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Volcanoes on the Rim. 55 Million Years of Volcanism in the Pacific NW. Mt. St. Helens, 1980. Major Events of the Cenozoic. Volcanism. Tectonics. Olympics. Sedimentary Events. 65. 55. Challis Arc. Straight Creek Transform Fault. 45. Formation of Olympic Rocks. Major Sedimentary

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Volcanoes on the rim l.jpg

Volcanoes on the Rim

55 Million Years of Volcanism in the Pacific NW

Mt. St. Helens, 1980


Major events of the cenozoic l.jpg
Major Events of the Cenozoic

Volcanism

Tectonics

Olympics

Sedimentary Events

65

55

Challis Arc

Straight Creek

Transform Fault

45

Formation of

Olympic Rocks

Major

Sedimentary

Basins

35

Western

Cascade Arc

25

15

Columbia River Basalts

Accretion of

Olympic Rocks

5

High Cascade Arc

Ice Ages

0

Age (Myrs)


Volcanic episodes l.jpg
Volcanic Episodes

65

55

Challis Arc

(55-42 Myrs)

45

35

Western

Cascade Arc

(37-15 Myrs)

25

Columbia River Basalts

(17-6 Myrs,

Most 17-14 Myrs)

15

5

Yellowstone Hot Spot

(14-0 Myrs)

High Cascade Arc

(5-0 Myrs)

0

Age (Myrs)


Challis arc l.jpg
Challis Arc

G-2

Challis Arc


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Late Cretaceous/Early Tertiary Batholiths

Mark the plate boundary

Note the embayment



Formation of challis arc l.jpg

Kula Plate

North

American

Plate

Farallon Plate

Formation of Challis Arc

Straight Creek (Strike-Slip) Fault

Challis Arc


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Post Challis Arc

Arc now runs

north-south


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Cascade Arc

G-2

Challis Arc

Cascade Arc


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West &High Cascades

G-1

West Cascade Arc

(37-15 Myrs)

High Cascade Arc

(5-0 Myrs)


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Why did it shift eastward?

G-1

Shallow Subduction

Steep Subduction

100 km Depth

Change in dip of plate?

Consistent with younger age of Juan de Fuca Plate


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West Cascades in Washington

G-2

Include volcanic rocks and intrusions


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West

Cascade

Volcanics

West

Cascade

Batholiths

North vs. South

North Cascades

South Cascades

Young Basement Rocks (Terranes)


North vs south14 l.jpg
North vs. South

Erosion

More uplift to the north


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North vs. South

North Cascades

South Cascades

West Cascade Batholiths

West Cascade Volcanics

High Cascades

Young Basement Rocks (Terranes)


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Some Landmarks…

North Cascades

South Cascades

Mt. Baker

Snoqualmie

Batholith

Chilliwack

Batholith

Glacier Peak

Tatoosh

Batholith

Mt. Rainier


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West Cascade Rocks in WA

Fifes Peak

Formation

  • Basaltic andesite

  • Andesite

  • Rhyolite

  • Tuff

  • Conglomerate (lahars)

  • Greywacke

Stevens Ridge

Formation

Ohanapecosh

Formation


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West Cascade Rocks in WA

Granodiorite Batholiths


Erosion of the west cascade arc l.jpg

G-3

Erosion ofthe West Cascade Arc

Produces major sedimentary formations to the east and west


West of the arc mid eocene l.jpg
West ofthe ArcMid-Eocene

D-3

Tukwila Formation

Seattle


West of the arc late eocene oligocene l.jpg
West ofthe ArcLate-Eocene & Oligocene

D-4

Blakeley Formation

Seattle


West of the arc miocene l.jpg
West ofthe ArcMiocene

D-5

Seattle


East of the arc john day fossil beds national monument l.jpg
East of the ArcJohn Day Fossil Beds National Monument

Painted Hills (Pete Yamagata)


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G-3

John Day National Monument, Oregon

Rhino skull


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Clarno Formation (54-37 Myrs)

"Rhinoceros" - Hyrachyus

Creodont - Patriofelis

Small browsing "horse” - Orohippus

Crocodile - Pristichampsus

Brontothere - Telmatherium

Magnolia - Magnolia

Black walnut - Juglans

Palm - Sabalites

Horsetail - Equisetum

Chestnut - Castanea

Fig - Ficoxylon

"Grape" - Vitis

Cycad - Dioon

Sycamore - Platanusycamore Platanus


John day formation 39 18 myrs l.jpg
John Day Formation (39-18 Myrs)

Sabre-toothed "tiger" - Pogonodon

Oreodont - Eporeodon

Three-toed "horse" - Miohippus

Tortoise - Stylemys

Mouse-deer - Hypertragulus

"Dog" - Mesocyon

Oreodont - Promerycocherus

"Rhinoceros" - Diceratherium

Chestnut oak - Quercus

Hawthoren - Crataegus

Fern - Polypodium

Hackberry - Celtis

"Maple" - Acertis

"Maple" - Acer


Mascall formation 15 12 myrs l.jpg
Mascall Formation (15-12 Myrs)

Early mastodon - Zygolophodon

Rhinoceros - Teleoceros

Giraffe-deer - Dromomeryx

Mountain beaver - Mylagaulus

Dog - Telmatherium

Camel - Miolabis

Pony-sized horse - Merychippus

Swamp cypress - Taxodium

Ginkgo - Ginkgo

Sassafras - Sassafras

Serviceberry - Amelanchier

Cattail - Typhaer

Cattail - Typha


Rattlesnake formation 8 6 myrs l.jpg
Rattlesnake Formation (8-6 Myrs)

Short-faced bear -Indarctos

Single-toed horse - Pliohippus

Peccary - Prosthennops

Dog - Canis

Hyena-like dog - Osteoborus

Elephant - Tetralophodon

Elm - Ulmus

Sycamore - Platanus

Willow - Salix



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