Announcements:

Final Exam

Monday, Dec. 16, 11-1

this room

TODAY:

Structural Evolution of W. North America:

From Proterozoic to Present

Goals:

(1) Appreciation of "local" geology

(2) Interplay between plate tectonics and deformation

(3) Long and dynamic history of growth and deformation of continents

Archean – Middle

Proterozoic growth of

North America

Good old "Yankee" basement

Youngs from N to S

Middle Proterozoic to

Cambrian rifting of W.

U.S.

What rifted away???

Sedimentary evidence for a rifted continental margin: Late Proterozoic - Cambrian

Thermal subsidence following rifting

The margin of W. North America 500 Myr ago

All the crust to the west is either younger or was

torn off of some other continent and

subsequently attached to N.A.

Paleozoic passive margin sedimentation

along continental margin- beautifully preserved in

the Grand Canyon

But!: There was action going on to the west

during some of this time- Antler Orogen

(Devonian-Mississippian)

Cross section of the middle Paleozoic Antler Orogen

Growth of an outboard arc and disruption (by thrusting) of the passive margin

There was also action to the

east during late Paleozoic time

Collision between S.

America / Africa with SE U.S. to form ancestral

Rocky Mountains

The Permo-Triassic Sonoma orogeny:

"retro-arc" thrusting

The Sevier orogeny:

E-directed thrusting behind a magmatic

arc–

"retro-arc" fold-thrust belt and associated

foreland basin system

What's going on at this time (~60 myr ago?)

Eastward sweep in magmatism

Basement-involved deformation

"Laramide" orogeny

Magmatism starts sweeping back to west

– 45 Myr ago

More "Laramide" deformation

More westward sweep in magmatism-

Major change in style of deformation!

Rifting and development of

Cordilleran metamorphic core

complexes related to major crustal extension

Basin and Range Extension

Eruption of Columbia River basalts

Magmatism back to west

Growth of Basin and Range Province

Today!

Relating plate tectonics to continental deformation

Bigger picture: formation of the Cordilleras due to long-lived oceanic subduction

Concept of "Suspect" terranes- possibly far-traveled and torn off of other continents, rafted across large tracts of

oceans and finally accreted to W. N.A.

Crustal "immigration"

Reminder!:

Final Exam

Monday, Dec. 16, 11-1

this room

Next Lecture:

Review for final