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Articles 1 - 30 of 70
Full-Text Articles in Physical Sciences and Mathematics
New Insights Into The Diverse Intraplate Volcanism Present Within The Howland And Baker Island United States Exclusive Economic Zone, Nicholas Foresta
New Insights Into The Diverse Intraplate Volcanism Present Within The Howland And Baker Island United States Exclusive Economic Zone, Nicholas Foresta
UNLV Theses, Dissertations, Professional Papers, and Capstones
The origin of oceanic volcanism has been attributed to various mechanisms, such as upwelling mantle plumes, lithospheric extension driven decompression melting, and small-scale convective cells in the asthenosphere. Discovering the range of magmatic drivers present in the ocean basins aids in understanding mantle geodynamics and tectonic processes. A recent seafloor exploration campaign within the Howland and Baker Island (HBI) U.S. Exclusive Economic Zone (EEZ; approximately near the equator and the International Date Line) resulted in the collection of multiple lava flow samples, which offer valuable insights into the complex origins and dynamics of intraplate seamounts. According to current absolute plate …
Differential River Incision Due To Quaternary Faulting On The Río Jemez-Salado System At The Million-Year Timescale, Cameron Reed
Differential River Incision Due To Quaternary Faulting On The Río Jemez-Salado System At The Million-Year Timescale, Cameron Reed
Earth and Planetary Sciences ETDs
Analysis of long-term average bedrock incision rates along the Río Salado-Jemez system using fluvial terraces can be used to test and quantify the hypothesis that differential river incision reflects Quaternary fault slip during ongoing uplift of the Jemez and Nacimiento Mountains. Terrace flights were correlated from the Arroyo Peñasco to the Río Salado near the southern nose of the Nacimiento and along the Río Jemez. Using highest/oldest river terraces, resulting bedrock incision values average out glacial/interglacial cycles and are interpreted to reflect differential uplift. For previously mapped and correlated terraces, we applied lidar datasets to refine strath heights. We also …
Ice-Marginal Volcanic Sequence In Iceland Found On A Nondescript Gradual Hillslope: An Unexpected Record Of Ice Thickness Late In Deglaciation, Audrey R. Putnam, Kristen L. Siebach, Candice C. Bedford, Sarah L. Simpson, Michael T. Thorpe, Joseph J. Tamborski
Ice-Marginal Volcanic Sequence In Iceland Found On A Nondescript Gradual Hillslope: An Unexpected Record Of Ice Thickness Late In Deglaciation, Audrey R. Putnam, Kristen L. Siebach, Candice C. Bedford, Sarah L. Simpson, Michael T. Thorpe, Joseph J. Tamborski
OES Faculty Publications
Volcanism increases when glaciers melt because isostatic rebound during deglaciation decreases the pressure on the mantle, which enhances decompression melting. Anthropogenic climate change is now causing ice sheets and valley glaciers to melt around the world and this deglaciation could stimulate volcanic activity and associated hazards in Iceland, Antarctica, Alaska, and Patagonia. However, current model predictions for volcanic activity associated with anthropogenic deglaciation in Iceland are poorly constrained, in part due to uncertainties in past volcanic output over time compared to ice sheet arrangements. Further work specifically characterizing glaciovolcanic and ice-marginal volcanoes in Iceland is needed to reconstruct volcanic output …
How Often Do Radioisotope Ages Agree? A Preliminary Study Of 29,000 Radioisotope Ages In The Usgs National Geochronological Database, Micah D. Beachy, Benjamin R. Kinard, Paul A. Garner
How Often Do Radioisotope Ages Agree? A Preliminary Study Of 29,000 Radioisotope Ages In The Usgs National Geochronological Database, Micah D. Beachy, Benjamin R. Kinard, Paul A. Garner
Proceedings of the International Conference on Creationism
