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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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Three-dimensional evidence for biotite to vermiculite conversion controlling spheroidal weathering at Santa Margarita Ecological Reserve, Southern California, U.S.A.
In the Santa Margarita Ecological Reserve (SMER), southern California, U.S.A., spheroidally weathered corestones are common components within the regolith. At SMER, we undertook a study aimed at documenting the three-dimensional element redistribution patterns around a single spheroidally weathering corestone. In saprock surrounding the spheroidally weathered corestone, biotite, the most severely weathered mineral, commonly is split parallel to {001}, and seams of Fe and Mn oxides or oxyhydroxides parallel this cleavage direction. Additionally, pleochroism is anomalous. XRD data indicate that throughout the section of regolith containing the spheroidally weathered corestone, biotite has been converted mostly to vermiculite. Utilizing Ti as an immobile element, calculations show that the mass of K, relative to the corestone, is depleted. In contrast, only minor and irregular losses of Si, Al, Ca, and Na mass are evident, while no redistribution of P, Fe, Mn, and Mg mass occurred. The above observations are consistent with the idea that the oxidation of Fe produces a charge imbalance within the biotite structure, and as a result interlayer K is replaced with hydrated cationic complexes, and (001) d expands from 10 Å to ~14 Å. Complete transformation of a biotite grain to vermiculite would thus involve an ~40% volumetric expansion. Given that biotite makes up ~9% of saprock samples, average volumetric strains derived from the transformation of biotite to vermiculite would have been 40 * 0.09 = 3.6%. Such strains exceeded the breaking strength of the host rock, and are the main causes of spheroidal weathering in the studied outcrop., San Diego State University
Timeline review of Cenozoic seabirds
Seabirds have existed since at least the Late Cretaceous Period (99‐65 million years ago). While it might be assumed that they are one descriptive group, they are rather many groups of seabirds that have developed sea adaptations separately from each other. Seabirds are well represented in the fossil record and the highest diversity of seabirds was apparently during the Late Miocene and Pliocene. Warheit (1991) provides an overview of Tertiary evolution of seabirds in the North Pacific and the factors that influence their evolution. Methods: The methods of this research involved library research using scholarly books and peer reviewed articles in professional journals. The data was assembled into an excel sheet formatted using the time scale from Warheit (1991). Data was based on which species was introduced and the area it was found. The information was divided upon using the time markers from Warheit’s paper and adding the Holocene and Anthropocene. After the data was assembled, interpretation of the data was undertaken. Results: From the results it can be seen that aquatic birds did not prosper long in the Miocene. There’s was not that much behavior for them to be found in Isla Cedros LS, Mexico when it comes to the seabird species. Marine Birds appear to be more diverse in California, Washington, Oregon, Columbia, and Britain in the Pleistocene‐Pliocene. The explosion of bird diversity in both areas slightly appears in the late Miocene and upwards on the time scale. Discussion: Based on the compiled data tables, it appears that the species Plopteridae and Pelganothoris existed from the Eocene to the Miocene, making it appear at this time these species were doing very well in these time periods. The data reveals that Phalaocroax was a very successful species from the beginning of the Miocene to today. While marine birds have survived to this day, this data shows how the birds have been affected throughout time., San Diego State University
Trace metal analysis of sediments from Lake Tahoe, California-Nevada
