Jurassic Exotic Paleogeography, Southwestern US



Early Jurassic Exotic Paleogeography, Southwestern US (200 Ma). The Stikine arc, back arc basin, and Stikine microcontinent approach the west coast


Middle Jurassic Exotic Paleogeography, Southwestern US (170 Ma). As the Stikine arc moves towards North America, another back arc basin developes as the arc-trench complex moves at a faster rate than the remainder of the trailing plate. Each of the back arc basins is represented today by Jurassic ophiolites in northern California and adjacent Oregon


Late Jurassic Exotic Paleogeography, Southwestern US (158 Ma). The Stikine arc collides with North America and the first (or Sierran) phase of the Nevadan orogeny occurs in central and northern California. A triangular ocean basin separates the Stikine arc from North America; the remnant basin closes fron north to south as the oblique collision occurs. A fore arc subduction complex lies to the south. The Wrangellia oceanic plateau moves in from the southwest


Latest Jurassic 1 Exotic Paleogeography, Southwestern US (155 Ma). The Sierra phase of the Nevadan orogeny is near its climax as the Stikine arc completes its collision with North America. A developing arc-trench system to the north with east-dipping subduction zone developes a back arc basin (between the arc and North America). The Stikine microcontinent begins its collision with southern Oregon


Latest Jurassic 2 Exotic Paleogeography, Southwestern US (150 Ma). The collapse of the northern back arc basin and accompaning collision of the Stikine microcontinent initiate the northern or Klamath phase of the Nevadan orogeny. At the conclusion of these events, an east-dipping subduction zone dips under a continental arc from Mexico northward into Canada



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