In young-earth analyses of radioisotope age discordance, there have not yet been statistical studies involving age information for large numbers of rock units at a time. Austin (2005), Snelling (2005) and others have published in-depth studies of discordance on individual rock units, including new radioisotope ages based on their own samples. This was a logical approach because it maximized the number of ages per rock unit and eliminated the potential “file drawer” problem where ages that differ wildly from the expected values may be less likely to be published. Nevertheless, we believe it is time for a larger-scale project that …
Late Neoarchean To Middle Paleoproterozoic Geology Of Devon And Ellesmere Islands, Canadian Arctic, Joshua P. Laughton
Late Neoarchean To Middle Paleoproterozoic Geology Of Devon And Ellesmere Islands, Canadian Arctic, Joshua P. Laughton
Electronic Thesis and Dissertation Repository
The northernmost exposure of the Laurentian shield in Canada outcrops on Devon and Ellesmere islands within the Canadian Arctic Archipelago. Due to the remote location, the basement rocks of these islands have received little attention. From this study, zircon crystallization ages demonstrate that Devon Island is underlain by a late Neoarchean terrane comprising orthogneisses emplaced at ca. 2.55–2.51 Ga and an interleaved metasedimentary sequence deposited at ca. ≥2.47 Ga. On northern Devon Island, younger metasedimentary sequence(s) were deposited at ca. 2.2–1.9 Ga and intruded by ca. 2.01–1.95 Ga granitoids. Devon and Ellesmere islands experienced widespread metamorphic activity associated with the …
U-Pb Zircon Geochronology And Structure Of Regional Blueschist Units In The Easton Metamorphic Suite, Northwest Cascades, Wa, Katherine Lang
U-Pb Zircon Geochronology And Structure Of Regional Blueschist Units In The Easton Metamorphic Suite, Northwest Cascades, Wa, Katherine Lang
WWU Graduate School Collection
The Easton metamorphic suite of the Northwest Cascades Thrust System (NWCS) is a well-preserved subduction accretion complex in Washington State. The regional blueschist units of the Easton metamorphic suite include the Mt. Josephine semi-schist, Darrington Phyllite, and Shuksan greenschist/blueschist and all are interpreted to have accreted after the onset of Jurassic subduction beneath North America. This study uses zircon U-Pb geochronology, structure, and field observations to test the regional correlations between units in the Easton metamorphic suite and address models for the timing of subduction accretion along the North American margin in the Late Jurassic – Early Cretaceous. The results …
Pleistocene Deposits Of Lower Wahweap Creek And Its Tributaries, Southern Utah, Noah Slade
Pleistocene Deposits Of Lower Wahweap Creek And Its Tributaries, Southern Utah, Noah Slade
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The famous landscapes of the Colorado Plateau have been created over millions of years, primarily by erosive forces of wind and water. Interruptions in the long-term erosion of the landscape occur when streams gain more sediment than they can transport, which causes deposition along channels and floodplains. The resulting sequences of terrace deposits are used by geologists to study when and how river systems have evolved.
Mammoth bones were recently discovered in stream deposits along Wahweap Creek, a tributary of the Colorado River in southern Utah. Previous work indicates that the deposits pre-date the last ice age, making it one …
Conflicting Narratives In Geology: The Current Debate Surrounding The Beginning Of The Anthropocene Epoch, Carter Mitchell
Conflicting Narratives In Geology: The Current Debate Surrounding The Beginning Of The Anthropocene Epoch, Carter Mitchell
Student Writing
Geologists currently debate the addition a new Epoch of geologic time called the Anthropocene. The Anthropocene is characterized by changes in the lithosphere resulting directly from human activity. This paper analyses the arguments in favor of and against the Anthropocene as well as the conflicting narratives concerning the beginning and scope of the Anthropocene.
