The Geologic Framework of the Intermountain West project was launched with the goal of producing a new digital geologic map database and 3D geologic model of a transect from the Rio Grande rift to the Basin and Range, based on a synthesis of existing geologic maps with new targeted new mapping, subsurface data, and other data sets. This database will integrate disparate map data, resolve inconsistent stratigraphic assignments, and develop an integrated regional geologic map database to further the National Cooperative Geologic Mapping Program’s strategic goal of mapping the Nation. This effort will require development of new techniques for digital compilation and new procedures for reviewing and publishing large digital geologic data sets.
Digital Geologic Map Database
Geologic maps are the fundamental base data for regional geologic models of the earth’s composition, structure, and evolution. Integrated with analytical data and numerical modeling of earth’s physical systems, these maps underpin the analytical framework necessary to understand geologic processes critical to mineral, water, and energy resource management, environmental health, hazard mitigation, and ecosystem impact. Digital geologic map databases are consequently the starting point for all geologic research and natural resource assessments at local, regional, and nation scales. However, existing regional-scale (1:100K to 1:250K) geologic map coverage of the Great Basin and Rocky Mountains is inconsistent, mismatched across map and administrative borders, and often decades out-of-date.
Creating a digital, data-rich, geologic map database of an area the size of the Intermountain West transect requires innovative new database frameworks and map compilation workflows, while serving the database to the public will require new approaches to the review and publication process. Our mapping strategy is based on digital synthesis of the best available geologic information at a compilation scale no less detailed than 1:250K—and as detailed as 1:100K, where possible—along a crustal transect that spans many administrative boundaries and thus forces reconciliation across borders. This strategy requires coordination of a large research team at a level considerably beyond previous FEDMAP projects, as well as the development of new technical infrastructure and database frameworks that could ultimately provide a template for National-scale data sets. Our goal is to produce a peer-reviewed digital database that is regularly updated with new content and revisions, served digitally to users on a variety of platforms.
Research Themes
Magmatism in the western United States—The transect area encompasses the full range of continental magmatic systems, including batholiths, explosive silicic calderas, and bimodal volcanic fields. Better understanding of the timing, style, and extent of magmatism will further our understanding of how mineral resources form and where new resources are likely to be found in the future.
Tectonic evolution of the Cordillera—The transect area includes rocks that record all of the major episodes of orogeny, magmatism, continental extension, and basin formation that have shaped the Cordillera since the Early Paleozoic. Better understanding of the timing and style of deformation along the transect will allow us to understand the role of faulting in formation and post-ore disruption of mineral deposits and the formation of structural basins that hold water and energy resources.
Landscape evolution—The weathering, transport, and deposition that shaped the topography of Intermountain West transect also governs the enrichment and availability of critical mineral deposits, the extent of groundwater resources, and the distribution of nutrients critical to ecosystems and agriculture. Better understanding how surface processes have been influenced by tectonics and climate will improve the knowledge base necessary to make effective land-use decisions.
Stratigraphy and basin evolution—Older stratified rocks along the transect are key stratigraphic markers but pose challenges with respect to long-distance correlation, and younger basin fill is the most important repository of energy and water resources. Better regional correlation and stratigraphic synthesis combined with new data on age, provenance, and sedimentary environments will enhance our understanding of regional tectonic evolution and provide a critical building block for groundwater models.
Regional subsurface structure—3D geologic models have been constructed at the site or basin scale, but no regional-scale models exist for the western U.S. The project will begin building a data warehouse of subsurface data to enable construction of regional 3D geologic models, but better understanding of the subsurface structure is needed, particularly in the many areas that lack control from well data.
Geochronology and isotope geochemistry—Understanding the timing of geologic processes and events as well as quantifying rates and timescales is key to geologic mapping, mineral and energy resource assessments and natural hazard assessments. While collecting new data, the project is working to compile existing geochronology data into an accessible database to support research and geologic mapping.
Database development and visualization—Regional compilation of geologic mapping and other data sets at this scale requires new workflows and data infrastructure to allow efficient synthesis of new and existing data and provide data to stakeholders and the public in a useful and timely manner.
