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.

Authors hold full copyright ownership of their original works. Please contact the repository manager at digital@sdsu.edu for any further questions.

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Analysis of fluvial geomorphology on Santa Rosa Island, Northern Channel Islands, California
The Northern Channel Islands offshore from Santa Barbara, CA hold several archaeological sites, with many dating to older than 11ka. The location and contents of the sites indicates that people living on the islands during this time used coastal and fluvial resources. However, due to eustatic sea-level change associated with advance and retreat of ice sheets, the coastline at the time of this early occupation would have been much different. In fact, during the Last Glacial Maximum (LGM) (~20ka), the four modern islands were joined into one landmass known as Santarosae, with the paleocoastline located ~106 m below the modern coast. Therefore, it is likely that some of the oldest archaeological sites in the area are now submerged. To help locate these submerged sites, high-resolution geophysical data were collected to map the location of paleochannels across the now submerged Channel Islands platform. These data imaged different paleochannel morphology offshore from several modern drainages, with a notable difference between north and south flowing drainages. The same behavior can be observed onshore. We hypothesize that the observed differences in paleochannel morphology could be explained by differences in modern drainage basin characteristics. Santa Rosa Island is bisected by an ~E-W trending oblique-slip fault that roughly divides the island drainages into north or south flowing. As a first step to address this hypothesis, modern drainages were characterized using ArcGIS software based on their length, slope, sinuosity, and basin area. The data were then analyzed and compared to identify differences between north and south flowing rivers. In addition, statistical analyses of topographic patterns north and south of Santa Rosa Island Fault were performed using elevation distributions, skewness, and kurtosis. Results show that north of the fault the topography is dominated by a relatively flat marine terrace, while the southern drainages are located in much steeper topography. Drainages flowing north exhibit alower gradient, are longer, and have U-shaped morphology. Drainages flowing south are straighter, steeper, and characterized by V-shaped morphology. It is interpreted that the U-shaped channels draining north owe their morphology largely due to fluctuating sealevel where alluvium was deposited on marine terraces during sea level rise and incised into during more recent time (~500-1,000 years ago). Southward drainages (V-shaped) are more likely to have experienced continued erosion during sea-level rise, maintaining higher relief patterns and enabling continued slope failure to widen valleys and narrow channels through slope retreat. These results could be used in future archaeological models to predict submerged paleochannel morphology. The morphology of these channels could then be used to characterize the likelihood of finding associated archaeological sites (i.e., narrow steep valleys less likely to preserve sites compared to longer and wider valleys with floodplains in the north)., San Diego State University
Analysis of major cations and anions of cold springs in the Cuyamaca Rancho State Park
Cuyamaca Rancho State Park is host to a variety of springs within the San Diego Watershed. Located just 40 miles outside of San Diego nestled in the Lagunas Mountain Range, these spring provide us with an inside view on the hydrogeological processes that take place. The rocks in the area date back to Pre-Tertiary in age, and consist primarily of a crystalline complex. Residing at and around 5000 feet in elevation, this thesis focused on 6 springs, a snowmelt sample, and one culvert that channeled primarily surface water. Six of the seven locations visited in this thesis were previously sampled from 1975-1976 by Richard T. Higly, an SDSU Undergraduate student. He reported the rainfall, conductivity, temperature and discharge; additional lab data was provided for iron, silica, chloride, fluoride, and carbon dioxide levels. For the purpose of this thesis, the following sites were sampled: springs 102, 103, 204, 206, Culvert 101, Deer Spring and Azalea Spring. The springs are sorted into one of two categories: hard-rock springs, or soil zone springs. With the aid of the USGS, the samples were analyzed for all major cations and anions. The results were plotted on Piper diagrams and Stiff diagrams, and compared against each other as well as outside water samples. The soil zone springs contained similar results, while the contained aquifer leading to Azalea Spring contained a much higher amount of all of the major cations and anions. The exploration of these results may help to gain a better understanding of progression of impact upon the area., San Diego State University
