This spring, the Wyoming State Geological Survey (WSGS) released a new map for the west half of the Ramshorn quadrangle, which includes parts of the northwestern Wind River Range, the Wind River Basin, the southern Absaroka Range, and the town of Dubois.
The surficial map encompasses an area with some of the highest density of landslides in the state – and an area where U.S. Highway 26/287 connects central Wyoming with Yellowstone and Grand Teton National Parks.
Surficial geologic mapping helps scientists better understand what materials are on the surface, and is especially useful in documenting and characterizing geologic hazards.
The map offers a look into the geologic history of the region, and re-affirms how widespread and numerous landslides are along the southern flank of the Absarokas. This information also tells geologists that landslides have played a large role in the ongoing erosion of the mountain range.
James Mauch, a WSGS geologist who worked on the project, said that the map is particularly useful for present-day land-use planning.
“When considering whether to build a road or a house, or where to site infrastructure like that, this map can be used as a resource showing the distribution of landslides and other potentially problematic geologic deposits,” said Mauch. “And if a proposed site is located where a landslide is mapped, it's recommended to conduct a field geotechnical study to assess the stability of the ground in the shallow subsurface at that location.”
Over the past 25 years, the WSGS has been working to make updated surficial geologic maps at a 1:100,000 scale for the entire state.
The north half of the Ramshorn quadrangle is almost all designated Wilderness areas, which means no road access. Due to the relative inaccessibility of the area, researchers had to lean on the interpretation of digital datasets, like Lidar and aerial imagery.
“Most of our 1:100,000 scale mapping in other parts of the state involves integrating other pre- existing maps from various sources, but this wasn't really the case for the Ramshorn quadrangle because there just weren't many pre-existing maps to begin with,” said Mauch.
But the team still had to get out into the backcountry to complete the picture, which involved packing into the mountains on horseback.
For the geologist, getting to spend time in beautiful mountainous terrain was a big benefit of working on the Ramshorn map.
“You still have to get out into the field and ground truth. And you know, that's one of the things I love about geology – it's still inherently a field based science,” said Mauch.
The Ramshorn project took about a year from start to finish and was made possible by grant funding from the US Geological Survey. Researchers conducted the mapping over the summer, and then finished the project with cartography, map production, and report writing in the winter.
