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Papers by Ronald Counts

Research paper thumbnail of Shallow Faulting and Folding in the Epicentral Area of the 1886 Charleston, South Carolina, Earthquake

Bulletin of the Seismological Society of America

The moment magnitude (Mw) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886... more The moment magnitude (Mw) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886 is the largest historical earthquake in the United States east of the Appalachian Mountains. The fault(s) that ruptured during this earthquake has never been conclusively identified, and conflicting fault models have been proposed. Here we interpret reprocessed seismic reflection profiles, reprocessed legacy aeromagnetic data, and newly collected ground penetrating radar (GPR) profiles to delineate faults deforming the Cretaceous and younger Atlantic Coastal Plain (ACP) strata in the epicentral area of the 1886 earthquake. The data show evidence for faults folding or vertically displacing ACP strata, including apparent displacements of near-surface strata (upper ∼20 m). Aeromagnetic data show several northeast (NE)-trending lineaments, two of which correlate with faults and folds with vertical displacements as great as 55 m on the seismic reflection and radar profiles. ACP strata show o...

Research paper thumbnail of The Mississippian Section at Paddys Bluff, Crittenden County, Kentucky

Research paper thumbnail of The Nonglacial Surficial Geology of the Henrys Fork, Uinta Mountains, Utah and Wyoming

Abstract Surficial deposits below the glacial termini of the Henrys Fork drainage have been mappe... more Abstract Surficial deposits below the glacial termini of the Henrys Fork drainage have been mapped at 1:24,000 scale to develop a nonglacial Quaternary stratigraphic framework for the northeastern Uinta Mountains. This study area spans from Pleistocene glacial moraines, approximately 6 km south of the Utah-Wyoming border, to the termination of Henrys Fork at Flaming Gorge Reservoir near Manila, Utah. The Henrys Fork nonglacial stratigraphy contains nine distinct mainstem gravels, six piedmont gravels, and landslide deposits. Gravels on the Henrys Fork are grouped as older, high remnant gravels that cannot be directly linked to glacial units and younger gravels that can be traced from glacial till, through outwash plains, to stream-valley gravels with terraces formed upon them. Henrys Fork gravels are clast-supported, cobble gravel derived from the Uinta Mountain Group and Paleozoic limestone units. Near moraines, gravels are thicker but they quickly thin downstream and lie on planar bedrock straths, and so form strath terraces that converge downstream. No absolute age control currently exists for any of the Henrys Fork gravels or terraces. Henrys Fork terraces Qag2 and Qag3 can be correlated to relatively well-dated Wind River terraces and tentative incision rates for the Henrys Fork are estimated at 80-110 m/my over the late Pleistocene. These rates are similar to rates estimated for the Green River on the north slope of the Uintas in western Browns Park, but are significantly less than reported rates in other central Rocky Mountain ranges and are two to three times lower than incision rates, estimated without direct age control, for the south flank of the Uinta Mountains. Extrapolating a linear incision-rate suggests that the oldest gravels on the Henrys Fork were deposited in the early Pleistocene.

Research paper thumbnail of River Terrace Evidence of Tectonic Processes in the Eastern North American Plate Interior, South Anna River, Virginia

The Journal of Geology, 2021

Research paper thumbnail of The Quaternary Stratigraphy of the Henrys Fork and Western Browns Park, Northeastern Uinta Mountains, Utah and Wyoming

The landscape evolution of the northeastern Uinta Mountains and the manner in which climatic and ... more The landscape evolution of the northeastern Uinta Mountains and the manner in which climatic and tectonic forcing have influenced it are not well constrained. Surficial deposits covering ~325 km2 below the glacial termini in the Henrys Fork and ~50 km2 along the Green River in western Browns Park were mapped at 1:24,000 scale to develop a Quaternary stratigraphic framework for the northeastern Uinta Mountains. The Henrys Fork mapping area spans from late Wisconsinan moraines to Flaming Gorge Reservoir. The Henrys Fork stratigraphy contains 10 mainstem gravels, six piedmont gravels, and landslide deposits. Terraces preserved along the Henrys Fork converge downstream and are strath terraces underlain by clast-supported, cobble gravel derived from the Uinta Mountain Group and Paleozoic limestone units. The Henrys Fork terrace stratigraphy was correlated to the Wind River terrace stratigraphy for age control, and incision rates were estimated at 80-110 m/m.y. The Browns Park mapping are...

