The Bisti/De-Na-Zin badlands

Forty-five thousand acres of badlands, and barely a trail in any of it

South of Farmington in northwestern New Mexico, flat grassy plains break into valleys of grey, white, brown and purple clay hills. This is the Bisti/De-Na-Zin Wilderness, 45,000 acres of badlands managed by the Bureau of Land Management, set aside in 1984 and enlarged by about 2,250 acres in 2019, with three parcels of private Navajo land inside its boundary. Bisti comes from the Navajo Bistahí, "among the adobe formations"; De-Na-Zin, from Dééł Náázíní, means standing crane, and petroglyphs of cranes have been found to the south.

Its strangest shapes are the hoodoos, mushroom rocks where a hard brown cap of the Bisti Bed sandstone protects a stalk of softer white sandstone beneath it, and the highest brown peaks serve ferruginous hawks as nesting places. The rock is old. About 74 million years ago the Western Interior Seaway made its final retreat from here, and the land behind the shore became swamps and river plains. Grey shales and black coal record the swamps, white sandstones the river channels, and here and there a coal seam caught fire long ago and baked the shale around it into hard red clinker, the only bright colour in the lowest beds.

The beds tilt gently northeast, about five degrees, so a walk from southwest to northeast moves forward through time, across the end of the age of dinosaurs. Geologists consider this the longest, most complete and most richly fossiliferous sequence spanning the Cretaceous-Paleogene boundary in any single basin in the world. Some 200 species of plants and animals have been found in the oldest two formations alone: petrified logs, leaf impressions, hadrosaurs such as Parasaurolophus, the five-horned Pentaceratops, ankylosaurs, and meat-eaters including Tyrannosaurus and Daspletosaurus. The iridium-rich clay that marks the asteroid strike elsewhere is missing here, lost in a gap in the record, but above it the striped Nacimiento beds hold the earliest mammals of the age that followed, fossils so important that two of the first stages of the Paleocene are named for places in this basin.

There are no marked trails. Routes from the Bisti and De-Na-Zin trailheads are informal and rough, shared by hikers and riders, and visitors are free to wander off-trail across the clay hills. There is no water and little or no phone signal, campfires are banned, and the dirt access roads can turn impassable after rain or snow. The climax of William Friedkin's 1977 film Sorcerer was shot here.