Data release for geochronology and geochemistry of volcanic rocks in the Southern Rocky Mountains and Taos Plateau volcanic fields and other Oligocene to Pleistocene volcanic rocks within the southern San Luis Basin and San Juan Mountains, southern Colora
Thermochronologic data from the southern Stillwater Range, Nevada
Digital subsurface data of Paleozoic rocks in the Upper Colorado River Basin in Wyoming, Utah, Colorado, Arizona, and New Mexico from USGS Regional Aquifer System Analysis
Digital subsurface data of Mesozoic rocks in the Upper Colorado River Basin in Wyoming, Utah, Colorado, Arizona, and New Mexico from USGS Regional Aquifer System Analysis
Data release for Geologic Map of the Homestake Reservoir 7.5' quadrangle, Lake, Pitkin, and Eagle Counties, Colorado
Data Release for Geologic Map of Petroglyph National Monument and Vicinity, Bernalillo County, New Mexico
Digital data for three-dimensional geologic framework model of the Rio San Jose groundwater basin, New Mexico
Argon geochronology data for La Garita caldera
Data release of geospatial map database, argon geochronology and geochemistry data for: Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
Argon data for Poncha Pass Geologic Map
Surficial geology of the northern San Luis Valley, Saguache, Fremont, Custer, Alamosa, Rio Grande, Conejos, and Costilla Counties, Colorado
Geologic map of the Homestake Reservoir 7.5′ quadrangle, Lake, Pitkin, and Eagle Counties, Colorado
Geologic map of the Bonanza caldera area, northeastern San Juan Mountains, Colorado
Geologic map of Petroglyph National Monument and vicinity, Bernalillo County, New Mexico
Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
Below are publications associated with the Geologic Framework of the Intermountain West Project.
Field-trip guide to continental arc to rift volcanism of the southern Rocky Mountains—Southern Rocky Mountain, Taos Plateau, and Jemez Mountains volcanic fields of southern Colorado and northern New Mexico
State of stress in areas of active unconventional oil and gas development in North America
In this paper, we present comprehensive data on stress orientation and relative magnitude in areas throughout North America where unconventional oil and gas are currently being developed. We find excellent agreement between maximum horizontal principal stress (SHmax) orientations over a wide range of depths, using multiple methods. In all basins studied, we observed coherent stress fields that in
Downhill from Austin and Ely to Las Vegas: U-Pb detrital zircon suites from the Eocene–Oligocene Titus Canyon Formation and associated strata, Death Valley, California
In a reconnaissance investigation aimed at interrogating the changing topography and paleogeography of the western United States prior to Basin and Range faulting, a preliminary study made use of U-Pb ages of detrital zircon suites from 16 samples from the Eocene–Oligocene Titus Canyon Formation, its overlying units, and correlatives near Death Valley. The Titus Canyon Formation unconformably over
Magmatism, migrating topography, and the transition from Sevier shortening to Basin and Range extension, western United States
The paleogeographic evolution of the western U.S. Great Basin from the Late Cretaceous to the Cenozoic is critical to understanding how the North American Cordillera at this latitude transitioned from Mesozoic shortening to Cenozoic extension. According to a widely applied model, Cenozoic extension was driven by collapse of elevated crust supported by crustal thicknesses that were potentially doub
Hypogenic karst of the Great Basin
Detrital zircon record of magmatism and sediment dispersal across the North American Cordilleran arc system (28-48°N)
Evidence for variable precipitation and discharge from Upper Cretaceous–Paleogene fluvial deposits of the Raton Basin, Colorado–New Mexico, U.S.A.
Postcaldera intrusive magmatism at the Platoro caldera complex, Southern Rocky Mountain volcanic field, Colorado, USA
The grass is not always greener on the other side: Seasonal reversal of vegetation greenness in aspect-driven semiarid ecosystems
Timing of Cenozoic extension in the southern Stillwater Range and Dixie Valley, Nevada
Timing of Cenozoic extension in the southern Stillwater Range and Dixie Valley, Nevada
Dilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.)
