Geophysics and Seismology Commons^™

Archean (3.3 Ga) Paleosols And Paleoenvironments Of Western Australia, Gregory J. Retallack, Mark D. Schmitz

Geosciences Faculty Publications and Presentations

The Pilbara craton of northwestern Australia is known for what were, when reported, the oldest known microfossils and paleosols on Earth. Both interpretations are mired in controversy, and neither remain the oldest known. Both the microfossils and the paleosols have been considered hydrothermal artefacts: carbon films of vents and a large hydrothermal cupola, respectively. This study resampled and analyzed putative paleosols within and below the Strelley Pool Formation (3.3 Ga), at four classic locations: Strelley Pool, Steer Ridge, Trendall Ridge, and Streckfuss, and also at newly discovered outcrops near Marble Bar. The same sequence of sedimentary facies and paleosols was …

Two New Absolute Gravity Base Stations Established In Lincoln, Ne, Kris Guthrie, Irina Filina

Transactions of the Nebraska Academy of Sciences and Affiliated Societies

Two new absolute gravity base stations were established on the University of Nebraska-Lincoln City Campus in April 2022. The values were transferred with a relative gravity meter from four existing stations within 238 miles and were later validated by the National Oceanic and Atmospheric Administration. The final values at 22.5 cm above marker height are 980177.781 ± 0.010 mGal at the Lincoln Bell Tower Station and 980178.079 ± 0.010 mGal at the Lincoln Museum station with a gravity gradient of -3.105 µGal/cm. This paper describes the process of transferring gravity values and outlines recommendations for similar projects in the future.

Constraints On Near-Ridge Magmatism Using 40Ar/39Ar Geochronology Of Enriched Morb From The 8°20' N Seamount Chain, Molly K. Anderson, Michael R. Perfit, Leah E. Morgan, Daniel J. Fornari, Michael Cosca, V. Dorsey Wanless

Geosciences Faculty Publications and Presentations

Our understanding of the spatial-temporal-compositional relationships between off-axis magmatism and mid-ocean ridge spreading centers is limited. Determining the ⁴⁰Ar/³⁹Ar ages of mid-ocean ridge basalt (MORB) lavas erupting near mid-ocean ridges (MOR) has been a challenge due to the characteristically low K₂O contents in incompatible element-depleted normal MORB (NMORB). High-precision ⁴⁰Ar/³⁹Ar geochronology is used here to determine ages of young, basaltic lavas erupted along the 8°20' N seamount chain west of the East Pacific Rise (EPR) axis that have a range of incompatible element enrichments (EMORB) suitable for ⁴⁰Ar/³⁹Ar geochronology …

Is Macroporosity Controlled By Complexed Clay And Soil Organic Carbon?, Aaron N. Koop, Daniel R. Hirmas, Sharon A. Billings, Li Li, Alejandro Cueva, Xi Zhang, Hang Wen, Attila Nemes, Lígia F. T. Souza, Hoori Ajami, Alejandro N. Flores, Aoesta K. Rudick, Annalise Guthrie, Lola M. Klamm, Micah Unruh, Pamela L. Sullivan

Geosciences Faculty Publications and Presentations

Multi-scale evidence of rapid, climate-induced soil structural changes occurring at yearly to decadal timescales is mounting. As a result, it has become increasingly important to identify the properties and mechanisms controlling the development and maintenance of soil structure and associated macroporosity. This is especially relevant since macroporosity has disproportionate effects on saturated hydraulic conductivity (K_sat) which strongly influences water storage and flux, thus, affecting the water cycle. In this study, we use decision trees and piecewise linear regression to assess the influence of soil and climate properties on effective porosity (EP; a proxy of macroporosity) in both …

U-Pb Zircon Dates From North American And British Avalonia Bracket The Lower–Middle Cambrian Boundary Interval, With Evaluation Of The Miaolingian Series As A Global Unit, Ed Landing, Mark D. Schmitz, Stephen R. Westrop, Gerd Geyer

