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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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Stratigraphy of the Cerro Coronel Area, Northwestern Baja California, Mexico
Sedimentary and volcanic rocks of probable Tertiary age overlie Cretaceous sedimentary reeks in the Cerro Coronel Area, Northwestern Baja California, Mexico. The Tertiary(?) sequence is virtually flat-lying and consists of approximately 200 feet of sandstone and conglomerate overlain by 600 to 700 feet of basaltic flows and interbedded volcanic breccia. Assignment of Tertiary age to the strata in question is based on lithology and stratigraphic position. The conglomerate of tho sequence contains 50 to 60 per cent rhyolitic, dacitic, and dark hornfelsic clasts. These clasts are characteristic of Tertiary and younger conglomerates of the Pacific coast of northern Baja California and southern California. A mere precise age is suggested by cor­relation with similar volcanic units in La Mision area are overlain by marine fossiliferous sandstones and mudstones of Miocene age. On this basis, the Cerro Coronel sedimentary and volcanic sequence is no younger than mid-Tertiary; similarly, the unit is no elder than Eocene on the basis of lithologic correlation with Eocene conglomerates of San Diego County. Several unconformities are apparent in the area. An uncon­formity exhibiting 75 to 200 feet of relief is developed en a rock unit thought to be correlative with the lower Cretaceous Alisites Formation. A third unconformity occurs between the sedimentary and volcanic units of the Tertiary sequence; it exhibits a maximum of 100 feet of relief., San Diego State University
Stratigraphy, sedimentology, and paleontology of quaternary non-marine rocks exposed at Rancho Del Oro/Town Center North in Oceanside, California
Grading operations for the Rancho Del Oro/Town Center North shopping mall in Oceanside, California exposed and destroyed a series of Quaternary non-marine strata. These beds have been divided informally into three stratigraphic units. The lowest (unit 1) was deposited as a series of subaqueous sediment-gravity flows, and is inferred to represent deposition in a lacustrine setting. The middle unit (unit 2) is also inferred to represent a lacustrine setting, and consists of three fades representing beach, basin, and prograding delta depositional settings. Units 1 and 2 are the first recognized lake deposits in the Quaternary record of coastal San Diego County. Unit 3 is interpreted to represent stream deposition. Units 1 and 2 were fossiliferous, most notably including Deroceras aenigma, Anodonta, Physa, Microtus calijornicus, and Neochoerus. The occurrence of the fresh-water clam Anodontafrom unit 2 is the first record of this taxon from coastal San Diego County. The Neochoerus record from unit 1 is the first find of a capybara from the west coast of North America., San Diego State University
Stress analysis 98, a Visual Basic 5 program for analyzing stress: a tutorial approach
Stress, a core and essential concept in structural geology, is conceptually difficult for many undergraduate students. Part of the difficult is that the description of stress is inherently mathematical and thus to many students non-intuitive. Moreover, graphing, and/or calculating and converting to the various units of stress is a time consuming task that many students view as "busy work" or "mundane". In an attempt to cut-down on the amount of "busy work" needed to perform a simple stress analysis, a software program termed Stress Analysis 98, was written in Visual Basic 5. In addition, a detailed tutorial on the mathematics of stress and how to use Stress Analysis 98 to solve basic problems in stress analysis was written to accompany dissemination of the program. Essential topics covered in the tutorial include: (1) how force relates to stress using Newton's first and second laws, (2) the units of stress and how to convert one to another, (3) how tractions are defined and calculated, (4) how lithostatic pressures are calculated, (5) a graphical approach to understanding the stress tensor and how it relates to the definition of a-1, a-2,and a-3, (6) derivation of the normal and shear stress equations that define the Mohr circle of stress, (7) a graphical approach to using the Mohr circle for solving stress problems when two of the three principal stress directions and their magnitudes are known, (8) the effect of pore pressures on stress, and (9) Mohr Failure Envelope as approached from a graphical analysis of triaxial stress test data extracted from the literature. Stress Analysis 98 is currently a version that will undergo extensive testing in the Advanced Structural Geology and Introduction to Structural Geology classes at San Diego State University. Eventually, it is the authors' intentions that the program and tutorial will be offered to the general geological community through a paper published in the Journal of Geoscience Education., San Diego State University
Structural architecture of the termination of the Powerline Fault, San Felipe Hills, southern California: A geometric and clay mineral analysis
