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Articles 31 - 60 of 272
Full-Text Articles in Earth Sciences
Determining The P-Wave Velocity Structure In The Near-Surface Of Nw Miami, Florida, Using Quarry Blasts, Elham Moslemi
Determining The P-Wave Velocity Structure In The Near-Surface Of Nw Miami, Florida, Using Quarry Blasts, Elham Moslemi
USF Tampa Graduate Theses and Dissertations
The fact that Florida is an earthquake-free region has caused seismologists to pay less attention to it. Few earthquakes in this state mean it is not a usual practice to study the propagation of seismic waves. However, utilizing data from quarry blasts, we studied wave propagation in this region. The primary objective of the project is to investigate the near-surface P-wave velocity structure and factors that may affect it. We also analyzed the amplitude of signals versus distance and blast size. A network of up to 10 Raspberry Shake instruments around the NW Miami-Lakes mining area was deployed where four …
Investigating Mobility In The Northern Balkans During The Fifth Millenium Bc Through Strontium Analysis Of Human Tooth Enamel, Aurélien Tafani
Investigating Mobility In The Northern Balkans During The Fifth Millenium Bc Through Strontium Analysis Of Human Tooth Enamel, Aurélien Tafani
USF Tampa Graduate Theses and Dissertations
This research investigates how individual mobility among ancient populations in Romania during the Eneolithic, between 5000 and 4000 BC, may be related to the spread of the material culture known as Kodjadermen-Gumelniţa-Karonovo VI (KGK VI) that extended over most of southern Romania and Bulgaria. This work seeks to combine results on individual mobility with other lines of archaeological evidence to provide a better understanding of the social context and kinship relationships that were in place when these events took place.
Strontium isotopic analyses were performed on 130 individuals from two sites located in the southern Romania: 49 from Sultana and …
Examining Paleoshorelines In The Eastern Gulf Of Mexico: Insights On Sea Level History And Potential Areas Of Interest For Habitat Management, Catalina Rubiano
Examining Paleoshorelines In The Eastern Gulf Of Mexico: Insights On Sea Level History And Potential Areas Of Interest For Habitat Management, Catalina Rubiano
USF Tampa Graduate Theses and Dissertations
An inventory of multibeam bathymetry containing relict drowned and lithified paleoshorelines has been compiled and analyzed in the first ever shelf-wide investigation of paleo sea level indicators on the west Florida shelf (WFS). On the largest scale, the WFS is a wide and gently sloping terrain that is characterized by a carbonate-rich sediment regime. This framework coupled with the region’s tectonic stability provided a setting in which sea level changes since ~ 20 ka have been recorded to a remarkable degree of resolution in the form of paleoshorelines which formed at sea level and were subsequently drowned and preserved in …
Water Chemistry Variability In Peacock Springs Cave System And Spring Basin: Impacts On Continuous Monitoring Of Karst Aquifers, Mahnoor Kamal
Water Chemistry Variability In Peacock Springs Cave System And Spring Basin: Impacts On Continuous Monitoring Of Karst Aquifers, Mahnoor Kamal
USF Tampa Graduate Theses and Dissertations
The Upper Floridan Aquifer (UFA) is a highly transmissive and heterogeneous karst aquifer that makes it acutely susceptible to pollution. Rapid and extensive water quality changes in nutrients at springs draining the UFA have prompted intensive monitoring at several priority springs, including continuous and discrete water quality sampling. Springs, however, are a discrete discharge point of an often-expansive phreatic cave network that can intersect different land uses and thus drain distinct geographic areas of a springshed. The extensive network contains convergent passages from deep and shallow aquifer regions and may contribute to varying water chemistry across passages resulting in water …
Labile Dissolved Nickel (Ni) Concentrations In The North Pacific, Calyn M. Crawford
Labile Dissolved Nickel (Ni) Concentrations In The North Pacific, Calyn M. Crawford
USF Tampa Graduate Theses and Dissertations
Nickel (Ni) is an important micronutrient for phytoplankton and bacteria that serves as a required co-factor in several metalloenzymes. Despite these known biological uses, total dissolved Ni concentrations remain elevated in global surface waters, in contrast to the surface depletion commonly observed for macronutrients and other nutrient-type trace elements. A prevailing hypothesis for the muted depletion of dissolved Ni concentrations in surface waters is that dissolved Ni in seawater is not in a bioavailable form. The chemical lability of Ni in seawater provides insight into Ni speciation and bioavailability, but few measurements have been made in the open ocean to …
