Collection Description

The Department of Geological Sciences has a long-standing Senior Thesis research option for the B.S. Degree which involves a written thesis, and a public oral presentation done under the supervision of a faculty member. These independent research projects typically involve field work and laboratory analyses of samples, but can also include laboratory-based experimental projects, numerical modeling of geologic phenomena and literature reviews. Senior theses are kept in the permanent collection of the Malcolm A. Love Library on the SDSU campus.

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Geochemical analysis of the Alverson Formation volcanics in Painted Gorge, Coyote Mountains, Imperial County, California
The Alverson Formation consists of mid-Miocene, continental volcanic and sedimentary rocks exposed in various locations along the western edge of the Salton Trough from the Fish Creek Mountains in the north to the U.S-Mexico border in the south. This study focuses on exposures in Painted Gorge in the southeastern Coyote Mountains near Ocotillo, California where Ruisaard measured a well-exposed ~300 meter thick section of Alverson Formation volcanic rocks resting nonconformably on granitic and metamorphic crystalline basement and overlain unconformably by Pliocene Imperial Formation sedimentary rocks. Two distinct igneous events are represented in the Painted Gorge Alverson section: mid-Miocene olivine-phyric lava flows, followed by later dome-like plugs of andesite-dacite that make up the upper ~100 meters of the section. The dome deposits are easily distinguished from the main lava flows in the field. The result of this is a bimodal suite of igneous rocks, which is reflected clearly in the whole rock chemistry. The purpose of this study was to determine whole rock major and trace element concentrations for the Alverson Formation volcanic rocks in Painted Gorge, and discuss the implications of this data for the tectonic setting and regional context in which the volcanics were erupted. Plate reconstructions of the southern California margin indicate that the Alverson Formation volcanics are post-subduction and may record initial rifting and extension association with opening of the northern proto-Gulf of California and eventual establishment of the modern San Andreas Plate boundary. Samples were collected from the base to the top of the Painted Gorge section in November, 2014. X-ray fluorescence was utilized to determine the major and trace element content of the samples. The Alverson Formation volcanic rocks in Painted Gorge are calc-alkaline based on a standard SiO2 versus total alkali plot, similar to subduction-related volcanic rocks. The lower olivine phyric lava flows are basaltic andesite, while the domes are andesite, bordering on dacite. Trace element analysis however reveals much higher strontium concentrations for both groups of rocks compared to “typical” calc-alkaline magmas (~750-1000 ppm in the basaltic andesite and ~1500-2000 ppm in the dome deposits). Along with high strontium, the Yttrium content of the Painted Gorge rocks are lower than expected in typical continental arc magmas. These features categorize the Painted Gorge deposits as high magnesian andesites and adakites. This suggests the volcanics potentially originated as a result of slab melting of the underlying Farallon Plate., San Diego State University
Geochemical and petrological characteristics within the southeastern portion of the emigrant gap composite pluton, Northern Sierra Nevada, California
The Emigrant Gap composite pluton, northern Sierra Nevada, California is predominantly composed of a hornblende-biotite grandoiorite unit that grades into a two-pyroxene diorite through granodiorite unit along its margms. Field relationships indicate that a previously mapped unit of so called diorite, located in the southeastern portion of the pluton, is in fact a melanocratic granodiorite. Within the southeastern part of the Emigrant Gap composite pluton, the contact separating the two-pyroxene diorite through granodiorite unit from the hornblende-biotite granodiorite unit is gradational. The melanocratic granodiorite unit exhibits similar field relationships with the hornblende-biotite granodiorite unit. In addition, the mineralogy and melanocratic characteristic of the granodiorite unit closely resembles the granodiorite mapped as part of the two-pyroxene diorite through granodiorite unit. On silica variation diagrams, samples from the granodiorite unit plot in a transitional position between fields defined by specimens from the two-pyroxene through granodiorite and hornblende-biotite granodiorite units. Analyzed samples of the granodiorite unit are metaluminous, and may have been derived, along with the Emgirant Gap composite pluton as a whole, from a mantle or mixed sialic-mantle hybrid source., San Diego State University
Geochemical assessment of mixing advanced treated wastewater and groundwater in the Harmony Grove Basin, Southern California
