekindelfina, another excellent lower Desmoinesian fusulinid guide fossil, was found in parasequences one and three. However, the Eowaeringella biozone was not located. I conclude that this biozone was denuded in this area. The cause of this denudation is not known, but it is consistent with other regional studies and is further substantiated by expressions of subaerial exposure and repeated regressive and transgressive sequences. Because paleochannels were found in other parts of Bug Scuffle Canyon, it is believed that the denudation of this area is likely a combination of erosion and nondeposition.

Heavy Metals in Soil from the Mesa Quadrangle, Arizona, using NURE Data

Patricia Borrego
Department of Geological Sciences

Soils from the Mesa Quadrangle, Arizona, were sampled by the National Uranium Resource Evaluation (NURE) program, which is one of many databases that have been collected in the area. These types of databases may prove to provide inexpensive and useful data sets that may be adopted for statistical analyses in order to characterize the environmental quality of a specific area.

A number of metals, especially those that are of particular concern because of their potentiality to provide indications of contamination and pollution, were chosen for this study. These metals are arsenic, beryllium, copper, chromium, cobalt, nickel, lead, molybdenum selenium, tin, thorium, uranium, and zinc.

Descriptive statistics (e.g., central tendency, measures of dispersion), graphs, correlation, and mapping of the anomalous concentrations were employed to characterize the Mesa Quadrangle. Data were examined for sample size and below detection limit (BDL) values, and were graphed for asymmetry. The graphs were plotted in their original scale values to determine which data sets would benefit from a transformation to a different scale. This provides an analytical solution for which data sets need to be analyzed in their original scale. Outliers were detected by the utilization of the Box Plot Method. Since environmental data have a log normal distribution, the data sets that would benefit from a lognormal transformation were transformed using the natural logarithm.

Once the descriptive statistics were compiled, the data were transformed into the original scale to compare their values (concentrations) with other data sets accumulated from other studies and, therefore, provided a better understanding of the relationships. The values obtained from this analysis when compared to other values yielded similar anomalies. Many of the anomalous concentrations were plotted in known areas of high. metal content.

Integrated Gravity and Seismic Reflection/Refraction Study of a Potential Geothermal Source, McGregor Range, New Mexico

O'Donnell Jr., Terry M.
Department of Geological Sciences

The McGregor geothermal system lies on the eastern edge of the Hueco Bolson of southern New Mexico and west Texas within the Rio Grande rift system. Drilling in the 1950s and 1970s revealed warm waters in the area then known as the Hueco Tanks geothermal system. Further drilling and analysis found the warmest waters and the maximum heat flow of 700 mW/m², on the McGregor Range of southern New Mexico. In 1995, gravity and seismic data were collected in order to better understand the geohydrologic setting of the geothermal system. The gravity study included 148 gravity measurements that reveal a gravity high associated with the heat flow high. During the seismic reflection and refraction survey, 14.8 km of data were acquired along three profiles crossing the heat flow and gravity highs. Analysis of the seismic data shows that a bedrock uplift coincides with the heat flow high. The occurrence of overturned beds on the downthrown side of a reverse fault in one of the wells drilled into the thermal anomaly suggests that the uplift may have formed during the Laramide orogeny. A low velocity zone in the bedrock uplift coincides with a resistivity low and with water-filled caves encountered during drilling. Taken together, the data suggest that the bedrock uplift represents a zone of high permeability into which warm water is upwelling within a forced convection system. Thermal waters as high as 193^oF encountered during drilling have the potential for heating, geothermal desalinization, and small scale energy production for the U.S. Army's McGregor Range Base Camp which is located nearby.
 

An Integrated Lithospheric Study of the Rocky Mountain Region along the Deep Probe Seismic Profile

Snelson, Catherine

Department of Geological Sciences

The Rocky Mountain region has undergone a complex history which includes Proterozoic accretion to form the North American craton, late Paleozoic deformation, Cretaceous to early Tertiary shortening and Oligocene to Recent extension. Understanding the effects of these events on lithospheric structure was the primary goal of the Deep Probe seismic experiment. This experiment was a lithospheric scale study of the Rocky Mountain region which attempted to image crust and upper mantle structures up to 500 km depth to provide insights on the effect of various tectonic events on today's continental structure. To accomplish this goal, instruments were deployed along a 2400 km long transect from New Mexico to Canada to record explosions 10 times powerful than those employed in conventional crustal studies. The Deep Probe results provide new constraints on the location and geometry of the Archean/ Proterozoic boundary near the Colorado/Wyoming border, as well as new information on crustal thickness and uppermost mantle velocities along the profile. Geophysical modeling of the profile used well log and geologic data to constrain the composition and structure of the uppermost crust and seismic refraction and reflection, gravity, and receiver function studies to constrain properties of the lower crust and upper mantle structure. The final model shows that seismic velocities along the Deep Probe profile range from 3.5 km/s in the basins to over 8.2 km/s in the upper mantle. At the southern end of the profile, the model indicates a crustal thickness of about 35 km beneath the Basin and Range. The crust gradually thickens to about 40 to 45 km going north along the profile into the Colorado Plateau. An area of 50 km thick crust under northwestern Colorado may reflect Proterozoic tectonism related to the suture zone between Archean and Proterozoic terranes. Northwestward thinning of crust to about 35 km under Wyoming is interpreted as evidence for a relict (2.0 Ga) passive continental margin. The crust in the Archean Wyoming province thickens to over 50 km to the north and then thins again under southern Canada. This thickening is due to a lowermost crustal layer that is about 20 km thick and is confined to the Archean Wyoming province. This lower crustal layer has velocities ranging from 7.05 to 7.3 k/ms which corresponds to a mafic composition. Thus, this layer is interpreted as mafic material that was probably underplated during the Archean. The presence of a high-velocity, deep mantle layer at about 120 km is approximately coincident with the high-velocity layer. This deep mantle layer could have filled in the space created when the high-velocity layer was formed. The uppermost mantle of the Archean Wyoming province has lower velocities (~8.1 km/s) on average than other Archean cratons, which is consistent with it being located in and adjacent to the North American Cordillera which has undergone significant recent tectonism.
 

The Depositional History of the Mundy Breccia and the Lowermost Lanoria Formation

Ballard, Jenny
Department of Geological Sciences

The Mundy Breccia is a Precambrian unit composed primarily of monomict metabasalt fragments in a metamorphic matrix. It outcrops in Fusselman and Hitt Canyons located in the Franklin Mountains, El Paso County, Texas. The Mundy Breccia forms an irregular, contorted contact with the underlying 1.26 Ga Castner Marble; it has a uniform, erosive contact with the overlying quartzite cliffs of the Lanoria Formation. These formations have been intruded by the 1.15 Ga Red Bluff Granite Complex.

This study focused on exposures in Fusselman Canyon. The study has divided the Mundy Breccia into 4 informal members listed in stratigraphic order from the bottom: the breccia member, massive member, spheroidal weathered member, and upper contact bed. The breccia member is most voluminous, and it is exposed in all localities. The other three members only have continuous exposure over a 200-300 m section. The massive member is tortoise-shell jointed and ranges from 9 to 18 m in thickness. The spheroidal member is 7.5 to 12 m thick and contains breccia and massive pods that were rounded along fragment edges and fractures, respectively. The upper contact bed is ½ m thick and is composed of fine-grained clastics and remnant-deformed ash shards. A thin, discontinuous sandy mudstone outcrops directly below.

Stratigraphic sections were measured with detailed fragment data collected at 13 breccia member outcrops. Fragment data include: fragment length and width, orientation, roundness, and shape. Spreadsheet data summaries provided a comparison of average and median fragment size, roundness, orientation, width-to-length ratio, and percentage fragment area. A thorough analysis confirmed the absence of sorting, grading, or stratigraphy within the breccia member.

Classification of the Mundy Breccia is based on the breccia member. Its unsorted, unbedded nature is common in epiclastic or autoclastic deposits; however, the angular and amoeboid-shaped fragments would preclude an epiclastic history. The curviplanar, amoeboid, and pillow fragments, along with the extreme variations in fragment sizes concludes that the Mundy Breccia is a pillow fragment breccia of autoclastic origin.

Field relationships show that the Mundy Breccia basalt originated from an aphanitic basic sill located 13 m below the lower contact. This sill is fed from at least one diabase dike that diagonally cuts the Castner Marble and connects to a lower diabase sill.

The Mundy Breccia thins in the northern localities as a result of a predepositional topographic high created by the emplacement of the upper basic sill. The higher topography in the north resulted in thinner basalt deposits with gradient induced flow to the south or southwest. In the southern localities where the sill pinches out, flow was largely radial with the breccia exteriors insulating the massive interiors of flows.

Several field observations indicate a close temporal association of the Mundy Breccia and Castner Marble. Most convincing is a skam zone and garnet layer located 20 m above the lower contact which indicate continued carbonate deposition during magmatic lulls. Thus, the Mundy Breccia was syndepositional with the Castner Marble.
 

