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Did you know southern New Mexico contains parts of five geologic provinces and contains rocks that are nearly two billion years old?
Those are just two of the fascinating facts in a new book, “The Geology of Southern New Mexico’s Parks, Monuments, and Public Lands” (GSNM) published by the New Mexico Bureau of Geology and Mineral Resources, a research and service division of the New Mexico Institute of Mining and Technology in Socorro. The bureau has served as the state’s geological survey for 93 years. The book was edited by Peter A. Scholle, Dana S. Ulmer-Scholle, Steven M. Cather, Shari A. Kelley, Belinda Harrison and Jennifer Eoff, and includes a cover photograph of Organ Mountain-Desert Peaks National Monument by Las Cruces photographer Wayne Suggs.
The 400-page edition is broken into six parts, including these five “broad, overlapping geologic provinces: the Mogollon Slope/Colorado Plateau, the Basin and Range, the Rio Grande rift, the Mogollon-Datil volcanic field and the Great Plains, along with a separate section on the Permian Basin.
The book contains nearly 400 color photographs, plus maps and other illustrations that detail the state’s geology from the Precambrian Era through the Paleozoic and Mesozoic eras to the present-day Cenozoic. (We’re in the Holocene Epoch of the Quatenary Period of the Phanerozoic Eon.)
The iconic "elephant" of nearby Elephant Butte represents the remains of a volcanic neck or plug that it is two-three million years old. The rocks in which Carlsbad Caverns formed are 250-300 million years old, although the caves formed much later. The volcanic tuff (Kneeling Nun Tuff) exposed in City of Rocks State Park is about 36 million years old and tuffs visible on nearby Table Mountain are about 35 million years old. The Organ Mountains rose about 36 million years ago. During the Pennsylvanian Period, about 300 million years, ago, “as much as 80 percent of New Mexico submerged beneath warm, shallow, tropical seas, (because it) lay close to the equator at that time.” Human settlement, by contrast, began about 12,000 years ago.
Closer to home, GSNM says “the majority of rocks exposed in the Organ Mountains are intrusive or volcanic in origin, the latter including both ash-flow tuffs and lavas.” The oldest rocks in the area are 1.4-billion-year-old granites. And get this: “Thin layers of Pleistocene volcanic ash in the upper part of the Camp Rice Formation include those from the Yellowstone caldera in Wyoming and the Long Valley caldera in California. These far-traveled ashes are a testament to the explosive power of the these modern calderas.”
The earliest geologic history of the Organ Mountains region is well more than one billion years ago, the books says. Between 1.7 and 1.1 billion years ago, “volcanic islands and continents collided with the fledgling North American continent to build what is now much of the Southwest.”
You can find the same information about White Sands National Park, Prehistoric Trackways National Park, the Robledo Mountains – a total of 62 parks and public lands sites throughout southern New Mexico.
All told, the book “provides an understanding of the exposed rock units (and fossils) that record more than 1.7 billion years of geologic and biologic changes in this region.”
“We produce a lot of technical material that is aimed towards geologists, so the Southern Parks book is important in the sense that it's an approachable resource that educates our customer base about New Mexico's geology,” said Bureau Publications Resource Specialist Elena Taylor. “Most of our customers enjoy exploring public lands and it's definitely a plus that the southern parks book is written as a guidebook.”
With its amazing photography and some beautiful prose, this book is a work of art as well as a work of science.
GSNM costs $29.95 and is worth every penny.
Find it online at https://geoinfo.nmt.edu/publications/guides/nmparks/southern/.