Jurassic Paleogeography, Southwestern US



Early Jurassic Paleogeography, Southwestern US (200 Ma). The great Navajo sand sea has spread across much of the Wertern Interior. A continental arc has developed across the Southwest and some Navajo dunes spill westward into the topographically low arc. Farther north the arc is off shore separated from the continent by a back arc basin. The Stikine and Quesnell elements are separated by the Cache Creek interarc basin.



Middle Jurassic Paleogeography, Southwestern US (170 Ma). A long, narrow, epicontinental seaway extends into the Western Interior from the north. Dunes rim the southeast margin. The elements of the McCloud arc collapse against the continent and thrusting in Nevada creates uplands. The large Wrangellia oceanic plateau approaches from the south. Most interpretations consider Wrangellia to be an exotic terrain. However, the details of the history of this terrain and its collision with North America are greatly debated



Late Jurassic Paleogeography, Southwestern US (150 Ma). The uplift in Nevada reverses stream direction across the region and the Morrison fluvial system expands eastward across the Western Interior. Stresses related to the opening of the Gulf of Mexico oceanic basin caused oblique, transtensional basins to form across the southwest portion of North America. Thick continental and later marine deposits filled these basins. The collapse of Stikine arc against Quesnell and perhaps the initial collision of Wrangellia trigger the first phase of the Nevadan orogeny.



Latest Jurassic Paleogeography, Southwestern US (145 Ma). A large saline lake spread across the eastern Colorado Plateau. To the west, uplands sourced streams of the Morrison Formation. At the conclusion of the Nevadan orogeny, a continental arc extended along most of the western coast of North America



Jurassic Paleogeography, exotic interpretation, SW US.

These maps present a contrasting hypothesis to the ones shown above; interpretation based on Ingersoll and Schweickert, 1986, Tectonics, vol 5, p. 901-912


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