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- Creator:
- Woods, Adam D. and Kirton, Jennifer McCoy
- Description:
- Microbialites undergo a well – documented resurgence following the Permian – Triassic mass extinction. This comeback has been attributed to several causes, including the emptying of Early Triassic ecosystems by the severity of the extinction, a decline in burrowing activity and intensity, and the unusual chemistry of Early Triassic oceans. A laterally – continuous stromatolite horizon found within the Lower Triassic Virgin Limestone was examined at the Blue Diamond, NV U.S.A. locality in order to determine the factors that led to growth of the stromatolites, and by extension, the environmental conditions that led to the formation of widespread microbialites in the aftermath of the Permian-Triassic mass extinction. The Virgin Limestone at the study locality consists of ~6 m – thick cycles of shale and siltstone that pass upwards into bioturbated lime mudstone, and are capped by oolitic packstone or grainstone. Each ~6 m – thick cycle represents a rapid sea level rise that led to the deposition of fine – grained clastics below storm wave base, followed by deposition of coarsening – upwards carbonates that were deposited in progressively shallower environments. Analysis of redox-sensitive trace metals (U. V and Mo) from the shale and siltstone interbeds indicate that the fine – grained clastics were deposited under dysoxic waters, however, extensive bioturbation and macrofossils from the carbonate units indicates better aeration of shallower settings. The stromatolites occur within a single, laterally extensive horizon, and 4 distinct stromatolite morphologies are observed along a 3 km long transect, including: 1) aggregates of high-relief hemispherical domes and columnar stromatolites with well-developed laminae that are up to 0.75 m thick; 2) lozenge-shaped aggregates of intergrown columnar stromatolites with dimpled top surfaces; 3) isolated hemispheroids; and, 4) meandering ridges of intergrown domes that are small, low – relief (usually <7 cm), and have a clotted fabric. Isolated hemispheroids are found across the entire study area, while the large hemispherical and columnar aggregates, lozenge-shaped masses and the small intergrown domes are found in the southern, central and northern portion of the study area, respectively. Analysis of trace metals from shale directly underlying the stromatolites reveals an intensification of dysoxic conditions that may have initiated mound growth, while the occurrence of distinct burrows and a sparse fauna within the stromatolites indicates at least partially – oxygenated conditions as the stromatolites developed on the seafloor. Overall, stromatolite growth was controlled by a combination rapid calcification of the mounds related to the unusual carbonate chemistry of Early Triassic oceans, a microbial bloom driven by N – fixing diazotropic cyanobacteria, and possibly intermittent dysoxic conditions that limited grazing metazoans. Comparison of Lower Triassic stromatolites from the Blue Diamond locality to others from the western United States reveals the importance of localized conditions in initiating microbialite growth and determining the complexity of microbialite ecosystems.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Carlin, Joseph A.
- Description:
- Continental shelf environments are uniquely situated to capture some of the most dynamic processes on Earth including climatic variability and anthropogenic modifications to coastal systems. Understanding how these processes have affected sediment delivery and accumulation on the shelf in the past may provide insight into potential changes in the future. To address this, we investigated shelf sedimentation within Monterey Bay, California. Sediment cores were collected from four locations throughout the bay to capture both the modern and late Holocene sedimentological record using grain size analysis, and sediment chronologies determined from 210Pb, 137Cs, and 14C. From the grain size results we focused on the total percent sand, and established a Littoral Sand Fraction (LSF) index to assess sediment contribution from the littoral zone as a result coastal erosion. Grain size results from the multicores consistently showed an increase in sand over the past several decades (post 1970s). For the cores located within the bay proximal to three major rivers, the increase in sand corresponded to a general increase in the LSF over the same period. We attributed these trends to increased sediment contributions to the shelf due to accelerated coastal erosion in the region. This accelerated coastal erosion was likely the combined result of dam construction in the mid-twentieth century that limited fluvial supply to the coast, and a shift in climate toward wetter, stormier period. Applying these sediment characteristics back over the past ∼1,000 years we found that dry climatic periods resulted in deposits that were limited in total sand but enriched in littoral material suggesting elevated coastal erosion. During wet periods deposits were enriched in total sand but limited in littoral sand suggesting elevated fluvial supply and low erosion. Compared to the late Holocene record, the previous several decades represent a shift to a new regime, uncharacteristic of deposits over the past millennia, highlighting the impact humans have had on shelf sedimentation.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Kirby, Matthew