Understanding Controls On Spring Hydrographs In An Eogenetic Karst Aquifer In North-Central Florida, Ryan Almeqhem
Understanding Controls On Spring Hydrographs In An Eogenetic Karst Aquifer In North-Central Florida, Ryan Almeqhem
USF Tampa Graduate Theses and Dissertations
Florida has one of the largest karst aquifers in the United States, with a significant portion of its water resources originating from the eogenetic karst system in north central Florida. Despite the importance of this system, eogenetic karst still needs to be studied compared to telogenetic karst. The hydrological behavior of karst aquifers is complex, with numerous factors influencing the timing, magnitude, and shape of spring hydrographs. One hypothesis, by Florea and Vacher (2006), suggests that matrix permeability is the primary control of spring hydrographs in karst systems. However, this thesis challenges this hypothesis by presenting evidence that the recharge …
Mining Multibeam Transit Data For Deep Ocean Polymetallic Nodules: Case Study In Se Pacific Ocean, Mark E. Mussett
Mining Multibeam Transit Data For Deep Ocean Polymetallic Nodules: Case Study In Se Pacific Ocean, Mark E. Mussett
USF Tampa Graduate Theses and Dissertations
Occurrences of nodules on the seafloor represent benthic habitats and present potential deposits of economically important metals. Better understanding their extent throughout Earth’s oceans will aid in resource management and determining different factors which influence their formative factors and respective local characteristics. Multibeam bathymetry and backscatter data, along with auxiliary data suggest an area of seafloor near the Foundation Seamount chain in the southern Pacific Ocean, centered around -36.84° latitude, -119.75° longitude, contains a previously uncharted polymetallic nodule occurrence. Our analysis of Simrad EM12 DUAL (12 kHz) multibeam data, collected during a 1997 transit, shows an area of strong backscatter …
Flow Generation And Propagation From Headwater Wetlands To Downstream Waters, Leanne Marie Stepchinski
Flow Generation And Propagation From Headwater Wetlands To Downstream Waters, Leanne Marie Stepchinski
USF Tampa Graduate Theses and Dissertations
Headwater wetlands are connected to one another and to downstream waters by dynamic hydrologic flowpaths, functioning as integrated hydrologic networks at the watershed scale. Headwater wetlands perform a variety of hydrologic lag, sink, and source functions, including flow generation and propagation, thereby contributing to the natural flow regimes of downgradient waters. The functions of individual wetlands and their contributions to hydrologic connectivity and subsequently to the natural flow regime have been widely studied and are well understood. Comparatively, the functions and hydrologic connectivity within wetland complexes as a whole and their collective subsequent contributions to the natural flow regime of …
Detection Of Subsidence In West-Central Florida Using Persistent Scatterer Interferometry And Near-Surface Geophysics, Tonian R. Robinson
Detection Of Subsidence In West-Central Florida Using Persistent Scatterer Interferometry And Near-Surface Geophysics, Tonian R. Robinson
USF Tampa Graduate Theses and Dissertations
This dissertation consists of three studies that employ Persistent Scatterer Interferometry (PSI, also known as PSInSAR) to better understand how subsidence in west-central Florida relates to underlying geological processes. In the first study, near-surface geophysical methods (Ground Penetrating Radar (GPR) and Electrical Resistivity (ERT)), terrestrial remote sensing applications (Light Detection and Ranging (LiDAR) and Structure from Motion (SfM)), and PSI were used to monitor the spatial and temporal behaviors of a suspected growing sinkhole in the Sandhill Boyscout Reservation, Hernando County, Florida. The survey area was located within and around a topographic low assumed to be the surface of the …
Ice-Core Reveals Flavors Of Hydroclimate Extremes In The American Southwest, Laura Calabrò
Ice-Core Reveals Flavors Of Hydroclimate Extremes In The American Southwest, Laura Calabrò
USF Tampa Graduate Theses and Dissertations
A small number of caves and lava tubes worldwide host perennial ice deposits, which occur at elevations well below those of mountain glaciers and in areas outside the permafrost climatic belt, where no surface glaciation exists. These settings make any of the ice deposits in caves or lava tubes particularly susceptible to the current warming trend, leading to the imminent loss of some untapped cryospheric paleoenvironmental archives.
