The Geology of the Cenozoic Era

The Geology of the The Geology of the Cenozoic EraCenozoic Era

IntroductionIntroduction• 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 CenozoicEarly 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 FranceDefined the Eocene, Miocene, Pliocene, Pleistocene, and HolocenePaleocene and Oligocene were added later

Geologic Events CenozoicGeologic Events Cenozoic

Laramide uplifts eroded away

Mantle upwelling Colorado Plateau

Rockies

Washington

(Longest Tertiary Epoch)

• 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 realmCenozoic Pacific realm1. Subduction of the Farallon Plate and its Mid Ocean Ridge

2. Formation of Andean Cordillera San Andreas forms

Geologic Events CenozoicGeologic Events Cenozoic

Mantle upwelling Colorado Plateau

Rockies

Washington

(Longest Tertiary Epoch)

, Basin & Range

San Andreas Fault

• 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”

Cordillera Cordillera

Laramide Orogeny K to TLaramide Orogeny K to TBuoyant SubductionBuoyant 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

Basin and Range

shear stress

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

Basin and Range of CordilleraBasin and Range of Cordillera

Beginning in the Miocene, 2 mechanisms1.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

Columbia River Basalts

Basin and Range terminologyBasin and Range terminology

Extensional Featurew/ Normal Faults

DISCUSSION, SHIP HULLS

Geologic Events CenozoicGeologic Events Cenozoic

Mantle upwelling Colorado Plateau

Rockies

Washington

(Longest Tertiary Epoch)

San Andreas Fault, Basin & Range

San Andreas transformSan Andreas transform

Ridges Change Orientation 15 mya SAF forms

The Interior LowlandsThe 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 PlainThe Gulf Coastal Plain • The Tejas epeiric sea transgressed briefly over the southeastern coastal plains E. Tertiary– eight minor

transgressive-regressive sequences are recognized as sea level fell in general – reduced rifting

East CoastEast 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 AmericaEastern North America

Appalachians rejuvenated recently, probably glacial rebound

Allegheny Orogeny still high

Erosion due Transgression

Coastal Plain streams and marshes

1.Alpine Orogen1.Alpine Orogen

3. Vocabulary: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.

4.Closing of the Tethys Sea

Apennine Balkan Carpathian Caucasus Pyrenees Atlas

Isolation of the Mediterranean Basin: Evaporites

2. Eocene to Miocene

Nappe-folded mountainsNappe-folded mountains

http://www.geol-alp.com/chartreuse/3_tecto_chartreuse/1_ch_occ.html

New Orogen, Nappes still visible

source

Arabian-African RiftArabian-African Rift1. The underside of Europe collided with numerous microplates rifted from Africa Closing of the Tethys Sea between late Mesozoic and early Cenozoic time4. Thrusts not Subduction3. Messinian Salinity Crisis ~ 5.5 mya

2. Pliocene three way rift.

3. Arabia Microcontinent collision -> Zagros Mts

Himalayan OrogenyHimalayan Orogeny

Thin-skinned tectonics

Partly subducted so under AW

Subduction

Himalayan OrogenyHimalayan Orogeny

AW

FAB

Zoomed-in Views

Generalized Cross-SectionGeneralized Cross-Section

South North

DécollementDécollement

• 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 Cenozoic Climates, Currents, and VolcanismVolcanism

• 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 CoolingCenozoic Cooling

(Northern Hemisphere)

Australia separates Central America

constructionStarts see

Monterey Fm.

Geologic Events CenozoicGeologic Events Cenozoic

(Longest Tertiary Epoch)

Circumpolar Current Antarctica

Panama Closes

High CO2

Mediterranean Dries Out

Rockies

Antarctic Circumpolar CurrentAntarctic Circumpolar CurrentPaleocene to Mid-Eocene

WARM Currents from Tropics

Early Eocene Warm Early Eocene Warm Green River FormationGreen River Formation

Oil Shales

Green River FormationGreen River Formation

Lake (lacustrine) siltsOrganic-rich (oil) shales w/ fossils

Green River FormationGreen River Formation

Tropical Plants to High Latitudes

Antarctic Circumpolar CurrentAntarctic Circumpolar Current

4. Fauna changes. Example: Penguin relationshipsfrom S. American bird following current rich in fish.

2. Late EoceneSudden Antarctic cooling as warm currents barred

5. Longest continuous Ice Sheets

1. Australia pulls away

3.