Provenance Of The Northern Range, Trinidad Using Detrital Zircon U-Pb Geochronology: Implications For Northern South American River System Paleogeography, Cheyenne Bartelt
Provenance Of The Northern Range, Trinidad Using Detrital Zircon U-Pb Geochronology: Implications For Northern South American River System Paleogeography, Cheyenne Bartelt
Geology: Student Scholarship & Creative Works
The Northern Range of Trinidad is located in a key area for evaluating the Mesozoic-Cenozoic evolution of the Caribbean and South American plates. Here, we present detrital zircon U-Pb geochronology for 2391 grains from ten samples collected from metasedimentary rocks of the Northern Range. These data are used to bracket the maximum depositional age of the fossil-poor metasedimentary rocks from the Northern Range and to investigate the provenance of their sedimentary protoliths. Detrital zircon ages range between 3136.5 ± 22.9 Ma and 139.0 ± 5.4 Ma, reflecting apparent contribution from a variety of crustal affinities; however, since the youngest ages …
Chemical And Thermal Influence On Intermediate Magma Storage Conditions: Volcán Ollagüe, Chile-Bolivia, Central Andes, Drew Allen Laviada-Garmon
Chemical And Thermal Influence On Intermediate Magma Storage Conditions: Volcán Ollagüe, Chile-Bolivia, Central Andes, Drew Allen Laviada-Garmon
MSU Graduate Theses
Continental arc volcanoes are the single best portrayal of the evolution of recycled earth material stemming from subduction, one of the most important and foundational phenomena in global tectonics. Understanding the genesis of intermediate-composition magmas produced at arc volcanoes is a difficult process making them a focal point for investigation. Geochemical investigation of zircon and plagioclase mineral phases erupted from continental arcs can provide insight into magma process, generation, storage conditions, timescales and differentiation of sub-volcanic plumbing systems prior to eruption events. The Central Volcanic Zone is a prime example of continental arc volcanism through subduction, and is host to …
Disequilibrium Melting Of The Continental Crust During Emplacement Of The Mt. Princeton Batholith, Central Colorado Volcanic Field, Loren A. Bohannon
Disequilibrium Melting Of The Continental Crust During Emplacement Of The Mt. Princeton Batholith, Central Colorado Volcanic Field, Loren A. Bohannon
MSU Graduate Theses
Assimilation and crystallization are difficult to constrain at magmatic boundaries, including the interactions of magma with the surrounding country rock. The assumption of the relationship between a magma and what it is intruding upon is relegated to homogenous bodies or epizonal plutons. Realistically, wall rock influences chemical heterogeneity and isotopic variance at the outcrop scale and changes depending on distance from the magma-wall rock interface. Here, we present a case study of the 35 Ma Mt. Princeton Batholith and the host Precambrian rocks of the Central Colorado Volcanic Field. We assess chemical heterogeneity by whole rock and mineral trace element …
Geology Of The Jacksonville 7.5 Minute Quadrangle And U–Pb And (U–Th)/He Reveal Sediment Routing And Uplift In The Southern Appalachian Valley And Ridge Province, Derek L. Spurgeon
Geology Of The Jacksonville 7.5 Minute Quadrangle And U–Pb And (U–Th)/He Reveal Sediment Routing And Uplift In The Southern Appalachian Valley And Ridge Province, Derek L. Spurgeon
MSU Graduate Theses
The southern Appalachian Mountains have experienced multiple deformation events having undergone two full Wilson cycles. The foreland Valley and Ridge province is composed of sedimentary Paleozoic rock that range in age from earliest Cambrian to Middle Pennsylvanian. This sedimentary basin was intensely folded and faulted during the collision of Gondwana during the Middle to Late Carboniferous Period. From previous geologic structural mapping that has taken place, some large-scale structures in the Valley and Ridge Province seem to be out of sequence. To better understand the relationships in these structures, geologic mapping in high detail at the 1:24,000 scale coupled with …
U-Pb Apatite Chronometry Of Intrusions In An Accretionary Metamorphic Belt In Western Idaho, Usa, Colleen Grace Rankin
U-Pb Apatite Chronometry Of Intrusions In An Accretionary Metamorphic Belt In Western Idaho, Usa, Colleen Grace Rankin
MSU Graduate Theses
The Salmon River suture zone in west-central Idaho, USA records the tectonic processes where island arcs, similar to modern-day Japan, were accreted to the North American continent in the Jurassic and Cretaceous periods (160-90 million years ago). This suture zone contains metamorphic rocks that were buried deep within the crust at depths of 20 kilometers or more and have subsequently been brought to the surface. The exhuming processes responsible for the metamorphic rocks in the Salmon River suture zone remains unclear. Two competing hypotheses have been proposed to explain the transport of the rocks from the Salmon River suture zone …
