Cal Ruleman
Research Geologist constructing geologic maps and performing research related to our Nation's natural resources and hazards
Current Research:
Neotectonics and Structural Evolution of Intermountain Western North America
Geomorphic and Hydrologic Evolution of Plio-Pleistocene Fluvial Systems and Chronostratigraphy of Western North America
Geomorphology and Chronology of North American Pleistocene Glacial-Periglacial Systems
Geologic and Geomorphic History of Contaminants in Western North American River Systems
Professional Experience
2007-Present: Research Geologist, USGS
2004-2007: Geologist, USGS contractor and private sector
2002-2004: U.S. Peace Corp Volunteer, Suriname, South America
2000-2002: USGS student intern
Education and Certifications
1999: B.A., University of Montana, Missoula
2002: M.S., Montana State University, Bozeman
Affiliations and Memberships*
1996-Present: Geological Society of America
2000-Present: Colorado Scientific Society
Science and Products
Cosmogenic Al-26/Be-10 Isochron Burial Data for the Nussbaum Gravel at Baculite Mesa, CO Cosmogenic Al-26/Be-10 Isochron Burial Data for the Nussbaum Gravel at Baculite Mesa, CO
We have constrained the age of the Nussbaum Gravel at Baculite Mesa, CO using cosmogenic Al-26/Be-10 isochron burial dating. Two samples, a coarse sand and a fine gravel, were prepared for burial dating at the Reston Cosmogenic Nuclide (RECON) Lab and measured via accelerator mass spectrometry at the Purdue Rare Isotope Measurement (PRIME) Lab. The results of this work are summarized in...
Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map
This data release presents geologic map data for the surficial geology of the Aztec 1-degree by 2-degree quadrangle. The map area lies within two physiographic provinces of Fenneman (1928): the Southern Rocky Mountains province, and the Colorado Plateau province, Navajo section. Geologic mapping is mostly compiled from published geologic map data sources ranging from 1:24,000 to 1:250...
Surficial geologic map database of the Durango 1-degree by 2-degree quadrangle, southern Colorado: Contributions to the National Geologic Map Surficial geologic map database of the Durango 1-degree by 2-degree quadrangle, southern Colorado: Contributions to the National Geologic Map
This data release presents geologic map data for the surficial geology of the Durango 1-degree by 2-degree quadrangle and adjacent areas along the northern boundary of the quadrangle. The map area lies within two physiographic provinces of Fenneman (1928): the Southern Rocky Mountains province, and the Colorado Plateau province, Navajo section. Geologic mapping is mostly compiled from...
Data release for Geologic Map of the Homestake Reservoir 7.5' quadrangle, Lake, Pitkin, and Eagle Counties, Colorado Data release for Geologic Map of the Homestake Reservoir 7.5' quadrangle, Lake, Pitkin, and Eagle Counties, Colorado
The Homestake Reservoir 7.5' quadrangle lies at the northwestern end of the Upper Arkansas Valley, and headwaters of the Arkansas River, and the Roaring Fork, Fryingpan, and Eagle Rivers of the Colorado River system. The quadrangle lies within tectonic provinces of the 1.4 Ga Picuris Orogeny, the late Paleozoic Ancestral Rockies, Late Cretaceous-Paleocene Laramide orogeny, Oligocene to...
Data release for Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications Data release for Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications
This dataset includes tables of 3He-isotopic data used to calculate surface exposure ages for samples of basalt, and U- and Th-isotopic data used to calculate uranium-series age estimates (230Th/U method) and initial 234U/238U activity ratios for samples of pedogenic carbonate formed in soils on alluvial fans in the San Luis Valley, Colorado, USA. These data are included in the...