- Description:
- Records of past climate can inform us on the natural range and mechanisms of climate change. In the arid Pacific southwestern United States (PSW), which includes southern California, there exist a variety of Holocene records that can be used to infer past winter conditions (moisture and/or temperature). Holocene records of summer climate, however, are rare from the PSW. In the future, climate changes due to anthropogenic forcing are expected to increase the severity of drought in the already water stressed PSW. Hot droughts are of considerable concern as summer temperatures rise. As a result, understanding how summer conditions changed in the past is critical to understanding future predictions under varied climate forcings. Here, we present a c. 10.9 kcal BP δ18O(calcite) record from Lake Elsinore, California, interpreted to reflect δ18O(lake water) values as controlled by over-water evaporation from summer-to-early fall. Our results reveal three millennial scale intervals: (1) the highly evaporative Early Holocene (10.55–6.65 kcal BP), (2) the less evaporative Mid-Holocene (6.65–2.65 kcal BP); and (3) the evaporative Late Holocene (2.65–0.55 kcal BP). These results are coupled with an inferred winter precipitation runoff (sand content) record from Kirby et al. (2010). Using these data together, we estimate the duration and severity of centennial-scale Holocene droughts and pluvials (e.g., high δ18O(calcite) values plus low sand content = drought and vice versa). Furthermore, the coupled δ18O(calcite) and sand data provide a generalized Holocene lake level history. The most severe, long-lasting droughts (i.e., maximum summer-to-early fall evaporation and minimum winter precipitation runoff) occur in the Early Holocene. Fewer, less severe, and shorter duration droughts occurred during the Mid-Holocene as pluvials became more common. Droughts return with less severity and duration in the Late Holocene. Notably, the Little Ice Age is characterized as the wettest period during the Late Holocene.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Loyd, Sean
- Description:
- Major hydrocarbon accumulations occur in traps associated with salt domes. Whereas some of these hydrocarbons remain to be extracted for economic use, significant amounts have degraded in the subsurface, yielding mineral precipitates as byproducts. Salt domes of the Gulf of Mexico Basin typically exhibit extensive deposits of carbonate that form as cap rock atop salt structures. Despite previous efforts to model cap rock formation, the details of subsurface reactions (including the role of microorganisms) remain largely unknown. Here we show that cap rock mineral precipitation occurred via closed-system sulfate reduction, as indicated by new sulfur isotope data. 13C-depleted carbonate carbon isotope compositions and low clumped isotope-derived carbonate formation temperatures indicate that microbial, sulfate-dependent, anaerobic oxidation of methane (AOM) contributed to carbonate formation. These findings suggest that AOM serves as an unrecognized methane sink that reduces methane emissions in salt dome settings perhaps associated with an extensive, deep subsurface biosphere.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Kirby, Matthew
- Description:
- Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfossil analyses indicate that predominantly freshwater deposits bury relic intertidal deposits at three distinct depths. Radiocarbon dating indicates that the three burial events occurred in the last 2000 calendar years. Two of the three events are contemporaneous with large-magnitude paleoearthquakes along the Newport-Inglewood/Rose Canyon fault system. From these data, we infer that during large magnitude earthquakes a step-over along the fault zone results in the vertical displacement of an approximately 5-km2 area that is consistent with the footprint of an estuary identified in pre-development maps. These findings provide insight on the evolution of the saltmarsh, coseismic deformation and earthquake recurrence in a wide area of southern California, and sensitive habitat already threatened by eustatic sea level rise.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Bursztyn, Natalie
- Description:
