The Geology of the Cenozoic Era
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Transcript of 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)