A Crustal Structure Study of the Owens Valley-Death Valley Region, Eastern California

Duran, Alejandro
Department of Geological Sciences

This study is an integrated seismic refraction, gravity, and geologic investigation of the upper crustal structure of the southern Great Basin portion of the Basin and Range province and its boundary with the southern Sierra Nevada. The refraction data employed are a product of the 1993 Southern Sierra Nevada Continental Dynamics Project (SSCD) which consisted to two crossing refraction profiles in the Sierra Nevada region: 1) a 390 km long east-west line perpendicular to the Sierra Nevada, and 2) a 330 km long north-south line just east of the axis of the Sierra Nevada. The line analyzed in this study is the eastern portion of the east-west line, which extends across Owens Valley-Death Valley region. This region consists of a highly extended terrane which is characterized by fault block mountains, deep sediment-filled basins, and some strike-slip faults. The SSCD data show that the crustal thickness is uniform at about 30 km, which is surprising considering the large amount of regional extension and its local variation.

The objective of this study is to provide improved, geologically- motivated and constrained models of upper crustal structure of the Death Valley region. A variety of processing and modeling techniques were applied to the seismic and gravity data. However, seismic ray tracing was the primary technique employed. The resulting seismic models are consistent with both geologic constraints and Bouguer gravity anomalies in the area. These models indicate a thin sedimentary fill of less than 1 km in the Panamint Valley, while in the other valleys the fill is 2 to 3 km thick. Owens Valley was found to contain the most fill, about 3 km.

Secondary seismic arrivals indicate the existence of reflectors at depths of 10 to 15 km that indicate thinning of the upper crust. These reflectors suggest that the upper crust thins by as much as 50 percent over the region, meaning that extension in the upper crust had to be large. Since the Moho is nearly flat, the lower crust had to expand in some fashion to offset this thinning. This expansion could be due to flow or magmatism. However, volcanic activity in the region is relatively minor.
 

Depositional History and Sedimentary Petrology of the Huetamo Sequence, Southwestern Mexico

Guerrero-Suastegui, Martin
Department of Geological Sciences

The study area is located in southwestern Mexico near Huetamo area within the states of Michoacan and Guerrero. The western margin of Mexico consists of Late Jurassic to Early Cretaceous arc-related sequences known as the Guerrero Terrane. The Guerrero Terrane is divided in southwestern Mexico into three distinctive subterranes characterized by their own stratigraphic record, structural evolution, and geochermical features: the Teloloapan subterrane, the Arcelia-Palmar Chico subterrane, and the Zihuatanejo-Huetamo subterrane. The study area is located in the Zihuatanejo-Huetamo subterrane. The Early Cretaceous formations of the Huetamo sequence are coarse to fine clastic rocks, volcaniclastic, and scarce volcanic rocks (Angao and San Lucas formations), and limestone of the Comburindio Formation. The Angao and Lower San Lucas formation contain abundant conglomerates. These conglomerates contain volcanic, sedimentary, and metamorphic clasts. Conglomerate petrography suggests multiple sources for these clasts. These sources include basement rocks, Upper Paleozoic shallow marine deposits, continental, and oceanic volcanic units. Sandstones of the same units show different categories of sandstone and volcaniclastic rocks. Lithofacies analysis of the clastic and limestone rocks of the Angao, San Lucas, and Comburindio formations suggests that the Huetamo sequence is an apron deposit close to a volcanic arc that includes coastal and platform environments.
 

Stratigraphy and Structure of the Sierra Samalayuca, Northern Chihuahua, Mexico

Molina, Castulo
Department of Geological Sciences

The present study is concentrated on the Sierra Samalayuca area of northern Chihuahua. Samalayuca and Navarrete formations, as well as Tertiary igneous rocks and unconsolidated Quaternary deposits, outcrop in the study area.

Sierra Samalayuca is a linear northwest-trending ridge composed entirely of the Samalayuca Formation. This formation is constituted by a sedimentary sequence of sandstones, conglomerates, and shales which display low rank metamorphic effects. The surface thickness of the formation is 706 m; drilling data, however, implies that the formation could be as much as 1500 m in thickness. The most conspicuous depositional facies developed within the formation is that typical of turbidites. This sequence was deposited as a submarine fan, either in a rift-type basin or a continental border.

The depositional age of this formation is uncertain, as no characteristic fossils have been recovered. Attempts to determine the age by radiometric determinations have been unsuccessful. Geological criteria suggest that the youngest age for these sediments is Cambrian.

Petrographic analysis of the sequence indicates that these rocks were derived primarily from a metamorphic sedimentary source (quartzites, sandstone, and conglomerates) and, to a lesser extent, from basic igneous rocks. Determinations by current indicators suggest a north-south transport direction, from a source area located to the north.

Northeast of the main ridge there are a series of low relief hills of Late Jurassic-Early Cretaceous age which have been correlated with the Navarrete Formation in this work. These hills are constituted by limestones, sandstones, conglomerates, and shales. It has been determined that majority of this unit is overturned, based on sedimentary structures.

The most evident structures in the study area are related to the Laramide orogeny. The main ridge consists of an asymmetrical anticline striking N35^oW with a vergence to the northeast. This structure is in thrust contact over the Navarrete Formation hills located to the northeast. The deformation model proposed for the area is a combination of thrust-uplift and fold-thrust. The fold-thrust model, proposed for the southeast side of the area, explains the overturned blocks of the Navarrete Formation. These models are characteristic of thin-skin or thrust-and-fold deformational zones

Tertiary igneous rocks crop out in three different localities in the sierra. These rocks are basic-to-intermediate in composition and are probably associated with the early igneous phases of the Rio Grande Rift.
 

A Geophysical Study of the Salt and Valentine Basins, West Texas

Palsole, Sunay
Department of Geological Sciences

Trans-Pecos Texas has experienced complex tectonic history which has culminated in the development of the Rio Grande rift which is still active today. The basins in Trans Pecos Texas are one key to understanding the rift and are also important sources of groundwater. The Salt and Valentine basins are two of the important basins and have been the topic of few scientific studies. The Salt Basin trends about N10^oW along the Culberson-Hudspeth county line in Trans-Pecos Texas into southern New Mexico. The Valentine Basin occupies a major part of Jeff Davis county and a small portion of the northern part of Presidio county. Gravity and magnetic data have been used for a detailed analysis of these basins and to see the structural relations between them.

Gravity models constrained by well data indicate a maximum Neogene fill of about 650 m in the Salt Basin. The thin Neogene fill coupled with numerous well defined Quaternary fault scarps suggest that it is an embryonic basin formed during late phase rifting. Deep crustal structure indicates that the Salt Basin represents a transition zone between the thinner crust associated with the Rio Grande Rift to the west and the thicker crust associated with the Great Plains to the east, and indicates that the Salt Basin could define the easternmost limit of the Rio Grande rift.

The Valentine Basin is a graben with a Neogene fill of 1.9 km and demonstrates a evolution. The structural grain of the Valentine Basin was probably first formed by effects of Laramide compression, followed by widespread mid Cenozoic magmatism which aided in weakening the crust and aiding extensional processes. This grain was subsequently overprinted by the effects of Rio Grande rifting to create the present configuration of the basin. The Valentine Basin also exhibits a large amount of symmetry from east to west. This could mean that both sides of the basin are significant from the viewpoint of seismic activity and hazard analysis.
 

Heterogeneity and Water Quality in the Rio Grande Alluvium, Downtown El Paso, Texas

Perez-Santiago, Vilma
Department of Geological Sciences

UThe El Paso/Ciudad Juarez area is a border city which shares a growing population and resources between the sovereign states of the United States of America and the Republic of Mexico. One critical resource is water which is used for irrigation, domestic, and industrial purposes. The desert climatic conditions that prevail in the area dictate the importance and require careful use of the water which is obtained from four major sources: the Hueco and Mesilla bolsons, the Rio Grande Alluvium aquifer and the surface waters of the Rio Grande.

In the Rio Grande Alluvium aquifer the variable thicknesses and lithologies demonstrate characteristics of heterogeneity. This heterogeneity and groundwater flow may influence the behavior and movement of pollutants. The resultant deterioration in water quality and its potential for threatening the quality of the waters in the El Paso aquifer, the source of a large portion of the drinking water of the two cities, make it a critical problem.

The present study describes the physical properties of the Rio Grande Alluvium aquifer to test its heterogeneity and the effect of flow and movement of pollutants in its water. Stratigraphic, hydrologic and water quality data were obtained from Leaking Storage Tank (LST: CERCLA/RCRA) files at Texas Natural Resources Conservation Commission (TMRCC). Data on lithology logs description allowed, to some extent, the establishment of a stratigraphic sequence in the Rio Grande Alluvium. The results present changes and variations in facies: interlayering of predominant fine sediments with sand and gravel characterize the alluvial fans; layers of sand and gravel that extend lateral and become thicker vertically and intercalate with fine sediments characterize the floodplain.

Groundwater elevation and flow direction reflected changes in time. The factors influencing these changes are the river, the lithology beneath the sites, and the anthropogenic activities. In areas 1 and 2 the river is a gaining stream; in areas 3 and 4 it is a loosing stream. The lithology and the anthropogenic activities are the major factors producing changes in water elevation and variation in flow direction. Low permeability layers of fine sediments may prevent groundwater movement. Variations in groundwater flow have been observed in several sites to suggest a direction towards the city wells.

Water quality was interpreted in terms of TDS content (Total Dissolved Solids) and organics (TPH and BTEX). TDS content ranges from 1,000 to 4,000 ppm with the highest concentrations located near the irrigation fields. The common organic pollutants, TPH and BTEX, and some metals were detected in several sites. The highest concentrations of these pollutants were located in areas of intense anthropogenic activity where some spills reached the groundwater.

