The Modern World Emerges
Tectonics

• The volcanic null that corresponded with the Laramide
Orogeny starting in the late Cretaceous ended in the late
Eocene epoch (~40Ma) with the resumption of arc magmatism along the western margin of NA
• Starting in the Miocene (~20Ma), the collision of the East
Pacific Rise created a transform boundary between the
Pacific and NA plates; this brought on the Basin and
Range-style extension tectonics, the uplift of the
Colorado Plateau, the creation of the Rio Grande Rift, and shift in the motion of the Pacific plate
• The collision of India and various microcontinents spalled from Gondwana’s break-up closed the Tethy’s Sea and created the Alpine-Himalayan orogenic belt

Early Cenozoic (66-40 Ma)
Paleocene - Mid-Eocene
Laramide
Orogeny
Block uplift of the
Precambrian basement

Laramide Orogeny
Magmatic Null Zone – Shallow Slab Subduction

Sedimentation in Laramide
Intermontane Basins
GR
BH
WR
U
PR
Coal Seams in the Powder River Basin, WY
Lacustrine Shales Marls Bryce Canyon NP, UT
Lacustrine Shales of the Green River Basin, UT

Middle Cenozoic (40-20 Ma)
Late Eocene – Oligocene – Mid-Miocene
Resumption of continental volcanic arc magmatism as subduction of the Farallon
Plate steepens
Tectonics during the
Oligocene (~30 Ma)

Middle Cenozoic (40-20 Ma)
San Juan Volcanic Field
La Garita Caldera (28Ma)
San Luis Tuff, Wheeler Geologic Monument

Middle Cenozoic (40-20 Ma)
Burial and Exhumation of the Laramide Mountains
Laramide Mtns Exhumed
66Ma
35 Ma
Laramide Mtns Re-Buried
Laramide Mtns Buried
57 Ma
15 Ma
Laramide Mtns Re-Exhumed
50 Ma

Laramide Sediments and Volcanic Ash
Spreads across the Great Plains
Eocene –
Oligocene fluvial sediments of the
White River
Group,
Badlands, SD

Late Cenozoic (20-0 Ma)
Mid-Miocene – Pliocene –Pleistocene - Holocene
Mid-Miocene (~15 Ma) Pliocene (~5 Ma)
Collision of East Pacific Rise with NA plate creates the San Andreas
Transform Fault System, Basin and Range Province, Colorado Plateau and Rio Grand Rift

Basin and Range Province
Extensional Thinning of the Crust
Sevier Deformation
Listric Normal Faults

Basin and Range Province
Extensional Thinning of the Crust

Basin and Range Province
Extensional Thinning of the Crust
Extension due to mantle upwelling in area of Slab Gap

Extensional Thinning of the Crust
As the SA transform boundary grows, Basin and Range Extension migrates to the North. Establishment of rift zone in the Gulf of
California kills extension in the southern Basin and Range.

Narrow fault –bound basins rapidly fill with great thickness of sediment that are simultaneously deformed (e.g., Ventura Basin)
Pliocene (~5 Ma)

Uplift of the Colorado Plateau
Rejuvenation of Mature Rivers
Mantle
Upwelling?
Pliocene (~5 Ma)

Columbia River Basalts, Snake River
Basalts, and the Yellowstone Hotspot
Edge of
Craton
Yellowstone
Newberry

Mantle Plume-Generated Volcanism
Columbia River Basalts
Yellowstone Hydrothermal Field Newberry Rhyolite

Erosion of North America – River and Deltaic Deposits
Triassic-sourced Halite Deposits
Pangea Break-up – Shallow Marine Deposits

Rejuvenation of the Appalachians

The
Closing of the Tethys
Sea

4 Ma
Straits of Gibraltar open up
25 Ma
The Closing of the Tethys Sea
5-6 Ma
Mediteranean Dries
Up -Evaporites

Next Lecture
The Cenozoic
The Modern World Emerges
Climate and Life
Overview of Field Trip