1 Billion Years of PNW Geology in 10 (text) Slides or Less

Important Processes Tectonics Volcanism Erosion/Deposition Glaciation Discrete Disturbances

PNW Timeline A 4.5 BYA Earth Formed ~ 4.4 – 4. 2 BY Oldest Rocks (U in Zircon degradation to lead Pb) 2.7 BYA basement Rocks in MT, ID 1.5 BYA Purcell Belt Basin ~44o MYA Pangaea Starts to Assemble (Silurian Epoch of Paleozoic Era) Coastline ~ Idaho border. 30,000 feet of marine sediment accumulates ~ 400 mya Blue Mt. Terrane forming in tropical Pacific (limestone)(made of 5+ terranes) Klamath Arc Collides, Antler Highlands (proto-Sierras) Intermontane, insular terranes develop in S.W. Pacific Metamorphosed to Become

Geologic Time Scale EonEraPeriod Age at Base* (start) Phanerozoic Cenozoic Quaternary 1.6 Ma Tertiary 65 Ma Mesozoic Cretaceous 140 Ma Jurassic 205 Ma Triassic 250 Ma Paleozoic Permian 290 Ma Carboniferous 355 Ma Devonian 410 Ma Silurian 438 Ma Ordovician 510 Ma Cambrian 540 Ma Precambrian Proterozoic Vendian 680 Ma 2500 Ma Archean 3960 Ma Hadean 4550 Ma

Cenozoic Era (New Life) Two periods of Old Version: Quaternary Period 1.6 mya Holocene Pleistocene Tertiary Period 65 mya Pliocene Paleocene or Miocene Two periods of New Version: Neogene Period 23 mya Holocene Epoch ~15,000 to present Pleistocene Epoch 1.8 mya Pliocene Epoch 5.3 mya Miocene Epoch 23 mya Paleogene Period Oligocene Epoch 33 mya Eocene Epoch 55 mya Paleocene Epoch 65 mya

Cenozoic Era (New Life) Two periods of Old Version: Quaternary Period 1.6 mya Holocene Pleistocene Tertiary Period 65 mya Pliocene Paleocene or Miocene Two periods of New Version: Neogene Period 23 mya Holocene Epoch ~15,000 to present Pleistocene Epoch 1.8 mya Pliocene Epoch 5.3 mya Miocene Epoch 23 mya Paleogene Period Oligocene Epoch 33 mya Eocene Epoch 55 mya Paleocene Epoch 65 mya

PNW Timeline B ~245 MYA Pangaea Assembled (Permian Epoch of Paleozoic Era) Large, warm seas Several (lost) sub/mini continents/islands in Pacific Permian – Triassic Extinction Event ~251 mya Larger extinction event than K-T Impacts, Volcanism, Methane Hydrates from sea floor (?) ~200 MYA Pangaea Starts to Break up (Triassic Epoch of Mesozoic Era) Forms Laurasia (N) and Gondwanaland (S) Marine Seas changing to smaller back arc basins with volcanic chains ~ 140 mya Laurasia Breaks Up (Jurassic Epoch of Mesozoic Era) Ocean rift starts to form Atlantic Ocean N. America moves across Pacific and Farallon Plates (subduction) Intermontane Superterrane Collides with N. America

From Orr and Orr, 2005, p. 6

From Orr and Orr, 2005, p. 2

From Orr and Orr, 2005, p. 5

PNW Timeline C ~ 144 mya – 65 mya Cretaceous Epoch of Mesozoic Era Batholith intrusions throughout PNW N. Cascade Terrane Collides (started 500 mya) Insular and Blue Mt. Terranes Collide Idaho Batholith late Cretaceous Large Seas cover PNW BAM! Huge Meteor hits Earth, Extinction of Dinosaurs (K- T Extinction Event) Location: Yucatan Peninsula (others? SL-9) Deccan Traps alternative Hypothesis? Farallon Plate subducts with less angle, faster

Several km in Diameter; ~ hundreds of nuclear weapons

Timeline D ~58 mya Coast Range Mt. Volcanism (ocean) Pacific Rim, Crescent, Siletz Terranes “arrive” Farallon Plate subducts steeper, slower ~40 mya W. Cascade Volcanism Begins (old Cascades) ~ 36 mya Kula Plate completely subducted Blue Mts. Rotate/arch upward John Day Volcanism smothers fossils Wet, Warm Tropical Environment changes to dry temperate ~20 – 5 mya Coast Range (not BC) and Olympics uplift

Cenozoic Era (New Life) Two periods of New Version: Neogene Period 23 mya Holocene Epoch ~15,000 to present Pleistocene Epoch 1.8 mya Pliocene Epoch 5.3 mya Miocene Epoch 23 mya Paleogene Period Oligocene Epoch 33 mya Eocene Epoch 55 mya Paleocene Epoch 65 mya

From Alt and Hyndman, 1995, p. 171

Timeline E ~ mya Flood Basalts in WA and OR (Steens Basalt) 17 – 15 mya Basin and Range (fault-blocks from spreading) ~13 mya Snake River Plain Hotspot (at Yellowstone now) ~5.3 mya First High Cascades eruptions Cascade Rainshadow “renewed” Dry, cooler inland Climate  Continental Climate Temperate Climate to west  Maritime Climate

Timeline F ~2 – 3 mya Puget Lowlands and Willamette valley forming – rift faulting? Long dry spell Yellowstone (2.2 mya and 640,000 ya) eruption THEN Pleistocene 1.8 mya 100,000 years ago first glaciation Long series of glacial phases (colder – wetter/warmer – drier) Lake Missoula (+/- 100s?)and Bonneville (1) floods 10,000 years ago ice age ends E. Snake River basalts Mazama (5,677 (± 150) ya) eruption

/News/daily/2005/09/06/ _Bush_behind_Katrina/ Lake-Bonneville-and-Utah.jpg

Puget Sound At Glacial Maxima Seattle under up to 1000m of ice Lakes formed at edges of glaciers (Russell, Nisqually, Bretz, many others) Some drained into Chehalis River (underutilized drainage) Water changed from fresh to brine/salt (extinction) As Glaciers receded, glacial formations Mima Mounds Clays and Till Morraines

From Orr and Orr, 2005, p. 17

Sources Orr, W.N. and E.L. Orr Geology of the Pacific Northwest. Waveland Press, Long Grove, IL. Alt, D. and D.W. Hyndman Northwest Exposures. Mountain Press Publishing Company, Missoula, MT. Check out this website to reconstruct plate tectonic movements on your own: Check out KT Event: Also look at QuickTime movie of Puget Sound Glaciation at