The Harmony Grove basin aquifer is located in San Diego California. This location is of great interest by the Rincon del Diablo Municipal Water District for storage of advanced treated wastewater (ATW). After storage, pumping of groundwater is proposed for indirect potable reuse. The project consultant sampled and analyzed groundwater chemical concentrations from five wells in the project area (AECOM, 2010). From this, two representative wells of the region were chosen (wells B and C) and compared against a hypothetical ATW comprised of data from the Monterey Regional Water Pollution Control Agency (MRWPCA) and the North City Water Reclamation Plant (NCWRP). Monitoring data was analyzed with a geochemical program, PHREEQC, which is designed to perform a wide variety of low temperature aqueous geochemical calculations (Parkhurst, 1995). The focus of this study is on chemical ion speciation, mineral saturation index, redox and batch mixing. Potential changes in aquifer geochemistry from mixing with ATW are assessed by the modeling. The lack of accurate redox monitoring data was identified due to these parameters being analyzed in the laboratory. Further work should involve field measurement of redox and other parameters which can change after exposure to the atmosphere (pH, redox, dissolved oxygen, alkalinity)., San Diego State University
Geochemical studies of mafic enclaves within the alpine tonalite
Mafic enclaves within the Alpine tonalite have been observed for many years. A geochemical study was undertaken to compare different appearing enclaves found in the same outcrop and compare them to that of the host rock. The study area is approximately 30 kilometers east of San Diego, California. Enclave samples were selected based on differences in size, grain size, mafic percentage, and relative contrast to the surrounding host rock. Most of the enclaves have a bimodal distribution of mafic minerals. The mafic content varied from 28 to 30 percent. The Si02 content of the enclaves varied from 54.7 to 59.3 percent, and the Si02 content of the host rock is 61.3 percent. Some enclaves were rimmed with a mafic depleted margin in the surrounding host rock. The enclave chemistry compared with the host rock suggests that the enclaves were derived from a mafic relative of the host rock and vary by progressive interaction of that mafic rock with the magma which was the parent to the host rock., San Diego State University
Geochemical, geochronological, and petrological characteristics of the quartz monzonite unit of the emigrant gap composite pluton, northern Sierra Nevada, California
The Emigrant Gap composite pluton (EGCP), northern Sierra Nevada, California is subdivided into quartz monzonite, two-pyroxene, and hornblende granodiorite units. The latter two units make up the bulk of the pluton, and based on U-Pb zircon data are about 164.0 ± 1.5 Ma. Field relationships indicate that the quartz monzonite unit is the oldest phase of the EGCP. Using the Streckeisen - IGUS classification scheme, the mean of eighteen point counted samples is a quartz monzonite. Geochemical analysis indicates that the quartz monzonite unit is geochemically unlike the two younger units in terms of K20, Rb, and Sr values. In contrast, silica variation diagrams show little differences in other major and trace elements for the quartz monzonite and the younger two units. Analyzed samples of the quartz monzonite unit are metaluminus, and when plotted on magmatic setting discrimination diagrams they plot in the vocanic arc and vocanic arc + syn-collisional fields. These results suggest that the quartz monzonite unit is a member of the I-type plutonic suite. U-Pb zircon work indicates that one of three analyzed fractions is concordant at 168.0 ± 2.0 Ma. Thus, the quartz monzonite unit is the oldest dated Mesozoic intrusive body in the Sierra Nevada, east of the Melones fault zones at about the latitude of Lake Tahoe., San Diego State University
Geochemistry and depositional setting of the carboniferous peale formation haystack mountain area, Sierra Nevada, California
In 1994, R. W. Murray developed chemical criteria for identifying the depositional environment of chert. In brief, Murray's model predicts that Al and Ti should decrease in cherts deposited in successively more oceanward directions, while Fe and Mn should become more enriched. In addition, Ce depletion relative to Pr and La should be evident in sediment deposited in more distal and near-ridge environments. Thus, Murray argued that the geochemistry of cherts can be used to recognize continental margin, pelagic, and near-ridge depositional environments. To determine whether or not Murray's models are applicable to older cherts, I have applied his chemical criteria to data collected from samples of the Carboniferous Peale Formation from northwest of Haystack Mountain, Sierra Nevada, California. The Peale Formation has been divided into two members. Member 1 consists of thick-bedded iron-stained chert interstratified with thin laterally discontinuous seams of black to brown argillite. Member 2 is characterized by more abundant argillite and lesser amounts of chert. Application of Murray's model to data obtained during this study indicate that the Peale Formation was deposited either in a distal continental margin or transitional continental­margin/pelagic setting., San Diego State University
Geochemistry and lithostratigraphy of the carboniferous peale formation, haystack mountain area, Sierra Nevada, California