The present work is the result of a paleoclimate study based on ice deposits accumulated within lava tubes in El Malpais National Monument (ELMA, western New Mexico). The ice cores span from 7,000 …
Environmental Chemical Analysis Method Optimization And Application To Northwest Cuban Marine Sediment, Thea R. Bartlett
Environmental Chemical Analysis Method Optimization And Application To Northwest Cuban Marine Sediment, Thea R. Bartlett
USF Tampa Graduate Theses and Dissertations
A method for gas chromatography tandem mass spectrometry (GC-MS/MS) in selected reaction monitoring (SRM) mode has been optimized to quantify 250 compounds of a variety of compound classes such as polycyclic aromatic hydrocarbons (PAHs), oxidized PAHs, organochlorinated pesticides, polychlorinated biphenyls, biomarkers (hopanes, steranes, tri-aromatic steroids, and fecal sterols), aliphatic hydrocarbons, and plastic additives. This method was validated based on available QA/QC standards using several environmental samples, both sediment and biota, and standard reference materials. This contaminant-focused method can be used as a forensic geochemistry tool to evaluate oil contamination and other contaminant histories in future research studies. When applied to …
Applications Of Seismic And Geodetic Data To Earthquake Hazard Research, Mahsa Afra
Applications Of Seismic And Geodetic Data To Earthquake Hazard Research, Mahsa Afra
USF Tampa Graduate Theses and Dissertations
Being a part of a seismically active zone, including large and crowded cities such asTehran, Qazvin and Semnan, Central Alborz experiences many local earthquakes. Knowl- edge of crustal velocity structure in this area is thus necessary considering its economical and political importance, a large concentration of population, and relatively poor construc- tion practice which increases the earthquake risks in this region. In second chapter of this thesis, we aim at obtaining the 3D crustal velocity structure of the Central Alborz region in northern Iran using local earthquake tomography. We also validate anomalies inferred from our velocity model using an independent …
Geoarchaeology Of Estuarine Seascapes In Tampa Bay, Florida., Kendal R. Jackson
Geoarchaeology Of Estuarine Seascapes In Tampa Bay, Florida., Kendal R. Jackson
USF Tampa Graduate Theses and Dissertations
This dissertation investigates the geological, ecological, and archaeological histories of Tampa Bay, Florida’s largest open-water estuary system. Previous geoscientific and archaeological work has studied the evolution of Florida’s estuaries as ‘pre-anthropogenic’ ecosystems and conceptualized Indigenous maritime societies as mostly passive inhabitants of dynamic ‘natural’ environments. Further, the environmental legacies of more recent, industrial-scale estuary modification attending Florida’s 20th-century population boom have been understudied—leading to popular and scientific confusion about historical conditions. The work composing this dissertation research seeks to reconceptualize Tampa Bay as a complex mosaic of cultural seascapes that have been variously altered and modified by human societies across …
A Seismic Investigation Of Uturuncu Volcano And The Lazufre Volcanic Complex, Heather L. Mcfarlin
A Seismic Investigation Of Uturuncu Volcano And The Lazufre Volcanic Complex, Heather L. Mcfarlin
USF Tampa Graduate Theses and Dissertations
The following dissertation is a study of three seismological techniques used to determine the geophysical properties of two large, inflating magma bodies in the upper crust in South America: one under Uturuncu volcano and one beneath Lastarria and Cordon del Azufre volcanoes. First, I use the method of teleseismic receiver functions to image the top and bottom of the magma body beneath Uturuncu volcano. Depths to the top of this body vary between 6 and 12 km below sea level, while depths to the bottom vary between 13 and 22 km below sea level, with the thickness ranging from 6 …
