Honaker Trail Formation
The gray, fossil-rich Pennsylvanian marine limestone of the lower Cataract walls and the Goosenecks of the San Juan — the cyclic top of the Hermosa Group.
Also known as: Honaker Trail
Pennsylvanian — the great coal swamps
The world back then
Late Pennsylvanian, about 303 million years ago. A shallow sea rises and falls over a muddy shelf beside the ancestral mountains, laying down fossil-packed lime one cycle, sand and silt the next — over and over, sea level pulsing like a slow heartbeat. Warm, shallow, and crowded with shellfish and sea lilies. The same story, told a hundred times.
Those pulses are the stepped gray walls of the lower Cataract and the Goosenecks, and you float once the record the sea repeated a hundred times. It took the ocean ages to write; it takes you a day to read. Showing up warm and comfortable at the end of all that repetition is the good seat in the house.
Recognize it in the field
- Typical color
- gray to reddish-gray
- Weathers as
- Ledge-and-slope former — resistant fossiliferous limestone benches alternating with softer shale/siltstone; builds the stepped gray lower walls of Cataract Canyon.
- Grain
- fine-crystalline to coarsely granular limestone; sandy/silty clastics
Look for
- cyclic gray fossiliferous marine limestone with sandstone/siltstone
- fossil-rich limestone benches
- gray and red chert nodules and beds
- reddish-gray weathering
- grows sandier toward the Uncompahgre highland
- forms the lowest exposed canyon walls just above the river
How this rock was made
Pennsylvanian cyclothem deposition in the Paradox Basin beside the rising Uncompahgre highland of the Ancestral Rocky Mountains.
The setting: cyclic open (normal) marine shelf
GeoLex gives 0–1,750 ft (≈1,300 ft near Durango); NPS Canyonlands states ~3,000 ft 'in the park' — the conflict likely reflects differing unit definitions (post-Baars usage includes all beds between Paradox and the redbed disconformity).
In the rock record
Part of the Hermosa Group.
↑ Younger — rests above
↓ Older — sits beneath
Where to see it
Regions: Colorado Plateau (Paradox Basin)
- Honaker Trail / Goosenecks of the San Juan (type area)
- walls of Cataract Canyon (Colorado River)
- along the Moab Fault in Arches
Float past it: Cataract Canyon