North west of Haystack Mountain, Sierra Nevada, California, the Carboniferous Peale Formation separates the Upper Devonian to Lower Mississippian Sierra Buttes Formation from the Lower to Middle Jurassic Sailor Canyon Formation. Described in this thesis are the geochemistry and lithostratigraphy of two newly recognized members of the Peale Formation. Both members are well exposed and mapped northwest of Haystack Mountain, but their extent beyond this area is not known at this time. Member 1 consists of thick-bedded iron-stained chert interstratified with thin laterally discontinuous seams of black to brown argillite. Member 2 is characterized by more abundant argillite and lesser amounts of chert. Member 2, because of its large argillaceous component, has previously been included in the lower portion of the overlying Sailor Canyon Formation. In order to specifically address the question of whether or not member 2 is part of the Peale or part of the Sailor Canyon Formation, four samples from member 1 (three cherts, 1 argillite), five samples from member 2 (four argillites, 1 chert), and four argillite samples from the Sailor Canyon Formation were collected and analyzed for major, trace, and REE. For comparison purposes, averages of geochemical data were calculated using the Aitchison Measure of Location (AML). Uncertainties in the AML were estimated by the bootstrap technique. The results of the geochemical and statistical work show that argillites within members 1 and 2 have similar ma3or, trace, and REE chemistry. Similarly, the chemistry of cherts within both members is nearly identical. In contrast, the chemistry of argillites in both members is distinctly different than the chemistry of argillites in the overlying Sailor Canyon Formation. Thus, geo chemic al data support field o bse rv a tions which allowed the Peale Formation to be subdivided into the two distinctive members, but are inconsistent with the alternative hypothesis that member 2 1s a part of the Sailor Canyon Formation., San Diego State University
Geochemistry and petrography of pegmatite dikes at Blair Valley, San Diego County, California
Blair Valley is located approximately 120 km (75 mi) east northeast of San Diego, and is in the eastern zone of Peninsular Ranges Batholith (PRB). The pegmatite dikes at this location cut across gneissic granitic rocks with a ziron U-Pb age of about 94 ma. Other pegmatite dikes in the PRB range between 94 ma to 100 ma. The dikes show a random distribution within the study area. The focus of this study is to determine the nature of the source rocks that were melted to create the pegmatite dikes at Blair Valley. The dikes consist of quartz, potassium feldspar, plagioclase, biotite, muscovite, garnet, myrmekite, and are mainly syenogranite. Trace minerals include chlorite, allanite, and zircon. Rare earth element (REE) analysis of fine-grained portions of the pegmatite dikes shows either a steep slope with light REE depletion or a horizontal pattern with strong negative Eu anomaly, and in comparison to the data of Parrish (M.S. 1990) and un­published data from Tule Mountain near Jacumba, suggests that two melts were involved. The source region appears to have been a meta­graywacke consisting mainly of feldspar, quartz, biotite and muscovite. The reaction muscovite + plag + Q ---> melt + sill + Kfs left a bte-fs-sill-Q residue and melt with a strong(-) Eu anomaly. A second reaction bte + sill + plag + Q ---> melt + garnet + Kfs used up the remaining feldspar to produce dikes and small bodies of granite with a garnet signature., San Diego State University
Geochemistry of basaltic inclusions, Sierra City Melange: evidence for pre-upper devonian oceanic crust in the Northern Sierra Nevada, California
The objective of this paper is to evaluate the eruptive setting of basaltic inclusions in the Sierra City melange, northern Sierra Nevada, California, through a detailed geochemical and petrographical study. The Sierra City melange is part of the pre-Upper Devonian Shoo Fly Complex which contains the oldest known oceanic rocks in the northern Sierra Nevada. The results show that the basalts are tholeiitic in composition and that they were probably erupted in a mid-ocean ridge, or marginal basin setting. These results suggest that the melange contains fragments of pre-Upper Devonian oceanic crust that must have existed along the western Cordilleran margin., San Diego State University
Geologic communication of earth dynamics using images and multiple languages: examples of processes in the central Asia region
The Aral Sea region, located in Kazakhstan and Uzbekistan, is an area of major global change. Once the fourth-largest lake in the world, the Aral Sea is presently one-fourth of the size it was just thirty years ago. The Aral Sea sits in a half-graben basin, a result of extension along a fault produced by the large-scale impact of India into the Asian continent. Aside from the tremendous environmental disaster, this area also poses some of the greatest public health problems in the world. Kara-Bogaz-Gol, a small sea in Turkmenistan that comes out of the Caspian Sea, is another area of global change. Structurally, the Kara-Bogaz-Gol sits within a large syncline, continually deforming as a result of the collision of the Arabian Plate into Iran and the formation of parallel fold belts like the Zagros Mountains. The land in the region