Analysis of variations in groundwater elevations between fractured rock and alluvial aquifers: San Diego County
This study involved analyzing variations in groundwater elevation between fractured rock and alluvial aquifers following an abnormally wet precipitation year. I measured the depth to water at over 130 groundwater wells within San Diego County, selected the appropriate study area, then analyzed and modeled historical data at the chosen project sites. The study sites chosen were Warner Valley groundwater basin and a small residential area near Ramona, CA. For the purpose of this study I chose the 2004-2005 precipitation year. During this rain year, groundwater levels in the fractured rock rose an average of 58.7 feet, while groundwater levels rose 11.38 feet on average in the wells located in alluvium. Overall, the hydraulic head in wells located in fractured rock rose 5.17 times more than wells completed in alluvium. In producing the groundwater contour maps for each study site, I modelled and interpreted variations in groundwater flow direction and hydraulic gradient. The average hydraulic gradient changed from 0.0113 in 2004 to 0.0114 in 2005 within Warner Valley, a 1.39% increase. Ramona wells resulted in a change from 0.0368 in 2004 to 0.0246 in 2005 a 33.3% decrease in hydraulic gradient. Both study sites showed minimal change in average flow direction. Changes in hydraulic head between wells in the alluvium were more uniform than in the fractured rock. I produced a 3D model of the piezometric surface of the fractured rock aquifer that revealed areas of concentrated changes in hydraulic head from 2004-2005. I interpret this as an area of higher interconnected fractures, leading to an anomalous increase in groundwater elevations at that specific locale. Thus, studying the changes in groundwater elevations following heavy rain years may provide insight into the fracture patterns of the underlying geology, and potentially provide better prediction of depth to groundwater for fractured rock and alluvial aquifers in the future., San Diego State University
Analyzing mass change in the Wepawaug Schist, Connecticut, and the power of the student's T test: an assessment of the accuracy and reliability of the matlab program SACD
Analysis of mass and volume changes associated with prograde regional metamorphism is a complex, tedious, and time intensive process. In an attempt to make such a task less time intensive G. H. Girty wrote a Matlab 5.0, menu-driven program named Statistical Analysis of Compositional Data (SACD) which removes much of the tedium from such analyses. However, this program is a i version, and prior to this study had not been tested. Any new area of research focused on the statistics of elemental mass change and/or the power of the Student's t test in resolving mass change would be appropriate areas to test the usefulness of SACD. One of the most modern investigations of mass change in pelitic mudstones brought on by Barrovian metamorphism is the recently completed study of the Wepawaug Schist of Connecticut by Ague (1994), who utilized the Student's t test to evaluate whether or not elemental mass in the pelitic mudstones of the Wepawaug Schist were changed during prograde regional metamorphism. Though the study by Ague (1994) has received much acclaim, the statistical power of the Student's t test to recognize elemental mass differences as small as those calculated by Ague (1994) had not been attempted prior to this study. The results of this study indicate that SACD produces reliable data in a user-friendly format in a considerably shorter time period than does such an analysis using Excel and Mathematica. In addition, data indicate that in going from the biotite-chlorite zone to the garnet zone that Ca and Sr were removed from the Wepawaug Schist resulting in a change in rock mass of -10 :t: 4 grams/ 100 grams. In going from the garnet to the staurolite zone, Si and Na were lost while K was added, resulting in a total change in rock mass of -8 ± 5 grams/ 100 grams. In going from the staurolite to the kyanite zone, Ba appears to have been lost but there is no statistically detectable change in the total rock mass. These conclusions are supported not only by the results of the Student's t test but also by power values that are greater than 80%. However, power for all other elements analyzed by Ague (1994) falls below 80%, and, as a result, there is little statistical data that warrant acceptance of the null hypothesis that no change in mass has occurred for these nuclides. Thus, a consideration of power leads to some refinement of the general conclusions reached in the benchmark work by Ague (1994)., San Diego State University
Are chemical changes observed in La Posta profile #3 statistically significant