Data Release for Geologic Map of the Leadville North 7.5' Quadrangle, Eagle and Lake Counties, Colorado Data Release for Geologic Map of the Leadville North 7.5' Quadrangle, Eagle and Lake Counties, Colorado
The Leadville North 7.5' quadrangle lies at the northern end of the Upper Arkansas Valley, where the Continental Divide at Tennessee Pass creates a low drainage divide between the Colorado and Arkansas River watersheds. In the eastern half of the quadrangle, the Paleozoic sedimentary section dips generally 20-30 degrees east. At Tennessee Pass and Missouri Hill, the core of the Sawatch
Filter Total Items: 13
Geologic map of the Ute Mountain 7.5' quadrangle, Taos County, New Mexico, and Conejos and Costilla Counties, Colorado Geologic map of the Ute Mountain 7.5' quadrangle, Taos County, New Mexico, and Conejos and Costilla Counties, Colorado
The Ute Mountain 7.5' quadrangle is located in the south-central part of the San Luis Basin of northern New Mexico, in the Rio Grande del Norte National Monument, and contains deposits that record volcanic, tectonic, and associated alluvial and colluvial processes over the past four million years. Ute Mountain has the distinction of being one of the largest intermediate composition...
Geologic map of the Sunshine 7.5' quadrangle, Taos County, New Mexico Geologic map of the Sunshine 7.5' quadrangle, Taos County, New Mexico
The Sunshine 7.5' quadrangle is located in the south-central part of the San Luis Basin of northern New Mexico, in the Rio Grande del Norte National Monument, and contains deposits that record volcanic, tectonic, and associated alluvial and colluvial processes over the past four million years. Sunshine Valley, named for the small locale of Sunshine, is incised by a series of northeast...
Geologic map of the Mount Sherman 7.5' quadrangle, Lake and Park Counties, Colorado Geologic map of the Mount Sherman 7.5' quadrangle, Lake and Park Counties, Colorado
The Mount Sherman 7.5- minute quadrangle is located along the crest of the Mosquito Range in between Leadville and Fairplay, Colorado. There are eleven 13,000-foot peaks and one fourteener, Mount Sherman, within the quadrangle. General elevations range from 10,400–14,036 feet (3,200–4,278 meters). The western half of the quadrangle primarily consists of Proterozoic granitic rocks reverse...
Geologic map of the Bailey 30' x 60' quadrangle, North-Central Colorado Geologic map of the Bailey 30' x 60' quadrangle, North-Central Colorado
The Bailey, Colo. 1:100,000-scale quadrangle lies within two physiographic and geologic provinces in central Colorado: 1) the Front Range and 2) South Park. Most of the Front Range is composed of Proterozoic rocks ranging in age from 1,790 Ma to 1,074 Ma. Along the eastern flanks and within the Denver Basin, sedimentary rocks ranging from Pennsylvanian to Cretaceous are deformed and...
Geologic Map of the Sulphur Mountain Quadrangle, Park County, Colorado Geologic Map of the Sulphur Mountain Quadrangle, Park County, Colorado
The main structural element in the Sulphur Mountain quadrangle is the Elkhorn thrust. This northwest-trending fault is the southernmost structure that bounds the west side of the Late Cretaceous and early Tertiary Front Range basement-rock uplift. The Elkhorn thrust and the Williams Range thrust that occurs in the Dillon area north of the quadrangle bound the west flank of the Williams...
Geologic Map of the Elkhorn Quadrangle, Park County, Colorado Geologic Map of the Elkhorn Quadrangle, Park County, Colorado
The Elkhorn thrust is defined by the juxtaposition of Early and Middle Proterozoic metamorphic and igneous rocks against Mesozoic and Tertiary rocks. Within the mapped area, an imbricate frontal thrust system juxtaposes Upper Cretaceous rocks against Paleocene rocks of the South Park Formation. In the southeastern section of the quadrangle, Middle Proterozoic igneous rocks are thrust...
Filter Total Items: 17
Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications
The Rio Grande is the fourth longest river in North America extending over 3,000 km from the Rocky Mountains to the Gulf of Mexico. The Pleistocene evolution of this river from individual subbasins into a coalesced fluvial system has been long debated. Herein, we constrain the middle Pleistocene evolution of the northernmost and largest Rio Grande basin, the San Luis basin, and the...
Authors
Chester A. Ruleman, Adam M. Hudson, Ren A. Thompson, Daniel P. Miggins, James B. Paces, Brent M. Goehring
Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA
On active alluvial fans, debris-flow deposits and frequent avulsions produce a rough topographic surface. As is the case in many initially rough landforms produced by catastrophic processes, the topography of alluvial fans is progressively smoothed, producing textural differences useful in establishing relative age criteria for fans. Here, we outline an approach for defining a...