Using a variety of field and laboratory techniques we examine the characteristics of the fault fold fabric produced by the termination of the NW-striking dextral strike-slip Powerline fault in the San Felipe Hills, southern California. The area of study lies along the strike of the Clark segment of the San Jacinto fault, a major component of the San Andreas plate boundary fault system. Detailed mapping at a scale of 1:6000 shows that the fault-fold fabric is dominated by a major eastward plunging syncline, and the Alkali Wash oblique-slip and Artesian Trail thrust faults. Poles to bedding attitudes from four sections of the major syncline were plotted on lower hemisphere equal-area stereonets. The four segments were defined on the basis of the changing strike of the axial surface trace of the fold as seen in map view. Analysis of the resulting plots revealed an upright, open, cylindrical syncline that increases in plunge from west to east. Analysis of the structural characteristics of the Alkali Wash oblique-slip and Artesian Trail thrust faults were achieved through trenching and X-ray diffraction study of gouge collected from fault cores and adjacent damage zones. The EW trending Alkali Wash oblique-slip fault terminates into a major splay of the Powerline fault and extends over several kilometers across the study area. It dips ~86˚ to the north, and in trenches sharply truncates shallower dipping beds in both the hanging wall and footwall blocks. Trenching of the 30˚S dipping Artesian Trail thrust fault revealed a fault core defined by poorly to moderately developed slickenlines on foliated gouge. The slickenlines plunged down the dip of the principal slip surface and were produced by gouging of rigid clasts as the hanging wall moved from south to north along the principal slip surface. Additionally, a well-developed damage zone defined by microbreccia composed of rounded sandstone and conglomerate fragments is evident. XRD analysis of material collected from the fault cores of the Alkali Wash and Artesian Trail faults indicate that gouge is composed primarily of illite/smectite (I/S), with no more than 20% illite in I/S along with traces of quartz, calcite, and kaolinite., San Diego State University
Structural geology of Picacho State Recreation Area: implications for the transfer of Baja California to the Pacific plate
Approximately 5 to 9 Ma, Baja California was transferred from the North American to the Pacific plate. This transfer was accomplished through either strain partitioning into strike­slip motion along the Tosco-Abrejos fault and extensional opening in the Gulf Extensional province or through distributed dextral shear. PSRA is located in the southwest comer of the Colorado River corridor, roughly 25 miles north of Yuma, Arizona and 225 miles northeast of San Diego, California, and is therefore ideally located to assess which of the above proposals is most relevant to the geology of SE California. The stratigraphy of PSRC can be subdivided into three broad lithostratigraphic units. The oldest unit includes a basement complex comprised of Jurassic mylonitic gneisses, the latest Cretaceous-early Tertiary Orocopia Schist and the Jurassic Winterhaven Formation. An over 1 km thick section of mostly Oligocene volcanic rocks intervenes between the older units and capping middle to late Miocene gravels and basalt. A probable early Miocene detachment faults separate the Jurassic mylonitic gneiss from the Orocopia Schist while another probable detachment fault of the same vintage separates the Winterhaven Formation from the mylonitic gneiss and the schist. Though most previous workers have focused on the origin and characteristics of the detachment systems my work suggests that a younger series of structures overprinted the early detachment system and controls the current structural fabric of the park. For example, a major NW trending fault, herein referred to as the Taylor Lake fault, with as much 1 km of right-lateral displacement transects the central portion of PSRA. This fault on aerial photographs can be traced for over 25 miles southward to Yuma, Arizona. In addition, it appears to have developed contemporaneously with a set ofEW trending folds, a set ofEW trending reverse faults, and a set of NS trending normal faults. These structures fold or transect rocks as young as ~9 Ma, but do not appear to affect old gravels associated with the Colorado River (~4.7 Ma). Hence, the Taylor Lake fault and associated structures formed between about 9 and 5 Ma. I therefore speculate that the Taylor Lake fault and associated structures are part of a larger system and likely reflect the transfer of Baja California to the Pacific plate through a net work of distributed dextral shear., San Diego State University
Structural geometry of tertiary gravels in the middle to late Miocene Taylor Lake Fault Zone, Picacho State Recreation Area, SE California
The structural geometry and kinematics of structures associated with a prominent splay off the newly discovered and mapped Taylor Lake fault zone, Picacho State Recreation Area, SE California, may provide evidence for changing plate boundary conditions during Miocene time. Two prominent hypotheses exist as to how Baja California separated from mainland Mexico. According to Stock and Hodges (1989) Baja moved obliquely away from mainland Mexico as a result of partitioning ~350 km of strike-slip motion along the San Benito-Tosco-Abreojos fault zone and ~160 ± 80 km and 110 ± 80 km of ENE extension within the Gulf Extensional Province. Gans (1997) however noted that large scale extension in the Gulf Extensional Province predates the ~ 15 - 6 Ma time frame in which Baja was transferred to the Pacific plate. Detailed mapping of a small part of the Taylor Lake fault zone resulted in the recognition of the Little Picacho Wash splay. This splay subdivides the study area into western and eastern blocks. Cross-sections and plots of poles to beds indicate that the western block hosts an approximately cylindrical open upright SW plunging anticline­syncline pair that is truncated by the Little Picacho Wash splay. These characteristics however are not preserved across the splay into the eastern block where cross-sections reveal a complex geometry caused by high strain resulting from the eastern block being forced SE into the wedge defined by the Taylor Lake fault and the Little Picacho Wash splay. These and other data discussed herein favor the model of Gans (1997) in which intracontinental Middle to Late Miocene distributed dextral shearing allows Baja to separate from mainland Mexico., San Diego State University
