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Oxygen Isotopes Pollen and spores Micropaleontology- shifts in biozones Tree rings

The Quaternary is a time when paleoclimate change is becoming well established. Proxies for climate change include:. Oxygen Isotopes Pollen and spores Micropaleontology- shifts in biozones Tree rings Geochemical proxies Laminated sediments (varves) Ice cores Ice-rafted debris and dust.

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Oxygen Isotopes Pollen and spores Micropaleontology- shifts in biozones Tree rings

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  1. The Quaternary is a time when paleoclimate change is becoming well established. Proxies for climate change include: • Oxygen Isotopes • Pollen and spores • Micropaleontology- shifts in biozones • Tree rings • Geochemical proxies • Laminated sediments (varves) • Ice cores • Ice-rafted debris and dust

  2. Pollen and Spores

  3. Tree Rings

  4. Varves • Light-colored layer of silt and clay • formed during the summer • The dark layer made up of smaller particles and organic matter • Result from seasonal lake overturn

  5. Top friday

  6. Pleistocene Fluctuations You Are Here! Northern Hemisphere Glaciation Cyclicity

  7. Oxygen isotope curves provide information about temperature, ice volume as well as a chronostratigraphic tool

  8. Closing of the Isthmus of Panama • Shut off E/W global ocean flow American plates collided ~ 3.5 Ma

  9. This may have resulted in glaciation in the northern hemisphere Caribbean warms Gulf Stream moves warm water north Increases ocean evaporation and precipitation on land

  10. The Milankovitch Theory • Put forth by the Yugoslavian astronomer • Milutin Milankovitch during the 1920s • Minor irregularities in Earth's rotation and orbit • are sufficient to alter the amount of solar radiation that Earth receives at any given latitude • and hence can change climate - 100 ka, 40 ka and 20 ka are main cycles

  11. Three Variables Ellipticity • about 100,000 years

  12. Precession • Earth moves around the Sun • spinning on its axis • which is tilted at 23.5° to the plane of its orbit • Earth’s axis of rotation • slowly moves • and traces out the path of a cone in space Plane of Earth’s Orbit

  13. Effects of Precession • At present, Earth is closer to the Sun in January • In about 11,000 years, closer to the Sun in July

  14. Glaciers in North America

  15. Glaciers in Europe

  16. Four Glacial Stages • Detailed mapping reveals several glacial advances and retreats • North America had at least four major episodes of Pleistocene glaciation • Each advance was followed by warmer climates • The four glacial stages • Wisconsin • Illinoian • Kansan • Nebraskan • named for the states of the southernmost advance

  17. GLACIATIONS IMPACT • Climate Sea level change • Sediments • Landforms and topography • Isostatic rebound

  18. Isostatic Rebound in Eastern Canada • Uplift in meters • during the last 6000 years

  19. Terraces used to measure isostatic uplift

  20. Warming Trend • 10,000-6,000 years ago, a warming trend • pollen • tree rings • ice advance/retreat • Then the climate became cooler and moister • favoring the growth of valley glaciers on the Northern Hemisphere continents • Three episodes of glacial expansion took place during the neoglaciation

  21. Late Holocene Climate change

  22. Ice CoreRecordsshows rapidclimate shifts

  23. Little Ice Age • The most recent glacial expansion • between 1500 and the mid- to late 1800s • was a time of generally cooler temperatures • It had a profound effect on • the social and economic fabric of human society • accounting for several famines • migrations of many Europeans to the New World Pieter Bruegel the Elder (1525–1569)

  24. Decreasing Carbon Dioxide • One proposed mechanism for the onset of the cooling trend • is decreased levels of carbon dioxide (CO2) in the atmosphere • Carbon dioxide is a greenhouse gas • so if less were present to trap energy • Earth's overall temperature would perhaps be low enough for glaciers to form

  25. Eustasy and Coastal Evolution

  26. Isn't it stable? We can watch it breaking up

  27. Cape Cod Lobe • Position of the Cape Cod Lobe of glacial ice • 23,000 to 16,000 years ago • when it deposited the terminal moraine • that would become Cape Cod and nearby islands

  28. Recessional Moraine • Deposition of a recessional moraine • following a retreat of the ice front

  29. Cape Cod • By about 6000 years ago • the sea covered the lowlands • between the moraines • and beaches and other shoreline features formed

  30. Land Bridge • Large areas of today's continental shelves were exposed • The Bering Strait exposed • Alaska connected with Siberia via a broad land bridge • Native Americans and various mammals, such as the bison, migrated

  31. Gulf Coast Evolution

  32. N S 6 ms Corpus Christi Bay

  33. Rapid Evolution of Bays

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