Plio-Pleistocene Geology GY 112: Earth History UNIVERSITY OF SOUTH ALABAMA
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UNIVERSITY OF SOUTH ALABAMA GY 112: Earth History Plio-Pleistocene Geology Instructor: Dr. Douglas W. Haywick Last Time A) Cenozoic Tectonics • • Western North American tectonic provinces Plateaus and canyons 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 Uplift And uplift now affects the SW Today http://www.geology.wisc.edu/courses/g109/Additional/plate_motions.htm 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) Today’s Agenda 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 Web notes 37 Cenozoic Tectonics Key tectonic style: simple uplift Laramide Orogeny Cenozoic Tectonics One explanation for the uplift and high heat flow is shown here… ... low thrust angle shifts heat/magma generation eastward. Cenozoic Tectonics One explanation for the uplift and high heat flow is shown here… Another consideration is that we have increased convection associated with the East Pacific Rise that we ran over starting 20 million years ago Cenozoic Tectonics Several important basins and tectonic provinces are recognized in the western USA Cenozoic Tectonics Important Basins 1) Green River Basin 2) Uinta Basin 3) Washakie/Sandwash Basins 4) Piceance Creek Basin 1 3 2 4 Cenozoic Tectonics 1 3 2 4 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 3 2 4 Cenozoic Tectonics Important Tectonic Provinces http://www.huttoncommentaries.com/subs/PSResearch/Strain/Fig8.gif Cenozoic Tectonics 1) Basin and Range Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau Cenozoic Tectonics 1) 2) 3) 4) Basin and Range Colorado Plateau Columbia River Plateau Rio Grande Rift Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau Basin and Range Cenozoic Tectonics Basin and Range: Uplifted deformed strata Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau Colorado Plateau Cenozoic Tectonics Colorado Plateau: Uplifted undeformed strata Cenozoic Tectonics • Miocene – Columbia Plateau basalts • Up to 5 km thick Cenozoic Tectonics Columbia River Plateau: Basalt lava flow covered terrain Cenozoic Tectonics Rio Grande Rift: Uplifted rifting strata Cenozoic Tectonics Rio Grande Rift: Uplifted rifting strata 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 http://www.sfu.ca/~qgrc/subduction.JPG Cenozoic Tectonics 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 Is most notable for rapid, short duration shifts in temperature and ice volume. Why? 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 We now recognize two major Earth climatic phases 1) Greenhouse Earth (no continental glaciers present) 2) Icehouse Earth (continental glaciers present) http://www.snowballearth.org/end.html Paleoclimate Phases Icehouse Earths fluctuate between 2 stages: a) Glacial stage (18 KA) b) Interglacial stage (Today) 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. Time Chart 3 due Thursday April 30th 2. Lab exams for Haywick’s classes tomorrow Next Time 1. Review Session GY 112: Earth History Lectures 37: 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.
