The Wingate Sandstone is the star. This Jurassic eolian formation — wind-deposited sand from a desert that covered the Colorado Plateau 200 million years ago — forms the sheer, vertical walls that give Labyrinth its visual character. The faces run four to six hundred feet high, dark red and orange, streaked with desert varnish so thick and dark in places that the walls look black. Desert varnish is not paint — it's a mineral coating of manganese and iron oxides deposited and oxidized by water seeping through the rock over thousands of years. The darkness of the coating is a rough proxy for exposure age: the darkest panels have been weathering longest. Above the Wingate, the Kayenta Formation creates the ledgy, stepped cap that protects the cliff face from rapid erosion. Above that, the Navajo Sandstone rounds into the domes and fins visible on the skyline. The three alcoves at Trin-Alcove are the geological highlight — massive chambers formed where groundwater seeps through the Wingate and saturates softer beds behind the face, which then erode and collapse inward, leaving the harder outer wall as a roof. The entrenched meanders themselves are a geological statement: the river's sinuous course was established on a flat surface before the Colorado Plateau uplifted, and the meanders were preserved as the river cut downward — a textbook example of incised meandering that Leopold would have used to teach the concept.
Wingate Sandstone — Jurassic eolian deposits, 200 million years old — forms the sheer 400–600 foot walls. Desert varnish (manganese/iron oxide, deposited over millennia by seepage) streaks the faces dark brown to black. The Trin-Alcove chambers form where seepage saturates softer beds behind the Wingate face, causing internal collapse while the harder outer wall remains as a roof. The entrenched meanders are the geological signature: the river's sinuous course was established before plateau uplift and preserved as incision deepened — a textbook demonstration of antecedent meandering.