The Geology and Geochemistry of the El Sauzal Gold Prospect, Southwest, Chihuahua, Mexico

Sellepack, Steven M.
Department of Geological Sciences

Department of Geological SciencesThe El Sauzal gold prospect is located in the Sierra Madre physiographic province of Mexico, a region characterized by plateaus of Upper Volcanic Series rhyolites with deep, steep-sided, river cut barrancas, which in places expose Lower Volcanic Series andesites and plutons. El Sauzal is located 200 km southwest of Chihuahua City, and about 10 km west of the historic mining district of Batopilas. El Sauzal is located on the Rio Urique approximately 8 km north-northeast of the Rio Urique-Rio San Ignacio continence. The El Sauzal gold prospect was discovered in 1995 by Alain Charest while doing regional exploration for Minas de la Alta Pimeria SA de CV (a subsidiary of Francisco Gold Corporation). Multi-phase surface sampling, induced potential and resistivity geophysical surveys, and exploratory drilling phases of the El Sauzal prospect indicates a potential reserve of three and a half million ounces of gold.

The geologic structure in the area is complex and appears to contain at least three major fault systems, the youngest of which is extensional faulting as suggested by widespread listric fault blocks. The extensional faulting may have resulted in the formation of a large extensional shear basin to the south of el Sauzal called the Cuenca del Oro. Due to inconsistences of Lower Volcanic Series units, the exact nature of the older faulting is difficult to discern.

The volcanic stratigraphy is similar to that described by Bagby (1979). The country rock surrounding El Sauzal is composed of Lower Volcanic Series andesitic tuffs, agglomerates, and sediments which is overlain by a series of dacitic to andesitic tuffs, flows, and agglomerates and capped by the Upper Volcanic Series. Within the deposit, rock which crops out has generally been heavily altered and/or silicified, which makes identification of a protolith to be problematic.

Mineralization is concentrated at the intersection of northwest and northeast trending faults, and associated with argillic, hematite zones. The major gangue minerals are barite, pyrite, quartz, enargite, hematite, kaolinite/dickite and alunite/natroalunite.

Analytic work includes petrographic studies, SEM, EDS, and WDS analyses, x-ray diffraction studies, geochemical analyses, sulfur isotope analyses, fluid inclusion studies, and two age dates. The SEM, EDS, and WDS analyses, petrographic studies, and x-ray diffraction analyses helped to constrain mineralogy, zonation, and the paragenetic sequence. Statistical analyses of the geochemical sample data indicates gold to have a significant positive correlation with Ag, As, Co, Bi, and Sb with a significant negative correlation with Zn. Sulfur isotope analyses show a disequilibrium condition existed between co-existing alunite and pyrite. Fluid inclusion analyses from the Afloramiento de Jorge yield an average temperature of 300^oC. Additional fluid inclusion analyses from possible fringe mineralization yield an average temperature of 200^oC. Two ⁴⁰Ar/³⁹Ar age dates were determined for alunite samples which indicated an age for the mineralization of approximately 30 Ms.

The El Sauzal gold prospect is associated with an interesting though enigmatic hydrothermal system. It is an acid sulfate (high sulfidation) system possibly in association with a regional extensional event.

Seismotectonics of the Xianshuihe Fault System, Southwestern China

van Dusen, Shelley
Department of Geological Sciences

The Xianshuihe fault zone of the Sichuan Province, southwestern China, is one of the most active strike-slip faults in the world. It is one of the most extensively mapped faults in this region of China. However, it has not been studied as close geophysically. The fault is7unique because some fault segments both creep and produce large earthquakes, unlike the San Andreas fault where a segment either creeps or is locked and only fails in large "earthquakes. In order to study the long term behavior of the Xianshuihe fault system, with emphasis on the relation of the fault to the regional seismicity, I have conducted the following research:

1.Relocation of magnitude 4.5 to 6.5 earthquakes occurring within the region between 1923 and 1992 in order to determine which faults are currently active.

2.Determination of focal mechanisms from first motion data for events occurring between 1923 and 1992 in order to determine the present day stress of the region.

3.Body waveform modeling of four M>6.5 earthquakes that occurred within the region between 1923 and 1955 to determine the focal depths, causative faults and fault rupture processes of these large earthquakes.

This study helps to define structural features that control rupture segmentation and creep along the fault itself. Off-fault seismicity between large events along the Xianshuihe fault was studied to determine how the regional stress field readjusts between large earthquakes. The location and source mechanisms were also used to better understand the tectonic deformation that the region is undergoing in response to the collision of India with Asia.

Results from this study show that regional seismicity (M 6.5) is located mostly on the Yjanshuihe fault and local seismicity (4.5 M 6.5) is located off the fault. First motions in the area indicate a NW compressional trend with a SE extensional trend. Waveforms from the large (M 6.5) earthquakes show left-lateral strike-slip motion with shallow crustal deformation (<51 km) due to the tectonic collision of India with Eurasia.
 

Evaluation of Seismic Data for NASA Johnson Space Center, White Sands Test Facility (NASA-WSTF)

Maciejewski, Tim
Department of Geological Sciences

During the 1960s and 1970s, hazardous materials were released onto the ground surface at the National Aeronautics and Space Administration-White Sands Test Facility (NASA-WSTF) northeast of Las Cruces, New Mexico. Currently, NASA is seeking to identify and classify the nature and extent of the geologic units that influence migration of the hazardous constituents released at this facility. This thesis is part of this effort, and focuses on mapping the top of bedrock and any features contained within the bedrock and overlying alluvium which may influence groundwater flow in the vicinity of the facility.

Approximately 42 mi (67.6 km) of shallow seismic reflection data, well log information from over 80 wells, and a local gravity survey, were used to produce a new top of bedrock map. Several features on this map may affect groundwater flow. Remotely sensed data were used to examine the bedrock lithology and drainage patterns. There are three major faults crossing NNW across the facility, two of which combine to form the eastern boundary fault for the Jornada basin. There are two types of bedrock encountered through drilling on the NASA-WSTF, Tertiary andesite to the west and Paleozoic marine deposits to the east. Gravity modeling shows that the eastern basin boundary fault juxtaposes Paleozoic marine deposits against Tertiary volcanics. This fault has around 7900 ft (2400 m) of displacement. This same model also constrained the Western Boundary Fault Zone-1 to around 1700 ft (517 m) of down to the west displacement, producing a maximum alluvial thickness in the Jornada basin of 2600 ft (790 m).

Several minor faults and natural paleo-topographic features combine to produce two paleochannels trending westward away from the San Andres Mountains. Groundwater may be funnelled into these depressions by natural bedrock topography and faults, and channeled off to the west along with the contaminants.
 

A Study of the Effects of the Addition of Tellurium into the Acanthite- Naummanite (Ag₂S-Ag₂Se) System

Martinez, Ruben
Department of Geological Sciences

The effects of the addition of tellurium, in controlled quantities, into the Ag₂S-Ag₂Se solid solution system was studied using optical, electron microprobe and x-ray diffraction analysis. More than 80 samples were synthesized at high temperature using the evacuated silica tube technique. The Ag₂S-Ag₂Se (acanthite-naummanite ) system is characterized by two solid solution series at room temperature. One ranges from pure Ag₂S (acanthite) to about Ag₂S_0.4Se_0.6 and has a monoclinic structure; the other ranges from pure Ag₂Se (naummanite) to about Ag₂S_0.3Se_0.7 and has an orthorhombic structure. A compositional gap occurs between the two solid solutions. Perhaps four phases were found within the compositional range explored for this thesis project: a monoclinic, an orthorhombic, a crystalline phase, possibly cubic, and a hump in the XRD background which may be a poorly crystalline or amorphous phase. The analysis of the samples showed that the addition of tellurium into the system, in quantities from 0.025 to 0.125 mol fraction, into the Ag₂S (acanthite) side of the acanthite-naummanite solid solution field, from 0.025 to 0.225 mol fraction into the Ag₂Se (naummanite) side (including the orthorhombic phase field), and from 0.025 to 0.1 and 0.125 mol fraction into the field of the monoclinic phase, systematically increases the interplanar spacings of the solid phases, indicating anionic substitution of tellurium for selenium and sulfur at their specific structural positions. It also was observed that for a fixed tellurium concentration, the lattice spacings also increase as selenium concentration increases. Based on the naturally occurring mineral assemblages and in view of the experimental data of this project, it may be possible to find additional naturally occurring Te-substituted minerals within the acanthite-hessite-naummanite system.
 

Geology, Mineralogy, and Genesis of Supergene Enrichment at the Cananea Porphyry Copper Deposit, Sonora, Mexico

Virtue, Terence
Department of Geological Sciences

The Cananea porphyry copper deposit, in Northern Sonora is the largest in Mexico with an ore reserve of over 2.2 billion metric tons of 0.62% Cu at a cutoff grade of 0.40% Cu.

The purpose of this study is to explain the genesis of the 150 to 300 m thick supergene chalcocite blanket at Cananea and to describe its mineralogy. This is the first detailed study of supergene copper mineralization at Cananea.