A new stratigraphic framework and constraints for the position of the Paleocene-Eocene boundary in the rapidly subsiding Hanna Basin, Wyoming
- Overview
The Geologic Framework of the Intermountain West project was launched with the goal of producing a new digital geologic map database and 3D geologic model of a transect from the Rio Grande rift to the Basin and Range, based on a synthesis of existing geologic maps with new targeted new mapping, subsurface data, and other data sets. This database will integrate disparate map data, resolve inconsistent stratigraphic assignments, and develop an integrated regional geologic map database to further the National Cooperative Geologic Mapping Program’s strategic goal of mapping the Nation. This effort will require development of new techniques for digital compilation and new procedures for reviewing and publishing large digital geologic data sets.
Digital Geologic Map Database
Geologic maps are the fundamental base data for regional geologic models of the earth’s composition, structure, and evolution. Integrated with analytical data and numerical modeling of earth’s physical systems, these maps underpin the analytical framework necessary to understand geologic processes critical to mineral, water, and energy resource management, environmental health, hazard mitigation, and ecosystem impact. Digital geologic map databases are consequently the starting point for all geologic research and natural resource assessments at local, regional, and nation scales. However, existing regional-scale (1:100K to 1:250K) geologic map coverage of the Great Basin and Rocky Mountains is inconsistent, mismatched across map and administrative borders, and often decades out-of-date.
Map showing footprint (area within red outline) of the Intermountain West project in the western United States. Creating a digital, data-rich, geologic map database of an area the size of the Intermountain West transect requires innovative new database frameworks and map compilation workflows, while serving the database to the public will require new approaches to the review and publication process. Our mapping strategy is based on digital synthesis of the best available geologic information at a compilation scale no less detailed than 1:250K—and as detailed as 1:100K, where possible—along a crustal transect that spans many administrative boundaries and thus forces reconciliation across borders. This strategy requires coordination of a large research team at a level considerably beyond previous FEDMAP projects, as well as the development of new technical infrastructure and database frameworks that could ultimately provide a template for National-scale data sets. Our goal is to produce a peer-reviewed digital database that is regularly updated with new content and revisions, served digitally to users on a variety of platforms.
Diagram illustrating a proposed all-digital workflow for map database production to publication. Research Themes
Magmatism in the western United States—The transect area encompasses the full range of continental magmatic systems, including batholiths, explosive silicic calderas, and bimodal volcanic fields. Better understanding of the timing, style, and extent of magmatism will further our understanding of how mineral resources form and where new resources are likely to be found in the future.
Tectonic evolution of the Cordillera—The transect area includes rocks that record all of the major episodes of orogeny, magmatism, continental extension, and basin formation that have shaped the Cordillera since the Early Paleozoic. Better understanding of the timing and style of deformation along the transect will allow us to understand the role of faulting in formation and post-ore disruption of mineral deposits and the formation of structural basins that hold water and energy resources.
Landscape evolution—The weathering, transport, and deposition that shaped the topography of Intermountain West transect also governs the enrichment and availability of critical mineral deposits, the extent of groundwater resources, and the distribution of nutrients critical to ecosystems and agriculture. Better understanding how surface processes have been influenced by tectonics and climate will improve the knowledge base necessary to make effective land-use decisions.
Stratigraphy and basin evolution—Older stratified rocks along the transect are key stratigraphic markers but pose challenges with respect to long-distance correlation, and younger basin fill is the most important repository of energy and water resources. Better regional correlation and stratigraphic synthesis combined with new data on age, provenance, and sedimentary environments will enhance our understanding of regional tectonic evolution and provide a critical building block for groundwater models.
Regional subsurface structure—3D geologic models have been constructed at the site or basin scale, but no regional-scale models exist for the western U.S. The project will begin building a data warehouse of subsurface data to enable construction of regional 3D geologic models, but better understanding of the subsurface structure is needed, particularly in the many areas that lack control from well data.
Geochronology and isotope geochemistry—Understanding the timing of geologic processes and events as well as quantifying rates and timescales is key to geologic mapping, mineral and energy resource assessments and natural hazard assessments. While collecting new data, the project is working to compile existing geochronology data into an accessible database to support research and geologic mapping.
Database development and visualization—Regional compilation of geologic mapping and other data sets at this scale requires new workflows and data infrastructure to allow efficient synthesis of new and existing data and provide data to stakeholders and the public in a useful and timely manner.