Concentration of Al, Cu, Fe, Mo, Ni, and Zn were determined using atomic absorption spectrometry in a sediment core taken from Lake Tahoe, California-Nevada, in 1991. The pattern of their concentration with depth may reveal information about anthropogenic inputs diagenetic factors and changes in sources of sediments. Pb-210 dating of the sediments by D. Edgington revealed that there were three changes in sedimentation rate. The sedimentation rate was 0.24 cm/yr in the lower pan of the core from 30 cm to about 10-11cm (~1840 to I 920). The higher rate can be attributed to higher erosion rates related to the deforestation of the virgin timber around the lake as a consequence of nearby mining activity. The sedimentation rate decreased to 0.10 cm/yr between l920 and 1966. During this time, the local mining had stopped and forest had been allowed to grow and human activities in the lake basin were marginal. The third change occurred after l966 where the sedimentation rate increased to 0.24 cm/yr. This change occurred because of higher erosion due to construction activities around the basin higher productivity in the lake due to nutrient inputs and diagenetic remobilization. Biogenic activities have been a major concern in this area. By measuring the loss-on-­ignition (LOI), the amount of organics in the sediments may be approximated with depth. The LOI suggests that the organic content has increased in recent times as a consequence of the higher nutrient inputs. The insoluble fraction (which was not dissolved with HN03 and HCl) is fairly constant up to a depth of about 6 cm, which corresponds with the more recent change in sedimentation rate. Above this, the insoluble fraction decreases showing dilution by organic matter and other phases. The increase in sedimentation rate due to deforestation did not change the type of material sedimented, only the amount brought in. The concentration of AJ with depth in the sedimentary column is essentially constant. Thus, changes in sedimentation rates did not affect the Al content in this core. Since Al is associated with aluminosilicates, all metal concentrations were compared to Al to remove the effects of various dilutants. The Cu and V analyzes are similar to Al in that they showed no patterns. Some other metals show a distinctive pollution-type profile with an increase in concentration in more recent sediments. Pb and Zn both show the steady increase, however, Pb reaches a maximum at a deeper depth than Zn. Any anthropogenic input for the remainder of the metals studied is overwhelmed by diagenic processes. F and Mn are deposited as solid Fe/Mn oxide . As the organic matter decomposes, oxygen is removed resulting in the reduction and consequent dissolution of Mn at about 3 cm then Fe at 4-5 cm depth. Upon further burial, the Fe++ and Mn++ in the pore waters diffuses upward, gets oxidized and reprecipitates as the respective oxide just above each one's redox boundary yielding large peaks in their sediment concentrations. Cr, Mo and Ni were most probably carried to the sediments with these phases, and were redistributed during diagenesis resulting in diagenetic-type concentration profiles with depth., San Diego State University
Trace mineral variations across the La Posta Plutton, Southern California
The Peninsular Ranges Batholith (PRB) contains a series of "La Posta" type plutons that occur only in the eastern zone of the PRB. These plutons are concentrically zoned, single intrusive bodies with gradational internal contacts. The La Posta pluton is the largest of this type and is estimated to encompass an area of approximately 1400 square kilometers. Its mapped rock units vary inward from hornblende-biotite tonalite to large­biotite granodiorite, small-biotite granodiorite, to muscovite-biotite granodiorite in the core zone. A large roof pendant splits the pluton into lithologically, geochemically, and structurally similar eastern and western halves with zircon U-Pb ages of 94 (+/- 1) Ma. The purpose of this study is to use trace mineral variations from a transect across the La Pesta pluton to determine: l. If the eastern and western portions of the pluton are comagmatic and thus consistent in their trace mineralogy, 2. If different structural levels could be exposed on either side of the roof pendant, and 3. If the core facies shows any mineralogical evidence of being a separate but related intrusion The portion of the La Pesta pluton examined in this project lies along 1-8 between La Pesta, and Ocotillo, California. Trace mineralogy is consistent across the eastern and western halves of the pluton. Minerals found include: primary sphene (magnetic), secondary sphene (non-magnetic), allanite, epidote, clinizoisite, carbonate-fluorapatite, ferroaxinite, monazite and zircon These select minerals occur throughout the entire pluton, but may be more prominent in certain zones. Primary sphene (magnetic), zircon, and carbonate-fluorapatite occur most abundantly in the margins with lower concentrations toward the core. The presence of epidote primarily on the western half of the La Pasta pluton suggests that different structural levels are exposed on either side of the roof pendant. In addition, the color of primary sphene varies from brown on the west to yellowish-green on the east and may also support differing structural levels. The core facies is commonly identified by the Muscovite-Biotite Facies, but appears to include the eastern Small-Biotite Facies as well. This core region appears to produced by be a separate, but related magmatic event. Trace mineralogy indicates that secondary sphene (non-magnetic), monazite and clinozoisite occur only or primarily in the core region. Ferroaxinite, primary sphene (magnetic), and allanite which typically occur throughout the pluton are absent in the core., San Diego State University
