Caves of the ancient Delaware Basin – 10/1/13

Posted by on 09/30/2013
Infographic - Ancient Delaware Basin

The Ancient Delaware Basin

During the Permian period, about 250 million years ago, the Guadalupe mountains in southern New Mexico served as the northern coastline for an inland sea, now called the Delaware Basin.

The marine life of this era formed a coral reef called the Capitan reef, which contained bryozoans (Moss-like invertebrates), sponges, and other micro-organisms.

Millions of years pass, and the earth’s tectonic plates push the land thousands of feet upwards, and the Delaware Basin is left with 3 exposed coral reefs, which become 3 limestone mountain ranges over millennia:

On the ancient Capitan Reef.

The NMD crew looking for caves on the ancient Capitan Reef.

The Guadalupe, the Apache, and the Glass mountains, with the highpoint being Guadalupe peak at about 8400′.

Interestingly, Guadalupe peak is the highest point in Texas, often confused with the smaller, but iconic El Capitan peak.


During the late Cenozoic era, possibly the Neogene period about 10 million years ago, hydrogen sulfide (H2S) begins to seep upwards from the deep petroleum made from the organic matter from the earlier Permian period.

The combination of hydrogen sulfide and oxygen from rain water, form the highly corrosive sulfuric acid: H2S + 2O2 > H2SO4. This sulfuric acid pushes upwards, dissolving the limestone deposits to form caverns. The oil of vitriol, indeed!

Cavers in a Cavern

An unusually large cavern, likely formed by sulfuric acid.

As the acidic groundwater drains from the caverns, calcium carbonates and calcium sulfates (gypsum) are formed.  Gypsum is made from a reaction between sulfuric acid and limestone. So when you see gypsum in a cave, it can be a confirmation of this chemical process.

Together, these processes create the classic speleothems, or cave formations, that we see in the Carlsbad cavern complex.   There are over 100 caves in the Carlsbad Caverns National Park.

Typical for caves in this area, the erosion above ground creates holes and entrances into the caves.

This exposure to rain, causes water to pick up minerals and eventually create formations from the roof downward:  Stalactites.  Like holding tight to the roof.

JMar, DanO and Stalagmike

JMar, DanO and Stalagmike

Oppositely, water on the floor of the caverns can contain carbonic acid and generate mineral deposits by evaporation. Growths from the floor upward are known as stalagmites. Like they might reach the ceiling.

If they do, we call them columns.  Other stalagmites are the tall broomsticks, the funky totem poles, and the squat, yet flat, fried egg stalagmites.

Other speleothems include soda straws, draperies, helictites, and popcorn.

Helictites are funky little stalactites that go crazy and defy gravity, like ribbons, saws, fractals, and curly-fries.

DanO on the Delaware Basin

DanO on the Delaware Basin - 2 thumbs up!

Changes in the air temperature and rainfall affect the rate of growth of speleothems.  The color of speleothems is determined by the trace bits of minerals in the formation.


The 9/1/13 expedition of the ancient Delaware Basin led to the exploration of 4 new caves, including the stunning cave #60 (large cavern photo).  The NMD crew produced the content of this post (Contact for use).  Photography by Mike “Stalagmike” Ward and Justin “JMar” Marley. Info-graphic by Dan Otero.

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