Madison Limestone
The gray Mississippian limestone cliff of the Uinta canyons — a crinoid-packed carbonate resting on Cambrian rock across a huge gap.
Also known as: Madison
Mississippian — warm, shallow tropical seas
The world back then
Mississippian, about 345 million years ago. A warm, clear tropical sea floods the continent, its floor a garden of sea lilies and corals turning to lime — bright, shallow, and teeming. Later, water works the limestone into caves. Picture a Caribbean shallows, except it stretches over half a continent and nothing's watching from a beach.
Now it's the gray, cave-riddled cliff at Split Mountain, and you inherit the pleasant leftovers — a canyon, a current, a view. That tropical sea is 345 million years gone; the river that replaced it carries you for free. Being the comfortable creature who shows up for the good part is the whole deal, and it's a good one.
Recognize it in the field
- Typical color
- gray to white
- Weathers as
- Cliff- and ledge-forming massive carbonate; karst-prone (caves).
- Grain
- massive; bioclastic; oolitic
Look for
- massive gray bioclastic and oolitic limestone
- karst-prone (caves)
- richly fossiliferous (crinoids, corals)
- builds the tilted walls of Split Mountain
How this rock was made
A warm Mississippian sea transgressing over the continent's ancient core (craton).
The setting: warm, shallow marine lime seafloor (carbonate shelf)
Up to ~2,100 ft regionally; thinner on the Uinta shelf.
In the rock record
↑ Younger — rests above
↓ Older — sits beneath
Where to see it
Regions: Uinta Mountains (Middle Rocky Mountains province; NPS files Dinosaur NM under Colorado Plateaus)
- Split Mountain (Dinosaur NM)
- the Mississippian carbonate cliffs of the Uinta canyons
Float past it: Split Mountain · Whirlpool Canyon