Lying within an arid climatic belt La Posta Soil Profile #3 consists of from bottom to top (1) an R-horizon composed of hypidiomorphic granular granodiorite (Q33P60K6,), (2) a 5.08-cm-thick C-horizon composed of partially altered granodioritic material (Q33F60K7,), and (1) a 2032-cm-thick dark browm plant-supporting A-horizon (Q41P52K7). Previous work has shown that the C and A horizons are depleted in Ca, Na, Sr, and Ba relative to the unweathered R-horizon. This result has been interpreted to be the result of dissolution and removal of plagioclase during the development of the C and A horizons. Using a 10-step statistical protocol I evaluated the statistical significance of the above chemical changes. The results of my work suggest that between the R and C horizons Si, Ca, K, Na, Ba, Zn, Rb, and Sr show a statistically significant loss in elemental mass while Fe shows a gain at the 95% confidence level. These results translate into an overall loss in total mass of -7.6%+/-5% per 100 grams of rock. Between the R and A horizons Si, Ca, Mg, Na, P, Ba, Zr, Ga, Zn, and Sr show a statistically significant loss in elemental mass while Mn and Y show a gain at the 95% confidence level. These results translate into an overall loss in total mass of -10%+/-6% per 100 grams of rock. Thus, the results of my work support previous studies that show that even in an arid climate there is evidently sufficient moisture to produce significant degradation and removal of plagioclase during pedogenesis., San Diego State University
Are littoral cells from central California beaches closed systems? Insight from detrital heavy mineral distributions at Andrew Molera and El Capitan State Beaches
The California coast is divided into a series of geographical compartments called littoral cells, in which longshore current sand transport is predominantly north to south. It is thought that these littoral cells, being isolated by headlands and terminated at submarine canyons, have little to no transport of sand between them. However, there are still uncertainties regarding possible ‘leakage’ between cells. Most California beaches are dominated by monotonous quartz-feldspar rich sand, but on the central California coast, the Big Sur River delivers a distinctive garnet-magnetite-ilmenite rich sand into the system directly at Andrew Molera State Beach. This heavy mineral-rich sand is derived from Sur Series metamorphic rocks that are deep crustal exposures of the Cretaceous Salinian block batholith. This sand is presumably diverted offshore at the Partington submarine canyon at the south end of the Point Sur littoral cell. However, an isolated patch of distinctive garnet rich sand collected at El Capitan State Beach on April 8th 2017 from the uppermost part of the beach following a moderate amplitude spring high tide bears a strong resemblance to the Sur Series beach sand suggesting that this sand was transported from the Big Sur River ~300 kilometers to the north. This implies that the Big Sur sand bypassed Partington canyon and traversed the Morro Bay littoral cell to the south in order to arrive at El Capitan State Beach within the Santa Barbara littoral cell. The garnet-rich heavy mineral sand at El Capitan would not be expected to be derived from local marine sedimentary sections or Franciscan Assemblage rocks farther north. Samples collected from Andrew Molera and El Capitan State Beaches were separated into magnetite-ilmenite-garnet fractions using hand magnets and a Franz magnetic separator. The proportion of magnetite to ilmenite is nearly identical between the two (~1:2) but El Capitan has a higher proportion of garnet. The grain size of both sands were determined and document a unimodal well sorted medium to fine sand with a mean grain size of ~280 microns for both samples, although the El Capitan sample is slightly coarser-grained due to a component of feldspar we were unable to perfectly separate from the sample. Under the binocular microscope, El Capitan garnets are distinctly polished and rounded compared to Andrew Molera garnet which is more euhedral with well-developed crystal faces consistent with long-shore transport of the El Capitan garnet. Electron microprobe mineral analysis however demonstrates conclusively that at least a part of the El Capitan beach sand must come from another source. Gaviota Creek a short distance up the coast in back has been documented as a source of garnet delivered to the beach along this section of the coast. More work is required to determine whether or not the component of garnet at El Capitan that matches Andrew Molera is in fact Sur Series garnet from the same source., San Diego State University
Assessing element mobility/immobility patterns in a high level contact metamorphic aureole: Part I. major elements
In order to assess whether or not major elements in a group of Paleozoic argillites were mobilized and redistributed during the development of the contact metamorphic aureole associated with the Middle Jurassic emplacement of the Emigrant Gap composite pluton, 41 total samples were collected and analyzed for their major element chemistry. Ten of the 41 samples were collected from outside the contact metamorphic aureole, whereas 31 samples were collected from pelitic schists and phyllites within the aureole. The results of statistical tests, suggest that (1) the variances of data collected from outside and inside the aureole are similar, and (2) that the means of most major elements are not statistically different in going from outside to inside the aureole. These observations are highlighted by the /-factor analysis technique of Alex Woronow and Karen Love which shows that the difference in means for most major elements are not statistically different from zero. Thus, the results of this study support the idea that metamorphism associated with the emplacement of plutons high in the crust, is largely a static isochemical process., San Diego State University