Geosciences Faculty Publications and Presentations

High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeri Zone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eli Assemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages of 506.34 ± 0.21 Ma (Kiskinella cristata Zone) and 506.25 ± 0.07 Ma (Eccaparadoxides bennetti Zone). The composite unconformity separating the Brigus and Chamberlain’s Brook formations is constrained between these ages. An Avalonian Lower–Middle Cambrian boundary between 507.2 ± 0.1 …

Applications Of Observational Seismology: Insights Into Volcanic And Near Surface Processes, Justin T. Wilgus

Earth and Planetary Sciences ETDs

The field of observational seismology has made tremendous progress in the past two decades. This progress has been multi-faceted in form, but significant contributions emanated from 1) increases in both the quality and the quantity of seismic data 2) advances in computational power 3) advances in algorithmic capability, including machine learning. In this dissertation I report on three distinctly different seismic applications made possible by the aforementioned progress and discuss the insights these applications have provided in understanding volcanic and near surface processes of the Earth.

In the first chapter titled, “Shear Velocity Evidence of Upper Crustal Magma Storage Beneath …

Petrophysical Properties Of The Hed Meteorites And The Bushveld Igneous Complex: Implications For Future Asteroid Prospecting Missions, Lukas Louwerse

Electronic Thesis and Dissertation Repository

In this work, I make a quantitative and mineralogical comparison of Howardite-EuctriteDiogenite (HED) meteorites with terrestrial samples from the Bushveld Igneous Complex (BIC) to assess how geophysical surveys of 4 Vesta or of V-type asteroids could detect BIClike ore deposits. Petrophysical methods in this work include bulk and grain density, derived porosity (using helium pycnometry, the Archimedean method, and X-ray micro-computed tomography), magnetic susceptibility, induced polarization and resistivity, and P-wave velocity. Mineralogical methods in this work include optical microscopy, micro X-ray diffraction, micro X-ray fluorescence element mapping, and electron beam methods. Howardite NWA 15199 was classified as part of this …

Seismic Shadow Zone Investigation In The Upper Magma Reservoir Of The Yellowstone Caldera, Sarah Nolt-Caraway

Earth and Planetary Sciences ETDs

This study investigates whether the Yellowstone Caldera has enough melt to mute S-waves, creating a seismic shadow zone. Using a dense nodal deployment of ~650 stations, 7-9 earthquakes during the nodal deployment, and 21 broadband stations with 3,000-4,000 events per station; amplitude and noise maps, seismograms, and automatic phase picks probabilities from a deep learning model were analyzed to assess the potential role of melt, crustal attenuation, and noise in affecting body waves, particularly S-phases. The results are inconclusive, with unclear evidence whether observed amplitude decay is normal signal decay due to distance, noise-related, melt, or from scattering and intrinsic …

Seismic Analysis Of The Upper & Lower Falls Of The Yellowstone River, Loring Schaible

Earth and Planetary Sciences ETDs

Twelve years of concurrent hydrologic and continuous seismic data along with temporary seismic data demonstrate that the Upper and Lower Falls of the Grand Canyon of the Yellowstone River comprise a highly localized source of 0.5-5 Hz seismic energy that overwhelms anthropogenic contributions. In aggregate, seismic amplitude from 2008-2019 is linearly related to discharge with a correlation coefficient of 0.96. Repeated deviations from this linear relationship persist for 1-2 weeks prior to the date that Yellowstone Lake becomes clear of winter ice coverage. Seismic efficiency increases by ~50-250% during this period of ice-breakup, during which lake ice flows into the …

Partial Auto-Correlation Of Low Magnitude Earthquakes From The 2016 Iris Aray In Grant County, Oklahoma, Alex Christopher Eddy

Open Access Theses & Dissertations

The Anadarko Basin in is a seismically active basin that spans central and western Oklahoma into Kansas. In June and July of 2016, the IRIS Community Wavefield Experiment array was deployed for approximately a month, recording over 300 earthquakes. Using 4 of these earthquakes and an east â?? west array of 129 Fairfield Nodal Z-land 3C nodes, I present a novel application of correlation. These four earthquakes with a ML of 2.8-3.0 represent a varied azimuthal distribution and are between 9 and 40km from the array and have a frequency peak at approximately 10 Hz.

