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Papers by Nicholas Powell

Research paper thumbnail of Deciphering the “Footprint” of the Neoacadian Metamorphic Event in the Southern Appalachians: Insights from 40AR/39AR Geochronology in the Eastern Blue Ridge and Inner Piedmont of North Carolina

Abstracts with programs, 2021

Research paper thumbnail of The Alleghanian Orogeny in the Eastern Blue Ridge: Earlier and Hotter Than Previously Recognized

Abstracts with programs, 2020

Research paper thumbnail of Reconstructing the Paleozoic Structural, Metamorphic, and Exhumational History of the Southern Appalachian Blue Ridge and Inner Piedmont

Abstracts with programs, 2023

Research paper thumbnail of Did the Brevard Fault Zone Control Neoacadian Channel and Escape Flow in the Southern Appalachian Inner Piedmont? Evidence from Monazite U-PB Geochronology and Ree Geochemistry

Abstracts with programs, 2023

Research paper thumbnail of Defining Metamorphic Timing, Extent, and Conditions in the Southern Appalachian Blue Ridge and Inner Piedmont—Insights from Monazite Xenotime Geochemistry and Geochronology

Abstracts with programs, 2021

Research paper thumbnail of An Early and Hot Alleghanian Orogeny in the Eastern Blue Ridge of the Southern Appalachians

GSA 2020 Connects Online, 2020

Research paper thumbnail of Testing the Applicability of the Channel Flow Model in the Southern Appalachian Inner Piedmont Using Integrated Isochemical Psuedosection Modeling and Geochronology

GSA 2020 Connects Online, 2020

Research paper thumbnail of Evidence for Alleghanian Amphibolite-Facies Deformation and Metamorphism in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018

Research paper thumbnail of Conditions of Deformation and Metamorphism in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018

Research paper thumbnail of Microstructural Implications on Conditions of Doming in the Toxaway Dome, Eastern Blue Ridge

Abstracts with programs, 2018

Research paper thumbnail of Deformation and Kinematics in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017

Research paper thumbnail of Defining the Timing, Extent, and Conditions of Paleozoic Metamorphism in the Southern Appalachian Blue Ridge Terranes of Tennessee, North Carolina, and Northern Georgia

Tectonics, Oct 1, 2022

The tectonometamorphic evolution of the southern Appalachians, which results from multiple Paleoz... more The tectonometamorphic evolution of the southern Appalachians, which results from multiple Paleozoic orogenies (Taconic, Neoacadian, and Alleghanian), has lacked a consensus interpretation regarding its thermal‐metamorphic history. The Blue Ridge terranes have remained the focus of the debate, with the interpreted timing of regional Barrovian metamorphism and associated deformation ranging from early (Taconic) to late Paleozoic (Alleghanian). New monazite U‐Pb geochronology and thermobarometric data are integrated with previously reported geo‐ and thermochronology to delimit the Paleozoic thermal‐metamorphic evolution of these terranes. Monazite compositional, textural, and U‐Pb age systematics are remarkably consistent for all samples, yielding a single dominant age mode for each sample. The western, central, and eastern Blue Ridge terranes yield weighted mean monazite U‐Pb ages of 450–441, 459–457, and 458–453 Ma, respectively. Thermodynamic modeling using mineral assemblages yields peak conditions of 600°C–650°C and 5.8–8.9 kbar for staurolite and kyanite grade western Blue Ridge units, including the stratigraphically youngest unit in the Murphy syncline, which also yields a weighted mean monazite U‐Pb age of 441 Ma. The Taconic metamorphic core of the central Blue Ridge yields peak conditions of 775°C and ∼11.5 kbar. Combined, these ages indicate that the relatively intact Barrovian metamorphic progression mapped across the Blue Ridge of Tennessee, North Carolina, and northern Georgia is solely of Ordovician (Taconic) age. Synthesis of this new data with existing geo‐ and thermochronology support a model of Barrovian metamorphism resulting from construction of a Taconic accretionary wedge and subduction complex, followed by post‐Taconic unroofing during Neoacadian and Alleghanian thrusting.