Reconstructing The Transition From Laramide Contraction To Rio Grande Rift Extension, Aaron Conley
Reconstructing The Transition From Laramide Contraction To Rio Grande Rift Extension, Aaron Conley
Open Access Theses & Dissertations
Exposure of tilted Eocene-Oligocene volcanic and sedimentary units unconformably overlying folded and thrusted Mesozoic rocks in the southern Indio Mountains provide an important geologic record of the transition from Laramide contraction to Rio Grande rift extension. Detailed geologic mapping and cross-section reconstruction combined with sedimentary analysis and geo/thermochronologic methods are used to test the hypothesis that Laramide contractional structures and post-Laramide topography focused ignimbrite and sedimentary deposition within two paleovalleys located in the northwest and northeast portions of the study area. Laramide deformation in the study area is confined to Mesozoic units and includes a series of low-angle thrust faults …
The Birth And Incision History Of The San Juan River In The Past 5 Ma, Micael T. Albonico
The Birth And Incision History Of The San Juan River In The Past 5 Ma, Micael T. Albonico
Earth and Planetary Sciences ETDs
This study addresses the evolution of the San Juan River system and its confluence with the Colorado River, ~ 100 km above the regionally important Lees Ferry knickzone. The San Juan River is a 600-km-long continental-scale tributary of the Colorado River. From its headwaters in the San Juan Mountains in Colorado, the San Juan River flows across the Colorado Plateau, and into the Colorado River upstream of Grand Canyon. Published apatite fission track and apatite (U-Th)/He thermochronologic data show that rocks in Marble Canyon, as well as in middle and upper reaches of the San Juan River, were >75 °C …
Geology And Lithogeochemistry Of The Pickett Mountain Volcanogenic Massive Sulfide Deposit, Northern Maine, Michael J. Mccormick
Geology And Lithogeochemistry Of The Pickett Mountain Volcanogenic Massive Sulfide Deposit, Northern Maine, Michael J. Mccormick
Electronic Theses and Dissertations
The Pickett Mountain deposit is a volcanogenic massive sulfide (VMS) base-metal deposit located 15 miles north of Patten, ME. The deposit, discovered in 1979, was abandoned in 1989. The deposit remained abandoned until 2017, when Wolfden Mt. Chase LLC purchased the land for further development after Maine mining regulations changed. This project is a collaboration between the University of Maine, the University of Maine – Presque Isle, Wolfden Resources Corp., and the University of New Brunswick to better understand the regional and deposit-scale geology related to the deposit to fill in gaps of the geologic story of northern Maine as …
Evidence For Middle Miocene Elevated Topography Isolating The Southern Klamath Mountains Province: A U-Pb & Lu-Hf Detrital Zircon Study Of The Weaverville Formation, Dana J. Christensen
Evidence For Middle Miocene Elevated Topography Isolating The Southern Klamath Mountains Province: A U-Pb & Lu-Hf Detrital Zircon Study Of The Weaverville Formation, Dana J. Christensen
Cal Poly Humboldt theses and projects
The Klamath Mountains Province (KMP) records a robust history of active North American margin tectonics and crustal growth through the subduction-accretion of oceanic and island-arc terranes spanning Devonian through Cretaceous time. However, preservation of Cenozoic rocks is minimal, rendering the geologic record, topography, and tectonics during this timeframe difficult to reconstruct. The only Miocene terrestrial sedimentary unit that exists in the KMP is the fluvially deposited Tertiary Weaverville Formation (Tw) that is preserved in five fault-bounded basins in the southern part of the province. This study presents new uranium-lead (U-Pb) age data and epsilon hafnium (εHf) isotopic ratios from detrital …
Sedimentology, Sequence Stratigraphy, And High-Precision U-Pb Age Constraints On The Late Paleozoic Ansilta Formation, Calingasta-Uspallata Basin, Nw Argentina, John Ethan Malone
Sedimentology, Sequence Stratigraphy, And High-Precision U-Pb Age Constraints On The Late Paleozoic Ansilta Formation, Calingasta-Uspallata Basin, Nw Argentina, John Ethan Malone
Theses and Dissertations
The Ansilta Formation, located several kilometers east of the Astronomical Observatory El Leoncito near Barreal, San Juan Province, Argentina was deposited during the late Mississippian to early Pennsylvanian. This succession includes glacimarine, nearshore, and fluvial systems deposited at the mid-Carboniferous portion of the late Paleozoic ice age within the Calingasta—Uspallata Basin on the western margin of the Protoprecordillera. The lower member of the Ansilta Formation is equivalent to the nearby Leoncito, Majaditas, and Hoyada Verde formations, and is composed of diamictite, conglomerates, sandstones, pebbly mudstones, and laminated mudstone. Glacial environments are unique in that facies changes occur as a result …