Research paper thumbnail of Using Geophysics and Luminescence Geochronology to Determine the Age and Extent of the Adams Mill Fault at the Smithsonian National Zoological Park, Washington, DC

Geological Society of America Abstracts with Programs

Research paper thumbnail of A Tale of Two Quakes: Comparing the 2011 M5.7 Mineral Va and the 2020 M5.1 Sparta NC Earthquakes from a Geologic Mapping Viewpoint

Geological Society of America Abstracts with Programs

Research paper thumbnail of The Diversion of Glacial Meltwater from the Eastern St. Lawrence River Outlet Into the Ohio River Basin by an Mis 3 Advance of the Laurentide Ice Sheet: Evidence from Rapidly Aggraded Outwash and Slackwater Lake Deposits in the Lower Ohio River Valley

Geological Society of America Abstracts with Programs, 2020

Research paper thumbnail of Using Electrical Resistivity to Locate an Abandoned Fluorspar Mine as a Supplemental Water Source for the City of Marion, Kentucky

Research paper thumbnail of Synthesis of Recent Paleoseismic Research on Quaternary Faulting in the Eastern Tennessee Seismic Zone, Eastern North America: Implications for Seismic Hazard and Intraplate Seismicity

Bulletin of the Seismological Society of America, 2022

Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary ... more Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary seismicity. Modern seismicity records frequent seismic activity in plate-boundary seismic zones, but in fault zones where seismic activity is not frequent, plate boundary or intraplate, resolution of prehistoric earthquake activity is critical for estimating earthquake recurrence interval and maximum expected magnitude. Thus, documenting prehistoric earthquakes is crucial for assessing earthquake hazard posed to infrastructure, including nuclear reactors and large dams. The ∼400 km long eastern Tennessee seismic zone (ETSZ), United States, is the third most active seismic zone east of the Rocky Mountains in North America, although the largest recorded ETSZ earthquake is only Mw 4.8. Ironically, it is the least studied major eastern U.S. seismic zone. Recent ETSZ field surveys revealed an 80 km long, 060°-trending corridor containing northeast-striking Quaternary thrust, strike slip, and ...

Research paper thumbnail of Optically Stimulated Luminescence Chronology of Terraces of the Lower Ohio River Valley: Implications for Quaternary Climate Change and Neotectonic Deformation

Research paper thumbnail of Investigating Faulted Terrace Deposits at the Smithsonian National Zoo, Washington, D.C

Research paper thumbnail of A Seismicity/Quaternary Faulting Corridor in the Eastern Tennessee Seismic Zone: An Update

Research paper thumbnail of Late Holocene Deformation near the Southern Limits of the Wabash Valley Seismic Zone of Kentucky and Indiana, Central United States, with Seismic Implications

Bulletin of the Seismological Society of America, 2021

The Wabash Valley seismic zone (WVSZ) is a region of diffuse, modern intraplate seismicity in the... more The Wabash Valley seismic zone (WVSZ) is a region of diffuse, modern intraplate seismicity in the central United States with a history of strong, late Quaternary and Holocene seismicity as determined through paleoliquefaction studies. Yet, there are no specific faults linked to these strong WVSZ paleoearthquakes, some of which were as large as Mw 7.2–7.5. A multidisciplinary investigation of a linear, 5-kilometer-long and ∼3-meter-high scarp on the Ohio River floodplain in the southernmost WVSZ in western Kentucky evaluated whether the scarp is a fluvial landform or a tectonic feature. Geomorphic mapping and optically stimulated luminescence geochronology show that the age and orientation of the scarp are inconsistent with surrounding fluvial landforms. Trenching, core drilling, seismic reflection, electrical resistivity profiling, and cross sections of petroleum well logs all indicate a blind fault directly underlies the scarp. The scarp is interpreted to be the fold axis of a down...