Authors
Samuel Johnstone, Adam M. Hudson, Sylvia Nicovich, Chester A. Ruleman, Robert M. Sare, Ren A. Thompson
Geophysical expression of buried range-front embayment structure: Great Sand Dunes National Park, Rio Grande rift, Colorado Geophysical expression of buried range-front embayment structure: Great Sand Dunes National Park, Rio Grande rift, Colorado
Great Sand Dunes National Park and Preserve (GRSA, Colorado) lies along the eastern margin of the San Luis Basin and the tectonically active Sangre de Cristo fault system that are part of the northern Rio Grande rift. GRSA lies within a prominent embayment in the range front where two separate sections of the Sangre de Cristo fault system intersect. Fault scarps are observed along both
Authors
Benjamin J. Drenth, V. J. Grauch, Chester A. Ruleman, Judith A Schenk
Geomorphic evolution of the San Luis Basin and Rio Grande in southern Colorado and northern New Mexico Geomorphic evolution of the San Luis Basin and Rio Grande in southern Colorado and northern New Mexico
The San Luis Basin encompasses the largest structural and hydrologic basin of the Rio Grande rift. On this field trip, we will examine the timing of transition of the San Luis Basin from hydrologically closed, aggrading subbasins to a continuous fluvial system that eroded the basin, formed the Rio Grande gorge, and ultimately, integrated the Rio Grande from Colorado to the Gulf of Mexico...
Authors
Chester A. Ruleman, Michael Machette, Ren A. Thompson, Dan M Miggins, Brent M Goehring, James B. Paces
Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana
The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal...
Authors
Chester A. Ruleman, Mort Larsen, Michael C. Stickney
Identifying buried segments of active faults in the northern Rio Grande Rift using aeromagnetic, LiDAR,and gravity data, south-central Colorado, USA Identifying buried segments of active faults in the northern Rio Grande Rift using aeromagnetic, LiDAR,and gravity data, south-central Colorado, USA
Combined interpretation of aeromagnetic and LiDAR data builds on the strength of the aeromagnetic method to locate normal faults with significant offset under cover and the strength of LiDAR interpretation to identify the age and sense of motion of faults. Each data set helps resolve ambiguities in interpreting the other. In addition, gravity data can be used to infer the sense of motion...
Authors
V. J. S. Grauch, Chester A. Ruleman
Science and Products
Cosmogenic Al-26/Be-10 Isochron Burial Data for the Nussbaum Gravel at Baculite Mesa, CO Cosmogenic Al-26/Be-10 Isochron Burial Data for the Nussbaum Gravel at Baculite Mesa, CO
We have constrained the age of the Nussbaum Gravel at Baculite Mesa, CO using cosmogenic Al-26/Be-10 isochron burial dating. Two samples, a coarse sand and a fine gravel, were prepared for burial dating at the Reston Cosmogenic Nuclide (RECON) Lab and measured via accelerator mass spectrometry at the Purdue Rare Isotope Measurement (PRIME) Lab. The results of this work are summarized in...
Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map
This data release presents geologic map data for the surficial geology of the Aztec 1-degree by 2-degree quadrangle. The map area lies within two physiographic provinces of Fenneman (1928): the Southern Rocky Mountains province, and the Colorado Plateau province, Navajo section. Geologic mapping is mostly compiled from published geologic map data sources ranging from 1:24,000 to 1:250...
Surficial geologic map database of the Durango 1-degree by 2-degree quadrangle, southern Colorado: Contributions to the National Geologic Map Surficial geologic map database of the Durango 1-degree by 2-degree quadrangle, southern Colorado: Contributions to the National Geologic Map
This data release presents geologic map data for the surficial geology of the Durango 1-degree by 2-degree quadrangle and adjacent areas along the northern boundary of the quadrangle. The map area lies within two physiographic provinces of Fenneman (1928): the Southern Rocky Mountains province, and the Colorado Plateau province, Navajo section. Geologic mapping is mostly compiled from...