- In searching for ways to improve undergraduate success in introductory geoscience courses, the importance of experiential learning in engaging students has become clear—and in geoscience, that is encapsulated best by field trips. However, as general education class sizes increase, so do the cost, liability, and difficulty of running a field trip. A solution for economically and conveniently bringing kinesthetic field experiences to a broader audience lies in the integration of technology through mobile-device games, apps, and augmented reality (AR) field trips. We report here an examination of learning gains at five colleges after intervention with augmented reality field trips to Grand Canyon. The AR field trips cover three topics taught in introductory geoscience courses: geologic time, geologic structures, and hydrologic processes.Results involving nearly 1000 students show that overall gains are similar to control groups, with completion of the AR field trips being a predictor of student learning success in some cases. Prior interest in the geosciences, students’ base-level understanding of the material, and whether or not the student is a science, technology, engineering, and mathematics (STEM) major are strong predictors of improvement in geoscience learning. Gender and ethnicity had no statistical impact on the results, suggesting the AR field trip modules have broad reach across student demographics. Because these modules have been shown elsewhere to increase student interest in learning the geosciences, we advocate their adoption, leading to increases in student learning.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Loyd, Sean
- Description:
- Methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ∼0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixing of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
8. Timing and rates of Holocene normal faulting along the Black Mountains fault zone, Death Valley, USA
- Creator:
- Knott, Jeffrey
- Description:
- Alluvial fans displaced by normal faults of the Black Mountains fault zone at Badwater and Mormon Point in Death Valley were mapped, surveyed, and dated using optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) methods. Applying TCN methods to Holocene geomorphic surfaces in Death Valley is challenging because sediment flux is slow and complex. However, OSL dating produces consistent surface ages, yielding ages for a regionally recognized surface (Qg3a) of 4.5 ± 1.2 ka at Badwater and 7.0 ± 1.0 ka at Mormon Point. Holocene faults offsetting Qg3a yield horizontal slip rates directed toward 323° of 0.8 +0.3/–0.2 mm/yr and 1.0 ± 0.2 mm/yr for Badwater and Mormon Point, respectively. These slip rates are slower than the ~2 mm/yr dextral slip rate of the southern end of the northern Death Valley fault zone and are half as fast as NNW-oriented horizontal rates documented for the Panamint Valley fault zone. This indicates that additional strain is transferred southwestward from northern Death Valley and Black Mountains fault zones onto the oblique-normal dextral faults of the Panamint Valley fault zone, which is consistent with published geodetic modeling showing that current opening rates of central Death Valley along the Black Mountains fault zone are about three times slower than for Panamint Valley. This suggests that less than half of the geodetically determined ~9–12 mm/yr of right-lateral shear across the region at the latitude of central Death Valley is accommodated by slip on well-defined faultsand that distributed deformational processes take up the remainder of this slip transferred between the major faults north of the Garlock fault.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Leeper, Robert J., III
- Description:
- The present study contributes to the sociology of health and illness by applying Link and Phelan’s theory of fundamental causes of disease to the study of language competence and health. The study answers the following research question: How does being limited in English proficiency (LEP) influence the effects of being obese on the prospects of having been diagnosed with heart disease for California residents? The project examines interaction effects between English competence and obesity to determine the partial effects of obesity and English competence on heart disease using secondary data from the 2011-2012 California Health Interview Survey. Contrary to expectations, findings indicate that individuals who are limited in English proficiency and are not obese (or overweight) have the lowest odds of being diagnosed with heart disease. Furthermore, findings indicate, consistent with expectations, that individuals who lack English competence have higher chances of experiencing the effects of obesity and overweight on heart disease compared with English proficient counterparts. Findings suggest that LEP and English proficient individuals deal differently with mechanisms linked with disease.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Nadimi, Khadija