Evidence For Polyphase Deformation In The Shear Zones Bounding The Chester And Athens Domes, Southeastern Vermont, From 40ar/39ar Geochronology, Kristin Schnalzer
Evidence For Polyphase Deformation In The Shear Zones Bounding The Chester And Athens Domes, Southeastern Vermont, From 40ar/39ar Geochronology, Kristin Schnalzer
Graduate College Dissertations and Theses
The Chester and Athens Domes are a composite mantled gneiss dome in southeast Vermont. While debate persists regarding the mechanisms of dome formation, most workers consider the domes to have formed during the Acadian Orogeny. This study integrates the results of 40Ar/39Ar step-heating of single mineral grains, or small multigrain aliquots, with data from microstructural analyses from samples collected in multiple transects across the dome-bounding shear zone(s) in order to understand the relationship between metamorphism and deformation. Results from the sheared units along the north and south transects are presented from west to east. In the north, hornblende from the …
Timing And Conditions Of Metamorphism In The Cascades Crystalline Core From Garnet Lu-Hf And Sm-Nd Geochronology, Peter Baker
Timing And Conditions Of Metamorphism In The Cascades Crystalline Core From Garnet Lu-Hf And Sm-Nd Geochronology, Peter Baker
WWU Graduate School Collection
The Chiwaukum Schist and Tonga Formation of Cascades Crystalline Core experienced three distinct metamorphic events: (M1) an early metamorphism that predates regional pluton emplacement, (M2) low-pressure contact metamorphism in the aureoles of the Mount Stuart batholith and Beckler Peak pluton, and (M3) regional Barrovian metamorphism. The timing of these distinct metamorphic events is critical to testing models for the tectonic evolution of the region and mechanisms that lead to burial of rocks within the orogen. I present new garnet Lu-Hf and Sm-Nd isochrons, average pressure and temperature calculations, and pseudosection modeling from the Chiwaukum Schist and Tonga Formation in order …
Reinterpreting The Tectonic Model Of The Southern Part Of The Taconic Orogeny Through A Provenance Study Of Late Ordovician Sandstones, Juan Carlos Guerrero
Reinterpreting The Tectonic Model Of The Southern Part Of The Taconic Orogeny Through A Provenance Study Of Late Ordovician Sandstones, Juan Carlos Guerrero
LSU Master's Theses
A provenance study of quartz arenites that stratigraphically are closely associated with major Ordovician K-bentonites has been conducted in order to further our understanding of the tectonic setting of eastern Laurentia during the Late Ordovician. Using laser ablation ICP-MS, detrital zircons separated from Ordovician sandstone samples in the southeastern Appalachian Mountains (Virginia to Alabama) were dated using U-Pb geochronology. Analytical results show three dominate age ranges for the zircons from these sandstones: ~440-490 Ma, ~900-1300 Ma, and ~1300-1500 Ma. In addition, some zircon ages grouped into older ranges of ~1600-1800 Ma, ~1800-1900 Ma, and ~2600-2800 Ma. Zircon ages from ~900-2800 …
Integrating Geochronologic And Instrumental Approaches Across The Bengal Basin, Elizabeth L. Chamberlain, Steven L. Goodbred, Richard Hale, Michael S. Steckler, Jakob Willinga, Carol Wilson
Integrating Geochronologic And Instrumental Approaches Across The Bengal Basin, Elizabeth L. Chamberlain, Steven L. Goodbred, Richard Hale, Michael S. Steckler, Jakob Willinga, Carol Wilson
OES Faculty Publications
Constraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins. The geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem, because the viability of methods can be highly influenced by geomorphic attributes. For example, sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating. Similarly, the rate of sediment transport from source to sink may determine the maturity and/or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating. …
Petrogenesis Of The El Rechuelos Rhyolite, Jemez Mountains Volcanic Field, New Mexico, Usa, Kelsy Jo Konkright
Petrogenesis Of The El Rechuelos Rhyolite, Jemez Mountains Volcanic Field, New Mexico, Usa, Kelsy Jo Konkright
UNLV Theses, Dissertations, Professional Papers, and Capstones
The El Rechuelos Rhyolite represents volcanic activity preceding the multiple caldera collapse events of the Jemez Mountains volcanic field (JMVF) in northern New Mexico. This study focuses on seven rhyolitic units clustered north of the Valles caldera. These units have been studied in order to interpret their relationships to one another and the eruptive history of the JMVF. Additionally, this study adds to the research on the relationships between effusive and explosive rhyolitic volcanism, and understanding how caldera-forming eruptions develop from silicic systems.
