Take me to a tropical reef

With warmer weather approaching, I have been thinking about the Chinese Wall down in Montana. Along the front ranges of the rockies there are actually quite a number of fossilized tropical reefs. Montana is actually quite a good place to research these formations. Drywood is formed from stromatolites. There actually is a colony of these precambrian creatures still living in Shark Bay Australia. These ancient corals are what make the climbing at Drywood so interesting. Local geologists also call this formation fossil algae.

This band of fossil algae is actually fairly extensive. This is what looked to make that short section on Yarrow's east ridge difficult. The bear's hump is actually a slightly different formation called molar tooth limestone (for obvious reasons). Usually the fossil algae band presents a challenge when scrambling.