Deep Sea Drilling

1. Deep Sea Drilling

2. + O18/O16 - CaCO3 Layer by layer sampling of plankton reveals oxygen isotope record

4. Ice stores O16 so that oceans are O16 depleted in an ice age

5. The record for the last 730,000 years indicates that eight major glacial and interglacial events or climatic cycles of about 100,000 years' duration occurred during this interval. Similar cycles but of greater frequency and lesser magnitude continue back to the late Pliocene.

6. Isotopic record from the North Atlantic suggests the first major glaciation in that region occurred about 2,400,000 years ago, some 800,000 years before the start of the Pleistocene. It also suggests that the first glaciation likely to have covered extensive areas of North America and Eurasia occurred about 850,000 years ago during oxygen isotope stage 22.

7. Largest glaciations took place in stages 2, 6, 12, and 16; interglacials with the least global ice, and thus the warmest, may be stages 1, 5, 9, and 11. Last interglaciation was during all of stage 5 or just substage 5e, depending on location; last glaciation took place during stages 4, 3, and 2; and the current interglaciation falls during stage 1.

12. 120-140 m sea-level fluctuations Oxygen isotope record of climate cycles Saw tooth pattern: Slow ice sheet build-up, then rapid ice sheet collapse