- Data
Data release for geochronology and geochemistry of volcanic rocks in the Southern Rocky Mountains and Taos Plateau volcanic fields and other Oligocene to Pleistocene volcanic rocks within the southern San Luis Basin and San Juan Mountains, southern Colora
The dataset includes whole-rock geochemistry and 40Ar-39Ar geochronology for Pleistocene to Oligocene volcanic and intrusive rocks. These data support figures and tables in days 2 and 3 of the Field-trip guide to continental arc to rift volcanism of the southern Rocky Mountains-Southern Rocky Mountain, Taos Plateau, and Jemez Mountains volcanic fields of southern Colorado and northern New Mexico (Thermochronologic data from the southern Stillwater Range, Nevada
This dataset contains apatite and zircon U-Th(He)data, 4He/3He thermochronologic data, and apatite fission-track data from the southern Stillwater Range, NevadaDigital subsurface data of Paleozoic rocks in the Upper Colorado River Basin in Wyoming, Utah, Colorado, Arizona, and New Mexico from USGS Regional Aquifer System Analysis
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980’s and 1990’s, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). TheDigital subsurface data of Mesozoic rocks in the Upper Colorado River Basin in Wyoming, Utah, Colorado, Arizona, and New Mexico from USGS Regional Aquifer System Analysis
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980's and 1990's, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). TheData 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 Miocene, anData Release for Geologic Map of Petroglyph National Monument and Vicinity, Bernalillo County, New Mexico
This geologic map depicts and briefly describes geologic units underlying Petroglyph National Monument and immediately adjacent areas in Bernalillo County, New Mexico. The Monument is underlain dominantly by Quaternary basalts of the Albuquerque Volcanoes volcanic field, a series of basin-filling volcanic flows and associated vents from a monogenetic volcanic highland along the eastern margin of tDigital data for three-dimensional geologic framework model of the Rio San Jose groundwater basin, New Mexico
This data release contains a geospatial database related to a digital 3D geologic framework of the Rio San Jose watershed, New Mexico. The geospatial database contains two main data elements: (1) input data to the 3D framework model; (2) interpolated elevations and thicknesses of stratigraphic units as a cellular array. Input surface and subsurface data for 18 stratigraphic units have been condensArgon geochronology data for La Garita caldera
This dataset accompanies publication 'A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system', in review in Geology, which analyzed eruptive products from the La Garita caldera.Data release of geospatial map database, argon geochronology and geochemistry data for: Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
This dataset accompanies publication "Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado". Data presented here include the digital geologic database, 40Ar/39Ar geochronology and major and trace element chemistry from lava flows and an ignimbrite. The geologic database includes spatial feature classes and non-spatial tables that collectively contain the geologiArgon data for Poncha Pass Geologic Map
This dataset was collected by Leah E. Morgan and Michael A. Cosca in the Argon Geochronology Laboratory of the USGS in Denver, Colorado in 2015. The dataset contains full raw argon isotopic data for samples presented in: Geologic Map of the Poncha Map Area, Chaffee, Fremont, and Saguache Counties, Colorado. - Maps
Surficial geology of the northern San Luis Valley, Saguache, Fremont, Custer, Alamosa, Rio Grande, Conejos, and Costilla Counties, Colorado
The San Luis Valley and associated underlying basin of south-central Colorado and north-central New Mexico is the largest structural and hydrologic basin of the Rio Grande Rift and fluvial system. The surrounding San Juan and Sangre de Cristo Mountains reveal evidence of widespread volcanism and transtensional tectonism beginning in the Oligocene and continuing to the present, as seen in fault diGeologic 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 giga-annum (Ga) Picuris orogeny and includes the late Paleozoic Ancestral Rockies, Late Cretaceous-Paleocene Laramide orogenyGeologic map of the Bonanza caldera area, northeastern San Juan Mountains, Colorado
The San Juan Mountains in southwestern Colorado have long been known as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 22 major ignimbrite sheets (each 150–5,000 km³) and associated caldera structures active at 34–23 Ma. Recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Geologic map of Petroglyph National Monument and vicinity, Bernalillo County, New Mexico
This geologic map depicts and briefly describes geologic units underlying Petroglyph National Monument and immediately adjacent areas in Bernalillo County, New Mexico. The Monument is underlain dominantly by Quaternary basalts of the Albuquerque Volcanoes volcanic field, a series of basin-filling volcanic flows and associated vents from a monogenetic volcanic highland along the eastern margin of tGeologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
The geologic map of the San Antonio Mountain area in northern New Mexico and southern Colorado is located along the west-central part of the San Luis Valley. The San Luis Valley is the geomorphic expression of the San Luis Basin, an extensional basin associated with the northern Rio Grande rift. Deposits within the map area record volcanic, sedimentary, and tectonic processes over the last ~33 mil - Publications
Below are publications associated with the Geologic Framework of the Intermountain West Project.