Limited previous research includes K/Ar dates and a few inconsistent 40Ar/39Ar dates, in addition to whole rock …
High-Resolution Investigation Of Event Driven Sedimentation: Response And Evolution Of The Deepwater Horizon Blowout In The Sedimentary System, Rebekka A. Larson
High-Resolution Investigation Of Event Driven Sedimentation: Response And Evolution Of The Deepwater Horizon Blowout In The Sedimentary System, Rebekka A. Larson
USF Tampa Graduate Theses and Dissertations
This Dissertation combines the investigation of the sedimentological impacts of the Deepwater Horizon (DwH) blowout event in the deep-sea benthos, with the refinement and advancement of methods and approaches for high-resolution investigations of events preserved in sedimentary records. An approach that combined, rapid collection of cores, a continued annual time series collection of cores, and high-resolution sampling and analyses, in particular short-lived Radioisotopes (SLRad), enabled the temporal resolution required to detect the sedimentary response to the short-duration DwH event, and evaluate post-event sedimentation patterns at a comparable time scale (months).
The collection of 179 sediment cores from 80 sites between …
Late Devonian Sedimentary Record Of Appalachian Tectonics And Erosion: Geochronology And Geochemistry Of Detrital Muscovite And Zircon From Central Pennsylvania Strata, Cole T. Gardner
Honors Theses
Foreland basin sediment deposition in North-Central Pennsylvania during Late Devonian time records erosion of hinterland source terranes exhumed during regional plate convergence, including the collisional Acadian orogeny. The Catskill clastic wedge preserves a coarsening-upwards stratigraphic succession from marine to fluvial environments associated with sediment progradation and sea-level regression, yet depositional timescales and quantitative provenance data are largely unconstrained.
Detailed facies analysis of eight outcrops spanning >2 km of stratigraphy in Lycoming Co., Pennsylvania documents distinct upsection changes, interpreted to reflect changes in depositional environments consistent with previous sedimentology of the Catskill clastic wedge. Stratigraphy displays a transition from nearshore marine …
Geochronology And Depositional History Of The Sandy Springs Aeolian Landscape In The Unglaciated Upper Ohio River Valley, United States, Mathew P. Purtill, J. Steven Kite, Steven L. Forman
Geochronology And Depositional History Of The Sandy Springs Aeolian Landscape In The Unglaciated Upper Ohio River Valley, United States, Mathew P. Purtill, J. Steven Kite, Steven L. Forman
Faculty & Staff Scholarship
The study of active and stabilized late Quaternary aeolian landforms provides important proxies for past climate events and environmental transitions. Despite an overall increase in the study of aeolian landforms in previously glaciated and coastal settings in eastern North America, the history of aeolian sedimentation in many unglaciated inland alluvial settings remain poorly understood. This study reports on the geochronology and depositional history of aeolian landforms and sediments in the unglaciated upper Ohio Valley at the Sandy Springs site. Aeolian landforms and sediments include complex, linear, barchan-like, and climbing dunes; an interdune sand sheet; and sandy loess that blankets high …
The Ages2 (Awards For Geochronology Student Research 2) Program: Supporting Community Geochronology Needs And Interdisciplinary Science, Rebecca M. Flowers, J. Ramón Arrowsmith, Vicki Mcconnell, James R. Metcalf, Tammy M. Rittenour, Blair Schoene
The Ages2 (Awards For Geochronology Student Research 2) Program: Supporting Community Geochronology Needs And Interdisciplinary Science, Rebecca M. Flowers, J. Ramón Arrowsmith, Vicki Mcconnell, James R. Metcalf, Tammy M. Rittenour, Blair Schoene
Geosciences Faculty Publications
