Coral Reefs

As strange as it seems to have a webpage about coral reefs for a park known for its desert and mountain scenery, we do indeed have reefs here at Guadalupe Mountains National Park!

Around 273 million years ago, during a time period called the Permian, a shallow, tropical sea covered this part of Texas and New Mexico. Paleontologists call it the Delaware Sea, named for the Delaware Mountains that run south from Guadalupe Peak and El Capitan.

Because the Delaware Sea sat just north of the equator during the Permian Period, and because of its isolation via a narrow outlet to the world’s single great ocean, a reef was able to grow along its edge. You might be familiar with today’s coral reefs of the Florida Keys, the Great Barrier Reef, or numerous other locations in warm, shallow seas across the world. In any reef, organisms dependent on sunlight build tough skeletons to anchor themselves in place and protect themselves from predators. Over time, these organisms die, leaving their skeletons behind. These serve as a perfect perch for more of the same organisms to build upon, and, year after year, the reef grows up towards the sun and out towards the open ocean.

The big difference between the Capitan Reef, the barrier reef that formed along the edge of the Delaware Sea, and most of the reefs on Earth today is that this reef was formed primarily by algae and microbes rather than animals like corals. Sponges played a role in its construction, too, though they likely lived in cracks and crevices in the reef rather than forming its structure.

By 260 million years ago, sea levels around the world had begun to drop. This cut off the narrow outlet the Delaware Sea had to the world’s great ocean, and the Delaware Sea, Capitan Reef and all, were buried under layer upon layer of sediment. The reef stayed buried for almost 250 million years, while the dinosaurs evolved and died out, while the world saw ice ages and heat waves, and while continents shifted all around it.

Then, around 14 million years ago, tectonic forces deep beneath the surface put tremendous amounts of pressure on the rock layers containing the Capitan Reef. Eventually, this pressure was released in the form of a massive fault that split the reef, uplifting the Western Escarpment of the Guadalupe Mountains to elevations up to 8,751 feet above sea level. The highest point sits more-or-less along this fault, and the reef slopes gradually downwards until it disappears below the surface again northeast of Carlsbad Caverns National Park.

Today, we know the Capitan Reef as the Guadalupe Mountains of Texas and New Mexico, with other fragments visible above the surface in the Glass and Apache Mountains of West Texas. These mountain ranges preserve an incredible window into what the world was like during the Permian Period and what types of organisms were present in the Delaware Sea.

You are likely to see evidence of creatures that lived on the reef during your visit. Fossils are common in our park, and they preserve organisms that lived on the reef, taking advantage of the very productive ecosystem that developed there, as well as the reef building organisms themselves. Visitors most often see brachiopods, crinoids, bryozoans, ammonites, fusulinid forams, horn corals, sponges, and algal boundstone (the basic structure of the reef itself).

The best place in the park to see fossils of reef creatures is the Permian Reef Trail. This is a very strenuous out and back trail that begins at the McKittrick Canyon Visitor Center and works its way up the ancient structure of the reef. For visitors looking for a less challenging way to view the park’s fossils, the McKittrick Nature Trail has numerous fossils along its path, some even in the trail! Please remember that every fossil is a one-of-a-kind piece of our ancient Permian world, so take pictures home instead of fossils to make sure the next visitor can have the same connection to our distant past that you did.

The late Permian, after the reef was burried, was characterized by an 8-million-year cycle of extinctions. These events radically changed what sorts of organisms one could expect to see on Earth. The last one, around 252 million years ago, is known as the End-Permian Mass Extinction and led to the elimination of around 81% of all species on Earth.

We cannot test the process of extinction experimentally. Thus, we are reliant on Earth history to show us how this process happens, as well as what factors allow some species to survive while others disappear forever. The remains of the Capitan Reef provide one of the best glimpses into what life was like before the greatest extinction in multicellular life’s history. Thus, it is among the premier windows into how extinction occurs and what we can do to help life on Earth today weather it.

Last updated: August 31, 2023

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