Field-trip guide to continental arc to rift volcanism of the southern Rocky Mountains—Southern Rocky Mountain, Taos Plateau, and Jemez Mountains volcanic fields of southern Colorado and northern New Mexico
The southern Rocky Mountains of northern New Mexico and southern Colorado preserve the Oligocene to Pleistocene record of North American continental arc to rift volcanism. The 35–23 million year old (Ma) southern Rocky Mountain volcanic field (SRMVF), spectacularly preserved in the San Juan Mountains of southern Colorado, records the evolution of large andesitic stratovolcanoes to complex calderaAuthorsRen A. Thompson, Kenzie J. Turner, Peter W. Lipman, John A. Wolff, Michael A. DunganFilter Total Items: 21State of stress in areas of active unconventional oil and gas development in North America
In this paper, we present comprehensive data on stress orientation and relative magnitude in areas throughout North America where unconventional oil and gas are currently being developed. We find excellent agreement between maximum horizontal principal stress (SHmax) orientations over a wide range of depths, using multiple methods. In all basins studied, we observed coherent stress fields that in
AuthorsJens-Erik Lundstern, Mark D. ZobackDownhill from Austin and Ely to Las Vegas: U-Pb detrital zircon suites from the Eocene–Oligocene Titus Canyon Formation and associated strata, Death Valley, California
In a reconnaissance investigation aimed at interrogating the changing topography and paleogeography of the western United States prior to Basin and Range faulting, a preliminary study made use of U-Pb ages of detrital zircon suites from 16 samples from the Eocene–Oligocene Titus Canyon Formation, its overlying units, and correlatives near Death Valley. The Titus Canyon Formation unconformably over
AuthorsElizabeth L. Miller, Mark Raftrey, Jens-Erik LundsternMagmatism, migrating topography, and the transition from Sevier shortening to Basin and Range extension, western United States
The paleogeographic evolution of the western U.S. Great Basin from the Late Cretaceous to the Cenozoic is critical to understanding how the North American Cordillera at this latitude transitioned from Mesozoic shortening to Cenozoic extension. According to a widely applied model, Cenozoic extension was driven by collapse of elevated crust supported by crustal thicknesses that were potentially doub
AuthorsJens-Erik Lundstern, Elizabeth L. MillerHypogenic karst of the Great Basin
Discoveries in the 1980s greatly expanded speleologists’ understanding of the role that hypogenic groundwater flow can play in developing caves at depth. Ascending groundwater charged with carbon dioxide and, especially, hydrogen sulfide can readily dissolve carbonate bedrock just below and above the water table. Sulfuric acid speleogenesis, in which anoxic, rising, sulfidic groundwater mixes withAuthorsLouise D. Hose, Harvey R. DuChene, Daniel Jones, Gretchen M. Baker, Zoe Havlena, Donald S. Sweetkind, Doug PowellDetrital zircon record of magmatism and sediment dispersal across the North American Cordilleran arc system (28-48°N)
As zircon U-Pb geochronology has become a leading method in sediment provenance studies and basin analysis over the past 20 years, the volume of detrital zircon data made available in published literature has enabled researchers to go beyond source-to-sink provenance studies to explore increasingly complex geologic problems. In this review, we utilize the growing body of detrital zircon data acquiAuthorsTheresa Maude Schwartz, Kathleen D. Surpless, Joseph Colgan, Samuel Johnstone, Christopher Holm-DenomaEvidence for variable precipitation and discharge from Upper Cretaceous–Paleogene fluvial deposits of the Raton Basin, Colorado–New Mexico, U.S.A.
