lecture 36 - university of south alabama€¢major late tertiary flood basalt eruptions occur in...
TRANSCRIPT
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
eroz
oic
Introducing the Epochs (the smallest common divisions of geological time)
Cenozoic Time Frame C
enoz
oic
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 [email protected]
This is a free open access lecture, but not for commercial purposes. For personal use only.