As a proof of concept, …

Evaluating The Feasibility Of Using Strain Measured During Sinusoidal Rate Pumping Tests To Characterize An Aquifer, Riley Blais

All Theses

Pumping tests with sinusoidal variation in pumping rate have been proposed as a method for improving aquifer characterization. These tests can interrogate a larger aquifer volume than slug tests and they can be more sensitive to small variations in drawdown. Current methods of using sinusoidal variations of rate are based on measuring pressure signals from the reservoir or aquifer, which requires access to monitoring wells. An alternative approach has been developed that measures the strain in the vadose zone instead of pressure in the reservoir. An instrument has been developed at Clemson University that can measure small strains using optical …

Revisiting The Diffuse Layer Polarization Of A Spherical Grain In Electrolytes With Numerical Solutions Of Nernst-Planck-Poisson Equations, Qifei Niu

Geosciences Faculty Publications and Presentations

Induced polarization (IP) has been frequently used in solid earth geophysics, hydrology, and environmental sciences. A mechanistic understanding of the IP responses of geological materials is crucial for correctly interpreting field IP measurements. In this study, the fully-coupled, nonlinear Nernst-Planck-Poisson equations are numerically solved to analyze the electrochemical mechanism of diffuse layer polarization around a spherical grain immersed in electrolytes. The numerical results show diffuse layer polarization is formed by the charge separation between counterions in the diffuse layer and charges on the grain surface. Both tangential and normal movements of counterions in the diffuse layer are involved in the …

Whitewater Sound Dependence On Discharge And Wave Configuration At An Adjustable Wave Feature, Taylor A. Tatum, Jacob F. Anderson, Timothy J. Ronan

Geosciences Faculty Publications and Presentations

Stream acoustics has been proposed as a means of monitoring discharge and wave hazards from outside the stream channel. To better understand the dependence of sound on discharge and wave characteristics, this study analyzes discharge and infrasound data from an artificial wave feature which is adjusted to accommodate daily changes in recreational use and seasonal changes in irrigation demand. Monitorable sound is only observed when discharge exceeds ∼35 m³/s, and even above that threshold the sound-discharge relationship is non-linear and inconsistent. When sound is observed, it shows consistent dependence on wave type within a given year, but the …

Uav-Based Quantification Of Dynamic Lahar Channel Morphology At Volcán De Fuego, Guatemala, Jerry C. Mock, Jeffrey B. Johnson, Armando Pineda, Gustavo Bejar, Amilcar Roca

Geosciences Faculty Publications and Presentations

This study quantified erosional and depositional processes for secondary lahars in Las Lajas drainage at Volcán de Fuego, Guatemala, during the rainy season from May to October 2021. Abundant pyroclastic material from ongoing eruptive activity is remobilized seasonally during heavy precipitation, which can impact infrastructure and populations living near Fuego. Our region of focus was in an agricultural zone 6 to 10 km from the summit, surveyed with an unoccupied aerial vehicle (UAV) quadcopter at monthly intervals. Imagery was processed into overlapping time-lapse structure from motion digital elevation models (DEMs). DEMs were differenced to find volumetric changes as a function …

The Temporal Evolution Of Subduction Initiation In The Samail Ophiolite: High-Precision U–Pb Zircon Petrochronology Of The Metamorphic Sole, Matthew Rioux, Joshua M. Garber, Michael Searle, James L. Crowley, Sally Stevens, Mark Schmitz, Andrew Kylander-Clark, Kayla Leal, Tyler Ambrose, Andrew J. Smye