The Cananea porphyry copper deposit consists of disseminated and stockwork mineralization, breccia pipes, and skarns associated with a group of northeast-trending Laramide porphyry intrusions. These porphyries intrude Paleozoic sedimentary strata and Mesozoic volcanic units. Lithologies in the district include Precambrian Cananea Granite, Paleozoic sediments, Mesozoic volcanic andesite tuffs and rhyolites, Laramide porphyry intrusives and Quaternary alluvium. Structural controls in the district are associated with Basin and Range normal faulting and doming. Volcanic units, supergene enrichment, and breccia pipes are tilted 15^oE because of faulting and possibly doming.

Widespread propylitic alteration surrounds the quartz sericite and silica altered Cananea, Maria, Milpillas, and Mariquita ore bodies in the district. Within the Cananea orebody there is widespread pervasive phyllic alteration with some overprinting by argillic facies. Biotite-chlorite alteration assemblages occur below phyllic alteration in Mesozoic volcanic host rocks, but potassic alteration is limited, the main potassic core being below present mining levels. Potassic alteration is associated with the underlying protore.

Primary chalcopyrite is concentrated in breccia pipes, contact breccia zones, disseminations in porphyries and skarns. Also, abundant pyrite is found in breccia pipes and contact breccia zones and together with chalcopyrite providing the acid for strong enrichment that occurs in these structures.

The northeast-trending supergene enrichment blanket at Cananea formed as doming, uplift, and erosion exposed the hypogene mineralization to oxidation and enrichment. The supergene enrichment blanket has an areal extent of approximately 3 x 1.5 km and a thickness of at least 150 m. Hematite-goethite -jarosite oxide capping lies above enrichment between 2200 and 1800 m elevation. Relief limonite in the leached capping above the supergene chalcocite enrichment blanket suggests the presence of earlier enrichment. Supergene chalcocite enrichment occurs between elevations 1800 and 1650 m elevation. Mixed chalcocite enrichment and primary chalcopyrite mineralization is found between 1650 m and 1400 m elevation. mostly Primary chalcopyrite mineralization occurs below 1400 m elevation. Enrichment and oxidation often penetrates into fault and breccia zones as deep as 500 meters below the present surface. The thickest enrichment occurs in and around breccia pipes and in fractured contact zones near porphyries. In some contact zones enrichment is as thick as 300 m or more. Supergene enrichment is very weak in the Democrata skarn area, where only thin covellite replacement in fractured chalcopyrite occurs. However, some brochantite and malachite are found above primary mineralization in the Democrata area.

Enrichment at Cananea is related to water table fluctuation and primary pyrite and chalcopyrite distribution. Enrichment occurs as sulfides above the water table were oxidized by H₂SO₄ (sulfuric acid) bearing meteoric water. The pyrite to chalcopyrite ratio in the present primary ore is 4:1 or more and this promotes a relatively high acid producing system as a whole. As a result, liberated copper is transported below the water table where it deposits as chalcocite, digenite, and covellite under more reducing conditions.

The first phase of enrichment occurred as unroofing of late Cretaceous and early Tertiary volcanic and sedimentary units occurred. During this phase covellite replaced chalcopyrite in the primary chalcopyrite zone. Also, digenite and chalcocite began to replace earlier covellite and more chalcopyrite. After most chalcopyrite was replaced, pyrite was attacked and replaced by chalcocite, digenite, and covellite.

Late Tertiary Basin and Range faulting and uplift brought early enrichment at Cananea above the water table beginning the second phase of enrichment. As a result, first phase enrichment was subsequently oxidized to hematite-goethite jarosite bearing relief limonite. The present day enrichment blanket formed below a declining water table during this period.

The gradual drop in the water table that occurred during the Basin and Range period, 20 to 5 Ma ago is probably the cause of present enrichment formation at Cananea and at other porphyry copper deposits in the southwestern United States. K-Ar dating of alunite and jarosite mineralization from several Arizona porphyry copper deposits suggest a date between 9-5 Ma, the end of the Basin and Range period. It is not known exactly how long it took enrichment to form but a mathematical study of enrichment formation rates suggests that 1 million years are required for a typical 300 m thick supergene enrichment blanket to form. Significantly, the climatic and mineralogical conditions in this model are similar to Northern Sonora, and therefore are probably applicable to Cananea.

According to Cananea company data, there is 1.0 billion tons of 0.62% copper ore reserves contained in a 150 to 300 m thick supergene enrichment blanket. In addition to the supergene enrichment blanket the supergene enrichment in the mixed zone must also be considered. Approximately half of the 1.2 billion tons in the mixed zone is supergene digenite and covellite enrichment. When the 600 million tons of enrichment in the mixed zone is added to the 1.0 billion tons in the enrichment blanket, the result is 1.6 billion tons of enriched ore. Assuming the upper part of the protore had a grade of 0.20% Cu comparing to the 0.62%Cu supergene enrichment grade, a ratio of 3.1 results. Consequently, some 4.96 billion metric tons of protore have been oxidized and mobilized to form the presently identified supergene ore. If the assumed grade of the original primary mineralization is approximately correct, then supergene enrichment at Cananea enhanced the average grade by a factor of 3.1, so that the enriched ore is at a similar grade to the underlying deep primary sulfide ore.
 

The Development of a Multi-element Toxic Chemical Environmental Factor for a Southwestern New Mexico Target Region

Afseth, Daniel
Department of Geological Sciences

A method to assess the overall environmental status of a region has been developed and tested in this study utilizing regional geochemical mapping and elementary statistics. A geoaccumulation index called a "multi-element toxic chemical environmental factor," or F, was developed for a southwestern New Mexico target region which was comprised of the Las Cruces 1^o x 2^o quadrangle and the New Mexico portion of the Clifton, Douglas, and Silver City 1^o x 2^o quadrangles. The region was selected because of the large quantity of available data as well as density of high chemical element concentrations. F represents the sum of the ratios of chemical element concentrations to background concentrations for the following EPA (Environmental Protection Agency) toxic chemical elements: barium (Ba); beryllium (Be); cobalt (Co); chromium (Cr); copper (Cu); lead (Pb); manganese (Mn); nickel (Ni); phosphorus (P); thorium (Th); vanadium (V); and zinc (Zn). F was calculated for four different datasets: composite target region NURE, Silver City NURE, CUSMAP rock, and CUSMAP stream sediment. Each is unique in that background values are calculated using concentrations from each respective dataset. The composite target region NURE dataset was comprised of 597 sample sites in the Clifton quadrangle, 168 in Douglas, 1,390 in Las Cruces, and 566 in Silver City. All CUSMAP sample sites were in the Silver City quadrangle and consisted of 886 rock and 1,488 stream sediment sample sites. After calculating F, specific anomalies were selected. An anomaly was defined as the sum of the target region mean (m) and two standard deviations (2s) or (m+2s). The composite target region quadrangle contained 88 anomalous F values with 39 in the Silver City quadrangle, 33 in Clifton, 15 in Las Cruces, and 1 in Douglas. The CUSMAP rock and stream sediment datasets each contained 34 anomalous F values. F values were calculated for the Silver City NURE dataset using background values for the Silver City quadrangle to compare CUSMAP and NURE datasets. Based on the background values, the Silver City NURE dataset contained 15 anomalous F values; signficantly less than the 39 previously stated using composite target region background values. The discrepancy established the effect that background values have on F values. The final step was to attempt to explain the presence of anomalous F values. Literature and maps were used to identify locations of mineralization within the composite target region and contaminated areas-associated with anthropogenic reasons such as mining/milling/smelting activity and CERCLA (Comprehensive Environmental Resource Conservation Liability Act) sites. Maps were created using all of the aforementioned locations in an attempt to establish the cause of anomalous F values.

Regional geochemical mapping and geostatistics proved to be invaluable in the development of F. While statistical procedures defined and detected anomalous F values, their locations were identified using regional geochemical mapping. Four groups of anomalous F values were found to occur: A) those caused by Superfund Sites, such as the clusters around the Cleveland site; B) those related to mining/milling/smelting; C) those related to anthropogenic activity, such as the cluster south of White Sands Test Facility and the anomalous F value southeast of Lordsburg due to railroad activity; and 4) isolated, nonclustered anomalous F values that are found near ranch houses in the Clifton quadrangle. Although they posses mafic affiliation, they appear to be caused by ferro alloy metals (Co, Cr, Ni, and V) from rusting steel. Based on the results in this present study, it is concluded that the quantity F is sensitive to concentration fluctuations, whether due to mineralization or anthropogenic activity.
 

Integrated Study of Structure and Water Resources of the Tularosa Basin, South-Central New Mexico

Lanka, Kalidas
Department of Geological Sciences

The Tularosa basin is one of the largest basins in the Rio Grande rift. The region including this basin contains rocks ranging from Precambrian through Cenozoic in age. The basin itself is a downdropped block of crust bounded on both sides by range front faults attendant to adjacent uplifts. Because of our lack of knowledge about its structure, the Tularosa basin area remains inadequately evaluated for hydrocarbons and water resources. The purpose of this study is to analyze the structural setting of the Tularosa basin and the geometry of the Cenozoic fill.

Examination of numerous lithologic and geophysical well logs, facies and isopach maps, well data, completion of a gravity survey, and construction of four detailed cross-sections reveals a complex fault block structure in the subsurface of the Tularosa basin. On examining the four cross-sections, it appears that the Tularosa basin is divided into two grabens with a significant variation in thickness of both Paleozoic and Cenozoic sediments. The Tularosa basin changes from a northerly to a northeasterly trend in the north, and its gravity anomaly merges with that of the older Sierra Blanca basin. There is a general increase in Cenozoic fill thickness from south to north except that the Cenozoic fill is thin west of the Tres Hermanos in the central portion of the basin. The fill is about 2.5 km thick in the north and is about 1.0 km along the profiles which were modeled in the south. Near White Sands Missile Range Headquarters, a local gravity minima suggests greater fill thickness in this area.
 

