The Bisti/De-Na-Zin Wilderness is a wilderness area located in San Juan County in the U.S. state of New Mexico. Established in 1984, the Wilderness is a desolate area of steeply eroded badlands managed by the Bureau of Land Management, except three parcels of private Navajo land within its boundaries. The John D. Dingell, Jr. Conservation, Management, and Recreation Act, signed March 12, 2019, expanded the Bisti/De-Na-Zin Wilderness by approximately 2,250 acres.
Translated from the Navajo word , Bisti means "among the adobe formations." De-Na-Zin, from Navajo , translates as "Standing Crane." Petroglyphs of cranes have been found south of the Wilderness. It is on the Trails of the Ancients Byway, one of the designated New Mexico Scenic Byways.
Prehistory
The Bisti/De-Na-Zin Wilderness is the largest area of badlands in the San Juan Basin that is easily accessible to the public. The badlands expose the longest, most complete, and most richly fossiliferous sequence of beds spanning the Cretaceous-Paleogene boundary in any single sedimentary basin in the world. These include four geologic formations, which, in decreasing order of age, are the Fruitland Formation, the Kirtland Formation, the Ojo Alamo Formation, and the Nacimiento Formation.
These formations are exposed in an area of east-to-west valleys that drain to the Chaco River to the south. The beds dip about 5 degrees to the northeast so that the oldest beds (Fruitland Formation) are exposed to the southwest, where they are easily visible around the entrance area, while the youngest (Nacimiento Formation) are exposed to the northeast.
In the late Cretaceous, North America was divided by the Western Interior Seaway, whose western shoreline moved back and forth across what are now the mountain states of the United States. About 74 million years ago, the sea made its final retreat from the Bisti/De-Na-Zin area to the northeast, depositing the Fruitland Formation on top of the shoreline sandstone of the Pictured Cliffs Formation (which is exposed south of the Bisti/De-Na-Zin Wilderness.) The Fruitland Formation records flood plains and delta environments behind the receding shoreline, including swamps in which economical deposits of coal were formed. These are mostly found in the Ne-Nah-ne-zad Member of the Kirtland Formation. As the shoreline continued to recede, the Fossil Forest Member was deposited, which has much less coal but is rich in fossils. At the Bisti/De-Na-Zin Wilderness, the Fruitland Formation consists mostly of gray shales, with thin coal beds and with resistant beds of white sandstones deposited in river channels. The formation also contains brown to purple iron concretions. In some places, the coal caught fire and burned to produce a red, hard rock, called clinker or red dog.
The Kirtland Formation was deposited shortly after the Fruitland Formation, and consists of thick greenish shales and siltstones, with just a few thin coal beds and white sandstone beds. The lower part of this formation is called the Hunter Wash Member and is bounded by a white sandstone bed at its base and a distinctive brown sandstone bed (the Bisti Bed) at its top. Between is drab green siltstone. The middle part of this formation is called the Farmington Sandstone which consists of brown-topped sheets of sandstone. The upper part of the formation is called the De-na-zin Member and is similar to the Hunter Wash Member, but with purple beds near its top. The sandstone of the Farmington Member reflects a time of uplift somewhere nearby, producing high ground from which coarse sediments were eroded. Dinosaurs and other fossils are found scattered throughout the Kirtland Formation. Some 200 species of plant or animal fossils have been identified in the combined Fruitland and Kirland Formations, most of which are found in the Bisti/De-Na-zin Wilderness. The plant fossils include petrified logs, leaf impressions, and carbonized leaves.