Physical Sciences and Mathematics Commons^™

Textural And Mineral Analysis Of Pegmatites From The Pala And Mesa Grande Districts In San Diego, California, Gabrielle Potter

Williams Honors College, Honors Research Projects

San Diego pegmatites of the Pala and Mesa Grande mining districts are world renowned for their gem-quality minerals and their Li-bearing mineral phases. Pegmatite genesis, especially in San Diego mines, has been a debated topic since the 1900’s (Morgan and London, 2012). Pegmatite genesis is caused by partial melting processes and fractional crystallization that form granitic melts with high concentrations of rare earth elements (REE), such as lithium. Assessing the exact mineralogy and determining the overall textures can provide insight into the crystallization history of pegmatites. In the San Diego pegmatites, lithium-bearing phases, such as lepidolite and pink elbaite (a …

Petrology Of An Oxidized Blueschist Cobble From The San Onofre Breccia, California, Usa, Alaina A. Helm

Honors Papers

The mid-Miocene San Onofre Breccia (SOB) found along the southern California borderlands contains clasts of several lithologies including high-pressure metamorphic rocks commonly thought to be shed from the Catalina Schist. Sorensen concluded the San Onofre Schist was part of the Franciscan Complex, although at that time the Catalina subduction was considered to be part of the Franciscan Complex. In this study, a ~10 cm cobble collected from the San Onofre type locality was studied to describe its mineralogy and estimate its conditions of metamorphism. The cobble is composed of glaucophane (35%) + epidote (15%) + garnet (13%) + phengite (12%) …

A Diatom Proxy For Seasonality Over The Last Three Millennia At June Lake, Eastern Sierra Nevada (Ca), Laura Caitlin Streib

Theses and Dissertations--Earth and Environmental Sciences

The Sierra Nevada snowpack is vital to the water supply of California, the world’s sixth largest economy. Though tree ring and instrumental records show the dramatic influence of environmental change on California’s hydroclimate over the last millennium, few proxy archives assess winter precipitation variability farther back in time. Here, we use diatoms from a ~3,200 yr. old sediment core to reconstruct the paleolimnology of June Lake, a hydrologically closed glacial lake in the eastern Sierra Nevada. We test the hypothesis that limnologic and climatic changes control diatom assemblages at June Lake. Fossil diatom assemblages from June Lake sediments chiefly consist …

New Borehole Breakout Derived Stress Constraints And Their Implications For Stress Heterogeneity Near High Risk Fault Systems In The Santa Barbara Channel, Southern California, Edward Harris Pritchard

LSU Master's Theses

The Santa Barbara Channel represents the offshore portion of the Ventura Basin in Southern California. Ongoing transpression related to a regional left step in the San Andreas Fault has led to the formation of E-W trending en-echelon fault systems, with both north and south dips, which accommodate varying rates of localized shortening across the basin. Recent studies have suggested that faults within the northern region of the channel could be capable of a multisegment rupture and producing a M_w 7.7–8.1 tsunamigenic earthquake. However, dynamic rupture models producing these results have not accounted for stress heterogeneity, which is …

Climate Change Adaptation For Southern California Groundwater Managers: A Case Study Of The Six Basins Aquifer, Frank Lyles

Pomona Senior Theses

Groundwater has been very important to the economic development of Southern California, and will continue to be a crucial resource in the 21st century. However, Climate Change threatens to disrupt many of the physical and economic processes that control the flow of water in and out of aquifers. One groundwater manager, the Six Basins Watermaster in eastern Los Angeles and western San Bernardino Counties, has developed a long-term planning document called the Strategic Plan that mostly fails to address the implications of Climate Change, especially for local water supplies. This thesis presents an in-depth analysis of the Six Basin Watermaster’s …

Detrital Zircon Geochemistry Of The Nacimiento Block, Santa Ynez Mountains, California, Vincent Zhao