Lithospheric Structure of Northeastern and Central Tanzania from Gravity Interpretation

Tesha, Aloyce
Department of Geological Sciences

Previous geophysical and geological studies undertaken in northeast and central Tanzania have revealed anomalies which correlate with the major tectonic features in the region: the Gregory rift (eastern arm-East African rift system), the Mozambiquan belt and the Tanzania craton. However, the interrelations between these features are not clear. In order to address this situation, field work was conducted in the area fora period of three months and 1500 gravity data points were collected. The field procedure involved taking gravity readings around loops at a station interval of 1 to 2 km along motorable roads in the area. Loops were closed after every five readings and each day's work involved a closure at a gravity base station. Locations of gravity stations and elevations were determined using hand held GPS, topographical maps at a scale of 1:50,000 with 50 ft contour interval, and digital barometers. Field measurements and error analysis suggest that this approach of determining elevation was very satisfactory and yielded results with a typical accuracy of less than ± 1 m.

Analysis of crustal and upper mantle structure in these areas was conducted using a dataset formed by merging the collected and previously available gravity data. Three gravity profiles, one across northern Tanzania, one across the terminus of the Gregory rift and one across central Tanzania were modeled using constraints from recent geological and seismic investigations in Kenya and northern Tanzania.

A variety of filtered Bouguer anomaly maps were generated to assist in interpreting gravity anomalies related to the contact of the Tanzania craton with the mobile belts surrounding the craton (suture zone), and rift and upper mantle structures. Bouguer gravity anomaly maps show that:

1.The suture anomalies observed in gravity models are related to the collisional contact of the Proterozoic orogenic belts with the Tanzanian craton. The crust beneath these sutures thickens from 35 to 40 km.

2.The Gregory rift is shown to be associated with a broad negative Bouguer anomaly. This anomaly appears to die out south of about 50^oS near where the rift changes from a complex rift graben with volcanism to a more simple region of block faulting with an approximately E-W trend.

3.The gravity models show the crust to be thickened by more than 5 km compared to normal continental crust, which is postulated as a barrier for rift propagation into central Tanzania. Also in the area, Mozambiquan belt structures seem to swing to the southwest, thus this area may not as readily accommodate rifting as north-south trending structures in the north.

Uses of Seismic Methods in Geotechnical Studies, Southern New Mexico and West Texas

Kaip, Galen M.
Department of Geological Sciences

This project involved the use geophysical techniques for engineering studies. Seismic refraction (SR), spectral analysis of surface waves (SASW), downhole seismic (DS), and ground penetrating radar (GPR) methods were used. A total of three different studies utilizing combinations of the above-mentioned geophysical techniques were completed.

The first study involved using SR to determine rippability and a conservative bearing capacity for a proposed reservoir. The second study involved SR and DS to determine dynamic soil properties for the construction of a deflector dish used for a laser targeting system. The third study utilized SR, DS, SASW, and GPR to provide information on wetting front and pore pressures near an earth-fill levee. The first two of the three studies followed accepted industry standards. The third study was academic in the sense that represented different approaches to obtain this information.

The main objective of this project is to show how different geophysical techniques can be used in engineering studies. Each project involved the acquisition of field data, processing, interpretation of all data and formulation of recommendations.
 

Sand Provenance Within the Alboran Sea, Western Mediterranean

Latter, Kelly
Department of Geological Sciences

The Alboran Sea is a tectonically active basin in the westernmost Mediterranean Sea created during the Neogene collision of the African and European plates. It has a complex history that does not clearly fit a previously defined tectonic style. During Ocean Drilling Program Leg 161, Pliocene to Miocene sand-bearing sequences were cored at four sites (Sites 976-979) in an east-west transect across the Alboran Sea. More than 150 sand samples from these cores were air-dried and sieved to obtain the sand-sized fraction. Thin sections prepared from these samples were stained for recognition of feldspars. Sand detrital modes were determined for 34 samples from these sites in addition to 10 samples of beach sand collected along the southern Spanish coast. A maximum of 400 points were counted using the Gazzi-Dickinson method.

Site 976 is located at the base of a southward dipping slope on the Spanish Margin. At this site metarmorphic basement is overlain by a Miocene volcaniclastic interval. Pliocene sand is predominantly quartzolithic, whereas Pliocene sand is more quartzose. Sites 977 and 978 are located to the south and north, respectively, of the Al-Mansour Seamount in the Eastern Alboran Basin. Pliocene sand at these sites is quartzose, whereas the Pleistocene sand is principally quartzolithic. Site 979 is located in the southern Alboran Basin, in a narrow depression between the Alboran Ridge and the Moroccan coast. Sand at this site is glauconitic with significant glassy volcaniccomponents in the lowermost section.

Mean detrital modes for the most sands in the Alboran Basin plot in the Recycled Orogenic and Magmatic Are compositional fields. A few exceptions plot in the Dissected and Magmatic Arc fields. The quartzolithic composition and ratio of sedimentary to metamorphic lithic fragments in sand samples from Unit H at Site 976, Unit I at Sites 977 and 978, and Unit I at Site 979 reflect the proportion of metamorphic and sedimentary rock sequences exposed in the Betic Cordillera of southern Spain (Sites 976-978) and in the Rif in Northern Africa (Site 979). Analysis of coastal beach sand suggests that very quartzose sands from Unit II at Site 976 were likely derived from the Flysch Trough Units near Gibraltar. Upper Miocene samples from Site 976 contain a significant amount of volcanic debris. This sand composition is probably a result of widespread volcanic activity during basin inception and formation. In contrast, lower Pliocene volcanic sand from Site 977 is probably related to later intrabasinal volcanism.

Earthquake Studies of the Anninghe and Xiaojiang Faults of Southwestern China

Dober, Mark
Department of Geological Sciences

The Anninghe and Xiaojiang are major left-lateral, strike-slip faults in southwestern China. These faults are a result of India's penetration into Eurasia and form the southern extension of one of the most active fault systems in the world this century. Five earthquakes of magnitude >6.5 have occurred since 1927. The faults lie in the remote Sichuan and Yunnan provinces and have not been as extensively studied as other nearby faults (i.e. Xianshuihe and Red River faults), or major strike-slip faults in other regions (i.e. San Andreas, Anatolian and Alpine faults).

This study extensively characterized earthquake and faulting processes on the Anninghe and Xiaojiang faults. Travel time, first motion and waveform information was used to analyze earthquakes of magnitude >4.5 which have occurred along the fault systems between 1927 to the present. Earthquakes were relocated using a bootstrap location technique. Focal mechanisms were determined for earthquakes with adequate first motion data. Waveforms were modeled for earthquakes of magnitude >6.5.

This information was used to compare the Anninghe and Xiaojiang faults to other major strike-slip faults and to gain a better insight into this mode of faulting. The results show that the study area is a nearly pure strike-slip regime. The faulting is highly segmented and complex.
 

The Evaluation of Saline Lakes in Eastern New Mexico and Western Texas for Their Potential Utilization as Salinity-gradient Solar Ponds Region

Sandoval, Juan
Department of Geological Sciences

A favorability index equation is devised in order to evaluate saline, artificial, and playa lakes as potential salinity-gradient solar ponds (SGSPs). Three different sectors, physical, cost, and economic criteria, are evaluated by the favorability index equation. SGSP target sites which are located close to industry are targeted since a u ser of the SGSP heat is essential. Industries located in the southwestern portion of the Great Plains, in particular the Llano Estacado of the Texas panhandle and eastern New Mexico plus the eastern portion of the Pecos River drainage are evaluated. in tine, playa, and artificial lakes represent a potentially significant untapped source solar energy. A single 100 acre saline lake could provide the thermal equivalent of 600 million cubic feet of natural gas annually at an estimated cost of less than $1.50 or million BTUs.

The evaluation determined that salt, water, and a liner system are the most important criteria when searching for SGSP sites. The highest score obtained by the favorability index equation is by an artificial lake located at the Ozark-Mahoning I am sulfate plant in Seagraves, Texas. Other sites that scored high are at the '?P site, close to the Pennzoil Sul& Company in Culberson County, Texas, and in potash tailings piles located in the Potash Enclave of Carlsbad, New Mexico.

An Integrated Geophysical Analysis of the Great Divide Basin and Adjacent Uplifts, Southwestern Wyoming

Cline, Veronica J.
Department of Geological Sciences

The integrated analysis of this study, which relies heavily on the seismic reflection profiles released by Chevron USA, Inc., provides several new insights about the deep structure of the Great Divide basin and adjacent uplifts in southwestern Wyoming. A geologic cross-section constructed from 2-1/2 dimensional gravity models constrained by seismic reflection data, illustrates relationships between the Laramide thrusting and heterogeneity in the Archean basement. Spacial relationships evidenced by the overlay images (gravity and Landsat TM) provide additional information that corroborates previous studies.

A cross-sectional model based on the gravity models supports a maximum dip of 45^O to the northeast for the Wind River thrust. This supports previous studies based on the COCORP deep seismic reflection line. A shallower dip for the Emigrant Train thrust is displayed in the cross-section. The model also displays approximately 10 km of underlying sediments beneath the Wind River thrust.