Research paper thumbnail of Last glacial maximum ecology and climate from terrestrial gastropod assemblages in Peoria loess, western Kentucky

Journal of Quaternary Science, 2020

Research paper thumbnail of Confirming Quaternary Displacement Rates on the Meeman-Shelby Fault and Joiner Ridge Horst, Eastern Arkansas

Research paper thumbnail of Hydrogeologic Investigation of Subsurface Stratigraphy Using Ground Penetrating Radar in Southwestern Shelby County, Tennessee

Geological Society of America Abstracts with Programs, 2019

Research paper thumbnail of Possible Contribution to Southern Blue Ridge Relief from Quaternary Faulting in the Eastern Tennessee Seismic Zone

Research paper thumbnail of Quaternary Displacement on the Joiner Ridge Fault, Eastern Arkansas

Seismological Research Letters, 2019

The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind... more The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind structures that are not seismically active but may pose seismic hazards. The Joiner ridge fault (JRF) is the 35‐kilometer‐long east‐bounding fault of the Joiner ridge blind horst located in eastern Arkansas ∼50 km northwest of Memphis, Tennessee. Shallow S‐wave (SH‐mode) seismic reflection profiles, continuous cores, and radiometric dating of Quaternary alluvium across the JRF reveal down‐to‐the‐east reverse faulting and folding of Eocene strata and overlying Quaternary Mississippi River alluvium. The base of the Quaternary alluvium has an age of 20.3 ka and is vertically displaced 12 m, resulting in an average slip rate of 0.6±0.1 mm/yr over the past 20.3 ka. The overlying upper Wisconsinan and Holocene alluvial facies are also displaced by the JRF. These facies increase in thickness across the JRF and were used to calculate late Wisconsinan and Holocene slip histories. The JRF slipp...

Research paper thumbnail of Surficial Geologic Map of the Evansville, Indiana, and Henderson, Kentucky, Area

Scientific Investigations Map, 2009

Research paper thumbnail of Shallow Faulting and Folding in the Epicentral Area of the 1886 Charleston, South Carolina, Earthquake

Bulletin of the Seismological Society of America

The moment magnitude (Mw) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886... more The moment magnitude (Mw) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886 is the largest historical earthquake in the United States east of the Appalachian Mountains. The fault(s) that ruptured during this earthquake has never been conclusively identified, and conflicting fault models have been proposed. Here we interpret reprocessed seismic reflection profiles, reprocessed legacy aeromagnetic data, and newly collected ground penetrating radar (GPR) profiles to delineate faults deforming the Cretaceous and younger Atlantic Coastal Plain (ACP) strata in the epicentral area of the 1886 earthquake. The data show evidence for faults folding or vertically displacing ACP strata, including apparent displacements of near-surface strata (upper ∼20 m). Aeromagnetic data show several northeast (NE)-trending lineaments, two of which correlate with faults and folds with vertical displacements as great as 55 m on the seismic reflection and radar profiles. ACP strata show o...

Research paper thumbnail of The Mississippian Section at Paddys Bluff, Crittenden County, Kentucky

Research paper thumbnail of The Nonglacial Surficial Geology of the Henrys Fork, Uinta Mountains, Utah and Wyoming

