Introduction
• The Cenozoic began
~65 mya and continues until the present
– Cenozoic rocks are more easily accessible and less deformed than older rocks
– divided into the Tertiary and Quaternary

Early Work on the Cenozoic
• Charles Lyell England’s foremost geologist of his day.
• Author of Principles of Geology (1830)
• Supported James Hutton's concepts of
Uniformitarianism
• Teacher of Charles Darwin
Charles Lyell studied the Tertiary and Quaternary fossils of
France
Defined the Eocene, Miocene, Pliocene, Pleistocene, and
Holocene
Paleocene and Oligocene were added later

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Mantle upwelling
Colorado Plateau
Washington
Laramide uplifts eroded away
Rockies

• Cenozoic Tectonic activity concentrated in two areas
– Alpine-Himalayan belt deformation began in the Mesozoic and remains geologically active.
Isolation of Tethys to form the modern Mediterranean Sea
– circum-Pacific belt deformation occurred throughout the
Cenozoic

Cenozoic Pacific realm
1. Subduction of the Farallon Plate and its Mid Ocean Ridge
San Andreas forms 2. Formation of Andean Cordillera

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Mantle upwelling
Colorado Plateau
Washington
, Basin & Range
San Andreas Fault
Rockies

• Circum-Pacific Orogenic belt
–Laramide Lt. Jur - E Tertiary
–further inland than most - CLUE
–deformation was vertical uplift, with little volcanism
–shallow subduction angle
–“buoyant subduction”

Laramide Orogeny K to T
Buoyant Subduction
• One possible result of shallow angle of subduction and the drag that it causes with overlying lithosphere is uplift - Rocky
Mountain formation.
• Renewed normal subduction would restore normal volcanism within the western part of the mountains – Basin and Range

Uplift of the Rocky Mountains
Rockies shear stress
Basin and Range

Teton Range
Laramide uplifts eroded away in Oligocene, renewed uplifts Late Mio – Pleist.

Basin and Range of Cordillera
Columbia River Basalts
Basin and Range
Beginning in the Miocene, 2 mechanisms
1. lessening of the subduction angle allows dewatering volcanism further west.
2. Farallon pieces under the lithosphere cause uplift, lithosphere cracking and buoyant decompression magmas.

Basin and Range terminology
DISCUSSION, SHIP HULLS
Extensional Feature w/ Normal Faults

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Mantle upwelling
Colorado Plateau
Washington
San Andreas Fault, Basin & Range
Rockies

San Andreas transform
Ridges Change Orientation 15 mya SAF forms

The Interior Lowlands
• Sediments eroded from the Laramide highlands were deposited in the
Cannonball Sea Early Paleocene south to North Dakota.
– Terrestrial deposits are also found, but much of this area was experiencing erosion
– Igneous activity was significant in some areas - New Mexico, Colorado, Wyoming, and others
– East of the Great Plains, deposits other than glacial are rare until the eastern coastal plain.

The Gulf Coastal Plain • The Tejas epeiric sea transgressed briefly over the southeastern coastal plains
E. Tertiary
– eight minor transgressiveregressive sequences are recognized as sea level fell in general – reduced rifting

East Coast
• Passive margin sedimentation dominates
– rocks form a seaward thickening wedge that dips gently seaward
– Cenozoic uplift and erosion produced the present topography of the Appalachians
– Coastal Plain a thick clastic wedge
– Florida Carbonates Pliocene - Recent

Eastern North America
Allegheny Orogeny still high
Erosion due Transgression
Coastal Plain streams and marshes
Appalachians rejuvenated recently, probably glacial rebound

1.Alpine Orogen
2. Eocene to Miocene
Apennine Balkan Carpathian Caucasus Pyrenees Atlas
3. Vocabulary:
4.Closing of the Tethys Sea
Isolation of the Mediterranean Basin: Evaporites
Nappe
Large recumbent folds in thrust-fault zones where orogenic belts impinge craton margins
Flysch alternating thin shales and sandstones. Sandstones turbidites prior orogenic collision.
Molasse non-marine deposits accompanying the uplift of a mountain belt.

Nappe-folded mountains

New Orogen, Nappes still visible http://www.geol-alp.com/chartreuse/3_tecto_chartreuse/1_ch_occ.html

source

Arabian-African Rift
3. Messinian Salinity Crisis ~ 5.5 mya
1. The underside of Europe collided with numerous microplates rifted from Africa
Closing of the Tethys Sea between late
Mesozoic and early Cenozoic time
4. Thrusts not Subduction
2. Pliocene three way rift.
3. Arabia Microcontinent collision -> Zagros Mts

Himalayan Orogeny
Thin-skinned tectonics
Subduction
Partly subducted so under AW

Himalayan Orogeny
Zoomed-in Views
AW
FAB

South
Generalized Cross-Section
North

Décollement
• Décollement (from the French 'to detach from') is a gliding plane between two rock masses, also known as a basal detachment fault.
• Décollements result in independent styles of deformation in the rocks above and below the fault.
• Both compressional settings (involving folding and overthrusting) and extensional settings.

