Geology Commons^™

Cascadia Subduction Tremor Muted By Crustal Faults, Ray E. Wells, Richard J. Blakely, Aaron G. Wech, Patricia A. Mccrory, Andrew Michael

Geology Faculty Publications and Presentations

Deep, episodic slow slip on the Cascadia subduction megathrust of western North America is accompanied by low-frequency tremor in a zone of high fluid pressure between 30 and 40 km depth. Tremor density (tremor epicenters per square kilometer) varies along strike, and lower tremor density statistically correlates with upper plate faults that accommodate northward motion and rotation of forearc blocks. Upper plate earthquakes occur to 35 km depth beneath the faults. We suggest that the faults extend to the overpressured megathrust, where they provide fracture pathways for fluid escape into the upper plate. This locally reduces megathrust fluid pressure and …

Sedimentology And Taphonomy Of The Abydosaurus Mcintoshi Quarry, (Naturita Formation, Early Cretaceous, Latest Albian), Dinosaur National Monument, Utah, Aaron Daniel Holmes

Theses and Dissertations

The holotypic locality of the brachiosaurid titanosauriform sauropod, Abydosaurus mcintoshi, is quarry DNM-16, located in Dinosaur National Monument. The bones are preserved near the base of a heterolithic, trough cross stratified to planar bedded sandstone channel complex. The trough cross to planar bedded sandstones mark times of variable flow with times of high flow velocity based on bones whose upper surfaces were eroded before final burial. The abundance of mud with the dominant medium to fine sand, and poorly confined sandstone channels indicate the bones were transported and buried in medial to distal intermittent flows of a distributive fluvial …

Receiver Function And Gravity Constraints On Crustal Structure And Vertical Movements Of The Upper Mississippi Embayment And Ozark Uplift, Lin Liu, Stephen S. Gao, Kelly H. Liu, Kevin Lee Mickus

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The Upper Mississippi Embayment (UME), where the seismically active New Madrid Seismic Zone resides, experienced two phases of subsidence commencing in the Late Precambrian and Cretaceous, respectively. To provide new constraints on models proposed for the mechanisms responsible for the subsidence, we computed and stacked P-to-S receiver functions recorded by 49 USArray and other seismic stations located in the UME and the adjacent Ozark Uplift and modeled Bouguer gravity anomaly data. The inferred thickness, density, and V_p/V_s of the upper and lower crustal layers suggest that the UME is characterized by a mafic and high-density upper crustal …

Interpretive Geologic Cross Sections Across Lower Platte North Natural Resources District, Nebraska (Ccs-20), Dana Divine

Conservation and Survey Division: Faculty and Staff Publications

No abstract provided.

Formation Of Rapakivi Feldspars In The Deer Isle Granite Complex, Coastal Maine: In Situ Lead Isotope And Trace Element Analysis, William Desmond Obrien

Theses and Dissertations

Rapakivi and alkali feldspar phenocrysts from the Deer Isle Granite Complex were investigated using in situ trace element and Pb isotope geochemistry to see if magma mixing or isothermal decompression was responsible for their formation. Pb isotope and trace element profiles, along with CL imagery of quartz phenocrysts, indicate compositional changes in the magma chamber occurred during rapakivi and alkali feldspar growth. Repeated episodes of magma mixing/replenishment by relatively isotopically primitive and LREE enriched magmas (along with hybridized variations with the host magma) created localized disequilibration. Alkali feldspar phenocrysts proximal to these zones of thermal perturbation were first resorbed and …

The Effect Of Watershed Runoff And Sediment Resuspension On Turbidity And Sediment Deposition In St. John, Us Virgin Islands: Implications For Watershed And Marine Development And Restoration In Bays With Coral Reefs, Stephen E. Campbell

Theses

In the US Virgin Islands (USVI), land-based (terrigenous) sedimentation has been identified as a major cause of coral stress. Development, such as the building of unpaved roads in steep coastal watersheds, has increased sediment yields and marine terrigenous sedimentation by up to an order of magnitude above background levels. When activated during storm events, ephemeral streams transport sediment from the watershed to coastal waters. Once deposited on the seafloor, resuspension of benthic sediments can further increase turbidity and deposition. However, isolating the relative contributions of runoff and resuspension to turbidity and deposition using conventional sediment trap monitoring has been challenging. …

Evaluating Relationships Between Rock Strength And Longitudinal Stream Profile Morphometry In The Southern Guadalupe Mountains, Texas, Samuel T. Schoenmann

Theses and Dissertations

Landscapes record information about the tectonic, climatic, and lithologic environments in which they form (Yang et al., 2015). When one or more of these environmental conditions change spatially or temporally, the landscape responds through erosion and thus, develops representative geomorphic features (Ritter et al., 2011). Since the nineteenth century, it has been clear that bedrock strength and erodibility play an important role in landscape evolution and geomorphology (Lifton et al., 2009). However, the nuances of variable erodibility remain poorly understood. The implications of this limited understanding lies within landscape evolution models. While these models show strong qualitative relationships between longitudinal …

