The Amazing Geology of Union County, NM

The Amazing Geology of Union County, NM

Amazing Geology

Here in northeastern New Mexico we are blessed with amazing geology. The landscape here has been magnificently shaped over hundreds of millions of years by mountain building oregenies, inland seas, giant rivers, wind erosion and deposition, and recent volcanic activity.

I know rockhounds everywhere are going “wait we have amazing geology too.” They are not wrong. The difference is I get to live and be a caretaker here, so I’m biased.

Ancestral Rockies

Back to the geology and adventure. Where I live is about the southern terminus of Front Rangia a mountainous island in the Ancestral rockies.

This period of mountain building started about 300 million years ago. These early mountains appear to have significantly eroded away by the middle to late triassic period.

The Travasser Formation: Middle Triassic Geology

The Travesser formation dating back to approximately 240 million years ago is a geologic formation covering parts of New Mexico, Colorado, Oklahoma, and Texas. This formation features prominently especially in the Dry Cimarron valley between Kenton, OK to near Folsom, NM. This formation has been attributed to the Dockum group and also to the Chinle group. This is a controversial debate that is still occuring, and I’m staying out of. However, I think it’s cool to have a formation named for the creek that runs through my backyard. Travesser Creek originates 40 miles west near the base of the Sierra Grande shield volcano in Des Moines, NM

Amazing geology of Union County New Mexico.
1. Top of Travesser Formation 2. Travesser Creek

Around 60,000 to 45,000 years ago The Clayton-Raton Volcanic field was active to the south and west of here. There was also volcanic activity north in Colorado and to the east in the Oklahoma panhandle. So while we haven’t had recent volcanic activity in this area, there is still plenty of volcanic materials to collect. Ash and tuft are common. On some parts of the ranch we find rhyolites, as well as basalt and obsidian bombs. Also being downstream from volcanic features provides some interesting material.

Rockhound Collectibles

Additionally, we have amazing sandstones laid down by inland seas. Some of the erosion patterns are simply amazing. Petrified wood is not uncommon. We have some fossils. But my favorite is finding rosebud agate, a beautiful red, blue, and white agate material in chalcedony and a sandstone or limestone host matrix.

Rosebud Agate. Photo courtesy of Clint Nagel

Rosebud agate is a challenging material to work with, but when you can find pieces that are mostly out of the sandstone matrix, it is amazing.

If you want to visit and see this amazing geology while collecting rocks, I offer guided rockhounding on the ranch. I’m located in the middle of nowhere in north eastern New Mexico, so I recommend planning a weekend or a few days and maybe also seeing these local attractions.

Places of Interest in Union County & Nearby

If you want to plan a trip to come rockhounding, contact me to discuss options and pricing.

Additional Reading on Our Amazing Geology

For more information on Union County geology you can read Geologic Studies of Union County, New Mexico by Brewster Baldwin and William R. Muehlberger, Bulletin 63 New Mexico Bureau of Mines and Mineral Resources, 1959.

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