The Ramshorn 1:100,000 Surficial Geologic Map

The WSGS is continuing to map the surficial geology of The Ramshorn 30′ × 60′ quadrangle as part of its ongoing effort to complete 1:100,000-scale surficial geologic mapping across Wyoming. The quadrangle encompasses portions of the southern Absaroka Range and the northwestern Wind River Basin in Fremont, Park, and Hot Springs counties.

A map of the west half of the quadrangle was published in 2023 as WSGS Open File Report 2023-1. Current work is focused on completing the east half, which includes extensive landslide complexes along the southern front of the Absaroka Range, glacial deposits from the Pinedale glaciation, and recently identified fault scarps that offset Quaternary-age hillslope deposits.

Once completed, the project will produce a comprehensive surficial geologic map of the entire quadrangle, providing valuable data for understanding geomorphic evolution, natural hazards, and Quaternary geologic processes in northwestern Wyoming.

Mapping and Slip Rates of the East Gallatin-Reese Creek Fault System, Yellowstone

The WSGS and Montana Bureau of Mines and Geology are collaborating on a project in Yellowstone National Park, studying the 40-km-long East Gallatin-Reese Creek fault system (EGRCFS) that spans the Wyoming/Montana border. Geologists are mapping and measuring fault scarps—locations where past earthquakes have ruptured the ground surface—and dating deposits offset by fault scarps to better understand the geometry, extent, slip rates, and earthquake hazard of this fault system.

The motivation for this work came from the recognition of previously undocumented fault scarps along the EGRCFS from high-resolution lidar (light detection and ranging) topographic data published for Yellowstone National Park in 2021. These fault scarps cut across undated glacial sediments that were likely deposited at the end of the most recent ice age in the Rocky Mountains, known as the Pinedale glaciation, and indicate that the EGRCFS has experienced surface-rupturing earthquakes since that time. 

The project involves geologists collecting samples from glacial deposits near the fault scarps for cosmogenic radionuclide exposure dating—a method that measures the time that a rock has been exposed to cosmic rays at the earth’s surface.  The ages calculated from this exposure dating technique represent the time since these rocks were deposited and uncovered as glacial ice receded. Additionally, geologists are using lidar data to map the distribution and geometry of fault scarps along the EGRCFS and to calculate the vertical separation of surfaces across the fault scarps.

Knowing the exposure age of the deposits, and the vertical distance they are displaced across fault scarps, will provide important constraints on the faulting history of the EGRCFS, including the maximum age of the most recent surface-rupturing earthquake(s), how fast the fault is slipping, and whether the fault slip rates vary over time and along the length of the fault system. This information is fundamental to understanding the seismic hazard posed by the EGRCFS, and it will provide land managers and scientists with important data that can be used in making decisions to mitigate earthquake risk in the Yellowstone region.

Fox Park and Woods Landing 1:24,000 Geologic Maps

Geologists at the WSGS are mapping a pair of 1:24,000-scale geologic maps through the STATEMAP program. The adjacent Fox Park and Woods Landing 7.5-minute quadrangles occupy the southeastern corner of the Medicine Bow Mountains along the Wyoming–Colorado border. The area features predominantly 1.8–1.7 billion-year-old igneous and metamorphic rocks formed during the Medicine Bow Orogeny, along with 1.43 billion-year-old igneous rocks of the Sherman Batholith. Deformation during the Laramide Orogeny juxtaposed these older Precambrian rocks with younger Paleozoic and Mesozoic sedimentary units, while even younger sediments, possibly less than 23 million years old, blanket portions of the area.

These maps are part of the WSGS’s continuing effort to conduct high-resolution geologic mapping across the Medicine Bow Mountains—an area with a long history of mining and mineral exploration. Mapping is being completed using modern digital techniques that follow the U.S. Geological Survey’s Geologic Map Schema (GeMS) standards. Both maps are anticipated to be published in 2026.

Data Modernization — 1:24,000 GeMS Conversions

The Wyoming State Geological Survey (WSGS) is modernizing several older 1:24,000-scale geologic maps by converting them into digital formats that follow the Geologic Map Schema (GeMS). GeMS is a national standard developed by the U.S. Geological Survey (USGS) and state surveys to ensure geologic map data are consistent, accurate, and easy to share.

This work is especially important for interpreting new airborne geophysical data being collected across Wyoming. Many of the geologic maps in these areas were created before digital mapping technology and exist only as paper copies. To make them usable in modern analyses, the WSGS scans, georeferences, and digitizes the original maps, then validates the files against GeMS requirements.

Current 1:24,000-scale GeMS conversions focus on two key survey areas:

• South Pass–Granite Mountains: Whiskey Peak, Muddy Gap, Bradley Peak, Seminoe Dam, and Seminoe Dam NE quadrangles.
  