Assessing element mobility/immobility patterns in a high level contact metamorphic aureole: Part III. Rare earth elements
Eleven samples of argillite were collected from outside the aureole of the Emigrant Gap composite pluton, whereas 11 samples were collected from within the aureole. All 22 samples were analyzed for their REE concentrations. In order to avoid problems associated with the constant-sum constraint REE data were normalized to Ti (ppm) values on a sample-by-sample basis. The log to values of the resulting ratios were then calculated. F-tests were performed to assess the validity of equal or nonequal variances of log-transformed data for samples collected from outside and inside the aureole. The results of these tests consistently indicate that the variances of data from outside are not statistically unlike the variances of data from inside the aureole. Thus, student-t tests were conducted under the assumption of equal variances. The results of student-t tests indicate that the differences m means of log-transformed data on an element-by-element basis are not statistically different than zero. This result is significant because it suggests that the REE were immobile during the development of the contact metamorphic aureole associated with the Emigrant Gap composite pluton. Such a conclusion thus lends support to the commonly held, but often not well documented, belief that the REE are unaffected by pressures and temperatures common to the upper crust., San Diego State University
Assessing element mobility/immobility patterns in a high level contact metamorphic aureole: The residual model
San Diego State University
Assessing elemental mass changes across the northern imbricate of the Copper Basin Fault, SE California
The northern imbricate of the Copper Basin reverse fault is located west of Little Picacho Wash. At this site, the Quechan Volcanics occur in both the hanging and foot wall blocks, and the fault strikes EW and dips 52° S. Five samples from the fault core, 5 samples from the inner damage zone, and 4 samples from the least altered outer damage zone were collected from the hanging wall block and were analyzed for major element chemistry. Utilizing statistical tests provided in the software program, Assessing Element Immobility, revealed that Si, Fe, Al, and Mg are good candidates for an immobile reference frame. Using Si and Fe as the reference frame indicated that during development of the inner damage zone as much as 11– 15% of the P mass was lost. Though similar losses in phosphorous mass are indicated by an Al and Mg reference frame results are not statistically significant. In contrast to the inner damage zone, statistically significant increases of ~208% – ~256% Ca mass, ~143% – ~182% of LOI mass, and ~17% – ~35% of bulk mass are indicated by all 4 reference frame elements for the fault core. In addition, the reference frame Fe, Al, and Mg indicates an increase of ~13– 31% Ti mass. Even though a Reference frame of Fe and Al indicated that~13– ~18% of the mass of P was lost, a reference frame of Si and Mg indicates that such losses within the fault core are not statistically significant. In short, given that calcite is a prominent secondary mineral in the fault core, the above data indicate that the core was likely invaded by fluids supersaturated with Ca and CO2. In addition, to account for the increase in LOI mass, such fluids must have reacted with the comminuted silicate mineral framework to produce smectite + illite/smectite, the clay mineral assemblage identified by my colleague N. Seitz. Of some note, though Ti is commonly regarded as an immobile element, data from this study suggests the possibility of at least limited mobility of this element. The continued loss of P mass is nominal and likely the result of minor leaching of apatite., San Diego State University
Assessing the Rose Canyon fault zone through the Little Italy and Old Town areas of San Diego, California: Geotechnical data synthesis