Lithium And Lithium Isotope Behavior During High Temperature Solid/Fluid Exchanges: Examples From Iceland And The Izu-Bonin Forearc, Alex Maruszczak
Lithium And Lithium Isotope Behavior During High Temperature Solid/Fluid Exchanges: Examples From Iceland And The Izu-Bonin Forearc, Alex Maruszczak
USF Tampa Graduate Theses and Dissertations
The development of a method for lithium isotopic measurement was developed using a quadrupole, single-collector ICP-MS. Measured precision was ±1.00‰ 2σ over a 15-month period based on measurements of international rock standards. A 1-hour leach using cold, HCl was sufficient to remove alteration-related Li in minimally to moderately altered seafloor basalts. Measurements on the Holocene ages lavas from the neovolcanic zones of Iceland suggest no systematic Li isotopic variability among the differing Icelandic sources. Felsic samples from Hekla and Pumice contain elevated Li contents of >18ug/g while the tholeiitic and alkaline basalts are <8ug/g Li. Most of the island lies around MORB values of ~+3 to +5‰ with the exception of Western Volcanic Zone samples that show evidence for seawater inputs. The RN-17 drillcore, which penetrates >3000m through a hydrothermal system in the …8ug/g>
Land Use/Land Cover Uncertainty Analysis Using Hydrological Modeling In The Northern Watershed Of Lake Okeechobee, Andres Lora Santos
Land Use/Land Cover Uncertainty Analysis Using Hydrological Modeling In The Northern Watershed Of Lake Okeechobee, Andres Lora Santos
USF Tampa Graduate Theses and Dissertations
Over the past 150 years, Florida has undergone a major land-form transformation, transitioning from a natural to a primarily built environment. The state's population has grown exponentially, from less than 50,000 residents in the 1850s to approximately 22 million residents today. This population growth has led to significant changes in land use, including urbanization, mining, and agriculture. This trend is expected to continue, with projections indicating an increase in urbanization across the state. 2070 land use/land cover projections were used as input for the Watershed Assessment Model (WAM) to analyze the potential impact of these changes on flow, total nitrogen …
Quantifying A 21-Year Surface Water And Groundwater Interaction In A Ridge And Valley Lake Environment Using A Highly Constrained Modeling Approach, Richard T. Bowers Jr.
Quantifying A 21-Year Surface Water And Groundwater Interaction In A Ridge And Valley Lake Environment Using A Highly Constrained Modeling Approach, Richard T. Bowers Jr.
USF Tampa Graduate Theses and Dissertations
Karst lakes are ubiquitous in ridge terrain settings in limestone aquifer coastal plain environments. In west-central Florida, these lakes are frequently connected to the Upper Floridan aquifer and have unique aquifer recharge characteristics. They have been selectively studied because they commonly have no or very limited surface water discharge and limited drainage areas, have appreciable surface water and groundwater interaction and leak to the deep aquifer. An innovative modeling approach was developed to collectively understand and more precisely quantify this vertical leakage, both from a lake-specific and regional water budget standpoint, for a 21-year study period (2000-2020). A unique, calibrated …
Volcano And Tectonic Hazard Modeling Using Interdisciplinary Geophysical And Geodetic Methods, Mitchell Scott Hastings
Volcano And Tectonic Hazard Modeling Using Interdisciplinary Geophysical And Geodetic Methods, Mitchell Scott Hastings
USF Tampa Graduate Theses and Dissertations
Volcanic and tectonic hazards such as volcanic eruptions, earthquakes and tsunamis present risks to about ~45% of the global population. They have caused at least 1.5 trillion dollars in damages worldwide since the start of the 20th century, and the costs are accelerating as population increases. In this dissertation, new data are combined with existing information and novel modeling approaches to quantify volcanic, earthquake and tsunami hazards.