  

• Laramie Mountains: Fletcher Park, Johnson Mountain, Reese Mountain, and Hightower SW quadrangles.
  
  

By bringing these maps into modern digital formats, the WSGS is ensuring that Wyoming’s geologic framework can be accurately integrated with high-resolution geophysical surveys, advancing both scientific research and resource management.

WSGS Data Explorer and Interactive Maps Migration

The WSGS is developing a new ArcGIS open data site to serve as a centralized platform for discovering and exploring GIS data and mapping applications. Hosted on Esri’s ArcGIS Online platform, the forthcoming WSGS Data Explorer will provide a modern, intuitive interface that includes enhanced search functionality and a responsive design optimized for smartphones, tablets, and desktop computers. Users will also have the ability to download or stream authoritative GIS datasets derived from WSGS geologic maps and reports in multiple formats.

At the same time, the WSGS is migrating its suite of online interactive maps to Esri’s Experience Builder platform. This transition is driven by the scheduled retirement of the current web mapping platform in early 2026 and ensures the continued accessibility of these widely used public resources. Moving to Experience Builder will also allow for a seamless integration with the new Data Explorer site, creating a cohesive, user-friendly environment for accessing Wyoming’s geologic and geospatial data.

Osborne Well 1:24,000 Bedrock Geology “Map Blitz” – 2025

The WSGS is undertaking an innovative “Map Blitz” project to rapidly produce a 1:24,000-scale bedrock geology map of the Osborne Well quadrangle. This all-hands effort is designed as both a training exercise and a technology pilot, emphasizing efficiency, collaboration, and modernization of field and digital mapping workflows.

The Osborne Well project provides an opportunity for WSGS staff to test new approaches to geologic mapping, including real-time collaborative GIS editing, cloud-based project management, and the use of streaming data services in the field. The initiative also marks a transition away from single-user, locally stored datasets toward shared, dynamic mapping environments that improve consistency, coordination, and accessibility.

The Osborne Well area was selected because its relatively straightforward geology allows the team to focus on developing and refining these new workflows rather than navigating complex stratigraphy. The region also holds industrial importance, particularly for Wyoming’s uranium industry, making the resulting map useful for both scientific and applied purposes.

The final product will be a GeMS-compliant preliminary geologic bedrock map available to industry professionals, researchers, government agencies, and the public. Beyond producing a high-quality map, the project serves as a model for future rapid-response mapping initiatives and reflects the WSGS’s ongoing efforts to innovate in digital geologic data production.

Spanish Mine 1:24,000 Bedrock Geologic Map

In conjunction with the 2025 STATEMAP project on the adjacent Youngs Pass quadrangle, the WSGS is conducting complementary 1:24,000-scale bedrock mapping of the Spanish Mine quadrangle, located immediately to the east. The study area includes the northeastern portion of the Ferris Mountains and extends east from the Youngs Pass boundary to just west of County Road 497 (Buzzard Road), near Pathfinder Reservoir.

The Spanish Mine quadrangle exposes a diverse sequence of Precambrian through Quaternary units similar to those found in the neighboring Youngs Pass map area. New mapping will refine the geologic framework of the region, with particular emphasis on the structural and metamorphic history of the Spanish Mine suite and associated Precambrian plutonic complexes, including the Turkey Creek, Ferris Mountains, and Bear Mountain bodies. Detailed mapping will also help distinguish poorly defined Miocene sedimentary units along the margin of the Split Rock Syncline.

This work is being integrated with complementary geochemical and geochronologic sampling from the Youngs Pass area, regional lidar coverage, and newly acquired airborne geophysical data from the South Pass–Granite Mountains survey. Upon completion, the new Spanish Mine bedrock map will provide cohesive 1:24,000-scale mapping coverage across the northern flank of the Ferris Mountains, connecting the Youngs Pass and Muddy Gap quadrangles

Current STATEMAP Projects

Denver Basin Subsurface Stratigraphy Project

The WSGSis conducting a subsurface evaluation and mapping project of Cretaceous-age sedimentary intervals in southeastern Wyoming to identify key hydrocarbon-producing stratigraphic zones. The Denver–Julesburg (DJ) Basin, which extends across southeastern Wyoming, southwestern Nebraska, and northeastern Colorado, is a major hydrocarbon-producing region that contains both conventional and unconventional (low-porosity, low-permeability) oil and gas reservoirs.

