I assume the whitish color rock is limestone. I found this:

Limestone, siltstone, dolomite and mudstone make up the four different rock types that form the Claron Formation. Each rock type erodes at different rates which is what causes the undulating shapes of the hoodoos.

Limestone, siltstone and dolomite are very hard and form the protective caprock on most of the spires. These harder rocks are eroded predominantly by frost.