The seismic lines that lie approximately on the gravity profile of the cross-sectional model depict inhomogeneities in the Archean basement in this area that have not been previously recognized. The inhomogeneity of the basement is also evidenced by varying the density of the basement in the gravity model. The cross-sectional model derived from the gravity profile also provides information about the nature and location of the zones of thrusting, which is coincident with an area of inhomogeneity in the Archean basement.

Seismotectonic study of Kennedy Entrance, South-Central Alaska

Velasquez, Monique
Department of Geological Sciences

The southern Alaska margin is a composite terrane that interacts with the Pacific plate along the Aleutian megathrust fault system. Inboard of the megathrust system, are several fault zones that represent older suture zones that have helped build the southern Alaska margin through accretion. Reflection and refraction seismic studies have revealed a zone of reflectors caused by the underthrusting of oceanic crust between the Aleutian Trench and the Alaskan Peninsula magmatic arc, along with a series of basins and arcs offshore between the coast and the megathrust.

The March 28, 1964 (Mw -9.2) earthquake occurred in southern Alaska with the epicenter at 60.4° N and 147.73° W within Prince William Sound (PWS). Recent (post 1964) seismicity in the 1964 rupture zone between the southern Kenai Peninsula and the northern portion of Kodiak Island (the Kennedy Entrance Region) has never been studied in great detail, although there are good reflection/refraction data and structural control. This study attempts to identify how structure (revealed in seismic reflection and refraction studies and limited onshore exposure) controls the behavior of this portion of the megathrust. Seismicity is also compared with a detailed study of post-1964 PWS activity to examine differences between regions. The major asperity that ruptured in 1964 was in the Prince William Sound region to the northeast of the study area. A smaller asperity associated with the Kodiak Island region also ruptured in 1964. Although these two asperities are geographically close, it appears as though the asperities act independently of one another. Thus investigation of structure and seismicity of the Kennedy Entrance region helps to determine what controls the edges of these asperities.

Results show that there is seismic quiescence in southern Kenai peninsula in the vicinity of the southern end of the PWS asperity which represents the southern edge of the subducting Yakutat block. Earthquake relocations indicate a north westward movement for events at depths > 70 km and a northeast movement for shallow events (< 70 km). These movements of locations may be related to regional changes in velocity structure. First motion results give a preliminary overview of the mechanisms for the study area but body waveform models constrain the source parameters better. The majority of the focal mechanism solutions (from body waveform modeling) indicate that strike-slip to normal components of motion are predominant, especially at depths > 70 km, with strike slip and thrust component mechanisms to a lesser degree. The mechanisms and focal depths are consistent with a - 7 ° to - 8 ° dip of the subducting slab in Kennedy Entrance. This value is between the dip values suggested for the PWS asperity and the Kodiak asperity from geodetic and tsunami modeling.
 

A Seismotectonic Study of the South-central Alaskan Margin Between the 1938 and 1964 Great Alaskan Earthquake Rupture Zones

Brown. Wesley A.
Department of Geological Sciences

The south-central Alaskan margin forms a part of the Alaska subduction zone, which is one of the most seismically active area on our planet. The abundance in seismic activity is in relation to the Wadati-Benioff zone and is a direct result of the descending of the Pacific plate beneath the North American plate. Several fault zones found inboard of the Alaskan Aleutian megathrust mark the remains of suture zones that have built the southern Alaskan margin through accretion.

The great Alaskan earthquake of March 28, 1964 (Mw = 9.2) ruptured an 800 km long segment of the Alaska subduction zone from Prince William Sound to southwest of Kodiak Island. The great Alaskan earthquake of November 10, 1938 (Ms = 8.3) occurred off the Alaskan peninsula and ruptured a 300 km long segment of the Alaskan Arc, abutting the 1964 rupture zone on its northeast edge. The portion of the 1964 rupture zone that lies within the study area (the Kodiak asperity) appears to rupture with the PWS segment in some cases and independently in other cases.

The Kodiak Island portion of the 1964 rupture zone is estimated to rupture every 60 years, thus another large event is to be expected in the near future. In this study I have examined seismicity since the 1964 mainshock, using relocation, first motion analysis, and body waveform modeling techniques combined with previous geologic and seismic reflection studies look at structural controls in the area of the two (1938 and 1964) asperities.

Relocation results revealed no migratory trends in spatial and temporal locations of events in the study area, neither were there any noticeable correlation of magnitudes and spatial positions. Results of first motion studies show a dominance of thrust faulting in the region. Body waveform modeling and CMT results show more oblique strike-slip events, which suggest tearing or other deformation in the subducting slab. Empirical relationships of rupture width and magnitude suggest that there is potential for an mb > 7.0 event to occur across the plate interface within the region and the focal mechanism of an intra plate event (Mw = 7.0) in December 1999, is consistent with body waveform results and its occurrence could accelerate the next plate interface event.

Imaging Geological Materials using the Acoustic Microscope

Gillespie, Cindy Lorraine
Department of Geological Sciences

Acoustic microscopy, a process in which sound is emitted, echoes are reflected, and images are obtained, previously has not been applied to geological problems in any extensive or organized fashion. In contrast, other areas of research, such as materials science, electronics, and medical and dental fields, have already taken advantage of the abilities of acoustic microscopy. In this study, the acoustic microscope was used to image geologic materials and to measure sonic velocities on a fine scale.

Fossils illustrated the ability of the Scanning Acoustic Microscope (SAM) to do topographic (surface) imaging. A pisolite demonstrated nondestructive imaging of subsurface features. The pisolite was of particular interest because it generated three-dimensional images of grain orientation and pore geometry. A thin section of coral verified the ability of the SAM to do impedance contrast imaging of materials differing in elastic properties.

Common rock-forming minerals were sliced at various thicknesses and acoustic travel times through the specimens were recorded. Acoustic velocities in the samples were compared to standard values; the percent error ranged from .04 to over 60. These discrepancies can be explained in many cases by difficulty in discerning sample pulses from background noise and secondary reflections. Another source of error was comparison of calculated velocity values to velocity values in the literature, many of which were "averages" for anisotropic materials.

3-d Geometry and Velocity Structure of the Tacoma Basin, Western Washington

Hiett, Brett J.
Department of Geological Sciences

Within the highly populated Puget Lowland of western Washington, local faulting and the subduction of the Juan de Fuca plate pose a seismic threat that is compounded by the potential for amplification of ground shaking within basins that underlie the region. Studies of other basins on the west coast of the United States (e.g., in San Francisco and Los Angeles) show that they have the propensity to amplify seismic energy up to 15 times. Although the Pacific Northwest has been relatively aseismic compared to other subduction zones, studies have found that this region has M7.0+ earthquake potential on more than one seismogenic structure. The objective of the Seismic Hazards Investigation in Puget Sound (SHIPS) in March 1998 was to produce a 3-D velocity and structural model of the Puget Lowland to help identify and resolve structures not previously studied. Over 300 data acquisition systems were deployed in the Puget Lowland and recorded airgun shots every 16 seconds for an 18-day period. This study presents the results of tomographic inversion of SHIPS data in and around the Tacoma basin. Inversion of over 140,000 arrivals from 61 recorders produces a velocity model that shows that the Tacoma basin is made up of 3 sub-basins that trend northwest-southeast. Assuming velocities of 5.5 km/s as a proxy for the top of the Crescent Formation, depths of the sub-basins vary from 4.5 to 6 km. Previous studies had estimated the depth of the Tacoma basin to be 3 to 4.5 km depth. The Tacoma basin may have formed as the result of relief created by thrusting up the Seattle uplift. The sub-basins may have originated as pull-apart basins in an Eocene from north-south, strike-slip regime.
 

A Seismic Reflection, Gravity, and Remote Sensing Study of the Southeastern Sangre De Cristo Mountains, New Mexico

Quezada-Rodas, Oscar Andres
Department of Geological Sciences

This study is an integrated geophysical and remote sensing investigation of the Laramide and Precambrian influenced tectonic features in the southeastern Sangre de Cristo Mountains of northern New Mexico. Exposed geology of the Mora area includes abundant outcrops of intrusive and high grade metamorphic rocks. Bouguer gravity values over this southeastern area of the Sangre de Cristo Mountains are anomalously low and do not agree with the high measurements on the southwestern side of the range in the Picuris and Santa Fe Mountains as well as the northernmost part of the range in Colorado. Based on previous research and early results, the anomalous gravity composition could be produced by one of three possible scenarios:

• Anomalous low gravity signatures caused by an allochtonous Precambrian sheet thrusted over low density sedimentary rocks.
• The presence of an intra-basement batholith of lower density than the surrounding metamorphic and igneous rocks.
• The presence of an exposed low-density metamorphosed intrusive body.