Overwash Controls On Barrier Island Morphodynamics During Storms, Joshua H. Alarcon

LSU New Orleans Theses and Dissertations

Overwash, shoreface retreat, and barrier migration are common processes occurring in transgressive barrier island systems, the scale of which is exacerbated by sea level rise, subsidence and the frequency and magnitude of tropical and extratropical storms. Barrier morphology also clearly plays a key role in determining a morphological response to these processes. Using a hydrodynamic and sediment transport model (MIKE21) and selected barrier island and shoreface templates, informed by deltaic and coastal plain systems in the northern Gulf of Mexico, I performed simulations to determine barrier morphology in response to storms. A low dune with a gentle shoreface slope, characteristic …

Evidence Of Fault Movement During The Holocene In Southern Louisiana: Integrating 3-D Seismic Data With Shallow High Resolution Seismic Data, Joseph P. Frank

LSU New Orleans Theses and Dissertations

The Baton Rouge fault system of Louisiana is a well-known recently active system consisting of en echelon, east trending, down-to-the-south normal faults across the northeast periphery of the Mississippi River delta plain. Two, industry-donated, 3-D seismic surveys across 860 km² image deep-seated faults below Lake Borgne, along an east strike that parallels previously well mapped segments of the Baton Rouge system. Four major faults (> 6 km fault trace) are imaged within the seismic surveys across the Lake. The industry seismic data were not processed for reliable imaging at depths (m). To bridge the depth gap in seismic, high …

Paleohydrology And Paleoecology Of The Neogene Siwalik Rocks, Nepalese Himalaya Using Multi-Proxy Lipid Biomarker Isotopic Study, Prabhat Chandra Neupane

LSU New Orleans Theses and Dissertations

This study deploys compound-specific multi-proxy isotopic study of lipid biomarkers to understand Neogene climatic and ecological variabilities in the Himalayan foreland. The investigation of compound-specific carbon and hydrogen isotopes along with glycerol dialkyl glycerol tetraether (GDGT) is the first of its kind for the Nepalese Siwalik. A total of 49 mudstone (and some paleosol) samples were collected from the paleomagnetically age-constrained Siwalik strata in the Surai Khola and Karnali River sections.

δ¹³C results suggest a domination of C₃ trees between 12 and 8.5 Ma, and a stepwise expansion of C₄ grasses starting gradually at 8.5 Ma …

Groundwater Vulnerability Assessment For Nitrate Pollution In The Salinas Valley Using A Modified Drastic Model, Bernadette Boyle

Master's Projects and Capstones

Groundwater is an integral piece of California’s groundwater resources. One of the most common contaminants present in groundwater is nitrate. Nitrate contamination is often a result of agricultural land use activities on the ground surface. The study area for this analysis is the Salinas Valley Groundwater Basin, an agriculturally dominated basin in coastal California. The Salinas Valley Basin is both one of the most agriculturally productive areas of the state, as well as one of the most nitrate-contaminated basins in the state. The purpose of this research was to develop a groundwater vulnerability map for nitrate pollution in the Salinas …

Gravitational Study Of The Hastings Salt Dome And Associated Faults In Brazoria And Galveston Counties,Texas, Francis C. Okocha

Electronic Theses and Dissertations

Salt domes are important geological structures because they are potential major hydrocarbon traps and have a profound effect on overlying strata in the subsurface. Over five hundred salt domes have been located on the United States Gulf Coast region, including the Hastings Salt Dome. Hastings Oil Field is located about 40.2 km (25 miles) southeast of Houston, Texas. The Hasting oil field was discovered in 1934 and it was considered the largest oil reserve on the Gulf Coast. Its peak production of 75,000 BOPD (barrels of oil per day) was recorded in 1977 and it had a cumulative production of …

Structural And Stratigraphic Reconstruction Of The Whiting Dome Salt Structure In Viosca Knoll-Mississippi Canyon, Gom, Using 3d Seismic Data, Matthew R. Worrell

Electronic Theses and Dissertations

Understanding the complexities of salt tectonics is one of the most important factors regarding seismic interpretation of stratigraphy, structure, and geomorphology in the Gulf of Mexico. Evaluating the processes affecting recent mobilization of salt in the shallow, well-imaged section can help provide analogues for older, similar occurrences in the deeper section, thereby providing structural models for the autochthonous salt and its effect on stratigraphy and even potential timing and migration issues of hydrocarbons.

