david allio

The Lake Mead 1:100,000-scale quadrangle includes some of the most spectacular scenery in the Basin and Range Province, scenery that is the direct result of the complex geologic history of the region. Extending from near the mouth of the Grand Canyon westward almost to Las Vegas, Nevada, the quadrangle exposes 1.8 billion years of geologic history through a tremendous range of strata, including Proterozoic crystalline rocks, Paleozoic and Mesozoic sedimentary rocks, Tertiary sedimentary, volcanic and plutonic rocks, and Late Tertiary to Quaternary surficial deposits. This history begins with the suturing of continents to form the Proterozoic crystalline basement, followed by deposition of Paleozoic strata along a continental margin. Mesozoic sedimentation, responsible for many of the brilliant colors seen in the Lake Mead area, began first on the craton side of an island arc and later in the foreland of Late Mesozoic (Sevier) thrusting.¹