San Rafael Swell
A 75-by-40-mile Laramide dome, breached and eroded into canyons and badlands — a whole stack of Colorado Plateau formations exposed in concentric rings.
Also known as: San Rafael Swell east flank, San Rafael Swell rim
The San Rafael Swell is a giant blister of the Colorado Plateau — a roughly 75-by-40-mile dome kicked up during the Laramide Orogeny (~60–40 million years ago) and then flash-flooded into a wilderness of canyons, buttes, and badlands. Erosion has stripped its top to expose the rock in concentric rings: older Permian and Triassic layers at the breached center, younger Jurassic Navajo and Wingate sandstones flaring up around the flanks, and the whole eastern edge tilted on end as the San Rafael Reef. It is one of the best places on the Plateau to read a full stack of formations laid bare by a single upwarp.
Geology
Formation: A doubly-plunging anticline (dome) uplifted during the Laramide Orogeny, then breached and eroded so that progressively older rocks are exposed toward its center. The steeply upturned eastern limb forms the San Rafael Reef monocline.
A textbook breached anticline: a single upwarp exposes a near-complete Permian-through-Jurassic section in map-view concentric rings, making it one of the clearest large-scale structural exposures on the Colorado Plateau.
Primary formation: Navajo Sandstone
Age: Paleogene (50 Mya)
The east flank stands on end as the San Rafael Reef; the breached center (the 'Sinbad Country') exposes the oldest rocks.
History
Named for the San Rafael River, which drains the uplift.
Holds extensive Barrier Canyon-style and Fremont rock art (e.g., the Head of Sinbad and Buckhorn Wash panels).