- Description:
- Tsunami are a very real natural hazard for coastal Southern California; however, there are no geological records of past tsunami occurrence to determine their frequency and magnitude. For this study, a combination of five sedimentological analyses (sediment description, magnetic susceptibility, total organic matter, total carbonate content, and grain size analysis) were used to test our guiding hypothesis that the “wetlands of Southern California – specifically San Elijo Lagoon – record evidence for paleotsunami.”. And, provide the first geological evidence for paleotsunami in Southern California. The results of the study provide the first sedimentological record from San Elijo Lagoon that spans last 2200 years BP. Furthermore, the results indicate that depositional environment has changed significantly due to changes in the lagoon’s depositional environment over the last 2200 years BP. San Elijo Lagoon was selected for the investigation based on a number of factors, specifically: a historical tsunami database, generated mathematical models for Southern California tsunami, sedimentary structures reported from previous studies, and reconnaissance survey core results. Unfortunately, no sedimentological data were found in this study to support our hypothesis. Rather, the event unit we analyzed (CTU-I) is interpreted to reflect a storm deposit (or deposits) from the nearby Escondido Creek. So the main question now is why is there no unequivocal evidence for paleotsunami in San Elijo Lagoon? Absence of paleotsunami record in this region is may be due to following reasons: preservation potential of tsunami deposits, preservation potential of the catchment area, post-depositional alteration of tsunami deposits, Holocene sea level change, and limitation of paleotsunami proxies. Perhaps further research must be conducted to fill the gap between the geological records, a historical tsunami database and generated mathematical models for Southern California tsunami. Without such records, recurrence interval and vulnerability assessment is difficult to precisely reconstruct for this region.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Kloess, Peter Alfred
- Description:
- California has experienced significant climate change from the onset of the Miocene (~23Ma) to the present. The impact of past climate change is often recorded in the fossil record, and can be revealed by studying how ecological communities change through time. Fossil seabirds are the ideal taxon for studying faunal responses to environmental changes because they are numerous in collections, easily identified from fragmentary remains, and since modern seabirds respond quickly to immediate changes in their environments, we expect the fossil record of seabirds to faithfully represent past environments. The first study to look at fossil seabird diversity through the Tertiary of the North Pacific relied entirely on literature records to describe the appearance and disappearance of seabird species and correlated these patterns to geologic and climatic events. My thesis utilizes an empirical, specimen-based approach to accurately describe the seabird response to climate and tectonic change during ~12 million years of coastal California’s geologic history (middle Miocene to early Pliocene). The foundation of my dataset is a previously unstudied collection of 305 bird specimens from the John D. Cooper Center for Archaeology and Paleontology, representing a relatively complete sequence of strata (Topanga Group, Monterey Formation-equivalent, and Capistrano Formation). Representing the middle Miocene to early Pliocene of Orange County, these strata form the basis for delineating chronostratigraphic bins used for studying the diversity of the fossil seabird community of California. Comparison of this new collection with 378 seabird specimens from three other institutions across California provides a more complete and detailed view of the seabird community during this period. Diversity, taxonomic richness, and relative abundance were examined using quantitative statistical methods to understand the change in seabird populations over time and depth of deposition. Using these statistical techniques, my data show a clear increase of panalcid abundance and decline of sulid abundance that is coincident with global climatic and tectonic changes as well as enhanced nutrient upwelling. Upwelling through this time also accounts for morphological changes in salmon and speciation in marine mammals. In the future, the specimen-based methodology used here can be applied to contemporaneous taxa, such as marine mammals, to quantitatively analyze diversity and relative abundance during the late Neogene and further explore the relationship between physical drivers and faunal change.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Beach, Alyssa
- Description:
- Cetacean bonebeds containing multiple articulated individuals are extremely rare, with only a handful of occurrences documented worldwide. In 1997, three bonebeds containing mostly articulated and well preserved cetacean remains were uncovered during grading in sedimentary rocks assigned to the Paularino Member of the Topanga Formation near Bonita Canyon, Newport Beach, California. Multiple bonebeds within a single stratigraphic unit, such as those discovered at Bonita Canyon Planning Area 26, represent a rare class of deep marine fossil accumulations that have not been previously studied in detail. Taphonomic, stratigraphic, and geochemical data was collected from fourteen jacketed specimens removed from Bonita Canyon Planning Area 26 in order to determine the paleoenvironmental conditions that led to the accumulation of the bonebeds and to shed more light on these types of fossil accumulations. Results of this study indicate that the Bonita Canyon bonebeds do not represent a condensed facies, as previously proposed (The Keith Companies, 1998); rather they represent a composite concentration deposited in a continental shelf environment during a period of high sedimentation rates, where episodes of high energy gravity flows alternated with periods of low energy accumulation along a NE-SW trending submarine fan sequence. High net rates of sedimentation correspond with the creation of high accommodation space as the result of the opening of the Los Angeles Basin, a progressive marine transgression, and subsidence of the Topanga Basin as the result of the shift in the tectonic regime along western North America from a subduction zone to transform margin during the mid to late Miocene. Overall, this study provides valuable insight into the iii sedimentologic and taphonomic processes that lead to the formation of cetacean bonebeds, and demonstrate that high sedimentation rates may lead to well-preserved cetacean remains.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Caesar, Kylie
- Description:
- Gulf Coast salt domes occur in association with significant reserves of carbonate minerals, crude oil, natural gas, and elemental sulfur. As with other diagenetic carbonate minerals, cap rock calcites may form from microbial degradation of organic compounds. However, the specific natures of these microbial reactions remain largely unknown in salt dome systems. Here, carbon (δ13C) and sulfur (δ34S) geochemical signatures recorded in cap rock calcites are used to identify mineral-yielding processes in Gulf Coast salt domes. Calcite δ13C values reported here and elsewhere exhibit 13C-depleted compositions and express a large range from –55‰ (VPDB) to near neutral values, reflecting a mixture of carbon sources including a substantial methane component. Sulfur isotope data from carbonate-associated sulfate (δ34SCAS) exceed those of minor anhydrite associated with the Jurassic salt deposits (~ +15‰ VCDT), implying carbonate generation via microbial sulfate reduction under closed-system conditions. The co-occurrence of low carbonate δ13C values and high δ34SCAS values are evidence for sulfate-dependent anaerobic oxidation of methane (AOM) as the formation mechanism for Gulf Coast carbonate. Collectively, these data shed new light on a potential hotspot of microbial activity in the deep biosphere with potential environmental and economic ramifications.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Katona, Aaron
- Description:
- Measuring geomorphic indices is tedious and laborious, whereas Arc-GIS is inflexible, requires a license and substantial time to learn. This project demonstrates that geomorphic indices may be measured rapidly and accurately using Google Earth. First, Google Earth’s efficacy is shown by replicating parts of several previous studies. Then, mountain front sinuosity, valley floor width to height ratio, basin elongation ratio, basin area, fan area, basin relief, stream concavity index, range crest/piedmont profile, and range front strike are measured along the western White/Inyo Mountains using Google Earth. The geomorphic analysis indicates tectonic uplift rates increase northward. Interpretation of multiple geomorphic indices moves the Montgomery/Hammil and Hammil/Central section boundaries of the White Mountains fault zone (WMfz) to Birch Creek and Sacramento Canyon, respectively. South of the Waucoba Lake Beds, the westside-down of the WMfz ends and tectonic basin polarity shifts to east-side-down normal faults along the Sierra Nevada with the strike-slip Owens Valley fault zone beneath the Owens Valley. This tectonic change also coincides with the southwest extension of the Deep Springs fault (DSf) and the Big Pine volcanic field. I hypothesize that the DSf extends below the Waucoba Lake Beds and is important component of Owens Valley tectonics. Normalized longitudinal profiles reinforce previous work that indicated that tectonics is the primary control on fluvial system and lithology exerts greater control as tectonic activity lessens.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Aranda, Angela