Structural interpretation of CHIRP data from offshore central Oregon
A large number of archaeological sites have been found onshore in Central Oregon, but it is likely that archaeological evidence also extends into the offshore. During the Last Glacial Maximum (LGM), which was about 20,000 years ago, global sea level was ~120 meters lower than it is today. This significant difference in sea level could have allowed for the arrival and settlement of the First Americans in areas that are now submerged. The near 120-meter drop in sea level brought the LGM coastline out to the edge of the continental shelf. Paleochannels that stemmed from the Siuslaw and Umpqua Rivers would have traversed the shelf and created a viable natural resource for people living in the area. Archaeological sites onshore are often found near freshwater resources, so these are important places to look for sites offshore. A model of paleochannels across the shelf was previously created using modern bathymetry that showed the paleochannels flowing directly to the west. However, paleochannel mapping in sub-bottom Chirp data revealed a major difference in course of the Umpqua River, which shows a major southward bend before reaching the LGM coastline. The question then is why don’t the paleochannels follow the previously modeled patterns? One possibility is that geologic structures, such as folding and faulting along the shelf, could control the paleodrainage patterns. These structures were mapped in high-resolution Chirp sonar data across the shelf including numerous small-scale synclines, anticlines, and faults seen throughout the data. Largescale structures included some major folds, but the most notable features were bathymetric mounds. These mounds are interpreted to be related to expulsion of fluids and mud (e.g., mud volcanoes), which are common on convergent margins. The location of the mounds is thought to be fault controlled, but it is difficult to determine because of the lack of penetration depth in the Chirp data. These mounds appear to control the Umpqua River paleochannel by forming a bathymetric high offshore from the modern river mouth. This high appears to divert the flow of the paleodrainage to the south. Further research is currently being conducted to incorporate this information into archaeological resource models and to determine if there is archaeological evidence adjacent to the updated paleochannel locations., San Diego State University
Structural interpretation offshore Smuggler’s Cove in the Northern Channel Islands, CA
New high-resolution Chirp seismic and sidescan sonar data collected on the shelf offshore from the Northern Channel Islands image patterns of sediment distribution, extensive compressional deformation associated with reverse and strike-slip faulting, and submerged paleolandscapes that may contain archaeological resources. The four Northern Channel Islands were a unified landmass known as Santarosae during the last glacial maximum when sea level was ~120 meters lower than today. The presence of numerous paleocoastal archeological sites on the modern islands suggests that similar sites may exist on the submerged shelf, which was exposed during lower sea levels. Between Santa Cruz and Anacapa Islands, doubly-plunging folded beds of Monterey Shale are truncated by a strong acoustic reflector interpreted to be the transgressive surface created by eustatic rise since the last glacial maximum. Sediment thickness above the transgressive surface varies widely across the survey area due to differences in sediment sources, and tectonic and hydrographic influences. Additionally, the folding and truncation of the Monterey Shale results in paleolandforms which could have been important resources for the Santarosae people, and which may contain archeological resources. Understanding the structural controls on these paleolandforms will improve predictive modeling of submerged archaeological sites for better resource management., San Diego State University
Structure and petrology of a portion of the Sacotone Springs roof pendant at Tule Mountain
The La Pesta pluton is a 1400 km2 pluton in the eastern zone of the Peninsular Ranges batholith. The Sacotone Springs area is part of a roof pendant near the center of the pluton that contains igneous and sillimanite-grade metasedimentary rock. The metasedimentary rocks consist of sillimanite-bearing schists, gneisses, and quartzites whose grade is consistent with that found in adjacent areas. Temperature and pressure conditions were approximately 650° C and 4 kb. The plutonic rocks north and west of Tule Mountain are sphene-hornblende-biotite tonalities that have strong foliation, abundant dark inclusions and a low magnetic susceptibility. Dikes of leucogranite with both pegmatitic and aplitic textures cut the metasedimentary and older igneous rocks but terminate at the contact with the Las Pesta pluton. The tonalitic rocks are probably western zone rocks despite the low magnetic susceptibility. Their magnetism may have been destroyed during the emplacement of the La Pesta pluton. They represent the eastern most exposures of the western zone rocks. The leucogranite dikes are most likely products of anatexis of the metasedimentary package, which happened during the emplacement of the La Posta pluton., San Diego State University