Natural Resources Management and Environmental Sciences

The long-lived California section of the North American Cordillera is one of the most studied continental margins in the world; however, erosion and deformation in areas along the San Andreas Fault and the Sur-Nacimiento Fault has erased sections of the Cordillera which could provide insight in Cordilleran processes. The lost sections are partially preserved in detrital zircons deposited alongside the arc in fore-arc basins such as in the Toro Formation of the Nacimiento block which represents the coastal central California equivalent to the Great Valley Group, located in the Santa Ynez Mountains. Geochemical analysis of the detrital zircons from the …

Fault And Fluid Interactions In The Elsinore Fault-West Salton Detachment Fault Damage Zones, Agua Caliente County Park, California, Rebekah Erin Wood

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This study area provides a unique opportunity to study the intersection of the Elsinore and West Salton detachment faults in southern California, effusing warm springs, and alteration products in the midst of the fault intersection. Structural mapping and compiling previous maps supply an interpretation of the fault zone geometries within the Tierra Blanca Mountains. Geochemical analysis of the crystalline basement and altered protolith help determine the effects of faulting and fluid flow in the study area. In the Tierra Blanca Mountains, the Elsinore strike-slip fault system transitions from the double-stranded Julian segment and Earthquake Valley fault in the northwest, to …

Eclogites And Eclogites: Oxygen Isotope Evidence Of A Shared Subduction Origin For Franciscan Eclogites And Moses Rock Eclogite Xenoliths, William F. Hoover

Honors Papers

Eclogites can be found in two distinct tectonic settings in the western USA: in the Franciscan Complex as tectonic blocks in a fossil accretionary wedge, and in the Navajo Volcanic Field as xenoliths in diatremes. Intra-crystal oxygen isotope analyses of garnets from these two settings provide important information on the source, composition and timing of fluid interactions in both eclogite settings. Because of the well-documented relationship between Franciscan subduction and the volcanism in the Navajo Volcanic Field, the samples in this study can be directly compared to determine if they share a common origin. The Navajo eclogites in this study …

Ichnology And Paleoecology Of The Jurassic Aztec Sandstone, Heather Marie Stoller

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this study I describe and interpret tracks and trackways of the Jurassic Aztec Sandstone of southern Nevada and southern California. This study involved mapping of all known tracks and trackways, including foot length, stride length, and trackway width. Photogrammetric data, collected by Bureau of Land Management scientists, were utilized for several trackways in Red Rock Canyon National Conservation Area.

More than three hundred tracks belonging to five ichnotaxa were documented within the Aztec Sandstone, including about 165 tridactylGrallator, 250 tetradactyl (four-toed)Brasilichniumtracks, and 7 arthropod trackways ofOctopodichnusandPaleohelcura. Four of the five ichnotaxa were not previously reported from the Aztec Sandstone. …

The Chemical Evolution Of Oceanic And Continental Lithosphere: Case Studies In The Us Cordillera, Marlon Mauricio Jean

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Among the terrestrial planets, only Earth has volcanism and plutonism that is related to plate tectonics. At the bottom of the oceans, mid-ocean ridges form where tectonic plates drift apart. More visible, and explosively dangerous, is volcanism related to the subduction of oceanic plates back into the Earth’s mantle. Less clear is the origin of the third major type of volcanism, the so-called intra-plate volcanism, which is thought to represent thermally driven upwellings from the lower mantle. This dissertation investigates two of these unique volcano-tectonic settings which occur in the western United States.