With a population of ~1.3 million, the City of San Diego is the third largest city in California and it is traversed by the Holocene‐active Rose Canyon Fault Zone (RCFZ). The RCFZ is a strike‐slip fault with a slip rate of 1‐2 mm/yr and the potential to produce a M6.9 earthquake. This project focuses on the strands of the RCFZ that traverse from Old Town through the downtown San Diego area. The seismic hazard of the RCFZ has a direct impact on development in and around the city via the Alquist‐Priolo Earthquake Fault Zoning Act, which regulates locations of structures for human occupancy based on seismic assessments. To study the fault zone, geotechnical reports were gathered and examined. Projects were first identified, then reports were reviewed for usefulness. The next phase georeferenced data into an ESRI ArcMap project, which allows users to query data. Finally, the data were interpreted from a geologic perspective to give an understanding of the deformation and stratigraphy in the area. This work did not yield direct evidence of the fault through Little Italy nor through the Old Town area of San Diego. Nevertheless, the results did show that the stratigraphy could be correlated within short distances in the study area, which may yield evidence of faulting with future work., San Diego State University
Assessing the kinematic, chemical, and petrological development of protomylonite within the scove canyon segment, peninsular ranges, Southern California
The Scove Canyon segment, a ductile shear zone within the Peninsular Ranges, California, was produced during D2 deformation about 105-94 Ma. In order to understand the petrological, chemical, and structural development of the Scove Canyon segment, a small area of the shear zone underlain entirely by the -118 Ma Pine Valley granodiorite was mapped and sampled for thin section, chemical, and density analysis. Within the study area protomylonite, exhibiting a composite planar fabric, is mineralogically like Pine Valley granodiorite outside the Scove Canyon segment. When the composite planar fabric is viewed looking NW and perpendicular to XZ, S2 surfaces dip -700NE and are deflected in a dextral sense by -80-85° NE-dipping C2 surfaces. A well developed stretching lineation plunges steeply down the dip of S2. Though these relationships suggest an east-side-down normal-sense of movement, post­kinematic, Late Cretaceous to Tertiary anticlockwise rotations greater than -5-1 oo have been documented for the Peninsular Ranges, and, as a result, the Scove Canyon segment during the Late Cretaceous may have formed as a result of west-over-east reverse-sense movements. Microscopically, S2 surfaces are defined by ribboned to lensoid domains of quartz, alternating with similar shaped domains composed of K-feldspar+plagioclase± quartz± biotite. Bulbous grain boundaries suggest that grain boundary migration recrystallization was an important process during development of the Scove Canyon segment. In addition, new grains of quartz, plagioclase, and potassium feldspar indicate that temperatures were sufficiently high that dislocation climb was an effective process. Thus, temperatures were probably in excess of 5QOOC, whereas, strain rates were probably relatively low. The inferred high temperatures and low strain rates under which protomylonite of the Scove Canyon segment developed are conditions that commonly lead to significant mass and volume changes during mylonitization. Thus, the question of whether or not mass and/or volume changes occurred during mylonitization within the Scove Canyon segment was addressed. Six samples of the Pine Valley granodiorite and seven samples of protomylonite within the Scove Canyon segment were analyzed for major, trace, and rare earth elements. Mass balance arguments indicate that if no change in mass of some element i occurs during mylonitization, then c􀀁 = (M° / Mm)C:, where c􀀃 is the concentration of element i in protomylonite of the Scove Canyon segment, M0 is the mass of the Pine Valley granodiorite prior to mylonitization, Mm is the mass of Pine Valley granodiorite converted to protomylonite, and C;° is the concentration of element i in the Pine Valley granodiorite outside the Scove Canyon segment. In a plot of ct versus ct the above equation defines a line emanating from the origin with a slope equal to M0 / Mm. L. P. Baumgartner and S. N. Olsen developed a computerized x-y weighted least squares analysis routine that solves for M0 I Mm, and provides an estimate of the la uncertainty in this value. In addition, their program includes a subroutine, termed the overlapping cone technique, for evaluating which elements were probably immobile during mylonitization. The overlapping cone technique indicated that 38 out of 43 elements analyzed during this study were probably immobile. These 38 elements follow the relationship c􀀁 = 0.993(±0.0lS)c;'. This result indicates that 0 mM / is not statistically distinguishable from 1 at the lcr level, and therefore implies that the conversion of granodiorite to protomylonite was not accompanied by a mass change. However, differences in the elemental masses of Ba, Sr, Eu, Cu, and Ni were indicated by the least squares analysis, and, though not well understood, may be the result of the heterogeneous distribution of these elements prior to mylonitization. Finally, estimates of volume strain showed that mylonitization was not accompanied by a statistically significant volume change. Thus, the Scove Canyon segment is interpreted to be an example of an isovolume shear zone which probably evolved within a relatively dry system through only minor, if any, changes in elemental mass., San Diego State University

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