The Blackfoot Reservoir Volcanic Field (BRVF) is a bimodal volcanic field on southeastern margin of the Eastern Snake River Plain in Idaho. In the BRVF, gravity anomalies reveal two shallow silicic intrusions that …
Functional Morphology And Taphonomy Of Ordovician–Silurian Diploporan Echinoderms, Stephen Ashley Hill
Functional Morphology And Taphonomy Of Ordovician–Silurian Diploporan Echinoderms, Stephen Ashley Hill
USF Tampa Graduate Theses and Dissertations
Diploporan echinoderms were one of the most speciose groups of stemmed echinoderms during the Ordovician. Despite this widespread abundance, the fossil record of diploporan fauna consists primarily of incomplete specimens, with complete specimens being rare. While the theca, or body, is more commonly preserved, the feeding appendages and the attachment structures (i.e. stems or holdfasts) are seldomly preserved. Insight into these features is highly valuable to the understanding the paleoecology, like the feeding and respiratory strategies, of these enigmatic creatures.
One group of diploporan echinoderms which does have an extensive fossil record, is the Holocystites Fauna, primarily known from the …
Ice Deposits In Lava Tubes From West-Central New Mexico As Archives Of Past Volcanic Eruptions And Climate Change, Quinton Z. Vitelli-Hawkins
Ice Deposits In Lava Tubes From West-Central New Mexico As Archives Of Past Volcanic Eruptions And Climate Change, Quinton Z. Vitelli-Hawkins
USF Tampa Graduate Theses and Dissertations
The Southwest of the United States is currently in a megadrought phase. Recent studies have shown that three of the most severe droughts of the last two millennia have occurred in the last 120 years, while geo-archaeological evidence suggests there were five megadroughts just from 150 to 950 CE. To try to better understand the causes of the droughts across the Southwest, a 110-cm long ice core was drilled from an ice deposit in a lava tube (Cave 29) from El Malpais National Monument in west-central New Mexico. The δ18O values in the ice core (ranging from −11.78 to −3.54‰) …
A Technique-Based Approach To Structure-From-Motion: Applications To Human-Coastal Environments, Robert Van Alphen
A Technique-Based Approach To Structure-From-Motion: Applications To Human-Coastal Environments, Robert Van Alphen
USF Tampa Graduate Theses and Dissertations
Photogrammetry is a method by which physical information can be extracted from thecorrespondence of 2-dimensional images. In the geosciences, Structure-from-Motion (SfM) photogrammetry is a technique that has seen considerable interest in the past decade of research. Here I present three case studies of various scope and methodologies which can inform the use of SfM in the geosciences. First, I discuss the theoretical and algorithmic basis of SfM photogrammetry and its uses thus far in the geosciences. Chapters two through four show specific studies which highlight several approaches to SfM and the data which can be produced. Chapter five then concludes …
Determining Depth Of Closure Based On Time-Series Beach Profiles And Empirical Formulas: A Case Study Along The Florida Coast, Elizabeth Royer
Determining Depth Of Closure Based On Time-Series Beach Profiles And Empirical Formulas: A Case Study Along The Florida Coast, Elizabeth Royer
USF Tampa Graduate Theses and Dissertations
Depth of closure (DOC) is defined as the most landward depth seaward of which there is no significant change in bed elevation and no significant net sediment exchange between the nearshore and the offshore over a certain period of time, such as 5 to 20 years. DOC is an essential parameter used in beach and shore protection, sediment management, and many other aspects of coastal studies. Taking advantage of advancements in wave hindcast and bathymetry measurement in the past 20 years (2000-2019), this study determined the DOC at 12 locations along the Florida coast, including three from the northwest Gulf …
Isotopic Study Of The Waters From The Sulphur Springs Catchment, Tampa, Florida, Esra Zengin
Isotopic Study Of The Waters From The Sulphur Springs Catchment, Tampa, Florida, Esra Zengin
USF Tampa Graduate Theses and Dissertations
A stable isotope study was carried out using precipitation, spring water, groundwater well sample, and a seawater sample during the wet season in the Sulphur Springs watershed in Tampa, Florida. Studies that track long term isotopic variation over wet seasons are limited in the region. To fill this knowledge gap, this study aims to quantify the contributions of precipitation and diffuse sources to discharge in Sulphur Springs. A three-component mixing model was applied using δ18O and δ2H values to determine different source water contributions to spring water discharge. The three-component mixing model calculations suggest spring water consists mainly of diffuse …