In southeastern Wyoming, many producing fields target Cretaceous-age fine-grained sediments that host tight oil and gas accumulations. Building on a previously developed WSGS continuous reservoir geodatabase, geologists are correlating stratigraphic interpretations from more than 600 oil and gas wells using geophysical logs to construct regional subsurface maps. These include structure-contour and isopach-thickness maps that define the geometry and distribution of hydrocarbon-bearing formations.

The goal of this work is to produce a comprehensive, publicly available geodatabase and suite of subsurface maps that support energy research, exploration, and development in the region. By refining the stratigraphic framework of the Denver Basin, the project will help guide future studies of Wyoming’s petroleum systems and promote continued investment in the state’s rich energy resources.

This project will directly complement the airborne magnetic and radiometric survey that occurred in summer 2023 in the Medicine Bow and eastern Sierra Madre mountains. The goal is an integrated understanding of the geochemical, structural, petrological, and deformational processes that make up regional mineral systems; this will have the potential to aid mineral exploration efforts not only in the Medicine Bows, but also in areas with a similar geologic history, such as the Sierra Madre range to the west and elsewhere along the trend of the Cheyenne Belt.

Potential critical minerals in the project area: antimony, arsenic, barium, beryllium, bismuth, cobalt, chromium, fluorspar, gallium, germanium, hafnium, indium, magnesium, manganese, nickel, platinum group elements, scandium, tantalum, tellurium, tin, vanadium, zinc, and zirconium.

Statewide Cretaceous Sands Aquifers Report

The WSGS is undertaking a compilation project focused on Cretaceous sandstones that serve as minor aquifers across Wyoming. Although these aquifers are not as extensive as the Tensleep or Madison, they play an important role in understanding the state’s broader groundwater systems and subsurface resources.

“For the Madison aquifer project, we had compiled hydrogeologic information on all of the reservoirs located in oil and gas fields in Wyoming. Many of these reservoirs are Cretaceous sands,” says WSGS hydrogeologist Kurt Hinaman. “We also looked at chemistry data for production water from these oil and gas reservoirs and felt that we had enough data to put together a report. We are using our earlier work on the Tensleep and Madison aquifers as a template, compiling many of the same parameters we did in those pathfinding works.”

The study focuses on the Cloverly, Frontier, Mesaverde, and Fox Hills formations, along with the Muddy sandstone. While these are not major aquifers, improved characterization of their groundwater properties will enhance understanding of Wyoming’s hydrogeologic framework. This information will also support research and applications related to groundwater use, oil and gas exploration, and potential carbon sequestration.

Topics covered in the upcoming publication include groundwater quality, porosity, permeability, surface recharge, water drive, bottom-hole temperatures, and sample-water temperatures.

Madison Limestone Aquifer

WSGS hydrology staff have embarked on a compilation project focused on the Madison Limestone aquifer—an important aquifer in Wyoming.

“We are using our earlier work on the Tensleep aquifer as a template. We are compiling many of the same parameters as with our pathfinding Tensleep work,” says WSGS hydrogeologist, Kurt Hinaman. 

The Madison and its equivalent geologic formations occur statewide east of the Overthrust Belt and the Absaroka Range. They supply drinking and stock water along many basin margins in Wyoming. Additionally, the Madison is a reservoir for oil, and is one of the target aquifers in deep basins for the sequestration of carbon dioxide. Data about the Madison aquifer that will be covered in the publication include groundwater quality, porosity, permeability, surface recharge, water drive, bottom hole temperatures, and sample water temperatures. 

Fossil Preparation and Digitization – NGGDPP 2025

The WSGS is conducting a specialized fossil preparation and digitization project funded through the National Geological and Geophysical Data Preservation Program (NGGDPP). The project focuses on two exceptional Eocene-age specimens from the Green River Formation—a rare fossil bat (Icaronycteris?) and a large freshwater turtle (Axestemys byssinus). The Green River Formation is world renowned for its finely preserved fossils, which provide invaluable insights into ancient climates, ecosystems, and the evolution of life during the early Cenozoic.

Both specimens are undergoing expert preparation using micro–computed tomography (micro-CT) scanning, fine-point pneumatic tools, and air-abrasive techniques performed under magnification. These specialized methods ensure the long-term preservation and accessibility of these scientifically important fossils while maintaining the highest standards of conservation. A time-lapse video of the fossil preparation process will be created for educational and outreach purposes, highlighting the delicate techniques and scientific value of fossil conservation work.

In addition to producing fully prepared, research-ready specimens, the project supports the development of new collections management workflows within the WSGS paleontology program. Historical fossil records are also being digitized to expand the Survey’s data archive and improve public accessibility. 

Upon completion, the fossils will be available for scientific study, museum exhibition, and public outreach—continuing the WSGS’s mission to preserve and share Wyoming’s remarkable paleontological heritage.