Guadalupe Mountains

The Permian Sea that dominated this part of Pangaea 250 million years ago left the gypsum rich deposits that have now been recycled to form the dunes at White Sands (previous post). This sea (or some smaller connected seas) also gave rise to large carbonate reefs, one of which has been subsequently uplifted and exposed by erosion as the current Guadalupe Escarpment (Guadalupe Mountains National Park).

AERIAL VIEW

Guadalupe Peak is the highest point in Texas (8751'). El Capitan, the distinctive prow immediately to the south, marks the southern end of the Guadalupe Escarpment.  Carlsbad Caverns was carved (dissolved, actually) into the core of the reef much later, aided by the presence of hydrocarbons in the adjacent basin that leaked hydrogen sulfide and produced sulfuric acid, a much more effective cave-forming agent than the more common carbonic acid.

The Capitan Reef faced eastward across the Delaware Sea (an arm of the larger Permian Sea).  The Delaware Basin and the Midland Basin farther east are now both major oil and gas fields and driving south towards Carlsbad I was reminded of this by the pump jacks and well heads, the pipe yards, and the lines of red Halliburton trucks. I spent the fall of 1981 in Schlumberger's training program in Midland and spent weekends exploring west Texas in my new little pickup truck. That was a long time ago! 

I suppose there may have been beaches on the shores of this Permian ocean - but the environment behind these reefs was probably pretty quiet and the shores were probably muddy and perhaps vegetated (although I suspect they didn't look like the mangroves or salt marshes you might find in similar settings today).