Upper Cretaceous foraminiferida from Valle El Morro, Baja California, Mexico
An Cpper Cretaceous bed of claystone exposed along the southern bank of Valle El Morro, Baja California, Mexico yielded a large and diversified foraminiferal assemblage of late Campanian age. The 46 species and sub-species consist of arenaceous and perforate calcareous types in approximately equal number; benthonic forms predominate among the calcareous foraminifers. It is inferred that the faunule lived in a muddy benthic environment beneath warm, neretic waters of the outer sublittoral zone (100 to 200 meters in depth)., San Diego State University
Use of a gravity survey to characterize alluvium bedrock contact in Potrero Valley Groundwater Basin, San Diego, California
Geophysical exploration methods constrained by borehole data can provide detailed information about subsurface geometries. I conducted a gravity survey in a section of the Potrero Valley Groundwater Basin. The gathered data, which shows changes and trends in gravity at points on the Earth’s surface, was used to determine lateral density changes in the basin’s subsurface. These gravity measurements were collected along two lines using a LaCoste & Romberg Model D Gravimeter, with a station spacing of 10 meters. I processed the gravity data according standard gravity survey corrections. The corrections applied included an Earth tide correction, instrument drift correction, latitude correction, Free Air correction, and Bouguer Slab correction, and produced the relative Simple Bouguer Anomaly was produced for each survey line. Using the Bouguer Anomaly, two local well logs, and nearby bedrock outcrops, I estimated the contact geometry between the granite bedrock and overlying water bearing alluvium using 2D foreword modeling software (GRAVMAG). The two-layer model that I produced used a density of 2.3 g/cm3 for the alluvium upper layer and 2.65 g/cm3 for the lower granite bedrock. The model produced a detailed representation of the alluvium bedrock geometry. By extending and increasing the number of gravity survey lines, basins and their related aquifers can be modeled to estimate aquifer size and storage. With additional data such as well logs, groundwater basin characteristics can effectively be determined using gravity surveys., San Diego State University
Use of hyperspectral data in geology
Hyperspectral data has become an important tool in addressing numerous geological applications in the past few years. The increase in availability of the high resolution data, has resulted in more geologic research projects involving the use of this remote sensing imagery. The complexity of the data obtained from this high spectrometer has created a dramatic need for new software to manipulate the imagery. Groups such as the USGS Spectroscopy Lab have developed a sophisticated library of spectral signatures, algorithms to apply these signatures, and software for the analysis of this data type. This report uses the Cuprite Mining District to compare data analysis procedures that are available at this time. The location of Cuprite, Nevada has been used in many remote sensing research projects. The identifiable zones of hydrothermal alteration, distinctive mineralogy, and lack of vegetation provide and excellent working environment. There are a few groups that have used this location in the development of hyperspectral imaging techniques, verifying the results with field mapping, field and laboratory spectrometers, and X-ray analysis of hand samples. As large volumes of hyperspectral data will become available from several new satellites this summer, many researchers are trying to understand how to most effectively use these narrow-band spectral data. In contrast to the current major imaging product, Landsat 5 Thematic Mapper data that has 7 bands (broad band sensor), the hyperspectral satellite will image 224 channels or more. Although the handling of this vast amount of information may seem a hindrance, projects are reporting success of applications in research and commercial endeavors., San Diego State University
Using a ripple tank to study wave phenomena