Seismic reflection data acquired across the Mora-Taos area was reprocessed in order to enhance possible deep reflectors from either a granitic batholith or an allochtonous sheet of Precambrian material. Portions of these seismic lines reveal a highly reflective basement under the Sangre de Cristo Uplift interpreted as Proterozoic compressional features as well as multiple normal faults that appear to be reactivated Laramide thrust faults on the west central side of the southern Sangre de Cristo Mountains. The thickness of the Paleozoic section on the central part of the gravity profile was also constrained by the seismic reflection data. Preliminary modeling of a deep crustal feature as a cause of the low gravity values was ruled out since such a structure produces a broad anomaly that does not match the observed data. The consideration of these constraints and their integration with the surface features visible in remote sensing were the bases for the selection of one particular gravity model. This model shows a low density metamorphosed intrusive body at the surface in the Rincon Range that corresponds with the location of a granitic gneiss exposure. Well data from the adjacent Rainsville trough, where the gravity values are lowest, has reported high amounts of immature sediments eroded from these exposures. Low density sediments from the Rincon Range are therefore affecting the overall density of the trough and could be a possible cause of the low gravity anomaly. This research is an attempt to correlate gravity signatures, seismic reflection data and surface expressions from satellite imagery in order to understand the geophysical structure under this complexly deformed section of the Rocky Mountains. Results of this study will contribute to the Continental Dynamics-Rocky Mountain Project (CD-ROME; which seeks to understand the growth, stabilization and reactivation of the lithosphere of the North American southwest.

A Conceptual Model of the Hydrogeology of White Sands National Monument, South-central New Mexico

Barud-Zubillaga, Alberto
Department of Geological Sciences

White Sands National Monument is located in south-central New Mexico within the boundaries of the Tularosa Basin. The White Sands dune field occupies about 700 km2, of which only the southern 450 km2 are managed by the National Park Service since 1933. This investigation addresses the hydrogeology of the study area to determine the characteristics of the groundwater flow system in the subsurface of White Sands National Monument (WSNM). Physical, chemical, and isotopic dating analyses were performed in this study from different sites within the boundaries of WSNM. In situ spectral reflectance measurements were taken from several sites to construct a supervised classification map of the White Sands area. Data collected from sites outside the study area were used to complement the generated conceptual model and the hydrologic map of the midcentral Tularosa Basin.

Groundwater flow in the vicinity of White Sands is not to the south as in the Tularosa Basin in general, but has a strong westerly component. Some of this groundwater discharges in the hydraulic sink of Lake Lucero, a highly saline playa ephemeral lake. Physical and chemical parameters of groundwater beneath WSNM were strongly affected by seasonal precipitation. In fact oxygenrich precipitation infiltrated into a highly reducing groundwater environment creating sharp concentration gradients. Anomaleous high groundwater temperatures at the western margin of the WSNM, in addition to microbial and isotope evidence may support the possibility of a hydrothermal component discharging into the regional groundwater sink at Lake Lucero.

A supervised classification using landsat-7 data sets aided in the identification of different terrains leaded to a better understanding of the White Sands area where depth to water table is closer in areas with lower elevations and resulted in wetter or moister regions. The ancient Lake Otero floor has been carved deeper and deeper in the western margin of the White Sands area by water and wind since the Pleistocene. The Alkali Flat is now exposing the ancient deposits of the Lake Otero floor. The entire White Sands Dune Field today is increasing in size as the Alkali Flats and Lake Lucero shrink due to dryer conditions as time goes on. The active dune field is growing on top of the ancient Lake Otero floor to the east.

Satellite Detection of Land Use Changes in the Rio Grande Valley from Elephant Butte Dam, NM, to Fort Quitman, TX

Pérez, Adriana E.
Department of Geological Sciences

Satellite imagery in conjunction with historical land-use maps delineated urban, agricultural, and desert changes in the stretch of the Rio Grande Valley between Elephant Butte, NM, to Fort Quitman, TX. Other minor categories such as park areas, golf courses, and commercial-use areas were also mapped in the study. Agricultural records, which included crop type, crop acreage, water diversions from the river, and census data, provided ancillary information to the project. It was calculated that an approximately 3035% increase in urban areas occurred in the 15-year period from 1984 to 1999. Total agricultural acreage remained unchanged for this same period of time. Both of these results were supported by the supplementary agricultural and census data.

Satellite imagery provides a cost-effective, readily available data source from which land use maps can be made. These can be used to calculate water use and population trends for better management of resources in the area and planning of sustainable growth and economic development.
 

The Structural Framework and Mineralization of the Lluvia De Oro Mine, Sonora, Mexico

Rothemond, Kirk Lawrence
Department of Geological Sciences

The Lluvia de Oro gold mine is an open pit, low-grade (1.0 g/mt), disseminated, bulk-minable deposit located 12 km north-northwest of Magdalena de Kino, northern Sonora. The deposit is located within the high strain, western part of the Magdalena Core Complex. The lower plate rocks are composed of a metamorphosed Jurassic volcanic arc complex unconformably overlain by Upper Jurassic conglomerate and Lower Cretaceous marine beds. These formations have been intruded by three generations of Late Cretaceous to Middle Tertiary granite. Mid-Tertiary mylonitic structures include a southwest-vergent, mid-crustal ductile shear zone that formed by normal slip on the Magdalena Detachment Fault.

Locally, the Lluvia de Oro mine, has been developed by the El Creston pit within a brecciated and sheared Cretaceous sedimentary unit that may correlate with the Represo Formation of the Santa Ana quadrangle. This sedimentary unit contains quartz pebble conglomerates, fine to very fine-grained sandstones, siltstones and rare limestones that are exposed in a northeast-trending valley and bounded on the west side by a low angle detachment fault and to the east by a normal fault. The Represo Formation is bounded on both sides by lower plate, metamorphic and igneous rocks of the Magdalena Core Complex. These include two-mica, garnetiferous granite, leucogranite, metasediments, metavolcanics, granitoid gneisses and schist of greenschist and amphibolite metamorphic grade. Thin exposures of andesite overly the Represo Formation and probably are late Cretaceous- Early Tertiary age.

Mineralization is primarily related to the 200m wide brittle Lluvia shear zone, that strikes northeast along the valley and is characterized by fractures, many of which have dips greater than 70° and with a preferred strike of N50E. This shear zone provided conduits for metal-bearing fluids that permeated the sedimentary rock, probably in Late Oligocene to Middle Miocene time. Presently, the shear zone is marked by oxidation products that include jarosite, goethite, hematite and pyrolusite. The hydrothermal alteration is characterized by a sericite-pyrite-quartz- calcite assemblage and classified as phyllic alteration. Hematite and pyrolusite filled stockworks are common. Ankerite, siderite and calcite veinlets, on occasion are rimmed by black manganese oxide. Calcite veinlets are common; however quartz veinlets are rare, but have been reported to contain high gold values. Other mineralized areas are located at the El Pozo, Este, Pit Extension and the Lluvia Shear northeast areas.

Initial reserves were 4 million tons, averaging 1.0 g/mt Au and 2.9 g/mt Ag, defined by reverse circulation drill holes with an average depth of 100m. Mining began in 1994 but was suspended in June 1998 and was accomplished by open-pit methods, followed by cyanide leaching and recovery using carbon columns and an electrolytic method to produce dore. Drilling accomplished by September 1997 revealed an additional orebody in the northeastern part of the shear zone, located 300m from the Creston pit. In the future, the company plans to mine this orebody that averages 2.29 g/mt Au over an average thickness of 38 m.

Gravity and Seismic Studies of the Tularosa Graben for Groundwater Studies

Belzer, Wayne L.
Department of Geological Sciences

In the desert southwest, water resources are a prized commodity that are primarily being located by drilling expensive wells. An additional approach is to collect and analyze gravity and seismic data to locate faults and fractures that may control groundwater movement, and lows in bedrock where water may pool. This approach is used in this thesis for an area in the eastern Tularosa Basin. The objective of the study is to better define possible water resources by delineating subsurface stratigraphy and bedrock structure. Data collected for this study include three gravity profiles which trend normal to the strike of the Sacramento Mountains. Based on the information from the gravity profiles, a 1.6 km long seismic line was shot. A stacked seismic record was generated and forward modeling of the velocity field was performed on these data. A final integrated interpretation of all the data showed. that small grabens parallel the mountain uplift in the subsurface. The geophysical data also show that the bedrock is tilted towards the northeast suggesting that groundwater may flow northeastward within the graben system.

An Integrated Study of Landform Development Using Near-surface Geophysics, Remote Sensing, And Geomorphology, at The Great Sand Dunes National Monument

Couroux, Emile Gabriel
Department of Geological Sciences

The Great Sand Dunes National Monument (GSDNM) is located in the San Luis Valley, an internally drained basin of the Rio Grande Rift, in the south-central portion of Colorado. The GSDNM contains the tallest eolian dune deposits in North America (up to 200m) and is located in the eastern portion of the valley. Surrounding the dune field is an extensive vegetated sand sheet with degraded parabolic dunes, relict stream terraces, and scattered, isolated patches of active parabolic, barchan, reversing and coppice dunes.

This thesis was designed to delineate the sand sheet using remote sensing and geophysics and determine the depositional history and geomorphic processes that created it. The research was requested by, and supported in part by the National Park Service, because they intended to expand the monument boundaries to include the sand sheet region.

Landsat images were used to map geomorphic boundaries between landforms and refine the existing three classes into ten new classes. Near-surface geophysics, electromagnetic, ground penetrating radar and magnetometer measurements, were collected when crossing the geomorphic boundaries. Radiocarbon dating of buried soils was incorporated to restrict the ages of landform development.