Geochronology is essential in the geosciences. It is used to resolve the durations and rates of earth processes, as well as test causative relationships among events. Such data are increasingly required to conduct cutting-edge, transformative, earth-science research. The growing need for geochronology is accompanied by strong demand to enhance the ability of labs to meet this pressure and to increase community awareness of how these data are produced and interpreted. For example, a 2015 National Science Foundation (NSF) report on opportunities and challenges for U.S. geochronology research noted: "While there has never been a time when users have had greater …
Evaluating Stable Isotope And Geochronologic Techniques For Paleoclimate Reconstruction: Case Study Of The Santa Cruz Formation, Argentina, Robin B. Trayler
Evaluating Stable Isotope And Geochronologic Techniques For Paleoclimate Reconstruction: Case Study Of The Santa Cruz Formation, Argentina, Robin B. Trayler
Boise State University Theses and Dissertations
Stable isotope analysis has become the method of choice for many studies investigating the paleoecology and paleoclimate of fossil mammal faunas. While organic tissues (collagen, keratins, proteins) persist for < 105 years highly mineralized tooth enamel is resistant to alteration and degradation and faithfully preserves its isotopic composition for millions (> 106) years. Reconstructing past climates from these records relies on both understanding both micro-scale mechanisms of isotope incorporation into individual teeth, and macro-scale changes in isotope compositions over hundreds of thousands or millions of years. In this dissertation I address three questions.
First, how does the geometry and …
Zircon U-Pb Geochronology Of Two Basement Cores (Kentucky, Usa): Implications For Late Mesoproterozoic Sedimentation And Tectonics In The Eastern Midcontinent, David P. Moecher, J. Richard Bowersox, John B. Hickman
Zircon U-Pb Geochronology Of Two Basement Cores (Kentucky, Usa): Implications For Late Mesoproterozoic Sedimentation And Tectonics In The Eastern Midcontinent, David P. Moecher, J. Richard Bowersox, John B. Hickman
Earth and Environmental Sciences Faculty Publications
Basement cores from two wells drilled west and east of the Grenville front consist of feldspathic litharenite and granitic orthogneiss, respectively. Detrital zircon U-Pb ages for the litharenite define a broad dominant U-Pb age mode at ca. 1115 Ma. The dominant mode matches that for the type locality of the Middle Run Formation in the Ohio subsurface and is interpreted to consist of detrital zircons sourced from East Continent Rift volcanic sources (ca. 1100 Ma) and Grenville Shawinigan granites/gneisses (1120–1180 Ma). The youngest detrital zircon ages (ca. 1020 Ma) require a maximum depositional age that is at least 70 My …
Geochronologic Constraints On The Timing Of Metamorphism And Exhumation Of The Tillotson Peak Complex In Northern Vermont, Cheyne Aiken
Geochronologic Constraints On The Timing Of Metamorphism And Exhumation Of The Tillotson Peak Complex In Northern Vermont, Cheyne Aiken
Graduate College Dissertations and Theses
The Tillotson Peak Complex (TPC) in northern Vermont records high-pressure (HP) subduction zone metamorphism that occurred during the Ordovician Taconic Orogeny, and subsequent retrograde metamorphism and deformation that occurred during the Silurian Salinic Orogeny. Previous studies have documented a polymetamorphic history, with peak metamorphic pressures possibly up to 2.5 GPa and temperatures of 550°C. Prior to this research, constraints on the timing of metamorphism in the TPC were limited to a single Middle Ordovician 40Ar/39Ar total fusion age for glaucophane. This study integrates 40Ar/39Ar step heating analyses of multiple mineral phases and U-Pb dating of titanite with field and microstructural …