The crystalline Vishnu Basement Rocks underlie the Bass Limestone of the Unkar Group of the Grand Canyon Supergroup and the Tapeats Sandstone of the Tonto Group. These basement rocks consist of metamorphic rocks collectively known as the Granite Gorge Metamorphic Suite, sections of which contain granitic pegmatite, aplite, and granodiorite that have intruded into fractures as dikes. This photo was captured between Colorado River Miles 110-115 (measured downstream from Lees Ferry). Day 8 of 16 days rafting 226 miles down the Colorado River in Grand Canyon National Park, Arizona, USA.
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