- Description:
- This study utilized the stratigraphic record from the Seal Beach Wetlands (SBW), a coastal wetland in southern California straddling the active Newport-Inglewood Fault Zone, to: 1) Identify evidence of paleoseismic events and 2) Characterize wetland response and recovery to these events. The goal of this study was to better understand how a southern California coastal wetland evolves in response to seismic activity. To accomplish this, a suite of sedimentary and geochemical analyses were performed on one core collected from the SBW to characterize environmental changes resulting from seismic events, and the subsequent recovery following the events. Integrating results from these analyses, we classified sedimentary layers into three dominant facies: subtidal, mudflat, and vegetated marsh that represented paleo-elevation at this location in the wetland. Five possible coseismic events were identified, distinguished by a sharp contact at an abrupt facies change suggesting a decrease in elevation. When marsh facies were overlain by sandy subtidal sediment, we interpreted this to have represented the most substantial subsidence event. Apparent subsidence estimates diminished with time, culminating in a lack of subsidence evidence associated with the 1933 Long Beach earthquake. We interpreted this as evidence of the wetland becoming more resilient to coseismic subsidence overtime. This study highlights wetland response to rapid changes in sea level and places extreme events (i.e., earthquakes) in the context of wetland development that may provide insight into improving stratigraphic interpretation.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Chen, Nancy
- Description:
- Detrital zircon U-Pb geochronology provides a statistical basis for identifying provenance and correlating deformed volcanosedimentary rocks. Uranium-lead (U-Pb) detrital zircon ages from the Schoonover Sequence of the Golconda allochthon (GA) are compared with select metasedimentary pendants in the western Sierra Nevada foothills with the goal of providing new constraints for reconstructing the Paleozoic-Mesozoic tectonic evolution of western Laurentia. Comparison of U-Pb data with known basement rocks and other sedimentary units of Laurentia reveal the provenance of the Schoonover Sequence to be a combination of Peace River Arch (PRA) detritus mixed with 349 ± 2.0 Ma zircon likely derived from the Yukon-Tanana arcs (SE Alaska). These new data for the Golconda allochthon reveal the southward translation of the strata to approximately NW Nevada where the strata were thrust over the outermost edge of the passive margin. Two Sierra foothills pendants from the newly named Yokuts series have a provenance similar to the RMA mixed with zircon derived from the post-mid-Cambrian passive margin. Protoliths of the Yokuts pendants deposited near the RMA-GA collision zone within in the passive margin. Subsequent southward translation deformed and juxtaposed the Yokuts strata against undeformed passive margin strata preserved in the neighboring Slate Mountain and Sequoia pendants.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Hernandez, Edween Leonel
- Description:
- Paleozoic shallow marine communities differ considerably from Modern shallow marine communities. for example, Modern animals such as gastropods and bivalves occupy niches once occupied by Paleozoic brachiopods and echinoderms. Researchers suggest the end-Permian mass extinction reset the stage by reorganizing past marine communities, thus allowing new communities to take over. Once ocean chemistry conditions returned to normal in the Middle Triassic, modern communities stabilized and took on their modern ecological state. Bivalves and gastropods increased in diversity and abundance, grew thicker shells, and some began burrowing deeper into sediment. Scientists describe these changes in life habit as the Mesozoic Marine Revolution (MMR), a transition initiating in the Middle and Late Triassic. Previous research focused on European sites, however, data are lacking from western Panthalassa. Here, we present new taxonomic and environmental data from Favret and American Canyons, Nevada, which help piece together the story of how shallow marine communities modernized in the eastern Panthalassic Ocean. Results suggest low fossil abundance in outer ramp systems consistent with other Middle Triassic marine environments. Taxonomic data reveal a combination of Paleozoic and Modern Fauna, which suggests that the Marine Mesozoic Revolution (MMR) has begun but had not fully developed. This study is important because can be used as an analogue to understand how modern ecologies are and will be affected by climate change.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Mayer, Stefanie A.
