ON THE ROCKS Presents
Laramie mountains and Snowy Range stromatolites
July 18-19, 2026
Trip Leader: Emmett Evanoff and Kelli Trujillo
Trip Coordinator: David Schoderbek
Trip Description
Join us for a weekend of southern Wyoming highlights, highlighting both the enlightening Cenozoic history of the southern Laramie Mountains and Paleoproterozoic sedimentary strata of the Snowy Pass Supergroup, including some of the most spectacular & best preserved Precambrian stromatolites in the world!
Saturday, 18 August, will begin in Fort Collins, where we will meet our Day 1 leader, Dr Emmett Evanoff, Department of Earth and Atmospheric Sciences, University of Northern Colorado. After an orientation stop in Cheyenne, we will transect and dissect the Cenozoic geologic story exposed in the southern Laramie Mountains, heading north to Wheatland, then crossing the range and ending in Laramie. Travelling north along the east flank of the Laramie Mountains, it is as if we were travelling back in time through the Neogene and into the latest Paleogene. The Laramie Mountains are lower topographically (Laramie Peak, the highest mountain in the range, is only 10,272ft tall) than the Colorado Front Range, where uplift, erosion, and glaciation have removed most Cenozoic strata to form the Colorado Piedmont and Tertiary sediments of the Colorado High Plains. The Laramie Mountains preserve flanking upper Eocene to Miocene sediments, and Neogene tectonics, including faulting of the Hartville Uplift and regional eastward tilting reflected in the distribution of the Tertiary fill and the modern stream patterns. On this trip, we will see features that once were in and adjacent to the Colorado Front Range. An appreciation of the Cenozoic geology of the Wyoming Laramie Mountains will illuminate our understanding of the geologic history of the Colorado Front Range.
We'll stop for the night in Laramie, WY, where participants will have time to grab dinner and rest for day two. Attendees are responsible for their own accommodations for the night, but a room block has been reserved at the Hilton Garden Inn. Attendees will receive information about booking with the room block when they register. The block expires on 6/20/2026.
Sunday 19 August will begin at the Hilton Garden Inn, where we will meet our Day 2 leader, Dr Kelli Trujillo, University of Wyoming Geochronology Lab, Laramie, who will lead us through the geologic history of the Snowy Range in the Medicine Bow Mountains of southeastern Wyoming. The Snowy Range, part of the Medicine Bow mountain range in Wyoming, exposes metasedimentary rocks of the Snowy Pass Supergroup that were deposited along the passive southern margin of the Wyoming craton between 2.45 and 1.78 Ga. These rocks preserve a story of sea level change, volcanism, continental collision, and subsequent metamorphism, deformation, and uplift. The Nash Fork Formation within the upper part of the Snowy Pass Supergroup contains some of the most spectacular and best-preserved Precambrian stromatolites in the world. The hiking portion of the trip will cover approximately 2 miles and travel mostly along an old two-track road, all above 10,000ft in elevation. Along the way, we’ll stop to look at stromatolites and talk about the general geologic history of the area. We’ll finish the hike with a tour down the “Valley of the Stromatolites.” Once back to the vehicles, we will drive a short distance to see outcrops of the Towner Greenstone and French Slate, and then drive down the Barber Lake Road to access outcrops in the Mullen Creek-Nash Fork Shear Zone, before heading back home.
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For more information: The Wyoming State Geologic Survey published a useful guide to the stromatolites of the Medicine Bow Mountains: https://www.wsgs.wyo.gov/products/wsgs-2014-pic-45.pdf
Dr. Trujillo was featured on the PBS program “Prehistoric Road Trip” as the guide to these stromatolites, the oldest fossils featured on the 3-part program. You can view the short segment and get some background info here: https://www.wttw.com/prehistoric-road-trip/stops/breathe-oxygen-thankstromatolites
Cost
- $90 for members
- $125 for non-members. (not a member? click here to join)
- Are you a student? email staff@rmag.org