All energy travels as waves. Wave energy behavior is often well exhibited in water. A device was constructed to produce capillary water waves and variable conditions affecting them. The observation of water wave behavior provides for an understanding of all wave energy., San Diego State University
Using ground penetrating radar to determine stratigraphic architecture of the Cooloola Sand Mass, Southeastern, Queensland, Australia 
The Cooloola Sand Mass (CSM) is a major coastal dunefield situated within the Great Sandy Region of southeast Queensland, Australia and forms part of the terminus of the longest downdrift system of siliceous clastic sediments on the planet. The CSM is orientated roughly north-south. It extends 65 km and varies in width from less than 1 km to greater than 25 km. It is composed almost entirely of unconsolidated aeolian sands with parabolic dunes, blowouts, and degraded dune systems. The highest dunes reach 240 m above sea level and the entire sand sheet thickness is thought to be at least 500 m, if not 800 m thick. Other researchers have focused on understanding the soil stratigraphy of the thick, > 30 m podzols and timing of dune emplacement. The oldest dune forms date to 1.2 mya. Despite the extensive nature of these sand deposits, both the timing and causes of dune activation and stabilization remain little investigated. In this paper, a small subset of GPR data from the western side of the CSM was analyzed to examine the stratigraphic relationship of the high eastern dunes with the lower-elevation plain to the west and relationship to regional climate variations. The GPR data revealed a suite of stacked GPR facies suggestive of a migrating sand sheet with linear dunes. The stacked facies range in thickness from ~3 m to > 9 m. The varying thickness is potentially related to sediment availability and wind strength., San Diego State University
Using micro-gravity for near-surface fault detection in Downtown and Old Town San Diego, California
This thesis is a feasibility study of the use of micro-gravity in fault reconnaissance in the urban San Diego, California, area. Gravity readings were collected on nine profiles in downtown and Old Town San Diego. The results from downtown show the capability of the micro-gravity method by detecting the near-surface density contrast associated with the 13th Street Fault between E Street and Island Street. South of E Street, the gravity suggests the main contrast steps east from 13th Street, and remains midway between 14th and 15 Streets on the G Street profile and profiles further south. The Old Town profiles tended to show deeper contrasts and correlated well with the most recent fault maps of the area. The optimum station spacing for a project of this scale is 50 ft (15.2 m) and station elevations have to be known to 0.1 ft (0.03 m). The labor required for this study averaged 15 man hours per thousand feet of profile for field work, reduction, and qualitative interpretation. Given the cost and permitting requirements needed for exploratory drilling and exploratory trenching, a micro-gravity survey is a cost-effective method for fault reconnaissance., San Diego State University
Using sieving to deconstruct the regolith: A first attempt
H.W. Nesbitt and colleagues published in 1996 and 1997 two papers that outlined a general model for the integrated role that regolith development in plutonic terranes, erosion, and sorting during riverine transportation play in producing quartzofeldspathic sediments. In this model, sorting of the eroded regolithic material produces a mud-rich component that is more weathered than a size-fractionated sandy component. In A-CN-K space, as a result of progressive weathering, the mud-rich and sandy components lie at opposite ends of rays extending from the A apex, the composition of kaolinite and gibbsite, downward to the plagioclase-K-feldspar join where they reflect as a result of the preferential incongruent alteration of plagioclase decreasing ratios of plagioclase to total feldspar. In order to test this model, I collected eleven corestone, four transition zone, and four saprock samples from a single site located within Japatul Valley, California. Each of the four saprock samples was divided into two parts. One part was labeled the bulk fraction, and the remaining part was sieved into the three following size fractions: >63 microns, 63 to 45 microns, and <45 microns. Each sample was then analyzed for its major element composition. Thin section observations indicate that the corestone is a meta-granodiorite consisting of megacrysts of plagioclase and K-feldspar (~5 – 7.5 mm in size) embedded in an equigranular and finer grained matrix (~1 – 3 mm in size) of primarily plagioclase, quartz, biotite, and lesser amounts of hornblende. On an A-CN-K diagram (molar basis) corestone, transition