GEOLOGY FROM THE GREEN RIVER OVERLOOK, ISLAND IN THE SKY DISTRICT, CANYONLANDS NATIONAL PARK, SOUTHEASTERN UTAH

The Green River Overlook in the Island in the Sky District of Canyonlands National Park is one of Utah’s most iconic views, often appearing on book covers, scenic calendars, and postcards. Changes in the color, thickness, and composition of the strata, and the erosive work of running water and mass wasting combined to create the magnificent landscape seen at the overlook today. In 1869, Major John Wesley Powell stated, “The landscape everywhere, away from the river, is of rock—cliffs of rock; tables of rock; plateaus of rock; terraces of rock; crags of rock—ten thousand strangely carved forms,” while traveling through the area on his incredible journey to the Grand Canyon. From the overlook, the primitive and remote Maze District of Canyonlands is seen west of the Green River. The Henry Mountains, on the far horizon to the southwest, are the type locality for laccolithic intrusions as first described by G.K. Gilbert in 1877.

The exposed rocks viewed from the overlook include Early Permian (the Organ Rock Formation and White Rim Sandstone), Triassic (the Moenkopi and Chinle Formations, and the lower third of the Wingate Sandstone), and Early Jurassic (the upper two thirds of the Wingate Sandstone, the Kayenta Formation, and Navajo Sandstone). These formations were deposited in a wide range of environments: floodplain, nearshore marine to coastal dune, tidal flat, braided stream, and eolian. Several major unconformities are present.

Canyonlands is located in the Paradox Basin of southeastern Utah. The basin is an elongate, northwest-southeast-trending evaporitic basin that predominantly developed during Pennsylvanian time but continued into the Permian. The area received continental deposition in the Jurassic and the Early Cretaceous and shallow-marine deposition during the Late Cretaceous. Large uplifts and basins developed in the Colorado Plateau during the Laramide orogeny between the latest Cretaceous and the Eocene. The Island in the Sky District is located on the northern end of the broad Laramide-age Monument upwarp. The Colorado Plateau began rising during the Miocene. This changed the landscape from one of deposition to one of massive erosion. The Green River, as part of the formation of the Grand Canyon over the past 5 million years, rapidly downcut and created the incredible view from the Green River Overlook.