Subduction zones are regions of intense earthquake …

Paleoseismic Study Of The Stewart Valley And Northern Pahrump Segments Of The Stateline Fault System, Nevada, Jonathan Carter

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Stateline fault system (SFS) is a ~200 km long zone of dextral faults running NW along the NV/CA border from Primm, Nevada to Amargosa Valley in the western Central Basin and Range province (CBR). Because of size and proximity, the SFS poses a hazard to the 2.5 million people, most of who live within 10 km, in Pahrump, Nevada and within 40 km, in Las Vegas, Nevada. The goals of this thesis are to (1) understand if the SFS is accommodating faulting slip change in the CBR; (2) test the along strike continuity of the SFS in Pahrump and …

Determining Ancient Movement Of The Sur–Nacimiento Fault Zone Using Detrital Zircon Geochronology, Jennifer Per Lee

Natural Resources Management and Environmental Sciences

Middle Cretaceous movement along the Sur–Nacimiento Fault has implications for our understanding of how convergent tectonic margins evolve and for the architecture of forearc basins. Traditional explanations suggest an autochthonous California Mesozoic Forearc that underwent sinistral or thrust displacement; although recent research suggests either an allochthonous forearc or an isolated Nacimiento Block that experienced significant dextral displacement. Detrital zircons obtained from the Great Valley Group within the Nacimiento block provide age distribution patterns that can help identify sources of sediment deposition and therefore the past location of the Nacimiento block. Using U-Pb detrital zircon geochronology, we have discovered a dominance …

Petrogenesis Of The Greenwater Range: Comparison To The Crater Flat Volcanic Field And Implications For Hazard Assessment, Ashley Kaye Tibbetts

UNLV Theses, Dissertations, Professional Papers, and Capstones

Pliocene basalts of the Greenwater Range, California erupted from 24 volcanic vents now represented by volcanic plugs, craters and scoria mounds. Basaltic magmas originated in the asthenospheric mantle, but show evidence of a lithospheric component. Depths and temperatures of melting calculated using a silica activity geobarometer are 54.3–89.6 km and 1367-1435oC, placing melting in the asthenosphere. The preferred petrogenetic model involves melting of lithospheric mantle thermally and mechanically, but not chemically, converted to asthenospheric mantle. Melting depths correspond to low velocity zones in the mantle as revealed in seismic profiles. Chemical and lithologic similarities between basalt in the Greenwater Range …

Structural Characterization Of Three Southeast Segments Of The Clark Fault, Salton Trough California, Benjamin E. Belgarde

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We examine the structural complexities of a 28-km long part of the Clark fault of the San Jacinto fault zone in southern California in order to better document its lateral extent and the style of deformation of its southeast end. Changes in structural style are observed as the Clark fault’s damage zone widens from ~ 1-2 km in crystalline rocks of the Peninsular Ranges southeastward to ~ 18 km in the sedimentary rocks of the San Felipe-Borrego subbasin of the Salton Trough. The Clark fault extends into the San Felipe-Borrego subbasin as the Arroyo Salada segment for ~ 11-12 km …

The Evolution From Late Miocene West Salton Detachment Faulting To Cross-Cutting Pleistocene Oblique Strike-Slip Faults In The Sw Salton Trough, Southern California, Alexander N. Steely

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Field studies in the southwest Salton Trough between Yaqui Ridge and Borrego Mountain show that the West Salton detachment fault was active during the Pliocene and may have initiated during the latest Miocene. At Yaqui Ridge dominantly east-directed extension is recorded by slickenlines on the NW-striking detachment fault, and shows that the fault is actually a low-angle dextral oblique strike-slip fault. Crustal inheritance is responsible for the position of the fault at Yaqui Ridge, which reactivates a late Cretaceous reverse-sense mylonite zone at map scale.

Late Miocene to Pliocene basin fill deposits at Borrego Mountain display progressive unconformities, contain detritus …

The Quaternary Tectonic And Structural Evolution Of The San Felipe Hills, California, Stefan M. Kirby

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We examine the transition between extension and strike-s lip in the San Felipe Hills, western Salton Trough, southern California using new and compiled geologic mapping, measured stratigraphic sections, magnetostratigraphy, and structural analysis. A 625 m measured section describes the Borrego, Ocotillo , and Brawley formations in the SE San Felipe Hills and constrains a regional disconformity and correlative angular unconformity at ~ 1 Ma. Sedimentation rates for the Brawley Formation above the disconformity range from 1.0 to 1.2 mm/yr, palcoflow was to the ENE. The Brawley Formation consists of three interbeddcd lithofac ics; (I) fluvial and fluvio-d eltaic, (2) lacustrinc, …