Abstract Surficial deposits below the glacial termini of the Henrys Fork drainage have been mappe... more Abstract Surficial deposits below the glacial termini of the Henrys Fork drainage have been mapped at 1:24,000 scale to develop a nonglacial Quaternary stratigraphic framework for the northeastern Uinta Mountains. This study area spans from Pleistocene glacial moraines, approximately 6 km south of the Utah-Wyoming border, to the termination of Henrys Fork at Flaming Gorge Reservoir near Manila, Utah. The Henrys Fork nonglacial stratigraphy contains nine distinct mainstem gravels, six piedmont gravels, and landslide deposits. Gravels on the Henrys Fork are grouped as older, high remnant gravels that cannot be directly linked to glacial units and younger gravels that can be traced from glacial till, through outwash plains, to stream-valley gravels with terraces formed upon them. Henrys Fork gravels are clast-supported, cobble gravel derived from the Uinta Mountain Group and Paleozoic limestone units. Near moraines, gravels are thicker but they quickly thin downstream and lie on planar bedrock straths, and so form strath terraces that converge downstream. No absolute age control currently exists for any of the Henrys Fork gravels or terraces. Henrys Fork terraces Qag2 and Qag3 can be correlated to relatively well-dated Wind River terraces and tentative incision rates for the Henrys Fork are estimated at 80-110 m/my over the late Pleistocene. These rates are similar to rates estimated for the Green River on the north slope of the Uintas in western Browns Park, but are significantly less than reported rates in other central Rocky Mountain ranges and are two to three times lower than incision rates, estimated without direct age control, for the south flank of the Uinta Mountains. Extrapolating a linear incision-rate suggests that the oldest gravels on the Henrys Fork were deposited in the early Pleistocene.

Research paper thumbnail of River Terrace Evidence of Tectonic Processes in the Eastern North American Plate Interior, South Anna River, Virginia

The Journal of Geology, 2021

Research paper thumbnail of The Quaternary Stratigraphy of the Henrys Fork and Western Browns Park, Northeastern Uinta Mountains, Utah and Wyoming

The landscape evolution of the northeastern Uinta Mountains and the manner in which climatic and ... more The landscape evolution of the northeastern Uinta Mountains and the manner in which climatic and tectonic forcing have influenced it are not well constrained. Surficial deposits covering ~325 km2 below the glacial termini in the Henrys Fork and ~50 km2 along the Green River in western Browns Park were mapped at 1:24,000 scale to develop a Quaternary stratigraphic framework for the northeastern Uinta Mountains. The Henrys Fork mapping area spans from late Wisconsinan moraines to Flaming Gorge Reservoir. The Henrys Fork stratigraphy contains 10 mainstem gravels, six piedmont gravels, and landslide deposits. Terraces preserved along the Henrys Fork converge downstream and are strath terraces underlain by clast-supported, cobble gravel derived from the Uinta Mountain Group and Paleozoic limestone units. The Henrys Fork terrace stratigraphy was correlated to the Wind River terrace stratigraphy for age control, and incision rates were estimated at 80-110 m/m.y. The Browns Park mapping are...

Research paper thumbnail of Using Geophysics and Luminescence Geochronology to Determine the Age and Extent of the Adams Mill Fault at the Smithsonian National Zoological Park, Washington, DC

Geological Society of America Abstracts with Programs

Research paper thumbnail of A Tale of Two Quakes: Comparing the 2011 M5.7 Mineral Va and the 2020 M5.1 Sparta NC Earthquakes from a Geologic Mapping Viewpoint

Geological Society of America Abstracts with Programs

Research paper thumbnail of The Diversion of Glacial Meltwater from the Eastern St. Lawrence River Outlet Into the Ohio River Basin by an Mis 3 Advance of the Laurentide Ice Sheet: Evidence from Rapidly Aggraded Outwash and Slackwater Lake Deposits in the Lower Ohio River Valley

Geological Society of America Abstracts with Programs, 2020

Research paper thumbnail of Using Electrical Resistivity to Locate an Abandoned Fluorspar Mine as a Supplemental Water Source for the City of Marion, Kentucky

Research paper thumbnail of Synthesis of Recent Paleoseismic Research on Quaternary Faulting in the Eastern Tennessee Seismic Zone, Eastern North America: Implications for Seismic Hazard and Intraplate Seismicity

Bulletin of the Seismological Society of America, 2022

Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary ... more Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary seismicity. Modern seismicity records frequent seismic activity in plate-boundary seismic zones, but in fault zones where seismic activity is not frequent, plate boundary or intraplate, resolution of prehistoric earthquake activity is critical for estimating earthquake recurrence interval and maximum expected magnitude. Thus, documenting prehistoric earthquakes is crucial for assessing earthquake hazard posed to infrastructure, including nuclear reactors and large dams. The ∼400 km long eastern Tennessee seismic zone (ETSZ), United States, is the third most active seismic zone east of the Rocky Mountains in North America, although the largest recorded ETSZ earthquake is only Mw 4.8. Ironically, it is the least studied major eastern U.S. seismic zone. Recent ETSZ field surveys revealed an 80 km long, 060°-trending corridor containing northeast-striking Quaternary thrust, strike slip, and ...