Structure of the Mt. Tule dike swarm Jacumba, California
The Mt. Tule dike swarm is located approximately 65 miles east of San Diego near Jacumba, California. It is a layered pegmatite-aplite system forming a bowl-shaped structure in map view, opening to the north, and occurs within a metasedimentary roof pendant that lies near the center of the La Pasta pluton. Bordering the dike system on the south is a garnet-two-mica monzogranite. E. R. Mapper was used to plot this dike system on a SPOT panchromatic image with 10-meter resolution. Although showing a variety of strikes and dips, the general trend for the dikes is a north-northwest strike along the western side with a moderate dip to the southwest, an east-west strike along the southern side with a moderate dip to the south, and a north-northeast strike along the eastern side with a moderate dip to the southeast. A central zone in the dike structure contains sparse dikes with subhorizontal attitudes. The La Pasta pluton intruded and engulfed the Triassic (?) metasedimentary roof pendant at 94 ± 1 Ma, partially melting the roof pendant to create the garnet­-two-mica monzogranite which has been dated at 93 ± 1 Ma and the dike system around the borders. It is not clear why the steeply dipping dikes are limited to the margins of the roof pendant, but their distribution may be related to the degree of partial melting in the metasedimentary package., San Diego State University
TAU: Terrain assessment units for environmental monitoring and sensor development for acquiring remote earth system science information
TAU units are autonomous remote-sensing devices designed to accumulate environmental data and transmit these data in ESRI ArcView format to Internet websites. The units are equipped with duplex communication channels to send and receive instructions for individual operation by remote command. They are capable of operating multiple experiments, which are stowed in a sealed cargo bay. Video stream is provided by onboard video camera and a streaming Internet connection. TAU is designed to provide on-demand data ports to San Diego County organizations such as SDSU field stations connected to the campus and the world. Specific experiments that will be done with the TAU unit are to accumulate a variety of Earth Systems Science data. Because the TAU unit provides a platform to stage many types of experiments, it can support experiments gathering data about the Earth's atmosphere including both traditional meteorological data and Earth radiance and gas data. These atmospheric data are currently being gathered at a few sites within the SDSU group of field stations, but at a large cost because of the technology involved. The TAU unit, especially within the Santa Margarita watershed, can also gather data on water both at the surface and in the subsurface. Data on animals such as coyotes, birds, and reptiles will also be gathered, as sensors from several Life Sciences faculty will be mounted on the TAU units to gather video and audio information. By studying the nature of the information to be gathered, the variance in cycle time of observations and transmission, and the power needs for both sensor measurement and wireless transmission, the TAU unit will help prototype inexpensive means of making widespread remote observations. By integrating the different elements of Earth System Science, the TAU unit should enable scientists to break down barriers of academic discipline, such as Life Sciences, Atmospheric Sciences, and Geological Sciences, and study the broader patterns and interrelationships of Earth Systems., San Diego State University
Taxonomy and taphonomy of hadrosaurs (Dinosauria: Ornithiscia) found in the Point Loma Formation (Campanian) of San Diego County, California
Dinosaur skeletal remains in California are largely found in Campanian age marine sediments. Of those hadrosaurid fossils are the most common found due to the abundance in the late Cretaceous, though many of the bones are isolated or fragmentary and cannot be diagnosed at a species level without skull material. The two most complete hadrosaur specimens found in San Diego County are housed at the San Diego Natural History Museum. SDNHM 25342 is a right femur found in December 1983 during development of the Carlsbad Research Center. SDNHM 66640 is a section of 11 associated vertebrae found in December 1986 during grading for the College Boulevard Extension project in the city of Carlsbad. Both specimens were found within the Point Loma Formation, a fossiliferous marine mudstone unit within the Rosario Group of the late Campanian. From morphologic data the specimens are indeterminate at the subfamily or generic level, though geographically related finds of hadrosaurs in California and Baja California suggest them to be of the genus Saurolophus or Lambeosaurus. Taphonomic data suggests hadrosaurs in California occupied near-marine coastal bays or lagoons, with their remains either transported as isolated bones by fluvial processes or disassociating from floating carcasses to settle in shallow marine deposits., San Diego State University