Empirical And Modeled Δ13c And Δ15n Isoscapes In The Gulf Of Mexico And Their Application To Fish Eye Lens Migration Studies, Brianna Michaud
Empirical And Modeled Δ13c And Δ15n Isoscapes In The Gulf Of Mexico And Their Application To Fish Eye Lens Migration Studies, Brianna Michaud
USF Tampa Graduate Theses and Dissertations
Isoscapes are depictions of the spatial patterns of isotopic values in a given area. Isoscapes can be created using measurements form samples (empirical isoscapes) or using statistical models of spatial isotopic variation (modeled isoscapes). Isoscapes have a wide variety of potential applications though, in the realm of marine ecology, they are most often used infer ecological processes, food web linkages, the origin of samples, and the movements of marine organisms.
However, to use isoscapes for these applications, it is necessary to have isoscapes at spatial scales relevant to the application in question. It is also necessary to have isoscapes that …
Characterizing Explosive Volcanic Eruptions Using Tephra Fall Deposit Data, Robert Constantinescu
Characterizing Explosive Volcanic Eruptions Using Tephra Fall Deposit Data, Robert Constantinescu
USF Tampa Graduate Theses and Dissertations
This dissertation addresses the estimation of the magnitudes and intensities of explosive volcanic eruptions using tephra fall deposits and numerical modeling. Tephra fall deposits retain information about eruption dynamics. Volcanologists sample tephra fall deposits and measure the thickness, extent and grain size distribution to estimate the erupted volume and plume height of explosive eruptions. These terms are known as eruption source parameters. These parameters are used to classify the intensity and magnitude of the eruption on a scale such as the Volcanic Explosivity Index (VEI). Accurate estimation of the intensity and magnitude of explosive eruptions is a crucial factor in …
Factors Controlling Longshore Variations Of Beach Changes Induced By Hurricane Hermine Along Pinellas County Beaches, West-Central Florida, Wenhan Zhai
USF Tampa Graduate Theses and Dissertations
Hurricane Hermine, 2016, impacted the coast of west-central Florida and generated high waves superimposed on elevated wave levels which caused significant beach erosion. A total of 122 profiles, spaced about 300 m apart, were surveyed 2 weeks before and one week after the storm to examine the beach changes along three barrier islands along the coast of west-central Florida. including Sand Key, Treasure Island and Long Key. In order to investigates the longshore variations of beach/nearshore changes induced by storm, several parameters were defined and calculated including beach volume changes, berm height, beach width, foreshore slope, as well as sandbar …
Soil Accretion And Mass Accumulation In A Scrub And Fringe Mangrove Forest In Biscayne Bay, Florida, Jessica A. Jacobs
Soil Accretion And Mass Accumulation In A Scrub And Fringe Mangrove Forest In Biscayne Bay, Florida, Jessica A. Jacobs
USF Tampa Graduate Theses and Dissertations
This study estimated soil accretion and mass (organic carbon (OC), total nitrogen (TN), and total soil) accumulation in a scrub and fringe mangrove forest in Biscayne Bay, FL, to assess how forests of different morphologies (scrub vs. fringe) have kept pace with recently accelerating rates of sea-level rise. Accretion rates (AR) were estimated using the Constant Initial Concentration (CIC) model of lead-210 deposition and it was determined that the scrub forest has accreted at 1.3 ± 0.2 mm yr-1 over 75 years and the fringe forest at 2.8 ± 0.4 mm yr-1 over 92 years. The fringe forest estimate met …
Revisiting Darwin’S Little Pond As A Method To Liberate Phosphorus From Apatite Under Prebiotic Hadean Earth Conditions, Jennifer Lago
Revisiting Darwin’S Little Pond As A Method To Liberate Phosphorus From Apatite Under Prebiotic Hadean Earth Conditions, Jennifer Lago
USF Tampa Graduate Theses and Dissertations
Phosphorus is an essential element for life as we know it. Phosphorus, mainly in the form of phosphate, is key to biologic functions such as genetic material, energy production, and cellular framework. As phosphorus is key to so many important biological functions it is of no wonder the question of how phosphorus was incorporated into life initially is a fundamental question in how life began.