Fossils in volcanic tuff depositFossils in volcanic tuff deposit

Tree stumps, insects in Oligocene Ash, Florissant, ColoradoExtensive Volcanism Late Eocene to Oligocene

Cooler

Pre Gulf Stream CurrentPre Gulf Stream CurrentIsthmus of Panamaopen, same salinityAtlantic and Pacific

Early Pliocene

Modern Gulf Stream CurrentModern 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

2. Caused Formation of the present Gulf Stream Current in the Atlantic

3. Dramatic Cooling

Mediterranean Dried Out

Late Pliocene 5.96 to 5.33 myaLate Pliocene 5.96 to 5.33 mya

Evaporites, Gorges, Faunal Exchanges

Messinian Salinity Crisis – recall salt buoyancy, low competence

The Great ExchangeThe Great Exchange• Bears• Camels• Cats• Dogs• Elephants• Horses• Peccaries• Rabbits• Raccoons• Skunks• Tapirs• Weasels

AnteatersArmadillosCapybarasGlyptodontsMonkeysOpossumsPorcupinesSlothsToxodonts

South America

Late Pliocene, Isthmus of Panamaclosed, migrations North and South

North America

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

pursuedpursued. .

Geologic Events CenozoicGeologic Events Cenozoic

Laramide uplifts eroded away

Mantle upwelling Colorado Plateau

Rockies

Washington

(Longest Tertiary Epoch)

Pliocene 2000 m uplift of Colorado Plateau Pliocene 2000 m uplift of Colorado Plateau

(Grand Canyon - Colorado River incised )(Grand Canyon - Colorado River incised )

Evidence,Incised meanders

The Yellowstone PlumeThe Yellowstone Plume

• Miocene to RecentMiocene to Recent• Starts with flood basalts in Columbia Starts with flood basalts in Columbia

Plateau Washington and Oregon 15 Plateau Washington and Oregon 15 myamya

• Continues into Snake River BasinContinues into Snake River Basin

• Then to Yellowstone in HoloceneThen to Yellowstone in Holocene

Basalt flows - Columbia PlateauBasalt flows - Columbia Plateau

Miocene 15 – 12 myaStart of Plume forming Snake River Plateau

and recently Yellowstone

Just like the Watchungs

Craters of the Moon MonumentCraters of the Moon Monument

Migration of Yellowstone Park over the plume 2 mya to recent

Migration of Snake River Basin over the plume 10 mya

Geologic Events CenozoicGeologic Events Cenozoic

(Longest Tertiary Epoch)

Rockies

Pleistocene GlaciationPleistocene 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 AgesCauses 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 Milankovitch Cycles

100,000 years

Discussion: cool summers and wet wintersMoisture content of air masses

41,000 years

Cold Dry Winter Hot Summer

Warm Wet Winter Cool Summer

25,700 years

Discussion: Perihelion and Aphelion

Louis AgassizLouis 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 StagesGlacial and Interglacial Stages

65

(Many)

135

35

140

50

65 (ongoing)

Glacial advances named for states

C-14 works hereMedieval warm 900-1300Little Ice Age 1300 -1850

Foraminifera tests - Ice AgeForaminifera tests - Ice Age

1. Evap. water and CO2

removes 16O from oceans18O left in oceans used to make shells

3. Also spiral direction & diversity depends on Temp.

Nebraskan

Kansan

Illinoian

Wisconsinan

About 30 pulses in 4 or so major

groups

ColdWarm

2. Ice traps CO2 and water with light

oxygen

The Effects of GlaciationThe 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

Pleistocene Lakes - WestPleistocene Lakes - WestPluvial Lakes

Remnant of Bonneville

Lake Bonneville terracesLake Bonneville terraces

Much deeper that GSL

Terminal Moraine

(melting)