Research paper thumbnail of Effect of Dam Emplacement and Water Level Changes on Sublacustrine Geomorphology and Recent Sedimentation in Jackson Lake, Grand Teton National Park (Wyoming, United States)

Earth Science, Systems and Society

Dam installation on a deep hydrologically open lake provides the experimental framework necessary... more Dam installation on a deep hydrologically open lake provides the experimental framework necessary to study the influence of outlet engineering and changing base levels on limnogeological processes. Here, high-resolution seismic reflection profiles, sediment cores, and historical water level elevation datasets were employed to assess the recent depositional history of Jackson Lake, a dammed glacial lake located adjacent to the Teton fault in western Wyoming (USA). Prograding clinoforms imaged in the shallow stratigraphy indicate a recent lake-wide episode of delta abandonment. Submerged ∼11–12 m below the lake surface, these Gilbert-type paleo-deltas represent extensive submerged coarse-grained deposits along the axial and lateral margins of Jackson Lake that resulted from shoreline transgression following dam construction in the early 20th century. Other paleo-lake margin environments, including delta plain, shoreline, and glacial (drumlins, moraines) landforms were likewise inundat...

Research paper thumbnail of Understanding deformation band formation across a range of length scales in the Paradox Basin, Utah

Journal of Structural Geology

Research paper thumbnail of Integrating Petrology, Geochronology, and Thermochronology to Unravel the Complex Paleozoic Tectonometamorphic History of the Southern Appalachian Orogenic Core

Geological Society of America Abstracts with Programs

Research paper thumbnail of Combining diagnostic testing and student mentorship to increase engagement and progression of first-year computer science students

European Journal of Engineering Education

Research paper thumbnail of Quantifying Stress Conditions of Deformation Band Formation Adjacent to Salt Structures, Southern Utah, Usa

Geological Society of America Abstracts with Programs, 2021

Research paper thumbnail of Sublacustrine Geomorphology and Deepwater Chemostratigraphy Reveal Effects of Dam Installation at Jackson Lake (Wyoming, Usa)

Geological Society of America Abstracts with Programs, 2021

Research paper thumbnail of Role of smoking in functional dyspepsia and irritable bowel syndrome: three random population‐based studies

Alimentary Pharmacology & Therapeutics, 2021

SummaryBackgroundIt is uncertain if functional dyspepsia (FD) or irritable bowel syndrome (IBS) a... more SummaryBackgroundIt is uncertain if functional dyspepsia (FD) or irritable bowel syndrome (IBS) are linked to smoking, and smoking cessation is not part of the routine advice provided to these patients.AimTo assess if smoking is an independent risk factor for FD and IBS.MethodsThree population‐based endoscopy studies in Sweden with 2560 community individuals in total (mean age 51.5 years, 46% male). IBS (14.9%), FD (33.5%), and associated symptoms were assessed using the validated abdominal symptom questionnaire, and smoking (17.9%) was obtained from standardised questions during a clinic visit. The effect of smoking on symptom status was analysed in an individual person data meta‐analysis using mixed effect logistic regression, adjusted for snuffing, age and sex.ResultsIndividuals smoking cigarettes reported significantly higher odds of postprandial distress syndrome (FD‐PDS) (OR 10‐19 cig/day = 1.42, 95% CI 1.04‐1.98 P = 0.027, OR ≥20 cig/day = 2.16, 95% CI 1.38‐3.38, P = 0.001) b...

Research paper thumbnail of Chronic cigarette smoke exposure induces systemic hypoxia that drives intestinal dysfunction

JCI insight, Jan 8, 2018

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract (GIT). C... more Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract (GIT). Cigarette smoke (CS) exposure and chronic obstructive pulmonary disease (COPD) are risk factors for CD, although the mechanisms involved are poorly understood. We employed a mouse model of CS-induced experimental COPD and clinical studies to examine these mechanisms. Concurrent with the development of pulmonary pathology and impaired gas exchange, CS-exposed mice developed CD-associated pathology in the colon and ileum, including gut mucosal tissue hypoxia, HIF-2 stabilization, inflammation, increased microvasculature, epithelial cell turnover, and decreased intestinal barrier function. Subsequent smoking cessation reduced GIT pathology, particularly in the ileum. Dimethyloxaloylglycine, a pan-prolyl hydroxylase inhibitor, ameliorated CS-induced GIT pathology independently of pulmonary pathology. Prior smoke exposure exacerbated intestinal pathology in 2,4,6-trinitrobenzenesulfonic acid-i...