During this time a prebiotic phosphorus source would need to have originated in rock, as phosphorus has not volatile source on Earth. The most prevalent mineral source on a prebiotic Earth would likely have been …
Resolution Of Lava Tubes With Ground Penetrating Radar, Sanaz Esmaeili
Resolution Of Lava Tubes With Ground Penetrating Radar, Sanaz Esmaeili
USF Tampa Graduate Theses and Dissertations
Finding habitable places to keep astronauts safe from surface radiation, magnetic storms, and temperature fluctuations will be an important component of future planetary exploration missions. Remote sensing surveys on other planets indicate the presence of lava tubes. Ground Penetrating Radar (GPR) has shown great potential for detection of tunnels in terrestrial environments. In this research, the capabilities of this near surface rapid exploratory tool for detection of lava tubes are investigated. This dissertation describes terrestrial examples of how GPR can be utilized to explore tubes and addresses the capabilities of GPR for resolving tube-related features such as the floor, fractures, …
Three-Dimensional Intrusion Geometries In The Monogenetic San Rafael (Utah) Sub-Volcanic Field Revealed By Nonlinear Inversion Of Magnetic Anomaly Data, Troy A. Berkey
USF Tampa Graduate Theses and Dissertations
Distributed volcanic fields are common on Earth and nearby planetary bodies. Unlike their central-vent counterparts, these volcanic centers are comprised of many individual basaltic magmatic dikes, which are often only expressed at the surface in the form of vents, domes, and lava flows. In situ imaging of the shallow (<1 km) subsurface can reveal important details about the 3D geometry of fissure systems that feed distributed eruptive centers, with implications for the nature of these eruptions: their mass flow rates, explosivity, durations, and volcanotectonic interaction. Luckily, dikes, sills, conduits and related near-surface structures tend to carry high remnant magnetizations, creating magnetic anomalies at the surface where sufficient magnetic contrast exists with the host rocks they intrude. In the San Rafael Sub-volcanic field (SRSVF), basaltic dikes intrude fractured and horizontally bedded Jurassic sandstones, now eroded to a depth of about 800 m beneath the paleo-surface. Detailed mapping and profiles with a Cs-vapor magnetometer reveal far more complex anomalies than can be attributed to simple planar dikes, including: sills, buds, and domes. We image these geometries using MagCube-parallel, an open-source nonlinear inversion code we developed that models complex geometry with multiple (<= 1,000) vertical-sided prisms. I show one normally polarized fissure system to include along strike: An ~3-14 m thick, ~50 m wide dome-like feature or laccolith at depths of ~9-20 m, a roughly vertical conduit ~15 m thick, ~36-50 m wide, at ~1-16 m depth near the center of the mapped fissure-like system, and a ~8-48 m. wide dike at ~2-17 m depth that is <1-6 m thick, with reducing magnitude northward. While model depth and thickness vary with magnetization contrast, the main geometric relationships do not. Magnetic mapping of a nearby fissure reveals the same types of structures. The implication of these structures is that the small-volume fissure eruptions were likely pulsatory, with episodes of horizontal intrusion of sills, and sufficient time to develop gravitational instabilities.