CAS ES 351 Chapter Notes - Chapter 7: Ice Rafting, Oxygen-18, Continental Margin
25 Mar 2019
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Document Summary
Chapter 7: from greenhouse to icehouse: the last 50 million years. As climate cools, mountain glaciers and large ice sheets form. In the southern hemisphere, no ice exists until about 35 million years ago when ice- rafted debris was first deposited in ocean sediments on the nearby continental margin. The first continental ice sheets of significant size appeared about 2. 75 million years ago. The appearance of tundra and permafrost is thought to be linked to the onset of frigis winters and expanding sea ice. The shapes of trees leaves have also been used to reconstruct past climate. The most important climate record in the ocean is the oxygen isotope record. Formaminifera use ions dissolved in seawater as the source of carbon and oxygen for their shells, so it gives us climate proxy data. 18o variations come from changes in temp and the size of ice sheets on continents. So the more warm the water is, the more negative 18o is.
