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San Juan terranes- San Juan Thrust System. Decatur terrane- Jurassic to early Cretaceous-An ophiolite with a younger superimposed arc. Overlying clastic marine sequence. Imbricate Fault Zone- late Cretaceous-fault slices of many different rock types– most sheared and structurally complex.
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San Juan terranes-San Juan Thrust System • Decatur terrane- Jurassic to early Cretaceous-An ophiolite with a younger superimposed arc. Overlying clastic marine sequence. • Imbricate Fault Zone- late Cretaceous-fault slices of many different rock types– most sheared and structurally complex
San Juan terranes- San Juan Thrust System • Constitution Formation- Jurassic to early Cretaceous- clastic sequence of volcaniclastic sediments with some ribbon cherts, and pillow lavas • Garrison terrane- Permian to early Triassic– high pressure schist. Occurs as small fault slices along one of the thrust faults.
San Juan terranes- San Juan Thrust System • Deadman Bay Terrane- Triassic to early Jurassic- ribbon cherts, pillow basalts, and limestones; Tethyan-fusulinid limstone. • Turtleback Terrane- Cambrian to early Permian- plutonic complex of tonalite and gabbro. Upper unit consists of volcanic-arc with some limestones– Fusulinids are non-Tethyan.
San Juan terranes-External Units • Haro Terrane- late Triassic to early Cretaceous- marine sandstone, conglomerates, volcaniclastic sediments • Nanimo Group- late Cretaceous- marine and non-marine sandstones, conglomerates, and shale
San Juan terranes-Post Orogenic Unit • Chuckanut Formation- Eocene– nonmarine sandstone and conglomerate