--- title: "A Karst Masterclass: Devil's Canyon in Montana" --- Visit this spot in Southern Montana to see a unit famous among geologists for its extensive karst topography.  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­    ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­   | View in browser Thursday, 7 May, 2026 / Edition 109 A stop at Devil’s Canyon Overlook in southern Montana is a must for any true rock nerd. Located within the Bighorn Canyon National Recreation Area, this spot offers a dizzying 1,000-foot vertical drop into the canyon, exposing a nearly vertical timeline of Earthʼs history.   While the views are world-class, the real story lies in the plumbing of the rocks beneath your feet. Ali Jaffri of Applied Stratigraphix and I led an incredible field trip here several years ago, studying the beautiful “Facies and Fractures of the Tensleep, Madison, and Phosphoria.”   Molly Turko   Structural Geologist, Devon Energy   The Madison Limestone: A Karst Masterclass  View of the Bighorn River cutting Devil's Canyon/ Courtesy of Molly Turko The towering walls of Devil’s Canyon are primarily composed of Mississippian Madison Limestone. This unit is famous among geologists for its extensive karst topography—landforms created from the dissolution of soluble rocks such as limestone.     Area geology: During the Late Mississippian, a drop in sea level exposed these rocks to freshwater, which dissolved the limestone and created a vast network of caves, sinkholes, and underground rivers. When the seas returned, these voids were often filled with younger sediment, creating “paleokarst” features that we see today as brecciated pipes and filled-in caverns.  Why it matters: Understanding the karst at Devil’s Canyon isn't just an academic exercise; it has massive implications for the energy industry. In the subsurface of the Bighorn and Williston Basins, the Madison Limestone is a prolific reservoir.   Porosity and permeability: Karst features act as a Swiss cheese-type network. Large caverns (vugs) provide immense storage space for hydrocarbons, while interconnected fractures and conduits allow oil and gas to flow rapidly to a wellbore.   Operational challenges: Drilling into a large karst void can lead to lost circulation, where drilling fluids disappear into the cave system, causing expensive delays or safety risks.   Networks and patterns: Caverns and karst often take advantage of fracture networks. If you understand your paleostress history and likely orientations for fracture networks, you have a better chance at finding sweet spots along fracture corridors and karst networks. Devil’s Canyon is a great background for these types of discussions.  Go deeper: Learn more about the geology here.  Sponsored Pockets Full of Rocks? We’ve Got the Swag to Match!   Designs for those who know a GOOD ROCK when they see one. Shop graphic tees, hoodies, kids' gear, hats, magnets, and more. Fresh designs are added monthly at GeoSwag.shop SHOP NOW Hiking the State Line Trail  Geos viewing karst in the canyon walls/Courtesy of Molly Turko To get the most out of this landscape, head over to State Line Trail. This pretty easy hike straddles the Montana-Wyoming border, offering sweeping views of the Bighorn Basin and the Pryor Mountains.   A “secret” view: While the main trail is spectacular, I recommend deviating slightly from the path toward the canyon rim (use caution and stay back from unstable edges!). This short detour provides a unique perspective of the canyon's “tight” bends that you can’t see from the main overlook parking lot.  Mechanical stratigraphy: As you hike, look at how the different rock layers weather. The massive Madison Limestone forms sheer cliffs, while the overlying shales of the Amsden Formation create gentler, colorful slopes—a perfect example of how rock strength (mechanical stratigraphy) shapes the landscape.   Conjugate fractures: Be sure to look at the rocks under your feet as you hike. You’ll find some beautiful conjugate fracture patterns! My infamous Andy Cube was born on this field trip using a foam cube and some Sharpies. Grab an Andy Cube for yourself and learn more about Andersonian Faulting Theory here.  Trip tips: Getting there: Access the overlook and State Line Trail via Highway 37 north of Lovell, Wyoming.  Wildlife: Keep an eye out for Bighorn sheep. You can often see them navigating the “impossible” ledges of the canyon.   Best time to go: Sunset is the golden hour here: The limestone walls turn a brilliant orange-red against the deep blue of the Bighorn River below.   What to bring: This area is remote. Fill up your gas tank in Lovell and bring plenty of water, as the high desert sun can be unforgiving.  Sponsored Advancing Earth Science Together at GeoConvention 2026, Calgary   Join us for three days of innovation, collaboration, and technical insight highlighting subsurface imaging, CCUS, critical minerals, geothermal, and emerging geoscience technologies. REGISTER NOW Want to help AAPG grow? Consider supporting AAPG's free resources, like this one, by donating today. AAPG thanks our advertisers for their support. Sponsorship has no influence on editorial content. Advertise with us.   Was this email forwarded to you? Sign up now.   You received this email because you signed up for newsletters from AAPG. To stop receiving this newsletter, unsubscribe or manage your email preferences.   AAPG  1444 S. Boulder Ave., Tulsa, Oklahoma 74119, USA (918) 584-2555 \| 1 (800) 364-2274 (US and Canada) www.aapg.org   | | --- |