Research paper thumbnail of Optically Stimulated Luminescence Chronology of Terraces of the Lower Ohio River Valley: Implications for Quaternary Climate Change and Neotectonic Deformation

Research paper thumbnail of Investigating Faulted Terrace Deposits at the Smithsonian National Zoo, Washington, D.C

Research paper thumbnail of A Seismicity/Quaternary Faulting Corridor in the Eastern Tennessee Seismic Zone: An Update

Research paper thumbnail of Late Holocene Deformation near the Southern Limits of the Wabash Valley Seismic Zone of Kentucky and Indiana, Central United States, with Seismic Implications

Bulletin of the Seismological Society of America, 2021

The Wabash Valley seismic zone (WVSZ) is a region of diffuse, modern intraplate seismicity in the... more The Wabash Valley seismic zone (WVSZ) is a region of diffuse, modern intraplate seismicity in the central United States with a history of strong, late Quaternary and Holocene seismicity as determined through paleoliquefaction studies. Yet, there are no specific faults linked to these strong WVSZ paleoearthquakes, some of which were as large as Mw 7.2–7.5. A multidisciplinary investigation of a linear, 5-kilometer-long and ∼3-meter-high scarp on the Ohio River floodplain in the southernmost WVSZ in western Kentucky evaluated whether the scarp is a fluvial landform or a tectonic feature. Geomorphic mapping and optically stimulated luminescence geochronology show that the age and orientation of the scarp are inconsistent with surrounding fluvial landforms. Trenching, core drilling, seismic reflection, electrical resistivity profiling, and cross sections of petroleum well logs all indicate a blind fault directly underlies the scarp. The scarp is interpreted to be the fold axis of a down...

Research paper thumbnail of Last glacial maximum ecology and climate from terrestrial gastropod assemblages in Peoria loess, western Kentucky

Journal of Quaternary Science, 2020

Research paper thumbnail of Confirming Quaternary Displacement Rates on the Meeman-Shelby Fault and Joiner Ridge Horst, Eastern Arkansas

Research paper thumbnail of Hydrogeologic Investigation of Subsurface Stratigraphy Using Ground Penetrating Radar in Southwestern Shelby County, Tennessee

Geological Society of America Abstracts with Programs, 2019

Research paper thumbnail of Possible Contribution to Southern Blue Ridge Relief from Quaternary Faulting in the Eastern Tennessee Seismic Zone

Research paper thumbnail of Quaternary Displacement on the Joiner Ridge Fault, Eastern Arkansas

Seismological Research Letters, 2019

The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind... more The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind structures that are not seismically active but may pose seismic hazards. The Joiner ridge fault (JRF) is the 35‐kilometer‐long east‐bounding fault of the Joiner ridge blind horst located in eastern Arkansas ∼50 km northwest of Memphis, Tennessee. Shallow S‐wave (SH‐mode) seismic reflection profiles, continuous cores, and radiometric dating of Quaternary alluvium across the JRF reveal down‐to‐the‐east reverse faulting and folding of Eocene strata and overlying Quaternary Mississippi River alluvium. The base of the Quaternary alluvium has an age of 20.3 ka and is vertically displaced 12 m, resulting in an average slip rate of 0.6±0.1 mm/yr over the past 20.3 ka. The overlying upper Wisconsinan and Holocene alluvial facies are also displaced by the JRF. These facies increase in thickness across the JRF and were used to calculate late Wisconsinan and Holocene slip histories. The JRF slipp...

Research paper thumbnail of Surficial Geologic Map of the Evansville, Indiana, and Henderson, Kentucky, Area

Scientific Investigations Map, 2009