GY 112: Earth History

Lecture 36: Plio-Pleistocene Geology

Instructor: Dr. Douglas W. Haywick

UNIVERSITY OF SOUTH ALABAMA

Last Time

A) Cenozoic Overview and Tectonics • Western North American tectonic provinces • Plateaus and canyons

Cenozoic Time Frame

Era Years Cenozoic (0 to 65 MA)

Mesozoic (65 to 245 MA)

Paleozoic (245 to 550 MA)

Phan

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Introducing the Epochs (the smallest common divisions of geological time)

Cenozoic Time Frame C

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Period Epoch

Quaternary (1.6 - 0 MA)

Holocene (10,000 – 0 years)

Pleistocene (1,600,000 – 10,000 years)

Tertiary (65-1.6 MA)

Pliocene (5.0 – 1.6 MA)

Miocene (24-5.0 MA)

Oligocene (37 - 24 MA)

Eocene (58- 37 MA)

Paleocene (65-58 MA)

• Mammals diversified – Most modern orders present by Early Eocene

Cenozoic Life

• Primates modernized in Oligocene – Monkeys – Apelike primates

• Aegyptopithecus

Cenozoic Life

• Mammalian carnivores evolved by mid-Paleogene

Cenozoic Life

• Spread of C4 grasses – C4 plants

• Incorporate more carbon 13 than C3 grasses

• Five times more silica – Wears down teeth of

grazers

Cenozoic Life

Cenozoic Deep Ocean Currents

Chalk Board

Cenozoic Tectonic Events

•Final breakup of Gondwanna (Australia separated from Antarctica in the Latest Paleocene – earliest Eocene epochs) •India began to collide with Asia forming the Himalayan Mountain Range (Oligocene to Recent) •Africa started to shift northward, gradually sliding under Europe and uplifting the Alps (Oligocene to Recent) •Continued westward movement of North America and South America formed an on again off again land bridge between the two continents. This gave rise to some interesting animal exchanges (see evolutionary events below). •North American orogenies become dominated by strike-slip faulting and uplift. Mountain building in the northern part of the Cordilleran mountains (mostly Canada) slows down stop during the Oligocene. Activity shifts to the southern part of the mountain chain (Colorado, Nevada etc.). •Major late Tertiary flood basalt eruptions occur in Oregon and Washington state. Hot spot volcanism occurs in the area of Yellowstone (Pliocene to present). Composite volcanic eruptions (some incredibly explosive) periodically occurred and still do (e.g., Mt St Helen’s).

Tectonic Events

• Cordilleran region – Laramide orogeny – New tectonic style

Cenozoic Tectonics

Eocene Tectonic elements:

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Cenozoic Tectonics

Miocene Tectonic elements:

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Cenozoic Tectonics

Modern Tectonic elements:

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Cenozoic Tectonics

As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise Eocene

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Cenozoic Tectonics

As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise Oligocene

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Cenozoic Tectonics

As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise And uplift now affects the SW Today

http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm

Uplift

Cenozoic Tectonics

Key tectonic elements: 1) Farallon Plate (east of East Pacific Rise; east drift) 2) Pacific Plate (west of East Pacific Rise; west drift)

Cenozoic Tectonics

Key tectonic elements: 1) Farallon Plate (east of East Pacific Rise; east drift) 2) Pacific Plate (west of East Pacific Rise; west drift) 3) Juan de Fuca Plate (east of East Pacific Rise; east drift) 4) Cocos Plate (east of East Pacific Rise; east drift)

Cenozoic Tectonics

Key tectonic style: simple uplift Laramide Orogeny

Cenozoic Tectonics

Important Basins

1) Green River Basin 2) Uinta Basin

3) Washakie/Sandwash Basins 4) Piceance Creek Basin

All are rich in oil shale

1

2

3

4

Cenozoic Tectonics

1) Basin and Range

Cenozoic Tectonics

1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau

Basin and Range

Basin and Range: Uplifted deformed strata

Cenozoic Tectonics

Cenozoic Tectonics

1) Basin and Range 2) Colorado Plateau

Cenozoic Tectonics

1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau

Colorado Plateau

Cenozoic Tectonics

Colorado Plateau: Uplifted undeformed strata

Cenozoic Tectonics

1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau

Cenozoic Tectonics

• Miocene – Columbia Plateau

basalts • Up to 5 km thick

Cenozoic Tectonics

Columbia River Plateau: Basalt lava flow covered terrain

Cenozoic Tectonics

1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau 4) Rio Grande Rift

Cenozoic Tectonics

Rio Grande Rift: Uplifted rifting strata

A) Finish off Cenozoic Tectonics B) Cenozoic temperature and sea level shifts C) Plio-Pleistocene Glaciations (Milankovitch Orbital Variations)

