Sum11.208.NorthCascades

Sum11.208.NorthCascades - C-3 Our Story So Far… The...

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Unformatted text preview: C-3 Our Story So Far… The Growth of Western North America - Part II The Insular Superterrane, North Cascades & San Juan Islands C-3 Arrival of the Insular Superterrane C-3 After Accretion North Cascades Insular Superterrane Methow Intermontaine Basin Superterrane Insular Superterrane Methow Basin Intermontaine Superterrane Subduction zone relocates North Cascades at 100 Myrs 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 Oblique Collision Terrane Continent Oblique Collision Continent Oblique Collision Oblique Collision Continent Continent Terrane is “smeared out” along coast C-2 Insular Superterrane: Wrangellia C-6 Wrangellia & the North Cascades “Microterranes” Insular Superterrane Intermontaine Superterrane Methow Basin Insular Superterrane Time Modern Day Analogy for North Cascade Rocks Major Terrane Groupings (See list on C-9) Skagit Chelan Mountains Nason Shuksan Nooksak River Chilliwack Haro Turtleback Deadman Bay Garrison Decatur Western Melange Eastern Melange …and the rest… Cont. North Cascades & San Juan Islands C-4 Many Microterranes of the North Cascades & San Juan Is. • • • • • • • • • • • • • • C-6 Intermontaine Superterrane • • • • • • • • • • • • • • 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 C-4 Major Terrane Groupings Skagit Crystalline Core Skagit Gneiss Skagit Crystalline Core High Grade NW Cascades and San Juan Thrust System Cascade River Schist Melanges NW Cascades Thrusts Protolith: Shale Shuksan Blueschist Protolith: Basalt Low to Medium Grade -- Subducted Ocean Crust -- Darrington Phyllite Chilliwack Marble Twin Sisters Dunite C-4 Major Terrane Groupings NW Cascades & San Juan Islands Thrusts C-5 & 6 Skagit Crystalline Core High Grade Met. Skagit Crystalline Core NW Cascades and San Juan Thrust System Medium Grade Met. Separated by thrust faults Melanges Low Grade Met. C-7 San Juan Islands C-7 San Juan Islands Decatur Terrane Jurassic Chert Basalt Gabbro Serpentinite Ocean Crust Similar to Terrane rocks in Northern California C-7 C-7 San Juan Islands Deadman Bay Terrane Permian to Jurassic Chert Limestone W/Tethyan Forams Basalt San Juan Thrust Sheets Ocean Crust Similar to Cache Creek Terrane in Intermontaine Superterrane C-8 San Juan Island Thrust Sheets C-5 NW Cascades/San Juan Islands Nanaimo Formation: Overlap Sequence Mt. Stuart - Stitching Pluton 90 Myrs C-1 Timing of the North Cascades Collision Age of Accretion 115-90 Myrs Age of the Microterranes C-10 Meanwhile in Oregon… C-11 Terranes of the Wallowa Mountains ...
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This note was uploaded on 01/11/2012 for the course GEO 208 taught by Professor Robviens during the Summer '11 term at Bellevue College.

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