Data release for Geologic Map of the Homestake Reservoir 7.5' quadrangle, Lake, Pitkin, and Eagle Counties, Colorado Data release for Geologic Map of the Homestake Reservoir 7.5' quadrangle, Lake, Pitkin, and Eagle Counties, Colorado
The Homestake Reservoir 7.5' quadrangle lies at the northwestern end of the Upper Arkansas Valley, and headwaters of the Arkansas River, and the Roaring Fork, Fryingpan, and Eagle Rivers of the Colorado River system. The quadrangle lies within tectonic provinces of the 1.4 Ga Picuris Orogeny, the late Paleozoic Ancestral Rockies, Late Cretaceous-Paleocene Laramide orogeny, Oligocene to...
Data release for Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications Data release for Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications
This dataset includes tables of 3He-isotopic data used to calculate surface exposure ages for samples of basalt, and U- and Th-isotopic data used to calculate uranium-series age estimates (230Th/U method) and initial 234U/238U activity ratios for samples of pedogenic carbonate formed in soils on alluvial fans in the San Luis Valley, Colorado, USA. These data are included in the...
Data Release for Geologic Map of the Leadville North 7.5' Quadrangle, Eagle and Lake Counties, Colorado Data Release for Geologic Map of the Leadville North 7.5' Quadrangle, Eagle and Lake Counties, Colorado
The Leadville North 7.5' quadrangle lies at the northern end of the Upper Arkansas Valley, where the Continental Divide at Tennessee Pass creates a low drainage divide between the Colorado and Arkansas River watersheds. In the eastern half of the quadrangle, the Paleozoic sedimentary section dips generally 20-30 degrees east. At Tennessee Pass and Missouri Hill, the core of the Sawatch
Filter Total Items: 13
Geologic map of the Ute Mountain 7.5' quadrangle, Taos County, New Mexico, and Conejos and Costilla Counties, Colorado Geologic map of the Ute Mountain 7.5' quadrangle, Taos County, New Mexico, and Conejos and Costilla Counties, Colorado
The Ute Mountain 7.5' quadrangle is located in the south-central part of the San Luis Basin of northern New Mexico, in the Rio Grande del Norte National Monument, and contains deposits that record volcanic, tectonic, and associated alluvial and colluvial processes over the past four million years. Ute Mountain has the distinction of being one of the largest intermediate composition...
Geologic map of the Sunshine 7.5' quadrangle, Taos County, New Mexico Geologic map of the Sunshine 7.5' quadrangle, Taos County, New Mexico
The Sunshine 7.5' quadrangle is located in the south-central part of the San Luis Basin of northern New Mexico, in the Rio Grande del Norte National Monument, and contains deposits that record volcanic, tectonic, and associated alluvial and colluvial processes over the past four million years. Sunshine Valley, named for the small locale of Sunshine, is incised by a series of northeast...
Geologic map of the Mount Sherman 7.5' quadrangle, Lake and Park Counties, Colorado Geologic map of the Mount Sherman 7.5' quadrangle, Lake and Park Counties, Colorado
The Mount Sherman 7.5- minute quadrangle is located along the crest of the Mosquito Range in between Leadville and Fairplay, Colorado. There are eleven 13,000-foot peaks and one fourteener, Mount Sherman, within the quadrangle. General elevations range from 10,400–14,036 feet (3,200–4,278 meters). The western half of the quadrangle primarily consists of Proterozoic granitic rocks reverse...
Geologic map of the Bailey 30' x 60' quadrangle, North-Central Colorado Geologic map of the Bailey 30' x 60' quadrangle, North-Central Colorado
The Bailey, Colo. 1:100,000-scale quadrangle lies within two physiographic and geologic provinces in central Colorado: 1) the Front Range and 2) South Park. Most of the Front Range is composed of Proterozoic rocks ranging in age from 1,790 Ma to 1,074 Ma. Along the eastern flanks and within the Denver Basin, sedimentary rocks ranging from Pennsylvanian to Cretaceous are deformed and...
