Day 4 : Stop 2

DAY 4 (9/29/2025) - STOP 2

"Carlsbad Caverns National Park"

Map of Carlsbad Caverns

    At our next stop, we visited Carlsbad Caverns National Park, which lies within the Chihuahuan Desert, the largest desert in North America. During the early Permian, the area that is now southeast New Mexico lay near the equator and was submerged beneath a warm inland sea. This basin developed along the margin of the supercontinent Pangaea, formed from the collision of major landmasses at the start of the period. By the middle Permian, during the Guadalupian Epoch, carbonate production flourished, and the Capitan Reef began to grow along the rim of the Delaware Basin. The Capitan Reef is the only reef system on Earth that dates to the middle Permian, and its lifespan defines the Capitanian Age between roughly 266 and 260 million years ago. Tectonic uplift has exposed the reef in only three places, and this park helps to depict its structure. 

Fig. 28 Popcorn Texture on Cave Walls

    

Fig. 29 Flowstone Formation on Cave Walls

A major rocky type present at this site is massive limestone formed from carbonate-secreting organisms that thrived in the warm, shallow marine conditions of the basin margin. Where we observed popcorn-style textures along the walls (fig. 28), these features represent zones where prior dissolution of carbonate was followed by precipitation as unsaturated, warming fluids descended and deposited thin layers of carbonate minerals. These features were more noticeable on steeper surfaces where carbonate dissolved at higher elevations, then reprecipitated lower on the walls as fluids lost carbon dioxide.

    The formation of the caves themselves follows a speleogenetic pathway. While most of the world’s limestone caves originate through dissolution by carbonic acid, the Guadalupe caves, including Carlsbad Cavern, formed instead through the dissolution of sulfuric acid. Hydrogen sulfide gas rose from below the water table and reacted with oxygen near the top of the saturated zone to generate sulfuric acid, which dissolved the buried Capitan Reef. Over the past 20 million years, regional tectonic uplift elevated sections of the reef along the western margin of the old Delaware Sea. As the Guadalupe Mountains rose, new cave levels developed at each position of the water table. The highest cave passages began forming around 12 million years ago, whereas the lowest levels are much younger, developing roughly two million years ago. Once the caves opened to the surface, meteoric processes began producing a wide range of speleothems. Stalactites, stalagmites (fig. 30), flowstones (fig. 29), columns (fig. 30), soda straws, and more features record the slow drip of mineral-rich water, while the presence of iron and manganese oxides explains the diverse colors seen throughout the system. More than 100 caves are known within the park, and at least 180 miles of passages have been mapped. 

    A unique feature of this park is that Carlsbad Cavern hosts a major seasonal colony of Brazilian free-tailed bats, with as many as 400,000 during the warmer months!

Fig. 30 Temple of the Sun Formation (Columns, Stalagmites, & Stalactites)

Note: Information, aside from field notes, was derived from informational signage in the Carlsbad Caverns National Park visitor center. 

External References:
Redirecting. (2025). Instructure.com. https://usflearn.instructure.com/courses/1985970/files/folder/Field%20trip%20materials/Carlsbad%20Caverns?preview=199515642