D) Sea level changes in our own back yard

Today’s Agenda

Web notes 37

Cenozoic Tectonics

Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone

http://people.uwec.edu/ERICKSKM/histor1.jpg

Cenozoic Tectonics

Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone 2) Crater Lake

http://people.uwec.edu/ERICKSKM/histor1.jpg

Cenozoic Tectonics

Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone 2) Crater Lake 3) Composite Volcanoes

http://people.uwec.edu/ERICKSKM/histor1.jpg

Cenozoic Tectonics ht

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Plio-Pleistocene Is most notable for rapid, short duration shifts in temperature and ice volume.

Plio-Pleistocene Is most notable for rapid, short duration shifts in temperature and ice volume.

Plio-Pleistocene

Why?

Is most notable for rapid, short duration shifts in temperature and ice volume.

Plio-Pleistocene • Glaciations started around

5 million years ago. • Isthmus of Panama

– Emplaced 3.5–3 M years ago

– Started modern circulation • Gulf stream carries salty

Atlantic north • Cools, sinks

– Oceanic conveyor belt • High latitudes cool

Milankovitch Cycles Three major changes in Earth’s orbit are linked to glacial oscillations

•Eccentricity •Obliquity •Precession

Milankovitch Cycles When taken together, the 3 cycles are capable of dropping temperatures globally

Milankovitch Cycles When taken together, the 3 cycles are capable of dropping temperatures globally. These cycles have been confirmed via stable isotope analysis of deep sea foraminifera (ice volume).

Paleoclimate Phases

1) Greenhouse Earth (no continental glaciers present)

2) Icehouse Earth (continental glaciers present)

We now recognize two major Earth climatic phases

http://www.snowballearth.org/end.html

Paleoclimate Phases

a) Glacial stage (18 KA) b) Interglacial stage (Today)

Icehouse Earths fluctuate between 2 stages:

http://www.ncdc.noaa.gov/paleo/abrupt/data2.html

The Present Ice House Earth

Glacial/ interglacial

stage

Name of stage Time frame

interglacial Holocene 0 - 10 KA

glacial Wisconsinian 10 – 75 KA

interglacial Sangamon 75 – 125 KA

glacial Illinoisan 125 – 265 KA

interglacial Yarmouth 265 – 300 KA

glacial Kansan 300 – 435 KA

interglacial Aftonian 435 – 500 KA

glacial Nebraskan > 500 KA

The Ice Age

• Glacial Maximum – Extent of continental

glaciation • Several lines of

evidence • 1) Erratic boulders

The Ice Age

• 2) Glacial till and basins associated with glaciation • 3) Depression of the land

– Hudson Bay

The Ice Age • Lowering of sea level

– Exposed continental shelves

The Ice Age

• Migration of species – Mammals crossed

Bering Strait on land corridors

– Vegetation changed in response to global changes

The Ice Age

• Ocean circulation changed during glaciation – Glacier in NJ – Tundra in Washington,

D.C.

The Ice Age • Great lakes

– Last glacial maximum • 35,000-10,000 years

ago • Wisconsin Stage

– Remained when ice sheets melted back

The Ice Age • Climate impacts were

felt globally – Steepened temperature

gradients – Increased aridity – Exception: Great Basin

• Lakes • Great Salt Lake

The Ice Age • Climate impacts were

felt globally – Sahara expanded – Rain forests restricted

• Isolated gorilla species

End of the Ice Age

• Glaciers began to retreat around 15,000 years ago – Waters drained to lakes – Sea level rose – Tundra shifted northward – Deciduous trees migrated

northward

Sea Level • Transgression

– Lagoonal complexes transgress over coastal plain sediments

• Regression – High sediment supply is causing coast to move offshore – Texas

Sea Level In southern Alabama, regressions caused the shoreline to shift 100 miles south. Base level of rivers dropped by 300 feet. The Mobile River carved a canyon, the remnants of which are still exposed along the Eastern Shore

Sea Level In southern Alabama, regressions caused the shoreline to shift 100 miles south. Base level of rivers dropped by 300 feet. The Mobile River carved a canyon, the remnants of which are still exposed along the Eastern Shore

The End

Today’s Homework 1. Study for finals!

2. Time Chart 3 due now 3. Do the online class survey (1% bonus)

4. Rate my Professor.com

Next Time 1. Final Exam

GY 112: Earth History

Lecture 36: Plio-Pleistocene

Instructor: Dr. Doug Haywick dhaywick@southalabama.edu

This is a free open access lecture, but not for commercial purposes. For personal use only.