zone, and bulk saprock samples define a very weak weathering trend oriented subparallel to the A-CN join. Utilizing Al as a reference frame element, mass balance calculations indicate that 19% (+10/-9) of the Ca mass, 15% (+9/-8) of the Na mass, 13% (+12/-10) of the Mg mass, and 47% (+11/-9) of the P mass was lost during the transformation of corestone to saprock. The loss of Ca and Na mass is attributed to the incongruent leaching of An-rich cores and zones within plagioclase, while losses in Mg mass are likely the result of the alteration of biotite. Leaching of apatite is responsible for the loss of P mass. If erosion were to remove the regolith at the study site, then the >63 micron fraction would be sorted into sand and pebble sized material, while the 63-45 micron fraction would represent coarse silt. The <45 micron fraction would include medium and fine silt along with clay-sized materials. On an A-CN-K diagram, the >63 micron fractions plot just to the right of and overlaps the cluster of bulk saprock samples. This relationship is consistent with the fact that the >63 micron fractions made up between 90 – 95% of the bulk fractions from which they were sieved. In contrast, the 63-45 and < 45 micron fractions make up less than 5-10% of the bulk fractions from which they were derived, and are significantly poorer in K then are the bulk and the >63 micron fractions. This diminishment in K is likely due to the fact that most of the megacrystic K-feldspar was retained within the >63 micron fraction while plagioclase and its weathering products were retained within the 45-63 micron and <45 micron fractions. Significantly, the <45 micron fraction is more depleted in Ca and Na than is the 45-63 micron fraction, and both fractions plot about a linear trend oriented parallel to the A-CN join. In addition, XRD work suggests that <2 micron clay fraction is dominated by mainly gibbsite (Al(OH)3) with minor amounts of kaolinite (Al2Si2O5(OH)4) and even lesser amounts of illite. The projection of the trend defined by the 45-63 micron and <45 micron fractions downward from the A apex, the composition of kaolinite and gibbsite, to the plagioclase-K-feldspar tie line indicates a total feldspar composition dominated by plagioclase rather than K-feldspar as predicted by the model of Nesbitt and colleagues (plagioclase to total feldspar ratio = 0.9). These results are not predicted by the model of Nesbitt and colleagues, and are in need of additional study., San Diego State University
Using smectite as a geothermometer to understand emplacement temperatures of Mount Calavera Dome, Carlsbad California
Clay minerals have been used as geothermometers to determine source rock maturation and basin analysis in the oil and gas industry, as well as to understand heat generation along faults during rupture. In both of these applications the proportion of discrete illite in mixed-layer illite/smectite is correlated to heat. However, in our study we will evaluate if the presence of smectite can be used to limit the temperature regime of emplacement of an andesitic dome, located in Carlsbad, CA. Until recently, Mount Calavera was thought to be the solidified neck of an ancient volcano. Notably, recent research by Mohammad El-Najjar suggests that the feature is instead extrusive in nature, and is most likely a dome with andesitic composition. Understanding the temperatures at which the dome was emplaced may help us further understand its genesis. On the northern, eastern, and southern sides of Mount Calavera,the Miocene andesitic dome is in contact with sediments of the middle Eocene Santiago Formation. A bake zone, the focus of this study, is exposed along the NW portion of the western flank of the dome. Seven samples were collected, four from the baked sediments, two from the unbaked sediments, and one from the andesite. All seven samples were analyzed for clay mineralogy by x-ray diffraction. In addition, thin sections of each sample were evaluated for changing textures and mineralogy across the baked zone. The < 4 μm fraction of samples CA 1, CA 2, CA 3, CA 4 (baked Santiago Formation), CA 5, and CA 6 (unbaked Santiago Formation), include smectite, illite, and lesser amounts of quartz. The < 4 μm fraction of CA 7 (andesite) was dominated by smectite with lesser amounts of quartz and feldspar. We view the strong presence of smectite in all the sediment samples as an indication that temperatures during emplacement were < 200 °C, the point at which smectite generally collapses to an illite structure. The determination of a low heat signature corroborates the idea that Mount Calavera is a surficial dome-lik feature, rather than a volcanic plug., San Diego State University