Cenozoic Climates, Currents, and
Volcanism
• Ocean current flow changes due to tectonics in Antarctic-Australian and
Central American regions
• Dramatic changes in climate
• Major plume under North America
• Continuous cooling, culminating in on-going Ice Age

Cenozoic Cooling
Australia separates
Central
America construction
Starts see
Monterey Fm.
(Northern
Hemisphere)

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Panama Closes
Mediterranean Dries Out
Circumpolar Current
Antarctica
High CO2
Rockies

Antarctic Circumpolar Current
Paleocene to Mid-Eocene
WARM Currents from Tropics

Oil Shales
Early Eocene Warm
Green River Formation

Green River Formation
Lake (lacustrine) silts
Organic-rich (oil) shales w/ fossils

Green River Formation
Tropical Plants to High Latitudes

Antarctic Circumpolar Current
2. Late Eocene
Sudden Antarctic cooling as warm currents barred
3.
5. Longest continuous Ice Sheets
4. Fauna changes. Example: Penguin relationships from S. American bird following current rich in fish.
1. Australia pulls away

Fossils in volcanic tuff deposit
Cooler
Tree stumps, insects in Oligocene Ash, Florissant, Colorado
Extensive Volcanism Late Eocene to Oligocene

Pre Gulf Stream Current
Isthmus of Panama open, same salinity
Atlantic and Pacific
Early Pliocene

Modern Gulf Stream Current
1. Terranes, Subduction, Volcanic Arc,
Isthmus of Panama closed, North Atlantic isol., higher salinity, dense cool water sinks before it reaches Arctic, polar sea freezes
Late Pliocene
Mediterranean Dried Out
2. Caused Formation of the present Gulf Stream Current in the Atlantic
3. Dramatic Cooling

Late Pliocene 5.96 to 5.33 mya
Messinian Salinity Crisis
– recall salt buoyancy, low competence
Evaporites, Gorges, Faunal Exchanges

• Bears
• Camels
• Cats
• Dogs
• Elephants
• Horses
The Great Exchange
North America
Anteaters
• Peccaries
• Rabbits
Armadillos
Capybaras
• Raccoons
• Skunks
Glyptodonts
Monkeys
• Tapirs
South America
Opossums
• Weasels
Porcupines
Sloths
Late Pliocene,
Isthmus of Panama
Toxodonts closed, migrations
North and South

With cooling comes drought. Grasses replaced forests, mammals adapted for a diet of grass, grew larger, faster as predators pursued .

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Mantle upwelling
Colorado Plateau
Washington
Laramide uplifts eroded away
Rockies

Pliocene 2000 m uplift of Colorado Plateau
(Grand Canyon - Colorado River incised )
Evidence,
Incised meanders

The Yellowstone Plume
• Miocene to Recent
• Starts with flood basalts in Columbia
Plateau Washington and Oregon 15 mya
• Continues into Snake River Basin
• Then to Yellowstone in Holocene

Basalt flows - Columbia Plateau
Miocene 15 – 12 mya
Start of Plume forming Snake River Plateau and recently Yellowstone
Just like the Watchungs

Craters of the Moon Monument
Migration of Snake River Basin over the plume 10 mya
Migration of Yellowstone Park over the plume 2 mya to recent

Geologic Events Cenozoic
(Longest Tertiary Epoch)
Rockies

Pleistocene Glaciation
• The Pleistocene began about 1.8 – 1.6 mya and ended about 10,000 years ago
– several intervals of widespread glaciation took place, separated by warmer intervals

Causes of Ice Ages
• Plate Tectonics
Moves Continents to Poles
Raises mountains above snowline
• Orbit distance, Axis Tilt and Wobble
– Moderates solar radiation north of 65 N
– Milankovitch Cycles ~ 100,000 years
– Low summertime radiation 65 N, glaciers expand

Milankovitch Cycles
Discussion: cool summers and wet winters
Moisture content of air masses
100,000 years

Warm Wet Winter
Cool Summer
Cold Dry Winter Hot
Summer
41,000 years

Discussion: Perihelion and Aphelion
25,700 years

Louis Agassiz
• Swiss Geologist
• Eventually Professor of Geology at
Harvard
• Familiar with Alpine Glaciers
• Recognized Moraines, erratic boulders, and scoured bedrock in Europe and N.Am
• Proposed huge glaciations Europe and N.
America

Glacial and Interglacial Stages
C-14 works here
Medieval warm 900-1300
Little Ice Age 1300 -1850
65 (ongoing)
50
140
35
135
65
(Many)
Glacial advances named for states

Foraminifera tests - Ice Age
Warm Cold
Wisconsinan
Illinoian
About 30 pulses in
4 or so major groups
Kansan
Nebraskan
3. Also spiral direction & diversity depends on Temp.
1. Evap. water and CO
2 removes 16 O from oceans
18 O left in oceans used to make shells
2. Ice traps CO
2 and water with light oxygen

The Effects of Glaciation
• The effects of glacial erosion and deposition are evident worldwide
– lowering of sea level affected base level of streams
– pluvial lakes
– proglacial lakes
– Compression of the Crust

Pluvial Lakes
Pleistocene Lakes - West
Remnant of Bonneville

Lake Bonneville terraces
Much deeper that GSL

(melting)