- Description:
- The majority of lacustrine studies from the Mojave Desert Region focus on Mojave River fed lakes, specifically Silver and Soda Lake. the Mojave River headwaters, located in the San Bernardino Mountains, feed the Mojave River lakes and thus contain an aggregate of coastal southwest United States and Mojave Desert climate signals. a multiproxy sediment study from Ford Lake, California provides the first paleohydrologic record with a Mojave-only signal spanning the late Holocene. Ford Lake is located in the eastern section of the Mojave National Preserve in San Bernardino County, California. It is a closed basin lake retaining exclusively Mojave Desert moisture. Consequently, it represents the first lake studied in the Mojave Desert Region where the climate signal is 100% Mojave controlled. the hydrologic reconstruction of Ford Lake reveals that the paleoclimate of the Mojave Desert Region was relatively dry during the Medieval Climatic Anomaly (MCA) whereas the Little Ice Age (LIA) was characterized with more, but variable precipitation. by comparing Ford Lake data to regional winter dominant lacustrine sites, specifically Silver Lake, Lower Bear Lake, Zaca Lake, Abbott Lake, Owens Lake, and Lake Elsinore it was assessed that there are similarities between the coastal climate signal and the Mojave climate signal. Further comparison to the Pacific sourced ocean-atmosphere phenomena (i.e. El Niño Southern Oscillation and the Pacific Decadal Oscillation) found that the prevailing climatic forcings driving the coastal climate are also driving the Mojave Desert climate.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Smirnoff, Marissa
- Description:
- Ancient authigenic dolomites (e.g., concretions) have been studied extensively in order to determine formation conditions and characterize shallow diagenetic environments. the formation of these dolomites is commonly attributed to the anaerobic microbial degradation of organic matter. Authigenic dolomites also occur in modern, “still soft” sediments that are rich in organic matter; however, a comprehensive carbon isotopic characterization of these precipitates has yet to be conducted. Ultimately, carbonates produced by organic matter degradation can be distinguished from primary marine carbonates by their non-seawater δ13C values (~0‰ VPDB in modern oceans). Authigenic dolomites from four modern sites, Gulf of California, Peru Margin, Cariaco Basin, and South Africa Margin, show a wide range of δ 13Cinorg values (about –14 to +13‰). and generally increase with depth, consistent with exposure to and precipitation in progressively deeper diagenetic zones, exhibiting variable mineralization pathways. Total insoluble organic carbon (TOCinsol) contents range from ~0.5 wt% to ~9 wt% and total inorganic carbon (TIC) contents range from ~1 wt% to ~12 wt%. TOCinsol concentrations generally decrease with depth, suggesting progressive degradation of organic carbon with burial. Unlike previous work on outcrop concretions, these dolomites do not express a significant correlation between TIC and TOCinsol. This suggests that authigenic carbonates may only protect organic matter during outcrop weathering, rather than during exposure to deeper organo-diagenetic environments in sediments.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Palermo, Jennifer
- Description:
- Crystal Lake is a small (0.02 km2), alpine lake in the San Gabriel Mountains. This hydrologically closed lake is one of the very few permanent, freshwater lakes in the range. as a result, it is ideal for recording coastal southwestern US hydrologic variability. This study presents a 1300 year sub-decadally resolved reconstruction of extreme hydrologic events (i.e., floods). Regional records of late Holocene floods are scarce and largely limited to marine sediment archives, making this research integral to better prepare the highly-urbanized area for, and to mitigate the effects of, excess water. Sediment cores were obtained in May 2014 from the lake’s depocenter. Magnetic susceptibility, LOI 550°C and 950°C, and grain size were measured at 1 cm contiguous intervals; Corg:Ntotal ratios and bulk δ13Corg were measured every 2 cm. an age model was generated by linear regression of 8 AMS 14C dates of discrete organic matter. Age control for the past 200 years is based on correlation to Rothenberg et al. (2010) core ages. Fourteen storm-induced, rapidly deposited layers are distinguished and characterized from ambient sediments. Regionally, these rapidly deposited event layers occur during both wet and dry climate states. Forcings related to Pacific Ocean-atmosphere interactions are explored as potential drivers of these hydrologic events. Ultimately, the Crystal Lake record shows that large flood-producing storm events, likely caused by atmospheric rivers, have occurred in the late Holocene and will occur in the future, regardless of the background climate state.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Duccini, Kalie
- Description:
