Some of the best geology road trips don’t require a long hike—just a full tank of gas, a curious eye, and a willingness to pull over. Driving through the Arbuckle Mountains of southern Oklahoma offers all three, plus a bonus stop at Arbuckle Mountain Fried Pies, where geology discussions are best paired with a warm pie (coconut, in my case).
The Arbuckle Mountains expose a spectacular cross-section through Paleozoic time, shaped by rifting, burial, inversion, and uplift. Within minutes of the fried pie counter, you can stand on world-class outcrops that reveal the tectonic heart of the Arbuckles and the sedimentary record caught up in that deformation.
Molly Turko
Structural Geologist, Devon Energy
The Tectonic Backbone of the Arbuckles
The Arbuckle Mountains. Astro23/Shutterstock.com
The Arbuckle Mountains are not mountains in the traditional sense, but rather an uplifted and inverted structural block formed during the Pennsylvanian Orogeny.
Area geology: Their story begins much earlier, with the development of the Southern Oklahoma Aulacogen, a failed intracontinental rift that formed during the breakup of Rodinia in the late Precambrian.
This rift system accumulated thick Cambrian through Mississippian sedimentary successions that became exposed during the Pennsylvanian Orogeny, producing large anticlines, faults, and overturned beds.
The Arbuckle Anticline is one of the most dramatic expressions of this inversion, tilting entire stratigraphic sections on their sides and bringing deep-time rocks to the surface.
Go deeper: Read more about the structural story here.
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Stop 1: The Fried Pies Outcrop: Deformation on the North Limb
Fried Pies outcrop from the 2023 AAPG SWS Field Trip. Courtesy of Molly Turko.
Directly across the road from Arbuckle Mountain Fried Pies sits an unassuming, but structurally complex, outcrop of the Mississippian Sycamore Formation, exposed on the overturned northern limb of the Arbuckle Anticline.
Geological intrigue: Beds dip steeply, around 75° to the south, and the rocks display abundant intra-bed deformation, rotated blocks, and minor faulting.
This deformation is an excellent place to study the mechanical response of mixed siliciclastic–carbonate rocks to compression.
Bedding-parallel shortening, floating blocks of calcareous siltstone, and disrupted contacts suggest that significant deformation occurred before the full folding of the Arbuckle Anticline.
Go deeper: Read more on this outcrop here and keep your eye out for Bigfoot while eating a pie!
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Stop 2: The Heart of the Arbuckles: Source Rocks and Fractures
Geologist checking out the Heart of the Arbuckles. Courtesy of Molly Turko.
A short drive behind Arbuckle Mountain Fried Pies leads to the Heart of the Arbuckles, a roadside exposure of the Devonian Woodford Shale that packs an extraordinary amount of geologic information into a small footprint.
About the Woodford shale: The Woodford shale is a world-class source rock that has charged many of the prolific petroleum systems of the Midcontinent.
Although commonly referred to as a “black shale,” the Woodford at this outcrop appears light tan to ivory. This misleading appearance results from the oxidation of phosphatic minerals and pyrite on weathered surfaces.
About the outcrop: The outcrop is best known for its complex fracture network, where researchers have identified at least five distinct fracture sets.
Some fractures are fold-related, while others clearly predate folding and bed overturning.
Many fractures are partially or completely filled with bitumen, indicating hydrocarbon migration through the Woodford.
Small normal faults with only a few inches of throw cut the exposure, including one through the “heart.”
When the beds are restored to horizontal, it becomes clear that this fault also predates folding, capturing an early phase of deformation later overprinted by Arbuckle uplift.
Plan Your Visit
Turner Falls/ Olga Lyobochkina
Trip Tips:
Location: Arbuckle Mountain Fried Pies is located just off I-35 at exit 51.
Don’t miss: Another must-stop is the Turner Falls Overlook, located approximately two miles past Arbuckle Mountain Fried Pies on U.S.-77.
Best stop order: Start with the Fried Pies outcrop across the road, then drive behind the gas station to access the High Road (towards Falls Creek Camp).
Safety: Both outcrops are roadside, so use caution when parking and stay well clear of traffic.
A fried pie sugar high: Coconut is my go-to, but honestly, you can’t go wrong.
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