The Capitan Reef
A 600-kilometre Permian reef, built by sponges rather than corals, now stands as mountains in Texas.
- When
- Known to
- ± 5 million years
- Era
- Permian, Paleozoic
The Capitan Reef fringed the Delaware Basin in what is now west Texas and New Mexico. Unusually it was constructed not by robust corals but by fragile sponges and bryozoans, bound together by encrusting algae and carbonate cement. Uplift and erosion have exposed it as the Guadalupe Mountains, one of the finest fossil reef exposures anywhere, and the basin behind it holds enormous petroleum reserves.