Geologic Map of the Sulphur Mountain Quadrangle, Park County, Colorado Geologic Map of the Sulphur Mountain Quadrangle, Park County, Colorado
The main structural element in the Sulphur Mountain quadrangle is the Elkhorn thrust. This northwest-trending fault is the southernmost structure that bounds the west side of the Late Cretaceous and early Tertiary Front Range basement-rock uplift. The Elkhorn thrust and the Williams Range thrust that occurs in the Dillon area north of the quadrangle bound the west flank of the Williams...
Geologic Map of the Elkhorn Quadrangle, Park County, Colorado Geologic Map of the Elkhorn Quadrangle, Park County, Colorado
The Elkhorn thrust is defined by the juxtaposition of Early and Middle Proterozoic metamorphic and igneous rocks against Mesozoic and Tertiary rocks. Within the mapped area, an imbricate frontal thrust system juxtaposes Upper Cretaceous rocks against Paleocene rocks of the South Park Formation. In the southeastern section of the quadrangle, Middle Proterozoic igneous rocks are thrust...
Filter Total Items: 17
Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications
The Rio Grande is the fourth longest river in North America extending over 3,000 km from the Rocky Mountains to the Gulf of Mexico. The Pleistocene evolution of this river from individual subbasins into a coalesced fluvial system has been long debated. Herein, we constrain the middle Pleistocene evolution of the northernmost and largest Rio Grande basin, the San Luis basin, and the...
Authors
Chester A. Ruleman, Adam M. Hudson, Ren A. Thompson, Daniel P. Miggins, James B. Paces, Brent M. Goehring
Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA
On active alluvial fans, debris-flow deposits and frequent avulsions produce a rough topographic surface. As is the case in many initially rough landforms produced by catastrophic processes, the topography of alluvial fans is progressively smoothed, producing textural differences useful in establishing relative age criteria for fans. Here, we outline an approach for defining a...
Authors
Samuel Johnstone, Adam M. Hudson, Sylvia Nicovich, Chester A. Ruleman, Robert M. Sare, Ren A. Thompson
Geophysical expression of buried range-front embayment structure: Great Sand Dunes National Park, Rio Grande rift, Colorado Geophysical expression of buried range-front embayment structure: Great Sand Dunes National Park, Rio Grande rift, Colorado
Great Sand Dunes National Park and Preserve (GRSA, Colorado) lies along the eastern margin of the San Luis Basin and the tectonically active Sangre de Cristo fault system that are part of the northern Rio Grande rift. GRSA lies within a prominent embayment in the range front where two separate sections of the Sangre de Cristo fault system intersect. Fault scarps are observed along both
Authors
Benjamin J. Drenth, V. J. Grauch, Chester A. Ruleman, Judith A Schenk
Geomorphic evolution of the San Luis Basin and Rio Grande in southern Colorado and northern New Mexico Geomorphic evolution of the San Luis Basin and Rio Grande in southern Colorado and northern New Mexico
The San Luis Basin encompasses the largest structural and hydrologic basin of the Rio Grande rift. On this field trip, we will examine the timing of transition of the San Luis Basin from hydrologically closed, aggrading subbasins to a continuous fluvial system that eroded the basin, formed the Rio Grande gorge, and ultimately, integrated the Rio Grande from Colorado to the Gulf of Mexico...
Authors
Chester A. Ruleman, Michael Machette, Ren A. Thompson, Dan M Miggins, Brent M Goehring, James B. Paces
Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana
The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal...
Authors
Chester A. Ruleman, Mort Larsen, Michael C. Stickney
Identifying buried segments of active faults in the northern Rio Grande Rift using aeromagnetic, LiDAR,and gravity data, south-central Colorado, USA Identifying buried segments of active faults in the northern Rio Grande Rift using aeromagnetic, LiDAR,and gravity data, south-central Colorado, USA
Combined interpretation of aeromagnetic and LiDAR data builds on the strength of the aeromagnetic method to locate normal faults with significant offset under cover and the strength of LiDAR interpretation to identify the age and sense of motion of faults. Each data set helps resolve ambiguities in interpreting the other. In addition, gravity data can be used to infer the sense of motion...
Authors
V. J. S. Grauch, Chester A. Ruleman
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government