Progradation of delta front and shelf to slope transitional sediments has expulsed and emplaced an allochthonous salt structure (Whiting Dome) in the Viosca Knoll and Mississippi Canyon …

Insights On Magmatic Addition Beneath The Mid-Atlantic Coastal Plain From Crustal Seismic Refraction Data, Thomas W. Luckie

Earth and Planetary Sciences ETDs

Magmatic addition can lead to intraplate crustal growth through plume-generated voluminous underplating of mafic material, particularly during early syn-rift processes. In addition, magmatism facilitates crustal growth and rift development by assisting extensional tectonic forces. Therefore, understanding the relationship between magmatism and rifting may help explain both these processes. In the summer of 2015 the GeoPRISMS Eastern North American Margin (ENAM) Community Seismic Experiment collected two margin-dip active source seismic refraction profiles in eastern North Carolina and southeastern Virginia using five onshore explosive shots on a northern profile and six on a southern profile (see figure). Analysis of these data resulted …

Validating A Universal Model Of Particle Transport Lengths With Laboratory Measurements Of Suspended Grain Motions, Robert C. Mahon, Brandon Mcelroy, Suleyman Naqshband

Earth and Environmental Sciences Faculty Publications

t The mechanics of sediment transport are of fundamental importance for fluvio-deltaic morphodynamics. The present study focuses on quantifying particle motions and trajectories across a wide range of flow conditions. In particular, a continuous model is presented that predicts particle travel distances for saltation and suspension based on Rouse number and relative grain roughness. By utilizing a series of eight video cameras in a plexiglass flume direct measurements of the distributions of particle travel distances (excursion lengths) were obtained. To this end, experiments were carried out in dark under black lights with fluorescent painted plastic and quartz sand particles. For …

Characterizing Subsurface Void Spaces And Water Distribution And Flow Patterns In Cave Hill Karst Using Resistivity, Jacob A. Gochenour

Senior Honors Projects, 2010-2019

Describing the distribution of groundwater is essential in understanding the evolution of geomorphologic features in karst topography. Electrical resistivity allows us to find a model of subsurface distribution of resistivity that enables the visual recognition of groundwater and void spaces. The purpose of this research is to implement electrical resistivity to describe the spatial relationship of groundwater and karstic features at Grand Caverns National Natural Landmark, Grottoes, Virginia. Two locations of interest, a karstic swale and sinkhole area, were identified for the deployment of electrical resistivity. Both, dipole-dipole and Schlumberger arrays were collected for each deployment. A total of ten …

Evaluating Fault-Line Escarpment Exposure In The Guadalupe Mountains Of West Texas And New Mexico, Audrey Anne Happel

Theses and Dissertations

The Permian stratigraphy of the Guadalupe Mountains is well-known due to the impeccable exposure of Permian strata along distinct escarpments that define the boundaries of the range. Even though the Permian strata have been closely examined to understand the associated petroleum reservoirs in the adjacent Delaware basin, little work has been done on the escarpments that expose the well-known rocks at the surface by way of tectonic and erosional processes. The development of escarpments are directly affected by multiple processes that create the landscape, and can be used as a tool to temporally and spatially constrain tectonic and erosional activity …

Nutrient Variations Of Six Surface Water Bodies In Mchenry County, Il, Jacob Piske

Celebration of Learning

This research analyzes water quality from several ponds in McHenry County, Illinois, with a goal of developing a understanding of pollution sources and temporal variations in concentrations of nitrate, potassium, phosphorus, chlorine, and sodium. Over the past 25 years, the population of McHenry County has grown rapidly, with residential developments expanding into former farmlands. Yet, the county remains heavily agricultural, with roughly 60% of the surface area used for agricultural purposes. Concentrations of NO3-, P+, K+, Cl-, and Na+ were analyzed from six sites: two in subdivisions, two in farmland, and two near major highways. Data were collected once a …

Elemental Contamination Of An Ancient Copper Mine In Killarney, Ireland, Courtney Chouinard

Celebration of Learning

Ross Island Copper Mine, located in Killarney National Park, Killarney, Ireland, is known for archeological artifacts of copper from the Bronze Age. Copper production surged in the late 1700s and into the mid-1800s. The mine included both open pits (e.g. Blue Hole) and underground excavations (e.g. Western Mine). Copper veins were found in the Mississippian-aged limestone bedrock along with chalcopyrite and tennantite ore. In 1912, tourism had become the main source of income in the area, and the mines and the land surrounding them were remediated and became a part of the national park. Mine shafts were filled in, waste …

Dendrochronological Analysis Of Historical Structures In Southwestern Ohio Dewitt House Oxford, Ohio.

Historic Structures

Dating historical structures in Oxford Ohio using dendrochronology. The Historical Structures collection consists of reports that are the result of dendochronological analysis of timbers from structures in Pennsylvania and Ohio. Contributors: Fetters, Caitlin; Krivicich, Mike; Lehmann, Sophie; Wiles, Greg