Research paper thumbnail of Deciphering the “Footprint” of the Neoacadian Metamorphic Event in the Southern Appalachians: Insights from 40AR/39AR Geochronology in the Eastern Blue Ridge and Inner Piedmont of North Carolina

Abstracts with programs, 2021

Research paper thumbnail of The Alleghanian Orogeny in the Eastern Blue Ridge: Earlier and Hotter Than Previously Recognized

Abstracts with programs, 2020

Research paper thumbnail of Reconstructing the Paleozoic Structural, Metamorphic, and Exhumational History of the Southern Appalachian Blue Ridge and Inner Piedmont

Abstracts with programs, 2023

Research paper thumbnail of Did the Brevard Fault Zone Control Neoacadian Channel and Escape Flow in the Southern Appalachian Inner Piedmont? Evidence from Monazite U-PB Geochronology and Ree Geochemistry

Abstracts with programs, 2023

Research paper thumbnail of Defining Metamorphic Timing, Extent, and Conditions in the Southern Appalachian Blue Ridge and Inner Piedmont—Insights from Monazite Xenotime Geochemistry and Geochronology

Abstracts with programs, 2021

Research paper thumbnail of An Early and Hot Alleghanian Orogeny in the Eastern Blue Ridge of the Southern Appalachians

GSA 2020 Connects Online, 2020

Research paper thumbnail of Testing the Applicability of the Channel Flow Model in the Southern Appalachian Inner Piedmont Using Integrated Isochemical Psuedosection Modeling and Geochronology

GSA 2020 Connects Online, 2020

Research paper thumbnail of Evidence for Alleghanian Amphibolite-Facies Deformation and Metamorphism in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018

Research paper thumbnail of Conditions of Deformation and Metamorphism in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018

Research paper thumbnail of Microstructural Implications on Conditions of Doming in the Toxaway Dome, Eastern Blue Ridge

Abstracts with programs, 2018

Research paper thumbnail of Deformation and Kinematics in the Toxaway Dome, Eastern Blue Ridge

GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017

Research paper thumbnail of Defining the Timing, Extent, and Conditions of Paleozoic Metamorphism in the Southern Appalachian Blue Ridge Terranes of Tennessee, North Carolina, and Northern Georgia

Tectonics, Oct 1, 2022

The tectonometamorphic evolution of the southern Appalachians, which results from multiple Paleoz... more The tectonometamorphic evolution of the southern Appalachians, which results from multiple Paleozoic orogenies (Taconic, Neoacadian, and Alleghanian), has lacked a consensus interpretation regarding its thermal‐metamorphic history. The Blue Ridge terranes have remained the focus of the debate, with the interpreted timing of regional Barrovian metamorphism and associated deformation ranging from early (Taconic) to late Paleozoic (Alleghanian). New monazite U‐Pb geochronology and thermobarometric data are integrated with previously reported geo‐ and thermochronology to delimit the Paleozoic thermal‐metamorphic evolution of these terranes. Monazite compositional, textural, and U‐Pb age systematics are remarkably consistent for all samples, yielding a single dominant age mode for each sample. The western, central, and eastern Blue Ridge terranes yield weighted mean monazite U‐Pb ages of 450–441, 459–457, and 458–453 Ma, respectively. Thermodynamic modeling using mineral assemblages yields peak conditions of 600°C–650°C and 5.8–8.9 kbar for staurolite and kyanite grade western Blue Ridge units, including the stratigraphically youngest unit in the Murphy syncline, which also yields a weighted mean monazite U‐Pb age of 441 Ma. The Taconic metamorphic core of the central Blue Ridge yields peak conditions of 775°C and ∼11.5 kbar. Combined, these ages indicate that the relatively intact Barrovian metamorphic progression mapped across the Blue Ridge of Tennessee, North Carolina, and northern Georgia is solely of Ordovician (Taconic) age. Synthesis of this new data with existing geo‐ and thermochronology support a model of Barrovian metamorphism resulting from construction of a Taconic accretionary wedge and subduction complex, followed by post‐Taconic unroofing during Neoacadian and Alleghanian thrusting.