is very flat, and the Caspian Sea is rising. This is a threat to the local infrastructure, and presents an environmental risk to the region as well. Satellite imagery provides a perspective view of these large-scale systems. These images also provide a temporal view, showing change through time, and change during time. Finally, they allow us to study the interaction between different dynamics, and to predict potential geologic and environmental hazards as well as public health threats. Although this is a study in geology and different earth system dynamics, it is really more of a study in communication. The images convey what is taking place in a region whose people know little about it. Presented in a digital format and with multiple languages, these images and text, and thus a story, can be transported globally and understood easily, hopefully affecting real people's lives., San Diego State University
Geologic investigation of the Kirby Hills Fault along the Sacramento River
New Chirp and Vibracore data collected from the Kirby Hills Fault Zone in the Sacramento River reveal extensive deformation associated with the fault. Deformation of the river floor, in particular, is indicative of recent activity on the fault. The Kirby Hills Fault is a reactivated right lateral strike-slip fault that is synthetic to the San Andreas and Hayward faults nearby. This fault cuts through the Sacramento- San Joaquin Delta (Delta), which is an important part of California’s freshwater system, a unique habitat that supports a variety of plant and animal species and is also home to many human communities. Since this fault presents a great risk to the people and species inhabiting the area, we aim to constrain the rupture history of the fault. Sediment cores collected along the fault zone provide age constraints on deformation through radiocarbon dating and geologic correlation. The work presented here adds to the overall project by correlating geologic units in the sediment cores based on lithologic characteristics and clay geochemistry. These results will ultimately give us a better understanding of the deformational history of the Kirby Hills Fault, which in turn will support more accurate seismic hazards assessments for the region and better inform Delta stakeholders., San Diego State University
Geological analysis and remote sensing of the Baghdad, Iraq, region for assisting military operations and humanitarian concerns
The geology of Iraq can be divided into three major zones because of its location within a subduction region. The western portion of Iraq is subducting beneath the eastern portion of the country, forming a portion of the major Zagros Mountain belt along this east-dipping subduction zone. The Precambrian Arabian plate composes the western portion of the country and is composed of fairly rigid rocks of the stable Arabian shield. The easternmost portion of the country is composed of small mountain ranges that are part of the Zagros orogenic zone, which is the upper plate above the subducting Arabian plate. The major valley between the upper and lower plates of the subduction complex is filled with sediments deposited by the major Tigris and Euphrates Rivers, which flow along the length of the subduction system and cover most of the faults of the system. These meandering rivers are filling a wedge-shaped basin on which the city of Baghdad sits. Baghdad is built on these superficial deposits and is just west of the major subduction seismic zone, so has been built with some regard for seismic shaking. In a military and humanitarian aid setting, the geology of Iraq and the imagery of the country can help military and humanitarian assistance leaders better understand the ground conditions, susceptibility to shaking, and potential for underground facilities. The Arabian shield areas are composed of strong and seismically rigid rocks that are also likely to support heavy vehicle traffic, but are not likely to contain major underground facilities. Seismic shaking in this region from impacts or earthquakes would be quite different than for similar impacts in the Baghdad sedimentary fill. In contrast to the Arabian shield region, digging subsurface facilities in the region of the sedimentary fill of sand, gravel, and mud associated with the Tigris and Euphrates River region would be very straightforward to do. The Zagros Mountain belt contrasts with both the Arabian shield and sedimentary fill in being composed of folded sedimentary rocks, much like the desert region around Las Vegas, Nevada and the anticlines and synclines of the Appalachian Mountains. Determining the geologic setting for water for refugee camps, sand areas amenable to laying mines, and topography or geology used to hide military facilities are all aided by geologic analysis and remote sensing. Landsat 7 scenes of the Baghdad area and the major reservoirs of the country offer particularly insightful views that will be useful to anyone involved in military or UN search for Weapons of Mass Destruction (WMD). Military and no-hit humanitarian targets can be better located and their site conditions understood by studying the geology of the region and providing this information to both decision makers and humanitarian efforts to help the people of this region., San Diego State University