San Rafael Swell

The San Rafael Swell is a giant dome-shaped anticline of sandstone, shale and limestone in south-central Utah, entirely within Emery County on the Colorado Plateau, about 16 miles west of Green River and spanning roughly 75 by 40 miles. It formed during the Laramide Orogeny, between about 60 and 40 million years ago, when deeply buried Precambrian basement rock faulted and shifted upward, folding the sedimentary layers above it into the broad swell seen today; since then, infrequent but powerful flash floods have carved the exposed sandstone, shale and limestone into an intricate maze of valleys, canyons, gorges, mesas, buttes and badlands, continually exposing older rock at the swell's eroded center while younger rock remains at its edges. Its steep eastern edge, the San Rafael Reef, displays prominent folded strata of resistant Jurassic and Permian sandstone, and the swell's drainage, carried by the San Rafael River and Muddy Creek, predates the uplift itself, cutting straight across the rising structure rather than around it. This entity documents the San Rafael Swell specifically as a geological formation.