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
Metamorphosed to Become
 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
Geologic
Time
Scale
Eon
Era
Cenozoic
Mesozoic
Phanerozoic
Paleozoic
Precambrian
Age at Base*
(start)
Quaternary
1.6 Ma
Tertiary
65 Ma
Cretaceous
140 Ma
Jurassic
205 Ma
Triassic
250 Ma
Permian
290 Ma
Carboniferous
355 Ma
Devonian
410 Ma
Silurian
438 Ma
Ordovician
510 Ma
Cambrian
540 Ma
Vendian
680 Ma
Proterozoic
2500 Ma
Archean
Hadean
Period
3960 Ma
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
http://en.wikipedia.org/wiki/Image:Impact_event.jpg
http://en.wikipedia.org/wiki/Image:Chicxulub_radar_topography.jpg
http://upload.wikimedia.org/wikipedia/commons/5/57/K-T_boundary.jpg
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
 ~17 -- 14 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
http://en.wikipedia.org/wiki/Image:3-Devils-grade-Moses-Coulee-Cattle-Feed-Lot-PB110016.JPG
http://en.wikipedia.org/wiki/Image:Horst_graben.jpg
http://en.wikipedia.org/wiki/Image:HotspotsSRP.jpg
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
http://en.wikipedia.org/wiki/Image:Northern_icesheet_hg.png
http://www.nwcreation.net/articles/missoulaflood.htm
http://www.greaterthings.com
/News/daily/2005/09/06/
6600916_Bush_behind_Katrina/
Lake-Bonneville-and-Utah.jpg
http://pubs.usgs.gov/fs/2002/fs092-02/
http://volcano.und.edu/vwdocs/volc_images/north_america/crater_lake.html
http://en.wikipedia.org/wiki/Image:HotspotsSRP.jpg
http://www.exodus2006.com/supervol.html
http://en.wikipedia.org/wiki/Image:Yellowstone_Caldera_map2.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
From Orr and Orr, 2005, p. 17
http://en.wikipedia.org/wiki/Image:Puget_Sound_from_Space_Needle_High_Rex.jpg
http://en.wikipedia.org/wiki/Image:Cascade_Range-related_plate_tectonics.svg
http://en.wikipedia.org/wiki/Image:Cascade_eruptions_in_the_last_4000_years.png
Sources
 Orr, W.N. and E.L. Orr. 2006. Geology of the Pacific Northwest.
Waveland Press, Long Grove, IL.
 Alt, D. and D.W. Hyndman. 1995. Northwest Exposures. Mountain
Press Publishing Company, Missoula, MT.
 Check out this website to reconstruct plate tectonic movements on your own:
http://www.odsn.de/odsn/services/paleomap/paleomap.html
 Check out KT Event: http://en.wikipedia.org/wiki/Cretaceous_extinction
 Also look at QuickTime movie of Puget Sound Glaciation at
http://exhibits.pacsci.org/puget_sound/graphics/ps_glaciationsm.mov