Historical Geology 102
Cenozoic Era I

Cenozoic Era

Traditional divisions of the Cenozoic
- Tertiary Period 66 - 1.6 m.y.
- Quaternary Period 1.6 m.y. - present
European/Modern divisions of the Cenozoic
- Paleogene Period 66 - 24 m.y.
- Neogene Period 24 m.y. - present

Epochs of the Cenozoic

"-cene" means recent
- Holocene "whole recent" epoch
- Pliestocene "most recent" epoch
- Pliocene "more recent" epoch
- Miocene "less recent" epoch
- Oligocene "small or scant recent" epoch
- Eocene "early recent" epoch
- Paleocene "old recent" epoch

Eocene Paleogeography
Miocene Paleogeography
Pleistocene Paleogeography
Holocene geography

Cenozoic Tectonic Events

Major tectonic event
- Laramide Orogeny
Eastern margin of North America
- continued erosion of Appalachians
- periods of minor uplift resulted in increased rates of erosion
- deposition on continental shelf
- mature passive margin fully developed
Western margin
- Cenozoic volcanism
- Colorado Plateau uplift and volcanism
- Basin and Range deformation
- San Andreas Fault development

Cenozoic Volcanism

Extensive volcanic activity throughout this Era
Four major areas of concentration
- Columbia River Plateau
- Snake River Plain
- Cascade Range
- Colorado Plateau

Columbia River Plateau

Late Miocene to Pleistocene age
Huge volumes of flood basalts erupted
- 500,000 km2 area covered
- 200,000 km3 volume erupted
The Roza Flow covers 40,000 km2 and is 300 km long (QCA to St. Louis)
Low viscosity flows capable of rapid flow
Related to mantle hot spot??

Snake River Plain

Eastward extension of the Columbia River Plateau.
Crustal depression filled with Pliocene and younger basalt flows.
Oldest flows are in the west, with younger flows located in the east.
This pattern suggests that North America is drifting over a hot spot that is currently located beneath Yellowstone N.P.
Others have argued that this region is the site of a rift zone which hasn't fully developed.

Cascade Range

Most recent continental volcanics
Located in N. California, Oregon and Washington
- Mount St. Helens
- Mount Hood
- Mount Lassen
- Mt. Shasta
- Mount Rainier
- Mount Baker
Related to the subduction of the Juan de Fuca Plate (remnant of Farallon Plate that is still being subducted).

Colorado Plateau

Area of uplift and volcanism
Area of relatively little deformation since Mazatzal-Yavapai Province addition, 1.8-1.6 b.y.
-area of marine and continental sediments
Pliocene to late Miocene
- series of uplifts
Large fault systems and gentle folding accompanied the uplifting
Area of erosion since uplift
- Grand Canyon N. P.
- Canyonlands N.P.
- Arches N.P.
Volcanism is also associated with the Colorado Plateau
Volcanic activity is located along the margins of the Plateau

Basin and Range Deformation

Tensional forces in the western portion of North America have resulted in extension of the crust
Extension began in late Miocene Large
North-south trending faults have developed in Nevada
Northwest-southeast trending faults in AZ, NM and TX
Basins result from down dropped blocks
Ranges from highland footwall blocks
Extension is active today

San Andreas Fault

Related to the subduction of the Farallon Plate
Boundary between the Farallon Plate and the Pacific Plate (mid-ocean ridge) was also subducted
North America came into direct contact with the Pacific Plate
San Andreas Fault develops as both North America and the Pacific Plate are moving in the same direction
Pacific Plate is moving faster than N.A.