Examination Of Exhumed Faults In The Western San Bernardino Mountains, California: Implications For Fault Growth And Earthquake Rupture, Joseph R. Jacobs

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The late Miocene Cedar Springs fault system is a high-angle transpressional system in the Silverwood Lake area, western San Bernardino Mountains, southern California. This thesis presents the study of oblique-slip faults with modest amounts of slip, which represent the early stages of fault development by using slip as a proxy for maturity. A structural and geochemical characterization is provided for six fault zones ranging from 39 m of slip to 3.5 km of offset in order to develop a model of fault zone geometry and composition. Basic geometric and kinematic results are provided for an additional 29 small-displacement (cm- to …

Geology Of The Cuesta Ridge Ophiolite Remnant Near San Luis Obispo, California: Evidence For The Tectonic Setting And Origin Of The Coast Range Ophiolite, Cameron A. Snow

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Cuesta Ridge ophiolite is one of the best-preserved remnants of mid-Jurassic ophiolite in California. Geologic mapping and petrologic studies show that it comprises (1) harzburgite mantle tectonite, (2) dunite-rich mantle transition zone (MTZ), (3) wehrlite and pyroxenite, (4) isotropic gabbro, (5) sheeted dike/sill complex, (6) volcanic rocks (7) late-stage dikes and flows, and (8) tuffaceous radiolarian chert.

The sheeted dike/sill complex is dominated by quartz diorite, with significant modal quartz and hornblende. The volcanic section is dominated by arc tholeiite and boninitic lavas. Boninites, with high MgO, Cr, and Ni comprise 40% of the volcanic rocks. Latestage dikes and …

Structural Analysis And A Kink Band Model For The Formation Of The Gemini Fault Zone, An Exhumed Left-Lateral Strike Slip Fault Zone In The Central Sierra Nevada, California, Matthew A. Pachell

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The structure and regional tectonic setting of an exhumed, 9.3-km long, left-lateral strike-slip fault zone eludicates processes of growth, linkage, and termination for strike-slip fault zones in granitic rocks. The Gemini fault zone is composed of three steeply dipping, southwest-striking, noncoplanar segments that nucleated and grew along preexisting joints. The fault zone has a maximum slip of 131 m and is an example of a segmented, hard-linked fault zone in which geometrical complexities of the faults and compositional variations of protolith and host rock resulted in nonuniform slip orientations, complex interactions at fault segments, and an asymmetric slip-distance profile. Regional …

Geochemistry And Petrogenesis Of The Bonanza King Mafic Intrusive Complex, Trinity Terrane Ophiolite, California, Keith R. Willse

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Bonanza King mafic intrusive complex (MIC) (>25 km^2₎ of the Trinity terrane ophiolite, northern California, consists of cogenetic plutonic and dike lithologies. Steep intrusive contacts exist between cumulate pyroxenite, isotropic gabbro, and peridotite country rock. Near vertical east-west trending, bimodal dikes intruded gabbro and are centered within the complex. Geochemical modeling indicates taht accumulation/fractionation of a gabbroic parental magma produced lithologic trends of cumulate pyroxenite and fractionated gabbro and dike lithologies. Similarities between all lithologies suggest cogenetic formation of all the elements of the Bonanza King MIC during the Late Silurian (431 +/- 3).

Parental magma …

The Orientation Of Quartz Grains In Unconsolidated Beach Sands Of San Luis Obispo County, California, David V. Pearson

Bachelors Theses and Reports, 1928 - 1970

The purpose of this investigation is to determine the orientation of quartz grains in unconsolidated beach sands, and if possible, to determine some of the physical factors involved in producing the orientation found.