Research paper thumbnail of Effect of Dam Emplacement and Water Level Changes on Sublacustrine Geomorphology and Recent Sedimentation in Jackson Lake, Grand Teton National Park (Wyoming, United States)

Earth Science, Systems and Society

Dam installation on a deep hydrologically open lake provides the experimental framework necessary... more Dam installation on a deep hydrologically open lake provides the experimental framework necessary to study the influence of outlet engineering and changing base levels on limnogeological processes. Here, high-resolution seismic reflection profiles, sediment cores, and historical water level elevation datasets were employed to assess the recent depositional history of Jackson Lake, a dammed glacial lake located adjacent to the Teton fault in western Wyoming (USA). Prograding clinoforms imaged in the shallow stratigraphy indicate a recent lake-wide episode of delta abandonment. Submerged ∼11–12 m below the lake surface, these Gilbert-type paleo-deltas represent extensive submerged coarse-grained deposits along the axial and lateral margins of Jackson Lake that resulted from shoreline transgression following dam construction in the early 20th century. Other paleo-lake margin environments, including delta plain, shoreline, and glacial (drumlins, moraines) landforms were likewise inundat...

Research paper thumbnail of Understanding deformation band formation across a range of length scales in the Paradox Basin, Utah

Journal of Structural Geology

Research paper thumbnail of Integrating Petrology, Geochronology, and Thermochronology to Unravel the Complex Paleozoic Tectonometamorphic History of the Southern Appalachian Orogenic Core

Geological Society of America Abstracts with Programs

Research paper thumbnail of Combining diagnostic testing and student mentorship to increase engagement and progression of first-year computer science students

European Journal of Engineering Education

Research paper thumbnail of Quantifying Stress Conditions of Deformation Band Formation Adjacent to Salt Structures, Southern Utah, Usa

Geological Society of America Abstracts with Programs, 2021

Research paper thumbnail of Sublacustrine Geomorphology and Deepwater Chemostratigraphy Reveal Effects of Dam Installation at Jackson Lake (Wyoming, Usa)

Geological Society of America Abstracts with Programs, 2021

Research paper thumbnail of Role of smoking in functional dyspepsia and irritable bowel syndrome: three random population‐based studies

Alimentary Pharmacology & Therapeutics, 2021

SummaryBackgroundIt is uncertain if functional dyspepsia (FD) or irritable bowel syndrome (IBS) a... more SummaryBackgroundIt is uncertain if functional dyspepsia (FD) or irritable bowel syndrome (IBS) are linked to smoking, and smoking cessation is not part of the routine advice provided to these patients.AimTo assess if smoking is an independent risk factor for FD and IBS.MethodsThree population‐based endoscopy studies in Sweden with 2560 community individuals in total (mean age 51.5 years, 46% male). IBS (14.9%), FD (33.5%), and associated symptoms were assessed using the validated abdominal symptom questionnaire, and smoking (17.9%) was obtained from standardised questions during a clinic visit. The effect of smoking on symptom status was analysed in an individual person data meta‐analysis using mixed effect logistic regression, adjusted for snuffing, age and sex.ResultsIndividuals smoking cigarettes reported significantly higher odds of postprandial distress syndrome (FD‐PDS) (OR 10‐19 cig/day = 1.42, 95% CI 1.04‐1.98 P = 0.027, OR ≥20 cig/day = 2.16, 95% CI 1.38‐3.38, P = 0.001) b...

Research paper thumbnail of Chronic cigarette smoke exposure induces systemic hypoxia that drives intestinal dysfunction

JCI insight, Jan 8, 2018

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract (GIT). C... more Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract (GIT). Cigarette smoke (CS) exposure and chronic obstructive pulmonary disease (COPD) are risk factors for CD, although the mechanisms involved are poorly understood. We employed a mouse model of CS-induced experimental COPD and clinical studies to examine these mechanisms. Concurrent with the development of pulmonary pathology and impaired gas exchange, CS-exposed mice developed CD-associated pathology in the colon and ileum, including gut mucosal tissue hypoxia, HIF-2 stabilization, inflammation, increased microvasculature, epithelial cell turnover, and decreased intestinal barrier function. Subsequent smoking cessation reduced GIT pathology, particularly in the ileum. Dimethyloxaloylglycine, a pan-prolyl hydroxylase inhibitor, ameliorated CS-induced GIT pathology independently of pulmonary pathology. Prior smoke exposure exacerbated intestinal pathology in 2,4,6-trinitrobenzenesulfonic acid-i...