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The Growth of Western North America - Part II

The Growth of Western North America - Part II. The Insular Superterrane, North Cascades & San Juan Islands. Our Story So Far…. C-3. Arrival of the Insular Superterrane. C-3. Methow Basin. Intermontaine Superterrane. Insular Superterrane. After Accretion. C-3. North Cascades. Methow

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The Growth of Western North America - Part II

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  1. The Growth of Western North America - Part II The Insular Superterrane, North Cascades & San Juan Islands

  2. Our Story So Far… C-3

  3. Arrival of the Insular Superterrane C-3 Methow Basin Intermontaine Superterrane Insular Superterrane

  4. After Accretion C-3 North Cascades Methow Basin Insular Superterrane Intermontaine Superterrane Subduction zone relocates

  5. North Cascades at 100 Myrs

  6. Insular Superterane: Wrangellia Terrane Rocks: Basalts top: vesicles bottom: pillows Limestone Type of Terrane: Hot Spot Islands Source: Fossil clams and forams western Pacific Paleomagnetics ±15° N/S Age: Triassic/Jurassic Photo: Dr. ML.Bevier

  7. ObliqueCollision Continent Terrane

  8. ObliqueCollision Continent

  9. ObliqueCollision Continent

  10. ObliqueCollision Continent Terrane is “smeared out” along coast

  11. Insular Superterrane:Wrangellia C-2

  12. Wrangellia & the North Cascades C-6 “Microterranes” Insular Superterrane Intermontaine Superterrane Methow Basin

  13. Modern Day Analogy for North Cascade Rocks

  14. Cont. C-6 Intermontaine Superterrane Insular Superterrane Time North Cascades & San Juan Islands

  15. Many Microterranes of the North Cascades & San Juan Is.(See list on C-9) C-4 • Skagit • Chelan Mountains • Nason • Shuksan • Nooksak River • Chilliwack • Haro • Turtleback • Deadman Bay • Garrison • Decatur • Western Melange • Eastern Melange • …and the rest…

  16. Major Terrane Groupings • Skagit • Chelan Mountains • Nason • Shuksan • Nooksak River • Chilliwack • Haro • Turtleback • Deadman Bay • Garrison • Decatur • Western Melange • Eastern Melange • …and the rest… Skagit Crystalline Core NW Cascades and San Juan Thrust System Melanges

  17. C-4 Major Terrane Groupings Skagit Crystalline Core NW Cascades and San Juan Thrust System Melanges

  18. Skagit Crystalline Core Skagit Gneiss High Grade Cascade River Schist

  19. NW Cascades Thrusts Darrington Phyllite Protolith: Shale -- Subducted Ocean Crust -- Shuksan Blueschist Protolith: Basalt Low to Medium Grade Chilliwack Marble

  20. Twin Sisters Dunite

  21. Major Terrane Groupings C-4 Skagit Crystalline Core High Grade Met. NW Cascades and San Juan Thrust System Medium Grade Met. Melanges Low Grade Met.

  22. C-5 & 6 Separated by thrust faults NW Cascades & San Juan Islands Thrusts Skagit Crystalline Core

  23. San Juan Islands C-7

  24. San Juan Islands C-7 Decatur Terrane Jurassic Chert Basalt Gabbro Serpentinite Ocean Crust Similar to Terrane rocks in Northern California

  25. San Juan Islands C-7 Deadman Bay Terrane Permian to Jurassic Chert Limestone W/Tethyan Forams Basalt Ocean Crust Similar to Cache Creek Terrane in Intermontaine Superterrane

  26. San Juan Thrust Sheets C-7

  27. San Juan Island Thrust Sheets C-8

  28. NW Cascades/San Juan Islands C-5

  29. Nanaimo Formation:Overlap Sequence

  30. Mt. Stuart - Stitching Pluton 90 Myrs

  31. Timing of the North CascadesCollision C-1 Age of Accretion 115-90 Myrs Age of the Microterranes

  32. Meanwhile in Oregon… C-10

  33. Terranes of the Wallowa Mountains C-11

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