- Rare olivine-pyroxene cumulates and hornblende gabbros of the ca. 150 Ma Summit gabbro are scrutinized with the goal of revealing initial differentiation trajectories and source characteristics of mafic magmas within the Late Jurassic Sierra Nevada arc. Geochemical analyses suggest that the magmas that produced the Summit gabbros were not primary, mantle-derived magmas, but rather experienced differentiation in the mid- to lower crust prior to their emplacement in the upper crust. Xenocrystic zircon grains in one cumulate sample document some amount of mid-crustal assimilation. in other samples, multi-shell coronas separate adjacent olivine and plagioclase crystals. Coronas likely formed by solid-state recrystallization during slow subsolidus cooling at relatively high (> 6 kbar) pressures, consistent with initial crystallization in the deep crust. Evidence for dissolution and reequilibration in early-formed minerals suggests disequilibrium with host magmas. Aphanitic-porphyritic textures in hornblende gabbros suggest that disquilibrium was induced by decompression during entrainment in upwardly migrating differentiated magmas, which transported cumulate autocrysts and autoliths of coronitic gabbros into the shallow arc crust. Field relations coupled with a range in crystal accumulation textures and rock types supports a model for emplacement of the Summit gabbro in a dike-sill complex similar to the Torres del Paine of the Miocene Andean arc. Existing geochronology suggests that the Summit gabbro may represent a deeper expression of the Independence dike swarm.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
- Creator:
- Williams, Dustin
- Description:
- Understanding the emplacement and evolution of large, long-lived plutons in the middle crust is essential in comprehending igneous crustal growth and how arcs operate. One challenge is that the plutonic rock record seldom preserves the initial stages of pluton growth. The initial stages of growth, however, may give us clues on the size and compositions of the first intruding magma batches and if and how they coalesce to form interconnected magma mush bodies. Early stages of pluton growth are preserved in the 95–93 Kuna Crest lobe of the 95–85 Ma, 1,100 km2, normally zoned Tuolumne Intrusive Complex (TIC) in the central Sierra Nevada batholith, CA. the Kuna Crest is composed of cm- to m-scale sheets at the margins to km-scale, irregular bodies in the interior of the lobe. Compositions range from granodiorite to gabbroic diorite with knife sharp to gradational contacts. Petrographic analysis reveals varying mineral abundances and textures across subunits, indicating different petrogenic histories. Magnesiohornblende signatures identify the sheeted sub-units as individual batches of magma that underwent complete in-situ fractional crystallization at intermediate to low magmatic temperatures and record the pre- and co-precipitation of other minerals in the assemblage. At the initiation of the Kuna Crest lobe of the TIC, magma increments intruded into the emplacement level as sheet-like bodies without coalescing to form larger magma mush bodies. in contrast, in the interior of the lobe, individual increments grew to larger interconnected magma mush regions represented by the lobe units.
- Resource Type:
- Masters Thesis
- Identifier:
- 9780438054479
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences
23. The Geology and Paleontology of a Vertebrate Bonebed from the Middle Eocene of Southern California
- Creator:
- Santos, Gabriel-philip F.
- Description:
- Eocene terrestrial vertebrate assemblages have been described from formations throughout Southern California, such as the Sespe Formation, the Mission Valley Formation, and “Member C” of the Santiago Formation. Vertebrate assemblages from these formations are similar but geographically distant from each other. In Orange County, outcrops of the Sespe Formation and undifferentiated Santiago Formation are in close proximity, but fossils from the Santiago Formation of Orange County have not been previously described. Paleontology mitigation monitoring of the Talega Housing Development in San Clemente, Orange County in 1998 excavated a vertebrate bonebed from the undifferentiated Santiago Formation and provides the first opportunity to study Eocene terrestrial vertebrates from the formation. The bonebed, named the Talega Bonebed, is approximately 10 cm thick and comprised of densely deposited, disarticulated skeletal elements with no obvious associations and varying states of preservation. the bonebed was excavated as 46 cubic meter blocks, five of which have been prepared. Thus far, the Talega Bonebed is a highly productive fossil stratum with 24 taxa identified to date. Due to the size of the bonebed and method of excavation, the Talega Bonebed is significant for the study of terrestrial vertebrates from late Uintan of Southern California as it has the potential to provide numerous specimens of macrovertebrates that are relatively rare in contemporaneous strata and provides the first opportunity to study the taphonomy of an Eocene-aged site from Southern California.
- Resource Type:
- Masters Thesis
- Identifier:
- 9780438379633
- Campus Tesim:
- Fullerton
- Department:
- Department of Geological Sciences