Geosciences Faculty Publications and Presentations

High-precision dating of the metamorphic sole of ophiolites can provide insight into the tectonic evolution of ophiolites and subduction zone processes. To understand subduction initiation beneath a young, well-preserved and well-characterized ophiolite, we performed coupled zircon laser-ablation inductively coupled mass spectrometry trace element analyses and high-precision isotope dilution-thermal ionization mass spectrometry U–Pb dating on 25 samples from the metamorphic sole of the Samail ophiolite (Oman-United Arab Emirates). Zircon grains from amphibolite- to granulite-facies (0.8–1.3 GPa, ~700–900°C), garnet- and clinopyroxene-bearing amphibolite samples (n = 18) show systematic trends of decreasing heavy rare earth element slope (HREE; Yb/Dy) with decreasing Yb …

Cambrian Explosion Condensed: High-Precision Geochronology Of The Lower Wood Canyon Formation, Nevada, Lyle L. Nelson, James L. Crowley, Emily F. Smith, Darin M. Schwartz, Eben B. Hodgin, Mark D. Schmitz

Geosciences Faculty Publications and Presentations

The geologically rapid appearance of fossils of modern animal phyla within Cambrian strata is a defining characteristic of the history of life on Earth. However, temporal calibration of the base of the Cambrian Period remains uncertain within millions of years, which has resulted in mounting challenges to the concept of a discrete Cambrian explosion. We present precise zircon U–Pb dates for the lower Wood Canyon Formation, Nevada. These data demonstrate the base of the Cambrian Period, as defined by both ichnofossil biostratigraphy and carbon isotope chemostratigraphy, was younger than 533 Mya, at least 6 My later than currently recognized. This …

Brief Communication: Is Vertical Shear In An Ice Shelf (Still) Negligible?, Chris Miele, Timothy C. Bartholomaus, Ellyn M. Enderlin

Geosciences Faculty Publications and Presentations

Vertical shear is recognized today as a key component of the stress balance of ice shelves. However, the first ice shelf models were built on the neglect of vertical shear. Partly due to its historical treatment, it remains common to discuss vertical shear as though it were still considered negligible in ice shelf models. Here, we offer a historical perspective on the changing treatment of vertical shear over time, and we emphasize the term's non-negligibility in current ice shelf modeling. We illustrate our discussion in the simplest context of an analytic, isothermal, shallow-ice-shelf model.

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 …

Apatite Reference Materials For Sims Microanalysis Of Isotopes And Trace Elements, James L. Crowley, Mark Schmitz

Geosciences Faculty Publications and Presentations

Twelve apatite samples have been tested as secondary ion mass spectrometry (SIMS) reference materials. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis shows that the SLAP, NUAN and GR40 apatite gems are internally homogeneous, with most trace element mass fractions having 2 standard deviations (2s) ≤ 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 μg g^-1, ²⁰⁶Pb/²⁰⁴Pb > 283, and homogeneous SIMS U-Pb data, have respective isotope dilution thermal ionisation mass spectrometry (ID-TIMS) ages of 2053.83 ± 0.21 Ma, 2040.34 ± 0.09 Ma, 868.87 ± 0.25 Ma, 478.71 ± 0.22 Ma and …

Early Permian Zircon Ages From The P. Confluens And P. Pseudoreticulata Spore-Pollen Zones In The Southern Bonaparte And Canning Basins, Northwestern Australia, A. J. Mory, J. Crowley, J. Backhouse, R. S. Nicoll, J. D. Gorter

Geosciences Faculty Publications and Presentations

The Pseudoreticulatispora confluens–P. pseudoreticulata spore-pollen zonal datum typically coincides with the end of widespread Permian glacial deposits in Western Australia. Although previously attributed to the mid-Sakmarian, chemical abrasion isotope dilution thermal ionisation mass spectrometry (TIMS) dating of zircons from volcanic tuffs in the Ditji Formation of the Bonaparte Basin and the Grant Group in the Canning Basin point to an Asselian age of about 295.25 Ma for this datum. All dated zircons from the Ditji Formation came from petroleum well cuttings but the accompanying palynology was mostly from sidewall cores; however, all Grant Group samples were from conventional core. TIMS …