The Raton Basin of Colorado–New Mexico, USA, is the southeasternmost basin of the Laramide intraforeland province of North America. It hosts a thick succession (4.5 km or 15,000 ft) of Upper Cretaceous to Paleogene marine and continental strata that were deposited in response to the final regression of the Western Interior Seaway and the onset of Laramide intraforeland deformation. The Upper CretaAuthorsTheresa Maude Schwartz, Marieke Dechesne, Kristine ZellmanPostcaldera intrusive magmatism at the Platoro caldera complex, Southern Rocky Mountain volcanic field, Colorado, USA
The Oligocene Platoro caldera complex of the San Juan volcanic locus in Colorado (USA) features numerous exposed plutons both within the caldera and outside its margins, enabling investigation of the timing and evolution of postcaldera magmatism. Intrusion whole-rock geochemistry and phenocryst and/or mineral trace element compositions coupled with new zircon U-Pb geo-chronology and zircon in situAuthorsAmy K. Gilmer, Ren A. Thompson, Peter W. Lipman, Jorge A. Vazquez, Amanda (Kate) SoudersThe grass is not always greener on the other side: Seasonal reversal of vegetation greenness in aspect-driven semiarid ecosystems
Our current understanding of semiarid ecosystems is that they tend to display higher vegetation greenness on polar-facing slopes (PFS) than on equatorial-facing slopes (EFS). However, recent studies have argued that higher vegetation greenness can occur on EFS during part of the year. To assess whether this seasonal reversal of aspect-driven vegetation is a common occurrence, we conducted a globalAuthorsNikul Kumari, Patricia M. Saco, Jose F. Rodriguez, Samuel Johnstone, Ankur Srivastava, Kwok P. Chun, Omer YetemenTiming of Cenozoic extension in the southern Stillwater Range and Dixie Valley, Nevada
The Dixie Valley fault bounds the east side of the Stillwater Range in west‐central Nevada and last ruptured in 1954. Offset basalts indicate that slip began more recently than ~14 Ma, and prior work has interpreted the southern segment as an active low‐angle normal fault. Oligocene igneous rocks in the southern Stillwater Range were steeply tilted during large‐magnitude extension prior to ~14 Ma.AuthorsJoseph Colgan, Samuel Johnstone, David L. ShusterTiming of Cenozoic extension in the southern Stillwater Range and Dixie Valley, Nevada
The Dixie Valley fault bounds the east side of the Stillwater Range in west‐central Nevada and last ruptured in 1954. Offset basalts indicate that slip began more recently than ~14 Ma, and prior work has interpreted the southern segment as an active low‐angle normal fault. Oligocene igneous rocks in the southern Stillwater Range were steeply tilted during large‐magnitude extension prior to ~14 Ma.AuthorsJoseph Colgan, Samuel Johnstone, David L. ShusterDilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.)
Integrated, multi-method provenance studies of siliciclastic sedimentary deposits are increasingly used to reconstruct the history of source-to-sink transport, paleogeography, and tectonics. Invariably, analysis of large-scale depositional systems must confront issues regarding how to best sample the system and adequately cope with the details of sediment mixing. Potential biases including variatAuthorsMatthew A. Malkowski, Glenn R. Sharman, Samuel Johnstone, Marty J. Grove, Dave L. Kimbrough, Stephen A. GrahamA new stratigraphic framework and constraints for the position of the Paleocene-Eocene boundary in the rapidly subsiding Hanna Basin, Wyoming
The Paleocene–Eocene strata of the rapidly subsiding Hanna Basin give insights in sedimentation patterns and regional paleogeography during the Laramide orogeny and across the climatic event at the Paleocene–Eocene Thermal Maximum (PETM). Abundant coalbeds and carbonaceous shales of the fluvial, paludal, and lacustrine strata of the Hanna Formation offer a different depositional setting than PETMAuthorsMarieke Dechesne, Ellen D Currano, Regan E Dunn, Pennilyn Higgins, Joseph Hartman, Kevin R Chamberlain, Christopher S. Holm-Denoma