Redwall Limestone
The sheer, iron-stained cliff of gray Mississippian limestone that forms the Grand Canyon's great mid-canyon barrier — cave-riddled and crinoid-packed.
Also known as: Redwall
Mississippian — warm, shallow tropical seas
The world back then
Mississippian, about 350 million years ago. A warm, clear equatorial sea covers the region — a bright carbonate shelf swarming with corals and sea lilies, the water bathtub-warm and turquoise. Tropical, shallow, and alive, a paradise for anything with a shell. The land nearby is bare; all the action is underwater.
That warm tropical reef is the sheer red cliff that turns most hikers around — and you glide beneath it while it just poses for you. The bathtub sea is 350 million years gone; you get the shade and the view without the drowning. The comfortable animal at the end of deep time keeps drawing the best hand.
Recognize it in the field
- Typical color
- gray (surface-stained red by iron oxide from the overlying Supai)
- Weathers as
- Massive cliff-former — the sheer 400–800 ft red cliff of the mid-canyon; the upper part is karstic (caves, overhangs).
- Grain
- thick-bedded, massive
Look for
- massive gray limestone stained red only on the surface
- four members (Whitmore Wash / Thunder Springs / Mooney Falls / Horseshoe Mesa)
- the banded Thunder Springs Member (carbonate + chert)
- an extensive cave and karst system
How this rock was made
A warm Mississippian sea transgressing west-to-east across a lime seafloor (carbonate shelf).
The setting: warm, shallow equatorial tropical sea (carbonate shelf)
~400–800 ft at the Grand Canyon (member sums).
In the rock record
↑ Younger — rests above
↓ Older — sits beneath
Where to see it
Regions: Grand Canyon / Colorado Plateau
- the continuous mid-canyon red cliff throughout the Grand Canyon
- Redwall Canyon (type locality)
Float past it: Grand Canyon