The sand sheet has been thought of as a relatively stable eolian feature with sand being transported across it to the more dynamic dune field of the GSDNM. This study indicated that the sand sheet was largely fluvial in origin and is much more complex and dynamic than previously thought. Geomorphic analysis indicates meandering stream channels cut through stabilized and active dunes, creating flat grassy meadow environments, consisting of reworked eolian sands. Buried organic-rich soil horizons, stream terraces, and abandoned channels illustrate a dynamic history between fluvial and eolian processes in this area, that consists of fluvial deposition in meandering and braided streams forming gently sloping alluvial fan surfaces. Subsequent reworking by wind fills abandoned channels and creates dune forms. West of the sand sheet and meadows is a lacustrine environment (sabkha). It consists of playa lakes that form in silts and clays deposited in an ancient lake floor. Several generations of buried lake shorelines under the sand sheet, east of the modern playa lakes.

This study reveals that the landform development at the GSDNM is a much younger and a more dynamic system that previously thought. Radiocarbon dates show that deposition of the youngest alluvial fans began during the last 2000 years, and that the terraces which they are incised into are younger than 5000 years old. Ground water and surface water interactions, with eolian processes is a strong influence on landform development, and is an indicator of how susceptible the landforms are to change. A lowering of the water table would undoubtedly increase the amount of eolian activity, which would bury the current water source (channels, ponds).

East-west extension associated with the second, extensional tectonic episode in the southern Indio Mountains is established from north striking calcite veins containing east-west trending growth fibers. Dextral-oblique displacement along the northwest striking extensional Indio normal fault is determined along the northwestern by slickenside orientations within the fault zone. The minimum vertical separation across the Indio fault is established to be 1685 m 95,520 ft). A minimum eastward tilt of the southern Indio Mountains of 18o during extension is constrained by orientation of the Oligocene volcanic deposits. Tilting of valley fill gravels record normal fault activity as recent as the Quaternary.

Both batch and model aquifer experiments were conducted to evaluate possible permeable barrier materials for retaining viruses in groundwater. Three materials, iron-coated sand, raw zeolite, and surfactant-modified zeolite, were used in the study. Due to its positively charged surface and probably the hydrophobic portion of the surfactant molecules, cationic surfactant-modified zeolite worked as a near-perfect permeable barrier. Iron-coated sand was also a good barrier material in model aquifer experiments although it did not adsorb the viruses in batch experiments. Pure zeolite did not behave as an adsorbent for either MS2 or X174 phage in fresh water, but it adsorbed the phages significantly in water with high ionic strength.

Minera Secotec began dry-wash placer mining operations in 1997 on two of the 11 lease concessions covering the El Boludo deposit. A unique rotary-air concentrating method has been developed to separate heavy minerals from dry alluvial placer materials Maximum throughput capacity of the mobile concentrating plant is 200 m³/hour with recovery rates on gold particles in the 80 micron to 14 mm size range exceeding 90% in extremely dry ground. The total resource of gold-bearing sediments contained in the Boludo placer field amenable to this mining method is currently estimated at 25 million in, grading 0.26 g/m³.

The Regional Tectonic Stress Field in the Buller Region, New Zealand: Evolution Through Time and Relation to Large Historical Earthquakes

Hincapie, Jaime Omar
Department of Geological Sciences

During the 1929 winter, five major earthquakes struck the Buller region in the South Island, New Zealand. This group of events, called "The Buller Sequence", includes the June 16 Ms 7.8 earthquake, the largest recorded in the South Island in the 20th century. Again, between 1962, and in 1991, earthquakes with Ms>.5.2 occurred in the same area. The greater of these was on May 23, 1968, an Ms 7.4 event. All these events were shallow (h<2Okm), and in an area where apparently there is no surface expression of any major fault. The area is bounded by Kongahu and Lyell faults, both currently active. These faults lie northwest to the Alpine fault, a northeast-southwest transform that accommodates and distributes stress along the Pacific-Australia plates interaction in the South Island.

This study is carried out in order to examine the evolution of the regional tectonic stress field through time in the Buller region, and how it readjusts between large earthquakes. The background tectonic stress field is determined by earthquake first motion studies. Then modeling of the perturbation of this stress field by the large historical earthquakes is performed. Through this analysis, we pretend:

1. Examine the possibility that some of these events could be stress-triggered by older events.
2. Determine how the regional stress field may serve to raise or lower stress across the Alpine fault.
3. Use this methodology to assess seismic hazard in other regions where seismic coverage is poor or non-existant.

As a result of this study, the basins in northernmost Chihuahua were delineated as well as the southern outline of the Hueco Basin and southern parts of the Mesilla Basin. In particular, a new basin named here as the El Parabien Basin was delineated. These basins are important groundwater resources that in the future will be utilized for the growing population in the area. However, the integrated analysis shows that the subsurface extent of the region where the thickness of the basin fill (potential aquifer) is significant, but is far less than the surface expression of each basin would suggest. This result may be of limited significance to studies of shallow aquifers but has greater significance to long term plans that call for exploitation of deep groundwater resources that are in all probability saline.

Seismic velocities in the upper mantle range from 7.9 km/s in the central Basin and Range, to 7.8 km/s in the southern Basin and Range and metamorphic core complex belt, to 7.9 km/s under the Colorado Plateau. Deeper mantle arrivals (P1) have been recorded and correlate across the Basin and Range, Transition zone, and southwesternmost Colorado Plateau. They have been modeled as a reflected wave off an interface at a depth of ~45 km under southeastern California, and dipping toward the northern Basin and Range and Colorado Plateau to a depth greater than 50 km with a seismic velocity decrease to 77 km/s. The reflection off the bottom of this low velocity layer (P2) is recorded in the Transition Zone at a depth of ~68 km (15 km thick) and the southwesternmost Colorado Plateau at a depth of ~58 km (10 km thick) exhibiting very large amplitudes. The Basin and Range geotherm crosses the dry basalt solidus at approximately 45 km depth suggesting that this low velocity layer could be due to the melting of mafic material. The bottom of this low velocity layer is clearly present in the Transition Zone and southwesternmost Colorado Plateau, but not in the Basin and Range.

The Cedar Mesa Sandstone appears to be a good analog to the Rotliegende sandstones in North Sea. Both settings are influenced by wet environments decreasing porosity through early cementation, and also show late stage dissolution of early cements due to isotopically light fluids that are probably related to hydrocarbon migration.

Puerto Rico lies in a zone of complex plate tectonic motion along the northern Caribbean plate boundary and has a long history of active seismicity. Historic offshore events near Puerto Rico, and events occurring in the Dominican Republic and the Virgin Islands, have triggered tsunamis in the coastal regions of the island. Even though Puerto Rico has not experienced a relatively large earthquake recently, there is still active seismicity on and off the coast of the island. Due to the prominence of recent activity in southwestern Puerto Rico and the recent discovery of faults with evidence of Quaternary movement, I have chosen to focus my research on this area. This region includes the area between 66⁰ 30 to -67^O 30 longitude and 17⁰ 45 to 18⁰ 15 latitude. Until recently, earthquakes and faults in southwest Puerto Rico had received scarce study. In the majority of cases basic faulting parameters, such as location, extent, geometry, kinematics, and space-time patterns of earthquakes have been lacking. The objective of this investigation, after analysis of the appropriate seismic data, is to identify potential seismogenic zones in this area of Puerto Rico. The majority of events in this region have magnitudes less than 4.5. This makes investigation of the seismic hazard in this region very difficult. Typical studies such as waveform modeling and single event relocation techniques cannot be performed. Therefore, a joint hypocenter determination technique was utilized to relocate the events in the study area. This technique treats the data as a cluster of events, and will relocate them simultaneously. The relocation of events in this manner provides a better sense of where the majority of the activity is occurring. Relocation of events with a joint hypocenter determination technique also allows for a larger number earthquakes to be relocated without extensive computing time. JHD also provides other components, such as station corrections and relocation residuals, which are used in the assessment of the quality of the events travel times and the quality of the relocations themselves. Station corrections also can be related to 3-D velocity complexity within the study area. This study has identified two regions within southwest Puerto Rico, Ponce and the Lajas Valley, where a higher frequency of microseismic events have occurred over the past 15 years. First motion studies have demonstrated a stress field for the study area matching the tectonics of the island; ₁ oriented NE-SW, ₃ oriented NW-SE near horizontal, suggesting strike-slip faulting. The Lajas Valley stress tensor suggested thrust faults optimally oriented for failure, whereas, the Ponce area stress field matched that of the complete study area. There appear to be some correlations between the relocated -events and structural features within these regions.

A digital network of 24 seismograph stations was operated from September 15, 1987 to September 30, 1988, by Lawrence Livermore National Labs and Unocal as part of the Salton Sea Scientific Drilling Project to study seismicity related to tectonics and geothermal activity near the drilling site. More than 200 microearthquakes were relocated in this study in order to image any pervasive structures that may exist within the Salton Sea geothermal field. First, detailed velocity models were obtained through standard 1-D inversion techniques. These velocity models were then used to relocate events using both single event methods and Double-Differencing, a joint hypocenter location method. An anisotropic velocity model was built from anisotropy estimates obtained from well logs within the study area. During the study period, the Superstition Hills sequence occurred with two moderate earthquakes of M_S 6.2 and M₅ 6.6. These moderate earthquakes caused a rotation of the stress field as observed from the inversion of first motion data from microearthquakes at the Salton Sea geothermal field. Coulomb failure analysis also indicates that microearthquakes occurring after the Superstition Hills sequence are located within a region of stress increase suggesting stress triggering caused by the moderate earthquakes.

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